1. Activty life cycle
activity life cycle
oncreate()->onstart()->onResume()->onPause()->onStop()->onDestory()
- onCreate():
When we click on the activity, the system will call the activity's oncreate() method, in which we will initialize the current layout setContentLayout() method.
- onStart():
After the onCreate() method is completed, the activity enters the onStart() method at this time. The current activity is visible to the user, but has no focus and cannot interact with the user. Generally, some animation initialization operations can be performed in the current method.
- onResume():
After the onStart() method is completed, the activity enters the onResume() method at this time, and the current activity state belongs to the running state (Running), which can interact with the user.
- onPause()
When another activity covers the current acitivty, the current activity will enter the onPause() method. The current activity is visible, but cannot interact with the user.
- onStop()
After the onPause() method is completed, the activity enters the onStop() method at this time. At this time, the activity is invisible to the user. When the system memory is tight, it may be recycled by the system. Therefore, resource recovery can generally be done in the current method.
- onDestory()
After the onStop() method is completed, the activity enters the onDestory() method to end the current activity.
- onRestart()
The onRestart() method is called when the user enters the current activity again after pressing home(). Calling sequence onPause()->onStop()->onRestart()->onStart()->onResume().
Four states about activity:
running-paused-stopped-killed
running->The activity currently displayed on the screen (at the top of the task stack), visible to the user.
paused-> is still visible to the user, but the interface focus has been lost, and this Activity cannot interact with the user.
stopped->The user cannot see the current interface, nor can it interact with the user. It is completely covered.
killed->The current interface is destroyed, waiting for the system to be recycled
The method executed when AActivity switches BActivity:
AActivity:onCreate()->onStart()->onResume()->onPause()
BActivity:onCreate()->onStart()->onResume()
AActivity:onStop()->onDestory()
The method executed when AActivity switches BActivity (this activity exists in the form of dialog):
AActivity:onCreate()->onStart()->onResume()->onPause()
BActivity:onCreate()->onStart()->onResume()
2. Activity startup process source code analysis
1) Start Activity through startActivity, onCreate
Start an activity by code:
Intent intent = new Intent(this, TestActivity.class);
this.startActivity(intent);
Related class introduction:
ActivityManagerService：ActivityResponsible for all life cycles in the system ;ActivityThread：The real entrance of the App, when the App is started, itsmain()method will be called to start execution, and the message loop queue will be opened. It is the legendary UI thread, the main thread. The management work completed together withActivityManagerServicecooperationActivity;ApplicationThread：Used to realize the interactionActivityManagerServicebetweenActivityThreadand. In the life cycle thatActivityManagerServiceneeds to be managed , the proxy object and communication passed;ApplicationActivityApplicationThreadActivityThread-
ClientLifecycleManager: This class is able to combine multiple client lifecycle transition requests/callbacks and execute them as a single transaction
scheduleTransaction(clientTransaction) Instrumentation：Each application has exactly oneInstrumentationobject, and eachActivityapplication has a reference to that object.InstrumentationIt can be understood as the housekeeper of the application process. WhenActivityThreadyou want to create or open a certainActivitytime, you need to passInstrumentationit to perform specific operations;ActvitityStack：ActivityIn the stack management of AMS, it is used to recordActivitythe sequence relationship, status information, etc. that have been started. ByActivityStackdeciding whether a new process needs to be started;ActivityRecord：ActivityStatckManagement objects,Activityone for each in AMSActivityRecord, to recordActivitystatus and other information. It can be understood as a mapping of objectsActivityon the server side ;ActivityActivityClientRecord：Corresponding to the record of ActivityRecord on the server side (AMS), it isActivitythe record on the client side (ActivityThread);TaskRecord：The concept of task stack abstracted by AMS. OneTaskRecordcontains severalActivityRecord. It is used by ASM to ensureActivitystartup and exit order. It isActivitydirectly related to the boot mode of .ActivityStarter：The startupActivitycontroller is mainly used to convertIntentandflagsintoactivityand related task stacks;ActivityStackSupervisor：Mainly managesmHomeStackandmFocusedStacktwoActivityStackother related information;
- frameworks/base/core/java/android/app/Activity.java
@Override
public void startActivity(Intent intent) {
this.startActivity(intent, null);
}
@Override
public void startActivity(Intent intent, @Nullable Bundle options) {
if (mIntent != null && mIntent.hasExtra(AutofillManager.EXTRA_RESTORE_SESSION_TOKEN)
&& mIntent.hasExtra(AutofillManager.EXTRA_RESTORE_CROSS_ACTIVITY)) {
if (TextUtils.equals(getPackageName(),
intent.resolveActivity(getPackageManager()).getPackageName())) {
// Apply Autofill restore mechanism on the started activity by startActivity()
final IBinder token =
mIntent.getIBinderExtra(AutofillManager.EXTRA_RESTORE_SESSION_TOKEN);
// Remove restore ability from current activity
mIntent.removeExtra(AutofillManager.EXTRA_RESTORE_SESSION_TOKEN);
mIntent.removeExtra(AutofillManager.EXTRA_RESTORE_CROSS_ACTIVITY);
// Put restore token
intent.putExtra(AutofillManager.EXTRA_RESTORE_SESSION_TOKEN, token);
intent.putExtra(AutofillManager.EXTRA_RESTORE_CROSS_ACTIVITY, true);
}
}
if (options != null) {
startActivityForResult(intent, -1, options);
// 此时 options 为空
} else {
// Note we want to go through this call for compatibility with
// applications that may have overridden the method.
// 调用startActivityForResult方法，此时requestCode为-1不返回结果
startActivityForResult(intent, -1);
}
}In the startActivityForResult method, if it is the first start and mParent is empty, the Instrumentation.execStartActivity method will be called, otherwise the Activity.startActivityFromChild method will be called
public void startActivityForResult(@RequiresPermission Intent intent, int requestCode) {
startActivityForResult(intent, requestCode, null);
}
-------
public void startActivityForResult(@RequiresPermission Intent intent, int requestCode,
@Nullable Bundle options) {
// 此时 mParent 为空，还没有调用 attach( 方法
if (mParent == null) {
options = transferSpringboardActivityOptions(options);
// requestCode =-1, options为空，
Instrumentation.ActivityResult ar =
mInstrumentation.execStartActivity(
this, mMainThread.getApplicationThread(), mToken, this,
intent, requestCode, options);
if (ar != null) {
mMainThread.sendActivityResult(
mToken, mEmbeddedID, requestCode, ar.getResultCode(),
ar.getResultData());
}
if (requestCode >= 0) {
// If this start is requesting a result, we can avoid making
// the activity visible until the result is received. Setting
// this code during onCreate(Bundle savedInstanceState) or onResume() will keep the
// activity hidden during this time, to avoid flickering.
// This can only be done when a result is requested because
// that guarantees we will get information back when the
// activity is finished, no matter what happens to it.
mStartedActivity = true;
}
cancelInputsAndStartExitTransition(options);
// TODO Consider clearing/flushing other event sources and events for child windows.
} else {
if (options != null) {
mParent.startActivityFromChild(this, intent, requestCode, options);
} else {
// Note we want to go through this method for compatibility with
// existing applications that may have overridden it.
mParent.startActivityFromChild(this, intent, requestCode);
}
}
}- frameworks/base/core/java/android/app/Instrumentation.java
@UnsupportedAppUsage
public ActivityResult execStartActivity(
Context who, IBinder contextThread, IBinder token, Activity target,
Intent intent, int requestCode, Bundle options) {
IApplicationThread whoThread = (IApplicationThread) contextThread;
Uri referrer = target != null ? target.onProvideReferrer() : null;
if (referrer != null) {
intent.putExtra(Intent.EXTRA_REFERRER, referrer);
}
。。。
try {
intent.migrateExtraStreamToClipData(who);
intent.prepareToLeaveProcess(who);
// binder 调用 ActivityTaskManagerService
int result = ActivityTaskManager.getService().startActivity(whoThread,
who.getOpPackageName(), who.getAttributionTag(), intent,
intent.resolveTypeIfNeeded(who.getContentResolver()), token,
target != null ? target.mEmbeddedID : null, requestCode, 0, null, options);
// 检查启动结果
checkStartActivityResult(result, intent);
} catch (RemoteException e) {
throw new RuntimeException("Failure from system", e);
}
return null;
}Look at ActivityTaskManager.getService(), what is called:
- frameworks/base/core/java/android/app/ActivityTaskManager.java
public static IActivityTaskManager getService() {
return IActivityTaskManagerSingleton.get();
}
// 可以看到是客户端调用服务端的方法
@UnsupportedAppUsage(trackingBug = 129726065)
private static final Singleton<IActivityTaskManager> IActivityTaskManagerSingleton =
new Singleton<IActivityTaskManager>() {
@Override
protected IActivityTaskManager create() {
final IBinder b = ServiceManager.getService(Context.ACTIVITY_TASK_SERVICE);
return IActivityTaskManager.Stub.asInterface(b);
}
};- frameworks/base/services/core/java/com/android/server/wm/ActivityTaskManagerService.java
public class ActivityTaskManagerService extends IActivityTaskManager.Stub {
private static final String TAG = TAG_WITH_CLASS_NAME ? "ActivityTaskManagerService" : TAG_ATM;
@Override
public final int startActivity(IApplicationThread caller, String callingPackage,
String callingFeatureId, Intent intent, String resolvedType, IBinder resultTo,
String resultWho, int requestCode, int startFlags, ProfilerInfo profilerInfo,
Bundle bOptions) {
return startActivityAsUser(caller, callingPackage, callingFeatureId, intent, resolvedType,
resultTo, resultWho, requestCode, startFlags, profilerInfo, bOptions,
UserHandle.getCallingUserId());
}
@Override
public int startActivityAsUser(IApplicationThread caller, String callingPackage,
String callingFeatureId, Intent intent, String resolvedType, IBinder resultTo,
String resultWho, int requestCode, int startFlags, ProfilerInfo profilerInfo,
Bundle bOptions, int userId) {
return startActivityAsUser(caller, callingPackage, callingFeatureId, intent, resolvedType,
resultTo, resultWho, requestCode, startFlags, profilerInfo, bOptions, userId,
true /*validateIncomingUser*/);
}
private int startActivityAsUser(IApplicationThread caller, String callingPackage,
@Nullable String callingFeatureId, Intent intent, String resolvedType,
IBinder resultTo, String resultWho, int requestCode, int startFlags,
ProfilerInfo profilerInfo, Bundle bOptions, int userId, boolean validateIncomingUser) {
assertPackageMatchesCallingUid(callingPackage);
enforceNotIsolatedCaller("startActivityAsUser");
userId = getActivityStartController().checkTargetUser(userId, validateIncomingUser,
Binder.getCallingPid(), Binder.getCallingUid(), "startActivityAsUser");
// TODO: Switch to user app stacks here.
return getActivityStartController().obtainStarter(intent, "startActivityAsUser")
.setCaller(caller)
.setCallingPackage(callingPackage)
.setCallingFeatureId(callingFeatureId)
.setResolvedType(resolvedType)
.setResultTo(resultTo)
.setResultWho(resultWho)
.setRequestCode(requestCode)
.setStartFlags(startFlags)
.setProfilerInfo(profilerInfo)
.setActivityOptions(bOptions)
.setUserId(userId)
.execute();
}
// 获取到activity 启动的控制器
ActivityStartController getActivityStartController() {
return mActivityStartController;
}
// 其中 ActivityStartController 的类的方法，返回 ActivityStarter 对象
ActivityStarter obtainStarter(Intent intent, String reason) {
return mFactory.obtain().setIntent(intent).setReason(reason);
}- frameworks/base/services/core/java/com/android/server/wm/ActivityStarter.java
int execute() {
try {
// Refuse possible leaked file descriptors
if (mRequest.intent != null && mRequest.intent.hasFileDescriptors()) {
throw new IllegalArgumentException("File descriptors passed in Intent");
}
final LaunchingState launchingState;
synchronized (mService.mGlobalLock) {
final ActivityRecord caller = ActivityRecord.forTokenLocked(mRequest.resultTo);
final int callingUid = mRequest.realCallingUid == Request.DEFAULT_REAL_CALLING_UID
? Binder.getCallingUid() : mRequest.realCallingUid;
launchingState = mSupervisor.getActivityMetricsLogger().notifyActivityLaunching(
mRequest.intent, caller, callingUid);
}
// If the caller hasn't already resolved the activity, we're willing
// to do so here. If the caller is already holding the WM lock here,
// and we need to check dynamic Uri permissions, then we're forced
// to assume those permissions are denied to avoid deadlocking.
if (mRequest.activityInfo == null) {
mRequest.resolveActivity(mSupervisor);
}
// Add checkpoint for this shutdown or reboot attempt, so we can record the original
// intent action and package name.
if (mRequest.intent != null) {
String intentAction = mRequest.intent.getAction();
String callingPackage = mRequest.callingPackage;
if (intentAction != null && callingPackage != null
&& (Intent.ACTION_REQUEST_SHUTDOWN.equals(intentAction)
|| Intent.ACTION_SHUTDOWN.equals(intentAction)
|| Intent.ACTION_REBOOT.equals(intentAction))) {
ShutdownCheckPoints.recordCheckPoint(intentAction, callingPackage, null);
}
}
int res;
synchronized (mService.mGlobalLock) {
final boolean globalConfigWillChange = mRequest.globalConfig != null
&& mService.getGlobalConfiguration().diff(mRequest.globalConfig) != 0;
final Task rootTask = mRootWindowContainer.getTopDisplayFocusedRootTask();
if (rootTask != null) {
rootTask.mConfigWillChange = globalConfigWillChange;
}
ProtoLog.v(WM_DEBUG_CONFIGURATION, "Starting activity when config "
+ "will change = %b", globalConfigWillChange);
final long origId = Binder.clearCallingIdentity();
res = resolveToHeavyWeightSwitcherIfNeeded();
if (res != START_SUCCESS) {
return res;
}
// 重点关注此方法
res = executeRequest(mRequest);
Binder.restoreCallingIdentity(origId);
if (globalConfigWillChange) {
// If the caller also wants to switch to a new configuration, do so now.
// This allows a clean switch, as we are waiting for the current activity
// to pause (so we will not destroy it), and have not yet started the
// next activity.
mService.mAmInternal.enforceCallingPermission(
android.Manifest.permission.CHANGE_CONFIGURATION,
"updateConfiguration()");
if (rootTask != null) {
rootTask.mConfigWillChange = false;
}
ProtoLog.v(WM_DEBUG_CONFIGURATION,
"Updating to new configuration after starting activity.");
mService.updateConfigurationLocked(mRequest.globalConfig, null, false);
}The request object is given to the executeRequest method, and some parameter checks will be done in it
class ActivityStarter {
// 执行活动启动请求，开启活动启动之旅。首先是执行几个初步检查。
// 通常的 Activity 启动流程会经过 {@link startActivityUnchecked} 到 {@link startActivityInner}。
private int executeRequest(Request request) {
int err = ActivityManager.START_SUCCESS;
....
// 我们找不到可以处理给定 Intent 的类。
if (err == ActivityManager.START_SUCCESS && intent.getComponent() == null) {
// We couldn't find a class that can handle the given Intent.
// That's the end of that!
err = ActivityManager.START_INTENT_NOT_RESOLVED;
}
// 我们找不到 Intent 中指定的特定类。
if (err == ActivityManager.START_SUCCESS && aInfo == null) {
// We couldn't find the specific class specified in the Intent.
// Also the end of the line.
err = ActivityManager.START_CLASS_NOT_FOUND;
}
....
// 检查启动activity的权限
boolean abort = !mSupervisor.checkStartAnyActivityPermission(intent, aInfo, resultWho,
requestCode, callingPid, callingUid, callingPackage, callingFeatureId,
request.ignoreTargetSecurity, inTask != null, callerApp, resultRecord, resultStack);
abort |= !mService.mIntentFirewall.checkStartActivity(intent, callingUid,
callingPid, resolvedType, aInfo.applicationInfo);
abort |= !mService.getPermissionPolicyInternal().checkStartActivity(intent, callingUid,
callingPackage);
boolean restrictedBgActivity = false;
if (!abort) {
try {
Trace.traceBegin(Trace.TRACE_TAG_WINDOW_MANAGER,
"shouldAbortBackgroundActivityStart");
// 检查是否允许后台启动activity，以下情况会允许后台启动activity
// 1、一些重要的UId比如System UID，NFC UID
// 2、callingUid具有可见窗口或是持久性系统进程（即persistent的系统进程）
// 3、callingUid具有START_ACTIVITIES_FROM_BACKGROUND权限
// 4、调用方的uid与最近使用的组件具有相同的uid
// 5、callingUid是设备所有者或者有伴侣设备
// 6、callingUid具有SYSTEM_ALERT_WINDOW权限
// 7、调用者在任何前台任务中有活动
// 8、调用者被当前前台的 UID 绑定
restrictedBgActivity = shouldAbortBackgroundActivityStart(callingUid,
callingPid, callingPackage, realCallingUid, realCallingPid, callerApp,
request.originatingPendingIntent, request.allowBackgroundActivityStart,
intent);
} finally {
Trace.traceEnd(Trace.TRACE_TAG_WINDOW_MANAGER);
}
}
// 如果权限需要审阅才能运行任何应用程序组件，我们将启动审阅活动，
// 并传递未决的意向以启动在审阅完成后现在要启动的活动。
if (aInfo != null) {
// 获取此包使用的某些权限是否需要用户审核才能运行任何应用程序组件。
if (mService.getPackageManagerInternalLocked().isPermissionsReviewRequired(
aInfo.packageName, userId)) {
....
// 启动权限审核
Intent newIntent = new Intent(Intent.ACTION_REVIEW_PERMISSIONS);
intent = newIntent;
....
}
}
....
// 创建ActivityRecord对象
final ActivityRecord r = new ActivityRecord(mService, callerApp, callingPid, callingUid,
callingPackage, callingFeatureId, intent, resolvedType, aInfo,
mService.getGlobalConfiguration(), resultRecord, resultWho, requestCode,
request.componentSpecified, voiceSession != null, mSupervisor, checkedOptions,
sourceRecord);
mLastStartActivityRecord = r;
// 进入启动activity的流程（跳过检查）
mLastStartActivityResult = startActivityUnchecked(r, sourceRecord, voiceSession,
request.voiceInteractor, startFlags, true /* doResume */, checkedOptions, inTask,
restrictedBgActivity, intentGrants);
....
return mLastStartActivityResult;
}
}
shouldAbortBackgroundActivityStart This method is very important. It mainly deals with the logic of whether to allow the background to start the activity (the higher version restricts the service to start the activity to prevent the flood of advertisements)
private int startActivityUnchecked(final ActivityRecord r, ActivityRecord sourceRecord,
IVoiceInteractionSession voiceSession, IVoiceInteractor voiceInteractor,
int startFlags, boolean doResume, ActivityOptions options, Task inTask,
boolean restrictedBgActivity, NeededUriGrants intentGrants) {
int result = START_CANCELED;
final Task startedActivityRootTask;
// Create a transition now to record the original intent of actions taken within
// startActivityInner. Otherwise, logic in startActivityInner could start a different
// transition based on a sub-action.
// Only do the create here (and defer requestStart) since startActivityInner might abort.
final Transition newTransition = (!mService.getTransitionController().isCollecting()
&& mService.getTransitionController().getTransitionPlayer() != null)
? mService.getTransitionController().createTransition(TRANSIT_OPEN) : null;
IRemoteTransition remoteTransition = r.takeRemoteTransition();
if (newTransition != null && remoteTransition != null) {
newTransition.setRemoteTransition(remoteTransition);
}
mService.getTransitionController().collect(r);
try {
mService.deferWindowLayout();
Trace.traceBegin(Trace.TRACE_TAG_WINDOW_MANAGER, "startActivityInner");
result = startActivityInner(r, sourceRecord, voiceSession, voiceInteractor,
startFlags, doResume, options, inTask, restrictedBgActivity, intentGrants);
} finally {
Trace.traceEnd(Trace.TRACE_TAG_WINDOW_MANAGER);
startedActivityRootTask = handleStartResult(r, result);
mService.continueWindowLayout();
mSupervisor.mUserLeaving = false;Hand over the start action to the startActivityInner method
class ActivityStarter {
....
// 启动一个活动，并确定该活动是应该添加到现有任务的顶部还是应该向现有活动传递新的意图。
// 还可以将活动任务操纵到请求的或有效的堆栈显示上。
int startActivityInner(final ActivityRecord r, ActivityRecord sourceRecord,
IVoiceInteractionSession voiceSession, IVoiceInteractor voiceInteractor,
int startFlags, boolean doResume, ActivityOptions options, Task inTask,
boolean restrictedBgActivity, NeededUriGrants intentGrants) {
// 处理activity启动模式
computeLaunchingTaskFlags();
// 确定是否应将新活动插入现有任务。如果不是，则返回null，
// 或者返回带有应将新活动添加到其中的任务的ActivityRecord。
final Task reusedTask = getReusableTask();
// 计算是否存在可以使用的任务栈
final Task targetTask = reusedTask != null ? reusedTask : computeTargetTask();
// 检查是否允许在给定任务或新任务上启动活动。
int startResult = isAllowedToStart(r, newTask, targetTask);
if (startResult != START_SUCCESS) {
return startResult;
}
final ActivityStack topStack = mRootWindowContainer.getTopDisplayFocusedStack();
if (topStack != null) {
// 检查正在启动的活动是否与当前位于顶部的活动相同，并且应该只启动一次
startResult = deliverToCurrentTopIfNeeded(topStack, intentGrants);
if (startResult != START_SUCCESS) {
return startResult;
}
}
....
if (mTargetStack == null) {
// 复用或者创建堆栈
mTargetStack = getLaunchStack(mStartActivity, mLaunchFlags, targetTask, mOptions);
}
if (newTask) {
// 新建一个task
final Task taskToAffiliate = (mLaunchTaskBehind && mSourceRecord != null)
? mSourceRecord.getTask() : null;
setNewTask(taskToAffiliate);
if (mService.getLockTaskController().isLockTaskModeViolation(
mStartActivity.getTask())) {
Slog.e(TAG, "Attempted Lock Task Mode violation mStartActivity=" + mStartActivity);
return START_RETURN_LOCK_TASK_MODE_VIOLATION;
}
} else if (mAddingToTask) {
// 复用之前的task
addOrReparentStartingActivity(targetTask, "adding to task");
}
....
// 检查是否需要触发过渡动画和开始窗口
mTargetStack.startActivityLocked(mStartActivity, topStack.getTopNonFinishingActivity(),
newTask, mKeepCurTransition, mOptions);
if (mDoResume) {
....
mRootWindowContainer.resumeFocusedStacksTopActivities(
mTargetStack, mStartActivity, mOptions);
....
}
....
return START_SUCCESS;
}
}
The task that startActivityInner is responsible for is to prepare the stack and make final preparations for starting the activity.
- frameworks/base/services/core/java/com/android/server/wm/RootWindowContainer.java
boolean resumeFocusedTasksTopActivities(
Task targetRootTask, ActivityRecord target, ActivityOptions targetOptions,
boolean deferPause) {
if (!mTaskSupervisor.readyToResume()) {
return false;
}
boolean result = false;
if (targetRootTask != null && (targetRootTask.isTopRootTaskInDisplayArea()
|| getTopDisplayFocusedRootTask() == targetRootTask)) {
// 执行 resumeTopActivityUncheckedLocked
result = targetRootTask.resumeTopActivityUncheckedLocked(target, targetOptions,
deferPause);
}
for (int displayNdx = getChildCount() - 1; displayNdx >= 0; --displayNdx) {
final DisplayContent display = getChildAt(displayNdx);
final boolean curResult = result;
boolean[] resumedOnDisplay = new boolean[1];
display.forAllRootTasks(rootTask -> {
final ActivityRecord topRunningActivity = rootTask.topRunningActivity();
if (!rootTask.isFocusableAndVisible() || topRunningActivity == null) {
return;
}
if (rootTask == targetRootTask) {
// Simply update the result for targetRootTask because the targetRootTask
// had already resumed in above. We don't want to resume it again,
// especially in some cases, it would cause a second launch failure
// if app process was dead.
resumedOnDisplay[0] |= curResult;
return;
}
if (rootTask.getDisplayArea().isTopRootTask(rootTask)
&& topRunningActivity.isState(RESUMED)) {
// Kick off any lingering app transitions form the MoveTaskToFront
// operation, but only consider the top task and root-task on that
// display.
rootTask.executeAppTransition(targetOptions);
} else {
resumedOnDisplay[0] |= topRunningActivity.makeActiveIfNeeded(target);
}
});
result |= resumedOnDisplay[0];
if (!resumedOnDisplay[0]) {
// In cases when there are no valid activities (e.g. device just booted or launcher
// crashed) it's possible that nothing was resumed on a display. Requesting resume
// of top activity in focused root task explicitly will make sure that at least home
// activity is started and resumed, and no recursion occurs.
final Task focusedRoot = display.getFocusedRootTask();
if (focusedRoot != null) {
result |= focusedRoot.resumeTopActivityUncheckedLocked(target, targetOptions);
} else if (targetRootTask == null) {
result |= resumeHomeActivity(null /* prev */, "no-focusable-task",
display.getDefaultTaskDisplayArea());
}
}
}
return result;
}- frameworks/base/services/core/java/com/android/server/wm/Task.java
Ensure that the top activity in the root task is resumed, ensure that the top activity in the stack is resumed
boolean resumeTopActivityUncheckedLocked(ActivityRecord prev, ActivityOptions options,
boolean deferPause) {
if (mInResumeTopActivity) {
// Don't even start recursing.
return false;
}
boolean someActivityResumed = false;
try {
// Protect against recursion.
mInResumeTopActivity = true;
if (isLeafTask()) {
if (isFocusableAndVisible()) {
// 执行下列方法
someActivityResumed = resumeTopActivityInnerLocked(prev, options, deferPause);
}
} else {
int idx = mChildren.size() - 1;
while (idx >= 0) {
final Task child = (Task) getChildAt(idx--);
if (!child.isTopActivityFocusable()) {
continue;
}
if (child.getVisibility(null /* starting */) != TASK_VISIBILITY_VISIBLE) {
break;
}
someActivityResumed |= child.resumeTopActivityUncheckedLocked(prev, options,
deferPause);
// Doing so in order to prevent IndexOOB since hierarchy might changes while
// resuming activities, for example dismissing split-screen while starting
// non-resizeable activity.
if (idx >= mChildren.size()) {
idx = mChildren.size() - 1;
}
}
}
// When resuming the top activity, it may be necessary to pause the top activity (for
// example, returning to the lock screen. We suppress the normal pause logic in
// {@link #resumeTopActivityUncheckedLocked}, since the top activity is resumed at the
// end. We call the {@link ActivityTaskSupervisor#checkReadyForSleepLocked} again here
// to ensure any necessary pause logic occurs. In the case where the Activity will be
// shown regardless of the lock screen, the call to
// {@link ActivityTaskSupervisor#checkReadyForSleepLocked} is skipped.
final ActivityRecord next = topRunningActivity(true /* focusableOnly */);
if (next == null || !next.canTurnScreenOn()) {
checkReadyForSleep();
}
} finally {
mInResumeTopActivity = false;
}
return someActivityResumed;
}The process came to resumeTopActivityInnerLocked
private boolean resumeTopActivityInnerLocked(ActivityRecord prev, ActivityOptions options,
boolean deferPause) {
if (!mAtmService.isBooting() && !mAtmService.isBooted()) {
// Not ready yet!
return false;
}
} else {
// Whoops, need to restart this activity!
if (!next.hasBeenLaunched) {
next.hasBeenLaunched = true;
} else {
if (SHOW_APP_STARTING_PREVIEW) {
next.showStartingWindow(false /* taskSwich */);
}
if (DEBUG_SWITCH) Slog.v(TAG_SWITCH, "Restarting: " + next);
}
ProtoLog.d(WM_DEBUG_STATES, "resumeTopActivityLocked: Restarting %s", next);
mTaskSupervisor.startSpecificActivity(next, true, true);
}
return true;
}The implementation of this method is very long, mainly to deal with the logic of the previous and next activity display, directly look at the implementation of startSpecificActivity
- frameworks/base/services/core/java/com/android/server/wm/ActivityTaskSupervisor.java
// 这个类后面估计也会被移除
public class ActivityStackSupervisor implements RecentTasks.Callbacks {
final ActivityTaskManagerService mService;
....
void startSpecificActivity(ActivityRecord r, boolean andResume, boolean checkConfig) {
// 此活动的应用程序是否已在运行？
final com.android.server.wm.WindowProcessController wpc =
mService.getProcessController(r.processName, r.info.applicationInfo.uid);
boolean knownToBeDead = false;
if (wpc != null && wpc.hasThread()) {
try {
// 真正启动activity的地方
realStartActivityLocked(r, wpc, andResume, checkConfig);
return;
} catch (RemoteException e) {
Slog.w(TAG, "Exception when starting activity "
+ r.intent.getComponent().flattenToShortString(), e);
}
// If a dead object exception was thrown -- fall through to
// restart the application.
knownToBeDead = true;
}
r.notifyUnknownVisibilityLaunchedForKeyguardTransition();
final boolean isTop = andResume && r.isTopRunningActivity();
// 启动失败，对应的应用程序没有运行，就创建一个进程
// 这里的mService即ActivityTaskManagerService
mService.startProcessAsync(r, knownToBeDead, isTop, isTop ? "top-activity" : "activity");
}
boolean realStartActivityLocked(ActivityRecord r, WindowProcessController proc,
boolean andResume, boolean checkConfig) throws RemoteException {
// 创建活动启动事务。
final ClientTransaction clientTransaction = ClientTransaction.obtain(
proc.getThread(), r.appToken);
// 在回调序列的末尾添加一条消息。
// 注意，这里会给客户端用于创建activity
// 这里添加了 LaunchActivityItem
clientTransaction.addCallback(LaunchActivityItem.obtain(new Intent(r.intent),
System.identityHashCode(r), r.info,
mergedConfiguration.getGlobalConfiguration(),
mergedConfiguration.getOverrideConfiguration(), r.compat,
r.launchedFromPackage, task.voiceInteractor, proc.getReportedProcState(),
r.getSavedState(), r.getPersistentSavedState(), results, newIntents,
dc.isNextTransitionForward(), proc.createProfilerInfoIfNeeded(),
r.assistToken, r.createFixedRotationAdjustmentsIfNeeded()));
// 设置所需的最终状态。
final ActivityLifecycleItem lifecycleItem;
// 这里创建的是 ResumeActivityItem
if (andResume) {
lifecycleItem = ResumeActivityItem.obtain(dc.isNextTransitionForward());
} else {
lifecycleItem = PauseActivityItem.obtain();
}
// 设置lifecycleItem
clientTransaction.setLifecycleStateRequest(lifecycleItem);
// 安排一个事务
mService.getLifecycleManager().scheduleTransaction(clientTransaction);
}
}
getLifecycleManager() returns a ClientLifecycleManager object
// 能够组合多个客户端生命周期转换请求和/或回调的类，并将它们作为单个事务执行。
class ClientLifecycleManager {
// 安排一个事务，它可能包含多个回调和一个生命周期请求。
void scheduleTransaction(ClientTransaction transaction) throws RemoteException {
// 拿到客户端的binder对象。即ActivityThread内部类ApplicationThread
final IApplicationThread client = transaction.getClient();
// 执行 schedule 方法
transaction.schedule();
if (!(client instanceof Binder)) {
transaction.recycle();
}
}
}
Finally, ClientLifecycleManager submits the creation of activity transactions to the client's ApplicationThread class.
In the startSpecificActivity method, it will judge whether the App has started according to whether the process and thread exist. If it has already started, it will call the realStartActivityLocked method to continue processing. If it is not started, call the ActivityManagerService.startProcessLocked method to create a new process. Here first analyze how to start the process.
1-1) mService.startProcessAsync starts the process
From AMS to ZygoteState, the dark blue class is executed in the system_server process, and the yellow class is the Socket cross-process communication tool class.
- frameworks/base/services/core/java/com/android/server/wm/ActivityTaskManagerService.java
void startProcessAsync(ActivityRecord activity, boolean knownToBeDead, boolean isTop,
String hostingType) {
try {
if (Trace.isTagEnabled(TRACE_TAG_WINDOW_MANAGER)) {
Trace.traceBegin(TRACE_TAG_WINDOW_MANAGER, "dispatchingStartProcess:"
+ activity.processName);
}
// Post message to start process to avoid possible deadlock of calling into AMS with the
// ATMS lock held.
// 执行 startProcess方法
final Message m = PooledLambda.obtainMessage(ActivityManagerInternal::startProcess,
mAmInternal, activity.processName, activity.info.applicationInfo, knownToBeDead,
isTop, hostingType, activity.intent.getComponent());
mH.sendMessage(m);
} finally {
Trace.traceEnd(TRACE_TAG_WINDOW_MANAGER);
}
}PooledLambda.obtainMessage() obtains a Message and assigns a Callback to it, that is, executes the ActivityManagerInternal::startProcess function of the mService.mAmInternal object. The function input parameters are 5 parameters including r.processName and r.info.applicationInfo. It can be seen that the startProcess() method of ActivityManagerInternal is the starting point for requesting to start the application process.
- frameworks/base/services/core/java/com/android/server/am/ActivityManagerService.java
@VisibleForTesting
public final class LocalService extends ActivityManagerInternal
implements ActivityManagerLocal {
@Override
public void startProcess(String processName, ApplicationInfo info, boolean knownToBeDead,
boolean isTop, String hostingType, ComponentName hostingName) {
try {
if (Trace.isTagEnabled(Trace.TRACE_TAG_ACTIVITY_MANAGER)) {
Trace.traceBegin(Trace.TRACE_TAG_ACTIVITY_MANAGER, "startProcess:"
+ processName);
}
synchronized (ActivityManagerService.this) {
// If the process is known as top app, set a hint so when the process is
// started, the top priority can be applied immediately to avoid cpu being
// preempted by other processes before attaching the process of top app.
// 调用 ActivityManagerService 内部的方法
startProcessLocked(processName, info, knownToBeDead, 0 /* intentFlags */,
new HostingRecord(hostingType, hostingName, isTop),
ZYGOTE_POLICY_FLAG_LATENCY_SENSITIVE, false /* allowWhileBooting */,
false /* isolated */);
}
} finally {
Trace.traceEnd(Trace.TRACE_TAG_ACTIVITY_MANAGER);
}
}
// startProcessLocked 方法
@GuardedBy("this")
final ProcessRecord startProcessLocked(String processName,
ApplicationInfo info, boolean knownToBeDead, int intentFlags,
HostingRecord hostingRecord, int zygotePolicyFlags, boolean allowWhileBooting,
boolean isolated) {
return mProcessList.startProcessLocked(processName, info, knownToBeDead, intentFlags,
hostingRecord, zygotePolicyFlags, allowWhileBooting, isolated, 0 /* isolatedUid */,
null /* ABI override */, null /* entryPoint */,
null /* entryPointArgs */, null /* crashHandler */);
}- frameworks/base/services/core/java/com/android/server/am/ProcessList.java
@GuardedBy("mService")
boolean startProcessLocked(HostingRecord hostingRecord, String entryPoint, ProcessRecord app,
int uid, int[] gids, int runtimeFlags, int zygotePolicyFlags, int mountExternal,
String seInfo, String requiredAbi, String instructionSet, String invokeWith,
long startTime) {
app.setPendingStart(true);
app.setRemoved(false);
if (mService.mConstants.FLAG_PROCESS_START_ASYNC) {
if (DEBUG_PROCESSES) Slog.i(TAG_PROCESSES,
"Posting procStart msg for " + app.toShortString());
mService.mProcStartHandler.post(() -> handleProcessStart(
app, entryPoint, gids, runtimeFlags, zygotePolicyFlags, mountExternal,
requiredAbi, instructionSet, invokeWith, startSeq));
return true;
} else {
try {
// 执行以下程序
final Process.ProcessStartResult startResult = startProcess(hostingRecord,
entryPoint, app,
uid, gids, runtimeFlags, zygotePolicyFlags, mountExternal, seInfo,
requiredAbi, instructionSet, invokeWith, startTime);
handleProcessStartedLocked(app, startResult.pid, startResult.usingWrapper,
startSeq, false);
} catch (RuntimeException e) {
Slog.e(ActivityManagerService.TAG, "Failure starting process "
+ app.processName, e);
app.setPendingStart(false);
mService.forceStopPackageLocked(app.info.packageName, UserHandle.getAppId(app.uid),
false, false, true, false, false, app.userId, "start failure");
}
return app.getPid() > 0;
}
} private Process.ProcessStartResult startProcess(HostingRecord hostingRecord, String entryPoint,
ProcessRecord app, int uid, int[] gids, int runtimeFlags, int zygotePolicyFlags,
int mountExternal, String seInfo, String requiredAbi, String instructionSet,
String invokeWith, long startTime) {
try {
Trace.traceBegin(Trace.TRACE_TAG_ACTIVITY_MANAGER, "Start proc: " +
app.processName);
// 通知 zygote 去开启一个进程
checkSlow(startTime, "startProcess: asking zygote to start proc");
final boolean isTopApp = hostingRecord.isTopApp();
final Process.ProcessStartResult startResult;
boolean regularZygote = false;
if (hostingRecord.usesWebviewZygote()) {
startResult = startWebView(entryPoint,
app.processName, uid, uid, gids, runtimeFlags, mountExternal,
app.info.targetSdkVersion, seInfo, requiredAbi, instructionSet,
app.info.dataDir, null, app.info.packageName,
app.getDisabledCompatChanges(),
new String[]{PROC_START_SEQ_IDENT + app.getStartSeq()});
} else if (hostingRecord.usesAppZygote()) {
final AppZygote appZygote = createAppZygoteForProcessIfNeeded(app);
// We can't isolate app data and storage data as parent zygote already did that.
startResult = appZygote.getProcess().start(entryPoint,
app.processName, uid, uid, gids, runtimeFlags, mountExternal,
app.info.targetSdkVersion, seInfo, requiredAbi, instructionSet,
app.info.dataDir, null, app.info.packageName,
/*zygotePolicyFlags=*/ ZYGOTE_POLICY_FLAG_EMPTY, isTopApp,
app.getDisabledCompatChanges(), pkgDataInfoMap, allowlistedAppDataInfoMap,
false, false,
new String[]{PROC_START_SEQ_IDENT + app.getStartSeq()});
} else {
// 开启进程
regularZygote = true;
startResult = Process.start(entryPoint,
app.processName, uid, uid, gids, runtimeFlags, mountExternal,
app.info.targetSdkVersion, seInfo, requiredAbi, instructionSet,
app.info.dataDir, invokeWith, app.info.packageName, zygotePolicyFlags,
isTopApp, app.getDisabledCompatChanges(), pkgDataInfoMap,
allowlistedAppDataInfoMap, bindMountAppsData, bindMountAppStorageDirs,
new String[]{PROC_START_SEQ_IDENT + app.getStartSeq()});
}
if (!regularZygote) {
// webview and app zygote don't have the permission to create the nodes
if (Process.createProcessGroup(uid, startResult.pid) < 0) {
Slog.e(ActivityManagerService.TAG, "Unable to create process group for "
+ app.processName + " (" + startResult.pid + ")");
}
}- frameworks/base/core/java/android/os/Process.java
public static final ZygoteProcess ZYGOTE_PROCESS = new ZygoteProcess();
public static ProcessStartResult start(@NonNull final String processClass,
@Nullable final String niceName,
int uid, int gid, @Nullable int[] gids,
int runtimeFlags,
int mountExternal,
int targetSdkVersion,
@Nullable String seInfo,
@NonNull String abi,
@Nullable String instructionSet,
@Nullable String appDataDir,
@Nullable String invokeWith,
@Nullable String packageName,
int zygotePolicyFlags,
boolean isTopApp,
@Nullable long[] disabledCompatChanges,
@Nullable Map<String, Pair<String, Long>>
pkgDataInfoMap,
@Nullable Map<String, Pair<String, Long>>
whitelistedDataInfoMap,
boolean bindMountAppsData,
boolean bindMountAppStorageDirs,
@Nullable String[] zygoteArgs) {
// 通过 zygote创建一个进程
return ZYGOTE_PROCESS.start(processClass, niceName, uid, gid, gids,
runtimeFlags, mountExternal, targetSdkVersion, seInfo,
abi, instructionSet, appDataDir, invokeWith, packageName,
zygotePolicyFlags, isTopApp, disabledCompatChanges,
pkgDataInfoMap, whitelistedDataInfoMap, bindMountAppsData,
bindMountAppStorageDirs, zygoteArgs);
}- frameworks/base/core/java/android/os/ZygoteProcess.java
public final Process.ProcessStartResult start(@NonNull final String processClass,
final String niceName,
int uid, int gid, @Nullable int[] gids,
int runtimeFlags, int mountExternal,
int targetSdkVersion,
@Nullable String seInfo,
@NonNull String abi,
@Nullable String instructionSet,
@Nullable String appDataDir,
@Nullable String invokeWith,
@Nullable String packageName,
int zygotePolicyFlags,
boolean isTopApp,
@Nullable long[] disabledCompatChanges,
@Nullable Map<String, Pair<String, Long>>
pkgDataInfoMap,
@Nullable Map<String, Pair<String, Long>>
allowlistedDataInfoList,
boolean bindMountAppsData,
boolean bindMountAppStorageDirs,
@Nullable String[] zygoteArgs) {
// TODO (chriswailes): Is there a better place to check this value?
if (fetchUsapPoolEnabledPropWithMinInterval()) {
informZygotesOfUsapPoolStatus();
}
try {
return startViaZygote(processClass, niceName, uid, gid, gids,
runtimeFlags, mountExternal, targetSdkVersion, seInfo,
abi, instructionSet, appDataDir, invokeWith, /*startChildZygote=*/ false,
packageName, zygotePolicyFlags, isTopApp, disabledCompatChanges,
pkgDataInfoMap, allowlistedDataInfoList, bindMountAppsData,
bindMountAppStorageDirs, zygoteArgs);
private Process.ProcessStartResult startViaZygote(@NonNull final String processClass,
@Nullable final String niceName,
final int uid, final int gid,
@Nullable final int[] gids,
int runtimeFlags, int mountExternal,
int targetSdkVersion,
@Nullable String seInfo,
@NonNull String abi,
@Nullable String instructionSet,
@Nullable String appDataDir,
@Nullable String invokeWith,
boolean startChildZygote,
@Nullable String packageName,
int zygotePolicyFlags,
boolean isTopApp,
@Nullable long[] disabledCompatChanges,
@Nullable Map<String, Pair<String, Long>>
pkgDataInfoMap,
@Nullable Map<String, Pair<String, Long>>
allowlistedDataInfoList,
boolean bindMountAppsData,
boolean bindMountAppStorageDirs,
@Nullable String[] extraArgs)
throws ZygoteStartFailedEx {
ArrayList<String> argsForZygote = new ArrayList<>();
// --runtime-args, --setuid=, --setgid=,
// and --setgroups= must go first
argsForZygote.add("--runtime-args");
synchronized(mLock) {
// The USAP pool can not be used if the application will not use the systems graphics
// driver. If that driver is requested use the Zygote application start path.
return zygoteSendArgsAndGetResult(openZygoteSocketIfNeeded(abi),
zygotePolicyFlags,
argsForZygote);
}
}
// 最后调用创建了对象result
private Process.ProcessStartResult attemptZygoteSendArgsAndGetResult(
ZygoteState zygoteState, String msgStr) throws ZygoteStartFailedEx {
try {
final BufferedWriter zygoteWriter = zygoteState.mZygoteOutputWriter;
final DataInputStream zygoteInputStream = zygoteState.mZygoteInputStream;
zygoteWriter.write(msgStr);
zygoteWriter.flush();
// Always read the entire result from the input stream to avoid leaving
// bytes in the stream for future process starts to accidentally stumble
// upon.
Process.ProcessStartResult result = new Process.ProcessStartResult();
result.pid = zygoteInputStream.readInt();
result.usingWrapper = zygoteInputStream.readBoolean();
if (result.pid < 0) {
throw new ZygoteStartFailedEx("fork() failed");
}
return result;
} catch (IOException ex) {
zygoteState.close();
Log.e(LOG_TAG, "IO Exception while communicating with Zygote - "
+ ex.toString());
throw new ZygoteStartFailedEx(ex);
}
}
// 看一下：openZygoteSocketIfNeeded
@GuardedBy("mLock")
private ZygoteState openZygoteSocketIfNeeded(String abi) throws ZygoteStartFailedEx {
try {
attemptConnectionToPrimaryZygote();
if (primaryZygoteState.matches(abi)) {
return primaryZygoteState;
}
if (mZygoteSecondarySocketAddress != null) {
// The primary zygote didn't match. Try the secondary.
attemptConnectionToSecondaryZygote();
if (secondaryZygoteState.matches(abi)) {
return secondaryZygoteState;
}
}
} catch (IOException ioe) {
throw new ZygoteStartFailedEx("Error connecting to zygote", ioe);
}
private void attemptConnectionToPrimaryZygote() throws IOException {
if (primaryZygoteState == null || primaryZygoteState.isClosed()) {
// 通过socket通信的方式让Zygote进程fork出一个新的进程
// ZygoteState是内部类
primaryZygoteState =
ZygoteState.connect(mZygoteSocketAddress, mUsapPoolSocketAddress);
maybeSetApiDenylistExemptions(primaryZygoteState, false);
maybeSetHiddenApiAccessLogSampleRate(primaryZygoteState);
}
}
static ZygoteState connect(@NonNull LocalSocketAddress zygoteSocketAddress,
@Nullable LocalSocketAddress usapSocketAddress)
throws IOException {
DataInputStream zygoteInputStream;
BufferedWriter zygoteOutputWriter;
final LocalSocket zygoteSessionSocket = new LocalSocket();
if (zygoteSocketAddress == null) {
throw new IllegalArgumentException("zygoteSocketAddress can't be null");
}
try {
//请求与服务端（zygote 进程）建立 socket 连接
zygoteSessionSocket.connect(zygoteSocketAddress);
zygoteInputStream = new DataInputStream(zygoteSessionSocket.getInputStream());
zygoteOutputWriter =
new BufferedWriter(
new OutputStreamWriter(zygoteSessionSocket.getOutputStream()),
Zygote.SOCKET_BUFFER_SIZE);LocalSocket is the socket of the client (system_server process), which establishes a socket connection with the server (zygote process) to realize cross-process communication; zygoteSocketAddress points to the server socket address.
This article is very good: Application process startup flow
Then, according to the passed "android.app.ActivityThread" string, reflect the object and execute the main method of ActivityThread to initialize it.
In the ActivityThread.main method, the ActivityThread is initialized, the Looper object of the main thread is created and the Looper.loop() method is called to start the Looper, and the object of the custom Handler class H is used as the handler of the main thread.
- frameworks/base/core/java/android/app/ActivityThread.java
public static void main(String[] args) {
Trace.traceBegin(Trace.TRACE_TAG_ACTIVITY_MANAGER, "ActivityThreadMain");
...
Looper.prepareMainLooper();
// Find the value for {@link #PROC_START_SEQ_IDENT} if provided on the command line.
// It will be in the format "seq=114"
long startSeq = 0;
if (args != null) {
for (int i = args.length - 1; i >= 0; --i) {
if (args[i] != null && args[i].startsWith(PROC_START_SEQ_IDENT)) {
startSeq = Long.parseLong(
args[i].substring(PROC_START_SEQ_IDENT.length()));
}
}
}
ActivityThread thread = new ActivityThread();
thread.attach(false, startSeq);
if (sMainThreadHandler == null) {
sMainThreadHandler = thread.getHandler();
}
...
Looper.loop();
...
}After the process where the Activity is located is created and the main thread is initialized, it is time to actually start the Activity. In the ActivityThread.attach method, an Application will be bound to the application through the ActivityManagerService first, and then a garbage collection observer will be added. Whenever the system triggers garbage collection, it will calculate how much memory the application uses in the run method. If More than three-quarters of the total will try to free memory. Finally, add a config callback to the root View to receive information about config changes.
frameworks/base/core/java/android/app/ActivityThread.java
private void attach(boolean system, long startSeq) {
sCurrentActivityThread = this;
mSystemThread = system;
if (!system) {
...
final IActivityManager mgr = ActivityManager.getService();
try {
mgr.attachApplication(mAppThread, startSeq);
} catch (RemoteException ex) {
throw ex.rethrowFromSystemServer();
}
// Watch for getting close to heap limit.
BinderInternal.addGcWatcher(new Runnable() {
@Override public void run() {
if (!mSomeActivitiesChanged) {
return;
}
Runtime runtime = Runtime.getRuntime();
long dalvikMax = runtime.maxMemory();
long dalvikUsed = runtime.totalMemory() - runtime.freeMemory();
if (dalvikUsed > ((3*dalvikMax)/4)) {
mSomeActivitiesChanged = false;
try {
mgr.releaseSomeActivities(mAppThread);
} catch (RemoteException e) {
throw e.rethrowFromSystemServer();
}
}
}
});
}
...
ViewRootImpl.addConfigCallback(configChangedCallback);
}
frameworks/base/services/core/java/com/android/server/am/ActivityManagerService.java
@Override
public final void attachApplication(IApplicationThread thread, long startSeq) {
synchronized (this) {
int callingPid = Binder.getCallingPid();
final int callingUid = Binder.getCallingUid();
final long origId = Binder.clearCallingIdentity();
attachApplicationLocked(thread, callingPid, callingUid, startSeq);
Binder.restoreCallingIdentity(origId);
}
}
private final boolean attachApplicationLocked(IApplicationThread thread,
int pid, int callingUid, long startSeq) {
...
// See if the top visible activity is waiting to run in this process...
if (normalMode) {
try {
if (mStackSupervisor.attachApplicationLocked(app)) {
didSomething = true;
}
} catch (Exception e) {
Slog.wtf(TAG, "Exception thrown launching activities in " + app, e);
badApp = true;
}
}
...
}
frameworks/base/services/core/java/com/android/server/am/ActivityStackSupervisor.java
boolean attachApplicationLocked(ProcessRecord app) throws RemoteException {
final String processName = app.processName;
boolean didSomething = false;
for (int displayNdx = mActivityDisplays.size() - 1; displayNdx >= 0; --displayNdx) {
final ActivityDisplay display = mActivityDisplays.valueAt(displayNdx);
for (int stackNdx = display.getChildCount() - 1; stackNdx >= 0; --stackNdx) {
final ActivityStack stack = display.getChildAt(stackNdx);
if (!isFocusedStack(stack)) {
continue;
}
stack.getAllRunningVisibleActivitiesLocked(mTmpActivityList);
final ActivityRecord top = stack.topRunningActivityLocked();
final int size = mTmpActivityList.size();
for (int i = 0; i < size; i++) {
final ActivityRecord activity = mTmpActivityList.get(i);
if (activity.app == null && app.uid == activity.info.applicationInfo.uid
&& processName.equals(activity.processName)) {
try {
if (realStartActivityLocked(activity, app,
top == activity /* andResume */, true /* checkConfig */)) {
didSomething = true;
}
} catch (RemoteException e) {
Slog.w(TAG, "Exception in new application when starting activity "
+ top.intent.getComponent().flattenToShortString(), e);
throw e;
}
}
}
}
}
if (!didSomething) {
ensureActivitiesVisibleLocked(null, 0, !PRESERVE_WINDOWS);
}
return didSomething;
}In the ActivityManagerService.attachApplication method, execute multiple jumps to the ActivityStackSupervisor.realStartActivityLocked method. That's right, it is the method that is called to start the Activity if the application process has already been started during the previous analysis.
1-2) Next execute realStartActivityLocked
boolean realStartActivityLocked(ActivityRecord r, WindowProcessController proc,
boolean andResume, boolean checkConfig) throws RemoteException {
// 创建活动启动事务。
final ClientTransaction clientTransaction = ClientTransaction.obtain(
proc.getThread(), r.appToken);
// 在回调序列的末尾添加一条消息。
// 注意，这里会给客户端用于创建activity
clientTransaction.addCallback(LaunchActivityItem.obtain(new Intent(r.intent),
System.identityHashCode(r), r.info,
mergedConfiguration.getGlobalConfiguration(),
mergedConfiguration.getOverrideConfiguration(), r.compat,
r.launchedFromPackage, task.voiceInteractor, proc.getReportedProcState(),
r.getSavedState(), r.getPersistentSavedState(), results, newIntents,
dc.isNextTransitionForward(), proc.createProfilerInfoIfNeeded(),
r.assistToken, r.createFixedRotationAdjustmentsIfNeeded()));
// 设置所需的最终状态。
final ActivityLifecycleItem lifecycleItem;
// 这里创建的是 ResumeActivityItem
if (andResume) {
lifecycleItem = ResumeActivityItem.obtain(dc.isNextTransitionForward());
} else {
lifecycleItem = PauseActivityItem.obtain();
}
// 设置lifecycleItem
clientTransaction.setLifecycleStateRequest(lifecycleItem);
// 安排一个事务
mService.getLifecycleManager().scheduleTransaction(clientTransaction);
}
}getLifecycleManager() returns a ClientLifecycleManager object
// 能够组合多个客户端生命周期转换请求和/或回调的类，并将它们作为单个事务执行。
class ClientLifecycleManager {
// 安排一个事务，它可能包含多个回调和一个生命周期请求。
void scheduleTransaction(ClientTransaction transaction) throws RemoteException {
// 拿到客户端的binder对象。即ActivityThread内部类ApplicationThread
final IApplicationThread client = transaction.getClient();
// 执行 schedule 方法
transaction.schedule();
if (!(client instanceof Binder)) {
transaction.recycle();
}
}
}
- frameworks/base/core/java/android/app/servertransaction/ClientTransaction.java
public void schedule() throws RemoteException {
mClient.scheduleTransaction(this);
}
// mClient即是以上描述的ApplicationThread
public static ClientTransaction obtain(IApplicationThread client, IBinder activityToken) {
ClientTransaction instance = ObjectPool.obtain(ClientTransaction.class);
if (instance == null) {
instance = new ClientTransaction();
}
instance.mClient = client;- frameworks/base/core/java/android/app/ActivityThread.java
@Override
public void scheduleTransaction(ClientTransaction transaction) throws RemoteException {
ActivityThread.this.scheduleTransaction(transaction);
}
Here ApplicationThread actually calls the scheduleTransaction method of ClientTransactionHandler
- frameworks/base/core/java/android/app/ClientTransactionHandler.java
// 又回到其 子类 handler 去处理
void scheduleTransaction(ClientTransaction transaction) {
transaction.preExecute(this);
sendMessage(ActivityThread.H.EXECUTE_TRANSACTION, transaction);
}
- frameworks/base/core/java/android/app/ActivityThread.java
Used to process message synchronization, and synchronize the messages of the binder thread to the main thread
// An executor that performs multi-step transactions.
private final TransactionExecutor mTransactionExecutor = new TransactionExecutor(this);
case EXECUTE_TRANSACTION:
final ClientTransaction transaction = (ClientTransaction) msg.obj;
mTransactionExecutor.execute(transaction);
if (isSystem()) {
// Client transactions inside system process are recycled on the client side
// instead of ClientLifecycleManager to avoid being cleared before this
// message is handled.
transaction.recycle();
}
// TODO(lifecycler): Recycle locally scheduled transactions.
break;- frameworks/base/core/java/android/app/servertransaction/TransactionExecutor.java
public void execute(ClientTransaction transaction) {
if (DEBUG_RESOLVER) Slog.d(TAG, tId(transaction) + "Start resolving transaction");
final IBinder token = transaction.getActivityToken();
if (token != null) {
final Map<IBinder, ClientTransactionItem> activitiesToBeDestroyed =
mTransactionHandler.getActivitiesToBeDestroyed();
final ClientTransactionItem destroyItem = activitiesToBeDestroyed.get(token);
if (destroyItem != null) {
if (transaction.getLifecycleStateRequest() == destroyItem) {
// It is going to execute the transaction that will destroy activity with the
// token, so the corresponding to-be-destroyed record can be removed.
activitiesToBeDestroyed.remove(token);
}
if (mTransactionHandler.getActivityClient(token) == null) {
// The activity has not been created but has been requested to destroy, so all
// transactions for the token are just like being cancelled.
Slog.w(TAG, tId(transaction) + "Skip pre-destroyed transaction:\n"
+ transactionToString(transaction, mTransactionHandler));
return;
}
}
}
if (DEBUG_RESOLVER) Slog.d(TAG, transactionToString(transaction, mTransactionHandler));
executeCallbacks(transaction);
executeLifecycleState(transaction);
mPendingActions.clear();
if (DEBUG_RESOLVER) Slog.d(TAG, tId(transaction) + "End resolving transaction");
}Execute the executeCallbacks() method
public void executeCallbacks(ClientTransaction transaction) {
final List<ClientTransactionItem> callbacks = transaction.getCallbacks();
if (callbacks == null || callbacks.isEmpty()) {
// No callbacks to execute, return early.
return;
}
if (DEBUG_RESOLVER) Slog.d(TAG, tId(transaction) + "Resolving callbacks in transaction");
final IBinder token = transaction.getActivityToken();
ActivityClientRecord r = mTransactionHandler.getActivityClient(token);
// In case when post-execution state of the last callback matches the final state requested
// for the activity in this transaction, we won't do the last transition here and do it when
// moving to final state instead (because it may contain additional parameters from server).
final ActivityLifecycleItem finalStateRequest = transaction.getLifecycleStateRequest();
final int finalState = finalStateRequest != null ? finalStateRequest.getTargetState()
: UNDEFINED;
// Index of the last callback that requests some post-execution state.
final int lastCallbackRequestingState = lastCallbackRequestingState(transaction);
final int size = callbacks.size();
// 遍历所有的 ClientTransactionItem
for (int i = 0; i < size; ++i) {
// 这里获取对应的 ClientTransactionItem ，ClientTransactionItem 是一个抽象类
final ClientTransactionItem item = callbacks.get(i);
if (DEBUG_RESOLVER) Slog.d(TAG, tId(transaction) + "Resolving callback: " + item);
final int postExecutionState = item.getPostExecutionState();
final int closestPreExecutionState = mHelper.getClosestPreExecutionState(r,
item.getPostExecutionState());
if (closestPreExecutionState != UNDEFINED) {
cycleToPath(r, closestPreExecutionState, transaction);
}
// mTransactionHandler 实际上是ActivityThread
item.execute(mTransactionHandler, token, mPendingActions);
item.postExecute(mTransactionHandler, token, mPendingActions);
if (r == null) {
// Launch activity request will create an activity record.
r = mTransactionHandler.getActivityClient(token);
}When the server submits the transaction, clientTransaction.addCallbackadd LaunchActivityItem to mActivityCallbacks by means
- frameworks/base/core/java/android/app/servertransaction/LaunchActivityItem.java
@Override
public void execute(ClientTransactionHandler client, IBinder token,
PendingTransactionActions pendingActions) {
Trace.traceBegin(TRACE_TAG_ACTIVITY_MANAGER, "activityStart");
ActivityClientRecord r = client.getLaunchingActivity(token);
// client为对应的ActivityThread，进程
client.handleLaunchActivity(r, pendingActions, null /* customIntent */);
Trace.traceEnd(TRACE_TAG_ACTIVITY_MANAGER);
}- frameworks/base/core/java/android/app/ActivityThread.java
@Override
public Activity handleLaunchActivity(ActivityClientRecord r,
PendingTransactionActions pendingActions, Intent customIntent) {
// If we are getting ready to gc after going to the background, well
// we are back active so skip it.
unscheduleGcIdler();
mSomeActivitiesChanged = true;
if (r.profilerInfo != null) {
mProfiler.setProfiler(r.profilerInfo);
mProfiler.startProfiling();
}
if (r.mPendingFixedRotationAdjustments != null) {
// The rotation adjustments must be applied before handling configuration, so process
// level display metrics can be adjusted.
overrideApplicationDisplayAdjustments(r.token, adjustments ->
adjustments.setFixedRotationAdjustments(r.mPendingFixedRotationAdjustments));
}
// Make sure we are running with the most recent config.
mConfigurationController.handleConfigurationChanged(null, null);
if (localLOGV) Slog.v(
TAG, "Handling launch of " + r);
// Initialize before creating the activity
if (ThreadedRenderer.sRendererEnabled
&& (r.activityInfo.flags & ActivityInfo.FLAG_HARDWARE_ACCELERATED) != 0) {
HardwareRenderer.preload();
}
WindowManagerGlobal.initialize();
// Hint the GraphicsEnvironment that an activity is launching on the process.
GraphicsEnvironment.hintActivityLaunch();
// 主要方法
final Activity a = performLaunchActivity(r, customIntent);
The performLaunchActivity method is mainly responsible for creating the activity
Mainly complete the following things:
- Obtain the component information of the Activity to be started from the ActivityClientRecord
- Create an activity instance using the class loader through the mInstrumentation.newActivity method
- The Application object is created through the makeApplication method of LoadedApk, and the class loader is also used internally through mInstrumentation. After creation, the instrumentation.callApplicationOnCreate method is called, which is the onCreate method of Application.
- Create a ContextImpl object and initialize important data through the activity.attach method, which is associated with the specific implementation of ContextImpl. The attach method also completes the window creation, so that the Window can pass it to the Activity after receiving external events.
- Calling the onCreate method of Activity is done through the mInstrumentation.callActivityOnCreate method.
mInstrumentation = new Instrumentation();
public final class ActivityThread extends android.app.ClientTransactionHandler {
// 活动启动的核心实现。
private Activity performLaunchActivity(ActivityClientRecord r, Intent customIntent) {
....
ComponentName component = r.intent.getComponent();
if (component == null) {
// component 为null，则通过intent查询指定的component
component = r.intent.resolveActivity(mInitialApplication.getPackageManager());
r.intent.setComponent(component);
}
// 创建context对象
ContextImpl appContext = createBaseContextForActivity(r);
Activity activity = null;
try {
// 通过反射的方式创建activity实例
ClassLoader cl = appContext.getClassLoader();
activity = mInstrumentation.newActivity(
cl, component.getClassName(), r.intent);
StrictMode.incrementExpectedActivityCount(activity.getClass());
r.intent.setExtrasClassLoader(cl);
r.intent.prepareToEnterProcess();
if (r.state != null) {
r.state.setClassLoader(cl);
}
} catch (Exception e) {
}
try {
// 创建Application实例
Application app = r.packageInfo.makeApplication(false, mInstrumentation);
if (activity != null) {
CharSequence title = r.activityInfo.loadLabel(appContext.getPackageManager());
// 创建配置信息
Configuration config = new Configuration(mCompatConfiguration);
if (r.overrideConfig != null) {
config.updateFrom(r.overrideConfig);
}
// 用于给activity创建PhoneWindow
Window window = null;
if (r.mPendingRemoveWindow != null && r.mPreserveWindow) {
window = r.mPendingRemoveWindow;
r.mPendingRemoveWindow = null;
r.mPendingRemoveWindowManager = null;
}
// 设置Resource加载器
appContext.getResources().addLoaders(
app.getResources().getLoaders().toArray(new ResourcesLoader[0]));
appContext.setOuterContext(activity);
// 调用activity的attach ，传入context，ActivityThread等参数，初始化window相关的内容
activity.attach(appContext, this, getInstrumentation(), r.token,
r.ident, app, r.intent, r.activityInfo, title, r.parent,
r.embeddedID, r.lastNonConfigurationInstances, config,
r.referrer, r.voiceInteractor, window, r.configCallback,
r.assistToken);
if (customIntent != null) {
activity.mIntent = customIntent;
}
r.lastNonConfigurationInstances = null;
checkAndBlockForNetworkAccess();
activity.mStartedActivity = false;
// 设置主题
int theme = r.activityInfo.getThemeResource();
if (theme != 0) {
activity.setTheme(theme);
}
activity.mCalled = false;
// 通知Instrumentation调用activity的onCreate方法
// 开始执行 onCreate方法
if (r.isPersistable()) {
mInstrumentation.callActivityOnCreate(activity, r.state, r.persistentState);
} else {
mInstrumentation.callActivityOnCreate(activity, r.state);
}
r.activity = activity;
mLastReportedWindowingMode.put(activity.getActivityToken(),
config.windowConfiguration.getWindowingMode());
}
r.setState(ON_CREATE);
// 保存token与ActivityClientRecord的映射
synchronized (mResourcesManager) {
mActivities.put(r.token, r);
}
} catch (SuperNotCalledException e) {
throw e;
}
....
return activity;
}
}
The process is here in Instrumentation
- frameworks/base/core/java/android/app/Instrumentation.java
public void callActivityOnCreate(Activity activity, Bundle icicle,
PersistableBundle persistentState) {
prePerformCreate(activity);
// 对应 activity 执行oncreate 方法
activity.performCreate(icicle, persistentState);
postPerformCreate(activity);
}
- frameworks/base/core/java/android/app/Activity.java
@UnsupportedAppUsage(maxTargetSdk = Build.VERSION_CODES.R, trackingBug = 170729553)
final void performCreate(Bundle icicle, PersistableBundle persistentState) {
if (Trace.isTagEnabled(Trace.TRACE_TAG_WINDOW_MANAGER)) {
Trace.traceBegin(Trace.TRACE_TAG_WINDOW_MANAGER, "performCreate:"
+ mComponent.getClassName());
}
dispatchActivityPreCreated(icicle);
mCanEnterPictureInPicture = true;
// initialize mIsInMultiWindowMode and mIsInPictureInPictureMode before onCreate
final int windowingMode = getResources().getConfiguration().windowConfiguration
.getWindowingMode();
mIsInMultiWindowMode = inMultiWindowMode(windowingMode);
mIsInPictureInPictureMode = windowingMode == WINDOWING_MODE_PINNED;
restoreHasCurrentPermissionRequest(icicle);
if (persistentState != null) {
onCreate(icicle, persistentState);
} else {
// 回调onCreate方法，即我们自己写的activity
onCreate(icicle);
}
EventLogTags.writeWmOnCreateCalled(mIdent, getComponentName().getClassName(),
"performCreate");
mActivityTransitionState.readState(icicle);
mVisibleFromClient = !mWindow.getWindowStyle().getBoolean(
com.android.internal.R.styleable.Window_windowNoDisplay, false);
mFragments.dispatchActivityCreated();
mActivityTransitionState.setEnterActivityOptions(this, getActivityOptions());
dispatchActivityPostCreated(icicle);
Trace.traceEnd(Trace.TRACE_TAG_WINDOW_MANAGER);
}2) onStart and other methods
At this point, the onCreate method of Activity is executed, so what about onStart and onResume?
The LaunchActivityItem seen above is used to start the Activity, that is, to the onCreate of the Activity, so is there "XXXActivityItem"? Yes:
- The onCreate life cycle transaction of LaunchActivityItem on the remote App side
- ResumeActivityItem The onResume lifecycle transaction on the remote App side
- PauseActivityItem onPause lifecycle transaction on the remote App side
- StopActivityItem onStop lifecycle transaction on the remote App side
- DestroyActivityItem Remote App side onDestroy lifecycle transaction
In addition, several classes involved in the combing process:
- ClientTransaction client transaction controller
- ClientLifecycleManager client lifecycle transaction controller
- TransactionExecutor remote communication transaction executor
There is an explanation about the TransactionExecutor class: Class that manages transaction execution in the correct order. A class that is used to ensure the correct order of transaction execution.
Let's review the TransactionExecutor#execute method
// 以正确顺序管理事务执行的类。
public class TransactionExecutor {
....
// 处理服务端传递过来的事务
public void execute(ClientTransaction transaction) {
....
// 该方法中通过遍历 transaction#callbacks 获取到LaunchActivityItem，然后调用onCreate方法
executeCallbacks(transaction);
// 然后接下来分析如下代码：
executeLifecycleState(transaction);
}
}Next analysis: executeLifecycleState
- frameworks/base/core/java/android/app/servertransaction/TransactionExecutor.java
/** Transition to the final state if requested by the transaction. */
private void executeLifecycleState(ClientTransaction transaction) {
final ActivityLifecycleItem lifecycleItem = transaction.getLifecycleStateRequest();
if (lifecycleItem == null) {
// No lifecycle request, return early.
return;
}
final IBinder token = transaction.getActivityToken();
final ActivityClientRecord r = mTransactionHandler.getActivityClient(token);
if (DEBUG_RESOLVER) {
Slog.d(TAG, tId(transaction) + "Resolving lifecycle state: "
+ lifecycleItem + " for activity: "
+ getShortActivityName(token, mTransactionHandler));
}
if (r == null) {
// Ignore requests for non-existent client records for now.
return;
}
// 循环到最终请求状态之前的状态
// Cycle to the state right before the final requested state.
cycleToPath(r, lifecycleItem.getTargetState(), true /* excludeLastState */, transaction);
// Execute the final transition with proper parameters.
lifecycleItem.execute(mTransactionHandler, token, mPendingActions);
lifecycleItem.postExecute(mTransactionHandler, token, mPendingActions);
}2-1) cycleToPath executes the onStart method
cycleToPath, here after getting lifeCyclePath, it is handed over to performLifecycleSequence
private void cycleToPath(ActivityClientRecord r, int finish, boolean excludeLastState,
ClientTransaction transaction) {
final int start = r.getLifecycleState();
if (DEBUG_RESOLVER) {
Slog.d(TAG, tId(transaction) + "Cycle activity: "
+ getShortActivityName(r.token, mTransactionHandler)
+ " from: " + getStateName(start) + " to: " + getStateName(finish)
+ " excludeLastState: " + excludeLastState);
}
final IntArray path = mHelper.getLifecyclePath(start, finish, excludeLastState);
performLifecycleSequence(r, path, transaction);
}
We come to the performLifecycleSequence method, which seems to be where all the cycles are handled
private void performLifecycleSequence(ActivityClientRecord r, IntArray path,
ClientTransaction transaction) {
final int size = path.size();
for (int i = 0, state; i < size; i++) {
// path 为 IntArray ，通过获取其对应值来走activity 的生命周期
state = path.get(i);
if (DEBUG_RESOLVER) {
Slog.d(TAG, tId(transaction) + "Transitioning activity: "
+ getShortActivityName(r.token, mTransactionHandler)
+ " to state: " + getStateName(state));
}
switch (state) {
case ON_CREATE:
mTransactionHandler.handleLaunchActivity(r, mPendingActions,
null /* customIntent */);
break;
case ON_START:
mTransactionHandler.handleStartActivity(r, mPendingActions,
null /* activityOptions */);
break;
case ON_RESUME:
mTransactionHandler.handleResumeActivity(r, false /* finalStateRequest */,
r.isForward, "LIFECYCLER_RESUME_ACTIVITY");
break;
case ON_PAUSE:
mTransactionHandler.handlePauseActivity(r, false /* finished */,
false /* userLeaving */, 0 /* configChanges */, mPendingActions,
"LIFECYCLER_PAUSE_ACTIVITY");
break;
case ON_STOP:
mTransactionHandler.handleStopActivity(r, 0 /* configChanges */,
mPendingActions, false /* finalStateRequest */,
"LIFECYCLER_STOP_ACTIVITY");
break;
case ON_DESTROY:
mTransactionHandler.handleDestroyActivity(r, false /* finishing */,
0 /* configChanges */, false /* getNonConfigInstance */,
"performLifecycleSequence. cycling to:" + path.get(size - 1));
break;
case ON_RESTART:
mTransactionHandler.performRestartActivity(r, false /* start */);
break;
default:
throw new IllegalArgumentException("Unexpected lifecycle state: " + state);
}
}The value corresponding to the life cycle is:
public abstract class ActivityLifecycleItem extends ActivityTransactionItem {
public static final int UNDEFINED = -1;
public static final int PRE_ON_CREATE = 0;
public static final int ON_CREATE = 1;
public static final int ON_START = 2;
public static final int ON_RESUME = 3;
public static final int ON_PAUSE = 4;
public static final int ON_STOP = 5;
public static final int ON_DESTROY = 6;
public static final int ON_RESTART = 7;Look at IntArray path = mHelper.getLifecyclePath to get the corresponding path
- frameworks/base/core/java/android/app/servertransaction/TransactionExecutorHelper.java
public IntArray getLifecyclePath(int start, int finish, boolean excludeLastState) {
if (start == UNDEFINED || finish == UNDEFINED) {
throw new IllegalArgumentException("Can't resolve lifecycle path for undefined state");
}
if (start == ON_RESTART || finish == ON_RESTART) {
throw new IllegalArgumentException(
"Can't start or finish in intermittent RESTART state");
}
if (finish == PRE_ON_CREATE && start != finish) {
throw new IllegalArgumentException("Can only start in pre-onCreate state");
}
mLifecycleSequence.clear();
if (finish >= start) {
if (start == ON_START && finish == ON_STOP) {
// A case when we from start to stop state soon, we don't need to go
// through the resumed, paused state.
mLifecycleSequence.add(ON_STOP);
} else {
// just go there
// 依次增加状态，保存在 IntArray
for (int i = start + 1; i <= finish; i++) {
mLifecycleSequence.add(i);
}
}
} else { // finish < start, can't just cycle down
if (start == ON_PAUSE && finish == ON_RESUME) {
// Special case when we can just directly go to resumed state.
mLifecycleSequence.add(ON_RESUME);
} else if (start <= ON_STOP && finish >= ON_START) {
// Restart and go to required state.
// Go to stopped state first.
for (int i = start + 1; i <= ON_STOP; i++) {
mLifecycleSequence.add(i);
}
// Restart
mLifecycleSequence.add(ON_RESTART);
// Go to required state
for (int i = ON_START; i <= finish; i++) {
mLifecycleSequence.add(i);
}
} else {
// Relaunch and go to required state
// Go to destroyed state first.
for (int i = start + 1; i <= ON_DESTROY; i++) {
mLifecycleSequence.add(i);
}
// Go to required state
for (int i = ON_CREATE; i <= finish; i++) {
mLifecycleSequence.add(i);
}
}
}
// Remove last transition in case we want to perform it with some specific params.
if (excludeLastState && mLifecycleSequence.size() != 0) {
mLifecycleSequence.remove(mLifecycleSequence.size() - 1);
}
return mLifecycleSequence;
}Go to the ON_START case and call the mTransactionHandler#handleStartActivity method. The specific implementation is still in ActivityThread
- frameworks/base/core/java/android/app/ActivityThread.java
@Override
public void handleStartActivity(ActivityClientRecord r,
PendingTransactionActions pendingActions, ActivityOptions activityOptions) {
final Activity activity = r.activity;
if (!r.stopped) {
throw new IllegalStateException("Can't start activity that is not stopped.");
}
if (r.activity.mFinished) {
// TODO(lifecycler): How can this happen?
return;
}
unscheduleGcIdler();
if (activityOptions != null) {
activity.mPendingOptions = activityOptions;
}
// Start
// 去回调 activity 的onStart 方法
activity.performStart("handleStartActivity");
// 设置状态
r.setState(ON_START);
if (pendingActions == null) {
// No more work to do.
return;
}
// 恢复实例的状态，即OnRestoreInstanceState周期
// Restore instance state
if (pendingActions.shouldRestoreInstanceState()) {
if (r.isPersistable()) {
if (r.state != null || r.persistentState != null) {
mInstrumentation.callActivityOnRestoreInstanceState(activity, r.state,
r.persistentState);
}
} else if (r.state != null) {
mInstrumentation.callActivityOnRestoreInstanceState(activity, r.state);
}
}
// 调用 postOnCreate() 周期
// Call postOnCreate()
if (pendingActions.shouldCallOnPostCreate()) {
activity.mCalled = false;
if (r.isPersistable()) {
mInstrumentation.callActivityOnPostCreate(activity, r.state,
r.persistentState);
} else {
mInstrumentation.callActivityOnPostCreate(activity, r.state);
}
if (!activity.mCalled) {
throw new SuperNotCalledException(
"Activity " + r.intent.getComponent().toShortString()
+ " did not call through to super.onPostCreate()");
}
}
// 将activity设置为可见，show 为 true
updateVisibility(r, true /* show */);
mSomeActivitiesChanged = true;
}
// 更新为activity 为true
private void updateVisibility(ActivityClientRecord r, boolean show) {
View v = r.activity.mDecor;
if (v != null) {
if (show) {
if (!r.activity.mVisibleFromServer) {
r.activity.mVisibleFromServer = true;
mNumVisibleActivities++;
if (r.activity.mVisibleFromClient) {
// 遍历设置为可见
r.activity.makeVisible();
}
}
} else {
if (r.activity.mVisibleFromServer) {
r.activity.mVisibleFromServer = false;
mNumVisibleActivities--;
v.setVisibility(View.INVISIBLE);
}
}
}
}To call back the onStart method of the activity
- frameworks/base/core/java/android/app/Activity.java
final void performStart(String reason) {
dispatchActivityPreStarted();
mActivityTransitionState.setEnterActivityOptions(this, getActivityOptions());
mFragments.noteStateNotSaved();
mCalled = false;
mFragments.execPendingActions();
// 通过 Instrumentation去回调 activity
mInstrumentation.callActivityOnStart(this);
EventLogTags.writeWmOnStartCalled(mIdent, getComponentName().getClassName(), reason);
if (!mCalled) {
throw new SuperNotCalledException(
"Activity " + mComponent.toShortString() +
" did not call through to super.onStart()");
}
mFragments.dispatchStart();
mFragments.reportLoaderStart();
frameworks/base/core/java/android/app/Instrumentation.java
public void callActivityOnStart(Activity activity) {
// 回调 activity 的onStart
activity.onStart();
}As can be seen from the above, the handleStartActivity method mainly calls onStart, OnRestoreInstanceStateand postOnCreate cycle. and set the activity to be visible at the end
Next, continue to look at: lifecycleItem.execute
- frameworks/base/core/java/android/app/servertransaction/TransactionExecutor.java
/** Transition to the final state if requested by the transaction. */
private void executeLifecycleState(ClientTransaction transaction) {
final ActivityLifecycleItem lifecycleItem = transaction.getLifecycleStateRequest();
if (lifecycleItem == null) {
// No lifecycle request, return early.
return;
}
final IBinder token = transaction.getActivityToken();
final ActivityClientRecord r = mTransactionHandler.getActivityClient(token);
if (DEBUG_RESOLVER) {
Slog.d(TAG, tId(transaction) + "Resolving lifecycle state: "
+ lifecycleItem + " for activity: "
+ getShortActivityName(token, mTransactionHandler));
}
if (r == null) {
// Ignore requests for non-existent client records for now.
return;
}
// 循环到最终请求状态之前的状态
// Cycle to the state right before the final requested state.
cycleToPath(r, lifecycleItem.getTargetState(), true /* excludeLastState */, transaction);
// Execute the final transition with proper parameters.
lifecycleItem.execute(mTransactionHandler, token, mPendingActions);
// 通知ActivityTaskManager
lifecycleItem.postExecute(mTransactionHandler, token, mPendingActions);
}2-2) lifecycleItem.execute executes the onResume method
lifecycleItem is an instance of ResumeActivityItem
- frameworks/base/core/java/android/app/servertransaction/ResumeActivityItem.java
public void execute(ClientTransactionHandler client, ActivityClientRecord r,
PendingTransactionActions pendingActions) {
Trace.traceBegin(TRACE_TAG_ACTIVITY_MANAGER, "activityResume");
client.handleResumeActivity(r, true /* finalStateRequest */, mIsForward,
"RESUME_ACTIVITY");
Trace.traceEnd(TRACE_TAG_ACTIVITY_MANAGER);
}- frameworks/base/core/java/android/app/ActivityThread.java
@Override
public void handleResumeActivity(ActivityClientRecord r, boolean finalStateRequest,
boolean isForward, String reason) {
// If we are getting ready to gc after going to the background, well
// we are back active so skip it.
unscheduleGcIdler();
mSomeActivitiesChanged = true;
// TODO Push resumeArgs into the activity for consideration
// skip below steps for double-resume and r.mFinish = true case.
if (!performResumeActivity(r, finalStateRequest, reason)) {
return;
}
if (mActivitiesToBeDestroyed.containsKey(r.token)) {
// Although the activity is resumed, it is going to be destroyed. So the following
// UI operations are unnecessary and also prevents exception because its token may
// be gone that window manager cannot recognize it. All necessary cleanup actions
// performed below will be done while handling destruction.
return;
}
final Activity a = r.activity;
if (localLOGV) {
Slog.v(TAG, "Resume " + r + " started activity: " + a.mStartedActivity
+ ", hideForNow: " + r.hideForNow + ", finished: " + a.mFinished);
}
final int forwardBit = isForward
? WindowManager.LayoutParams.SOFT_INPUT_IS_FORWARD_NAVIGATION : 0;
// If the window hasn't yet been added to the window manager,
// and this guy didn't finish itself or start another activity,
// then go ahead and add the window.
boolean willBeVisible = !a.mStartedActivity;
if (!willBeVisible) {
willBeVisible = ActivityClient.getInstance().willActivityBeVisible(
a.getActivityToken());
}
if (r.window == null && !a.mFinished && willBeVisible) {
r.window = r.activity.getWindow();
View decor = r.window.getDecorView();
decor.setVisibility(View.INVISIBLE);
ViewManager wm = a.getWindowManager();
WindowManager.LayoutParams l = r.window.getAttributes();
a.mDecor = decor;
l.type = WindowManager.LayoutParams.TYPE_BASE_APPLICATION;
l.softInputMode |= forwardBit;
if (r.mPreserveWindow) {
a.mWindowAdded = true;
r.mPreserveWindow = false;
// Normally the ViewRoot sets up callbacks with the Activity
// in addView->ViewRootImpl#setView. If we are instead reusing
// the decor view we have to notify the view root that the
// callbacks may have changed.
ViewRootImpl impl = decor.getViewRootImpl();
if (impl != null) {
impl.notifyChildRebuilt();
}
}
if (a.mVisibleFromClient) {
if (!a.mWindowAdded) {
a.mWindowAdded = true;
wm.addView(decor, l);
} else {
// The activity will get a callback for this {@link LayoutParams} change
// earlier. However, at that time the decor will not be set (this is set
// in this method), so no action will be taken. This call ensures the
// callback occurs with the decor set.
a.onWindowAttributesChanged(l);
}
}
// If the window has already been added, but during resume
// we started another activity, then don't yet make the
// window visible.
} else if (!willBeVisible) {
if (localLOGV) Slog.v(TAG, "Launch " + r + " mStartedActivity set");
r.hideForNow = true;
}
// Get rid of anything left hanging around.
cleanUpPendingRemoveWindows(r, false /* force */);
// The window is now visible if it has been added, we are not
// simply finishing, and we are not starting another activity.
if (!r.activity.mFinished && willBeVisible && r.activity.mDecor != null && !r.hideForNow) {
if (localLOGV) Slog.v(TAG, "Resuming " + r + " with isForward=" + isForward);
ViewRootImpl impl = r.window.getDecorView().getViewRootImpl();
WindowManager.LayoutParams l = impl != null
? impl.mWindowAttributes : r.window.getAttributes();
if ((l.softInputMode
& WindowManager.LayoutParams.SOFT_INPUT_IS_FORWARD_NAVIGATION)
!= forwardBit) {
l.softInputMode = (l.softInputMode
& (~WindowManager.LayoutParams.SOFT_INPUT_IS_FORWARD_NAVIGATION))
| forwardBit;
if (r.activity.mVisibleFromClient) {
ViewManager wm = a.getWindowManager();
View decor = r.window.getDecorView();
wm.updateViewLayout(decor, l);
}
}
r.activity.mVisibleFromServer = true;
mNumVisibleActivities++;
if (r.activity.mVisibleFromClient) {
r.activity.makeVisible();
}
}
r.nextIdle = mNewActivities;
mNewActivities = r;
if (localLOGV) Slog.v(TAG, "Scheduling idle handler for " + r);
Looper.myQueue().addIdleHandler(new Idler());
}performResumeActivity to call back activity's onResume
@VisibleForTesting
public boolean performResumeActivity(ActivityClientRecord r, boolean finalStateRequest,
String reason) {
if (localLOGV) {
Slog.v(TAG, "Performing resume of " + r + " finished=" + r.activity.mFinished);
}
if (r.activity.mFinished) {
return false;
}
try {
r.activity.onStateNotSaved();
r.activity.mFragments.noteStateNotSaved();
checkAndBlockForNetworkAccess();
if (r.pendingIntents != null) {
deliverNewIntents(r, r.pendingIntents);
r.pendingIntents = null;
}
if (r.pendingResults != null) {
deliverResults(r, r.pendingResults, reason);
r.pendingResults = null;
}
// 回调resume
r.activity.performResume(r.startsNotResumed, reason);
r.state = null;
r.persistentState = null;
r.setState(ON_RESUME);
reportTopResumedActivityChanged(r, r.isTopResumedActivity, "topWhenResuming");- frameworks/base/core/java/android/app/Activity.java
final void performResume(boolean followedByPause, String reason) {
if (Trace.isTagEnabled(Trace.TRACE_TAG_WINDOW_MANAGER)) {
Trace.traceBegin(Trace.TRACE_TAG_WINDOW_MANAGER, "performResume:"
+ mComponent.getClassName());
}
dispatchActivityPreResumed();
// 这里有restart 方法
performRestart(true /* start */, reason);
mFragments.execPendingActions();
mLastNonConfigurationInstances = null;
if (mAutoFillResetNeeded) {
// When Activity is destroyed in paused state, and relaunch activity, there will be
// extra onResume and onPause event, ignore the first onResume and onPause.
// see ActivityThread.handleRelaunchActivity()
mAutoFillIgnoreFirstResumePause = followedByPause;
if (mAutoFillIgnoreFirstResumePause && DEBUG_LIFECYCLE) {
Slog.v(TAG, "autofill will ignore first pause when relaunching " + this);
}
}
mCalled = false;
// 回调 resume
// mResumed is set by the instrumentation
mInstrumentation.callActivityOnResume(this);Finally came to the activity's performResume, calling the activity's onResume
public class Activity extends ContextThemeWrapper .... {
final void performResume(boolean followedByPause, String reason) {
// 将onResume开始事件分发给监听器ActivityLifecycleCallbacks
dispatchActivityPreResumed();
// 调用Activity的onResume方法
mInstrumentation.callActivityOnResume(this);
// 将OnResume周期分发给fragment
mFragments.dispatchResume();
// 调用onPostResume 周期
onPostResume();
// 将onResume结束的事件分发给监听器ActivityLifecycleCallbacks
dispatchActivityPostResumed();
}
}The process of executing onpause
reference:
In-depth understanding of Android's Activity startup process (Android 10)
The startup process of Activity is enough
Framework's Activity startup process