1 Introduction to AMS
AMS（Activity Manager Service）It is Androidthe core service in the company, managing the work of 四大组件的启动, 切换, , 调度and 应用进程的管理和调度so on. AndroidQ moved the Activity to ActivityTaskManagerService, but it is also associated with AMS.
AMSBy using some system resources and data structures (such as processes, task stacks, state machines that record the life cycles of the four major components, etc.) to manage the life cycle management of the four major components of Activity, Service, Broadcastand . ContentProviderIts responsibilities are similar to the process management and scheduling modules in the operating system, so it is Androidvery important in .
This article is based on the source code analysis of Android10 (Q)
2 AMS startup process
In our last chapter [Android Framework Series], Chapter 4 PMS Principles explained PMS. We know that PMS will parse the AndroidManifest.xml file of APK when booting/installing the app, and cache the parsed results in PMS.
We also AMSanalyze below.
PMSThe startup of both AMSis in the SystemServer process. After the system starts, Zygote进程the first fork exits SystemServer进程, enters SystemServer:main()->run()->startBootstrapServices() the startup boot service, and then completes PMS和AMS等核心服务的启动.
All core services in the Android system will be started SystemServer, AMSand PMSare the same. SystemServerIt starts running when the phone is turned on. About how SystemServer is started, you can check the article [Android Framework Series] Chapter 3 Zygote Process Related and [Android Vehicle Series] Chapter 10 System Services - SystemServer Source Code Analysis (API28)
2.1 AMS is activated
We know AMSthat it is SystemServer进程started in, let's see how it is started AMS:
/frameworks/base/services/java/com/android/server/SystemServer.java
348 public static void main(String[] args) {
349 new SystemServer().run();
350 }
......
370 private void run() {
......
507 // Start services.
508 try {
509 traceBeginAndSlog("StartServices");
// 引导服务
510 startBootstrapServices();
// 核心服务
511 startCoreServices();
// 其他服务
512 startOtherServices();
513 SystemServerInitThreadPool.shutdown();
514 } catch (Throwable ex) {
515 Slog.e("System", "******************************************");
516 Slog.e("System", "************ Failure starting system services", ex);
517 throw ex;
518 } finally {
519 traceEnd();
520 }
......
543 }
......
623 private void startBootstrapServices() {
......
658 ActivityTaskManagerService atm = mSystemServiceManager.startService(
659 ActivityTaskManagerService.Lifecycle.class).getService();
660 mActivityManagerService = ActivityManagerService.Lifecycle.startService(
661 mSystemServiceManager, atm);
662 mActivityManagerService.setSystemServiceManager(mSystemServiceManager);
663 mActivityManagerService.setInstaller(installer);
664 mWindowManagerGlobalLock = atm.getGlobalLock();
......
779 mActivityManagerService.setSystemProcess();
......
818 }
......
874 /**
875 * Starts a miscellaneous grab bag of stuff that has yet to be refactored and organized.
876 */
877 private void startOtherServices() {
......
// 安装ContentProvider
982 mActivityManagerService.installSystemProviders();
......
1023 wm = WindowManagerService.main(context, inputManager, !mFirstBoot, mOnlyCore,
1024 new PhoneWindowManager(), mActivityManagerService.mActivityTaskManager);
1025 ServiceManager.addService(Context.WINDOW_SERVICE, wm, /* allowIsolated= */ false,
1026 DUMP_FLAG_PRIORITY_CRITICAL | DUMP_FLAG_PROTO);
1027 ServiceManager.addService(Context.INPUT_SERVICE, inputManager,
1028 /* allowIsolated= */ false, DUMP_FLAG_PRIORITY_CRITICAL);
// WMS与AMS/ATMS关联起来
1032 mActivityManagerService.setWindowManager(wm);
......
// 所有的服务已经准备就绪
2035 mActivityManagerService.systemReady(() -> {
......
// 启动阶段500
2038 mSystemServiceManager.startBootPhase(
2039 SystemService.PHASE_ACTIVITY_MANAGER_READY);
......
2042 try {
// 监测Native Crash
2043 mActivityManagerService.startObservingNativeCrashes();
2044 } catch (Throwable e) {
2045 reportWtf("observing native crashes", e);
2046 }
......
2051 final String WEBVIEW_PREPARATION = "WebViewFactoryPreparation";
2052 Future<?> webviewPrep = null;
2053 if (!mOnlyCore && mWebViewUpdateService != null) {
2054 webviewPrep = SystemServerInitThreadPool.get().submit(() -> {
2055 Slog.i(TAG, WEBVIEW_PREPARATION);
2056 TimingsTraceLog traceLog = new TimingsTraceLog(
2057 SYSTEM_SERVER_TIMING_ASYNC_TAG, Trace.TRACE_TAG_SYSTEM_SERVER);
2058 traceLog.traceBegin(WEBVIEW_PREPARATION);
2059 ConcurrentUtils.waitForFutureNoInterrupt(mZygotePreload, "Zygote preload");
2060 mZygotePreload = null;
// 启动WebView相关
2061 mWebViewUpdateService.prepareWebViewInSystemServer();
2062 traceLog.traceEnd();
2063 }, WEBVIEW_PREPARATION);
2064 }
......
2073 try {
// 启动SystemUi
2074 startSystemUi(context, windowManagerF);
2075 } catch (Throwable e) {
2076 reportWtf("starting System UI", e);
2077 }
......
// 启动阶段600
2154 mSystemServiceManager.startBootPhase(
2155 SystemService.PHASE_THIRD_PARTY_APPS_CAN_START);
......
2249 }, BOOT_TIMINGS_TRACE_LOG);
2250 }
SystemServerAMSTwo main phases will be started and initialized:
The first stage : startBootstrapServices()start the boot service in the method:
- Create
ActivityTaskManagerService(ATMS)objects for managing Activity - Create
AMSan object and start the service - Incorporate
AMSthe current system进程SystemServerinto the AMS process management system
setSystemProcess(): add the framewok-res.apk information to the LoadedApk of the SystemServer process, build the ProcessRecord of the SystemServe process, and save it in AMS for unified management of the AMS process
The second stage : startOtherServices()start other services in the method:
- Install the ContentProvider object for the system process
installSystemProviders(): Install SettingsProvider.apk in the SystemServer process, - Initialize WMS and associate AMS and ATMS services.
setWindowManager()The method associates AMS with WMS, and manages Activity through ATMS - After the AMS startup is complete, notify the service or application to complete the follow-up work, or directly start a new process.
AMS.systemReady(): Many services or application processes must wait for AMS to complete the startup work before they can start or perform some follow-up work. AMS is in the process ofSystemReady()notifying or starting these waiting services and application processes, such as starting the desktop.
We see that in the first phase, both methods are called when the AMSand are created . The call is created , and the creation is actually the creation of the service that is called inside mSystemServiceManager. Let's take a look at the initialization below .ATMSstartService()AMSActivityManagerService.Lifecycle.startService()ATMSmSystemServiceManager.startService()ActivityManagerService.Lifecycle.startService()AMSLifecycleAMS
2.2 AMS initialization
/frameworks/base/services/core/java/com/android/server/am/ActivityManagerService.java
......
2209 public static final class Lifecycle extends SystemService {
2210 private final ActivityManagerService mService;
2211 private static ActivityTaskManagerService sAtm;
2212
2213 public Lifecycle(Context context) {
2214 super(context);
2215 mService = new ActivityManagerService(context, sAtm);
2216 }
2217
2218 public static ActivityManagerService startService(
2219 SystemServiceManager ssm, ActivityTaskManagerService atm) {
2220 sAtm = atm;
2221 return ssm.startService(ActivityManagerService.Lifecycle.class).getService();
2222 }
2223
2224 @Override
2225 public void onStart() {
2226 mService.start();
2227 }
2228
2229 @Override
2230 public void onBootPhase(int phase) {
2231 mService.mBootPhase = phase;
2232 if (phase == PHASE_SYSTEM_SERVICES_READY) {
2233 mService.mBatteryStatsService.systemServicesReady();
2234 mService.mServices.systemServicesReady();
2235 } else if (phase == PHASE_ACTIVITY_MANAGER_READY) {
2236 mService.startBroadcastObservers();
2237 } else if (phase == PHASE_THIRD_PARTY_APPS_CAN_START) {
2238 mService.mPackageWatchdog.onPackagesReady();
2239 }
2240 }
2241
2242 @Override
2243 public void onCleanupUser(int userId) {
2244 mService.mBatteryStatsService.onCleanupUser(userId);
2245 }
2246
2247 public ActivityManagerService getService() {
2248 return mService;
2249 }
2250 }
......
ATMS(ActivityTaskManagerService)It is a new change introduced by Android 10, and it is also a system service 管理Activity启动和调度，包括其容器(task、stacks、displays等). This article is mainly about AMSthe startup, so ActivityTaskManagerServiceI won't go into details here.
Android 10 moves the management and scheduling AMSof the original center to the middle, and puts the position on the bottom, so AMS is responsible for the management and scheduling of the other three (service, broadcast, contentprovider) of the four major components.activityATMSframeworks/base/services/core/java/com/android/server/wm/
Here Lifecycleis AMSthe inner class of . ActivityManagerService.Lifecycle.startService()What is finally returned is mServicethe created AMSobject, which we also know above ATMSis also created in this way.
A brief description of the AMS creation process:
1.SystemServer: call main(), , run(), startBootstrapServices()and then call Lifecylethe startService() method in sequence;
2.Lifecyle: the method called startService()in the method , and pass in Lifecyle.class; 3.SystemServiceManager: the method called by reflection The construction method generates an object; 4. Lifecyle: The construction method called in the construction method creates an object and returns the AMS object through the method.SystemServiceManagerstartService()startService()LifecyleLifecyleAMSAMSgetService()
Let's continue to look at the constructor of AMS:
/frameworks/base/services/core/java/com/android/server/am/ActivityManagerService.java
......
2435 public ActivityManagerService(Context systemContext, ActivityTaskManagerService atm) {
2436 LockGuard.installLock(this, LockGuard.INDEX_ACTIVITY);
2437 mInjector = new Injector();
// 系统上下文，是在SystemServer进程fork出来后通过createSystemContext()创建的，即与SystemServer进程是一一致
2438 mContext = systemContext;
2439
2440 mFactoryTest = FactoryTest.getMode();
// 系统进程的主线程 sCurrentActivityThread，这里是systemMain()中创建的ActivityThread对象。即也与SystemServer一样的。
2441 mSystemThread = ActivityThread.currentActivityThread();
2442 mUiContext = mSystemThread.getSystemUiContext();
2443
2444 Slog.i(TAG, "Memory class: " + ActivityManager.staticGetMemoryClass());
2445
2446 mHandlerThread = new ServiceThread(TAG,
2447 THREAD_PRIORITY_FOREGROUND, false /*allowIo*/);
2448 mHandlerThread.start();
// 处理AMS消息的handler
2449 mHandler = new MainHandler(mHandlerThread.getLooper());
// UiHandler对应于Android中的Ui线程
2450 mUiHandler = mInjector.getUiHandler(this);
2451
2452 mProcStartHandlerThread = new ServiceThread(TAG + ":procStart",
2453 THREAD_PRIORITY_FOREGROUND, false /* allowIo */);
2454 mProcStartHandlerThread.start();
2455 mProcStartHandler = new Handler(mProcStartHandlerThread.getLooper());
2456
2457 mConstants = new ActivityManagerConstants(mContext, this, mHandler);
2458 final ActiveUids activeUids = new ActiveUids(this, true /* postChangesToAtm */);
2459 mProcessList.init(this, activeUids);
2460 mLowMemDetector = new LowMemDetector(this);
2461 mOomAdjuster = new OomAdjuster(this, mProcessList, activeUids);
2462
2463 // Broadcast policy parameters
2464 final BroadcastConstants foreConstants = new BroadcastConstants(
2465 Settings.Global.BROADCAST_FG_CONSTANTS);
2466 foreConstants.TIMEOUT = BROADCAST_FG_TIMEOUT;
2467
2468 final BroadcastConstants backConstants = new BroadcastConstants(
2469 Settings.Global.BROADCAST_BG_CONSTANTS);
2470 backConstants.TIMEOUT = BROADCAST_BG_TIMEOUT;
2471
2472 final BroadcastConstants offloadConstants = new BroadcastConstants(
2473 Settings.Global.BROADCAST_OFFLOAD_CONSTANTS);
2474 offloadConstants.TIMEOUT = BROADCAST_BG_TIMEOUT;
2475 // by default, no "slow" policy in this queue
2476 offloadConstants.SLOW_TIME = Integer.MAX_VALUE;
2477
2478 mEnableOffloadQueue = SystemProperties.getBoolean(
2479 "persist.device_config.activity_manager_native_boot.offload_queue_enabled", false);
2480
//创建几种广播相关对象，前台广播、后台广播、offload。
2481 mFgBroadcastQueue = new BroadcastQueue(this, mHandler,
2482 "foreground", foreConstants, false);
2483 mBgBroadcastQueue = new BroadcastQueue(this, mHandler,
2484 "background", backConstants, true);
2485 mOffloadBroadcastQueue = new BroadcastQueue(this, mHandler,
2486 "offload", offloadConstants, true);
2487 mBroadcastQueues[0] = mFgBroadcastQueue;
2488 mBroadcastQueues[1] = mBgBroadcastQueue;
2489 mBroadcastQueues[2] = mOffloadBroadcastQueue;
2490
// 创建ActiveServices对象，管理 ServiceRecord
2491 mServices = new ActiveServices(this);
// 创建ProviderMap对象，管理ContentProviderRecord
2492 mProviderMap = new ProviderMap(this);
2493 mPackageWatchdog = PackageWatchdog.getInstance(mUiContext);
2494 mAppErrors = new AppErrors(mUiContext, this, mPackageWatchdog);
2495
2496 final File systemDir = SystemServiceManager.ensureSystemDir();
2497
2498 // TODO: Move creation of battery stats service outside of activity manager service.
2499 mBatteryStatsService = new BatteryStatsService(systemContext, systemDir,
2500 BackgroundThread.get().getHandler());
2501 mBatteryStatsService.getActiveStatistics().readLocked();
2502 mBatteryStatsService.scheduleWriteToDisk();
2503 mOnBattery = DEBUG_POWER ? true
2504 : mBatteryStatsService.getActiveStatistics().getIsOnBattery();
2505 mBatteryStatsService.getActiveStatistics().setCallback(this);
2506 mOomAdjProfiler.batteryPowerChanged(mOnBattery);
2507
2508 mProcessStats = new ProcessStatsService(this, new File(systemDir, "procstats"));
2509
2510 mAppOpsService = mInjector.getAppOpsService(new File(systemDir, "appops.xml"), mHandler);
2511
2512 mUgmInternal = LocalServices.getService(UriGrantsManagerInternal.class);
2513
2514 mUserController = new UserController(this);
2515
2516 mPendingIntentController = new PendingIntentController(
2517 mHandlerThread.getLooper(), mUserController);
2518
2519 if (SystemProperties.getInt("sys.use_fifo_ui", 0) != 0) {
2520 mUseFifoUiScheduling = true;
2521 }
2522
2523 mTrackingAssociations = "1".equals(SystemProperties.get("debug.track-associations"));
2524 mIntentFirewall = new IntentFirewall(new IntentFirewallInterface(), mHandler);
2525
//得到ActivityTaskManagerService的对象，调用ATM.initialize
2526 mActivityTaskManager = atm;
2527 mActivityTaskManager.initialize(mIntentFirewall, mPendingIntentController,
2528 DisplayThread.get().getLooper());
2529 mAtmInternal = LocalServices.getService(ActivityTaskManagerInternal.class);
2530
2531 mProcessCpuThread = new Thread("CpuTracker") {
2532 @Override
2533 public void run() {
2534 synchronized (mProcessCpuTracker) {
2535 mProcessCpuInitLatch.countDown();
2536 mProcessCpuTracker.init();
2537 }
2538 while (true) {
2539 try {
2540 try {
2541 synchronized(this) {
2542 final long now = SystemClock.uptimeMillis();
2543 long nextCpuDelay = (mLastCpuTime.get()+MONITOR_CPU_MAX_TIME)-now;
2544 long nextWriteDelay = (mLastWriteTime+BATTERY_STATS_TIME)-now;
2545 //Slog.i(TAG, "Cpu delay=" + nextCpuDelay
2546 // + ", write delay=" + nextWriteDelay);
2547 if (nextWriteDelay < nextCpuDelay) {
2548 nextCpuDelay = nextWriteDelay;
2549 }
2550 if (nextCpuDelay > 0) {
2551 mProcessCpuMutexFree.set(true);
2552 this.wait(nextCpuDelay);
2553 }
2554 }
2555 } catch (InterruptedException e) {
2556 }
2557 updateCpuStatsNow();
2558 } catch (Exception e) {
2559 Slog.e(TAG, "Unexpected exception collecting process stats", e);
2560 }
2561 }
2562 }
2563 };
2564
2565 mHiddenApiBlacklist = new HiddenApiSettings(mHandler, mContext);
2566
2567 Watchdog.getInstance().addMonitor(this);
2568 Watchdog.getInstance().addThread(mHandler);
2569
2570 // bind background threads to little cores
2571 // this is expected to fail inside of framework tests because apps can't touch cpusets directly
2572 // make sure we've already adjusted system_server's internal view of itself first
2573 updateOomAdjLocked(OomAdjuster.OOM_ADJ_REASON_NONE);
2574 try {
2575 Process.setThreadGroupAndCpuset(BackgroundThread.get().getThreadId(),
2576 Process.THREAD_GROUP_SYSTEM);
2577 Process.setThreadGroupAndCpuset(
2578 mOomAdjuster.mAppCompact.mCompactionThread.getThreadId(),
2579 Process.THREAD_GROUP_SYSTEM);
2580 } catch (Exception e) {
2581 Slog.w(TAG, "Setting background thread cpuset failed");
2582 }
2583
2584 }
The construction method of AMS is mainly to do some initial closing operations:
- Save your own runtime environment
ContextandActivityThread AMSResponsible for scheduling the four major components, initializationbroadcast,serviceandcontentProviderrelated variables, responsible for the management and scheduling of the three major components (service, broadcast, provider) (the activity is moved to the ActivityTaskManagerService, but the ActivityTaskManagerService object is also bound here),- Then it is initialized
电量统计服务to monitor memory, battery, permissions (you can learn about appops.xml) and performance-related objects or variables. mLowMemDetector, mBatteryStatsService, mProcessStats, mAppOpsService, mProcessCpuThread, etc. Created the first user of the system and initialized the basic configuration information - The core class of Activity scheduling is created, because Activity scheduling is more complicated, and the initialization of Activity-related information will be
ActivityStackSupervisorin
Let's continue to look at the start() method of ActivityManagerService:
2.2.1 ActivityManagerService的start()
/frameworks/base/services/core/java/com/android/server/am/ActivityManagerService.java
2594 private void start() {
// 移除所有的进程组
2595 removeAllProcessGroups();
// 启动CPU进程
2596 mProcessCpuThread.start();
2597
// 启动电池状态服务
2598 mBatteryStatsService.publish();
2599 mAppOpsService.publish(mContext);
2600 Slog.d("AppOps", "AppOpsService published");
2601 LocalServices.addService(ActivityManagerInternal.class, new LocalService());
// 创建本地服务并注册，将创建的本地服务放入本地服务集合完成注册
2602 mActivityTaskManager.onActivityManagerInternalAdded();
2603 mUgmInternal.onActivityManagerInternalAdded();
2604 mPendingIntentController.onActivityManagerInternalAdded();
2605 // Wait for the synchronized block started in mProcessCpuThread,
2606 // so that any other access to mProcessCpuTracker from main thread
2607 // will be blocked during mProcessCpuTracker initialization.
2608 try {
// 等待mProcessCpuThread完成初始化后，释放锁
2609 mProcessCpuInitLatch.await();
2610 } catch (InterruptedException e) {
2611 Slog.wtf(TAG, "Interrupted wait during start", e);
2612 Thread.currentThread().interrupt();
2613 throw new IllegalStateException("Interrupted wait during start");
2614 }
2615 }
AMSThe start()method is very simple, just start a few services, and save AMSthe service itself for localServicethe internal call of the program; in
AMSthe construction method and method , the initialization of some variables of the service and the initialization of related services start()are done .AMS
Then look at the next important method setSystemProcess:
2.2.2 setSystemProcess() method of ActivityManagerService
/frameworks/base/services/core/java/com/android/server/am/ActivityManagerService.java
2040 public void setSystemProcess() {
2041 try {
// 将AMS注册到ServiceManager中
2042 ServiceManager.addService(Context.ACTIVITY_SERVICE, this, /* allowIsolated= */ true,
2043 DUMP_FLAG_PRIORITY_CRITICAL | DUMP_FLAG_PRIORITY_NORMAL | DUMP_FLAG_PROTO);
// 注册进程状态服务
2044 ServiceManager.addService(ProcessStats.SERVICE_NAME, mProcessStats);
// 注册内存Binder
2045 ServiceManager.addService("meminfo", new MemBinder(this), /* allowIsolated= */ false,
2046 DUMP_FLAG_PRIORITY_HIGH);
// 注册图像信息Binder
2047 ServiceManager.addService("gfxinfo", new GraphicsBinder(this));
// 注册数据库Binder
2048 ServiceManager.addService("dbinfo", new DbBinder(this));
2049 if (MONITOR_CPU_USAGE) {
// 注册监控CPU使用状态Binder
2050 ServiceManager.addService("cpuinfo", new CpuBinder(this),
2051 /* allowIsolated= */ false, DUMP_FLAG_PRIORITY_CRITICAL);
2052 }
// 注册权限控制Binder
2053 ServiceManager.addService("permission", new PermissionController(this));
// 注册进程服务Binder
2054 ServiceManager.addService("processinfo", new ProcessInfoService(this));
2055
// 查询并处理ApplicationInfo
2056 ApplicationInfo info = mContext.getPackageManager().getApplicationInfo(
2057 "android", STOCK_PM_FLAGS | MATCH_SYSTEM_ONLY);
// 将Application信息配置到ActivityThread中
2058 mSystemThread.installSystemApplicationInfo(info, getClass().getClassLoader());
2059
2060 synchronized (this) {
// 创建并处理ProcessRecord
2061 ProcessRecord app = mProcessList.newProcessRecordLocked(info, info.processName,
2062 false,
2063 0,
2064 new HostingRecord("system"));
2065 app.setPersistent(true);
2066 app.pid = MY_PID;
2067 app.getWindowProcessController().setPid(MY_PID);
2068 app.maxAdj = ProcessList.SYSTEM_ADJ;
2069 app.makeActive(mSystemThread.getApplicationThread(), mProcessStats);
2070 mPidsSelfLocked.put(app);
2071 mProcessList.updateLruProcessLocked(app, false, null);
2072 updateOomAdjLocked(OomAdjuster.OOM_ADJ_REASON_NONE);
2073 }
2074 } catch (PackageManager.NameNotFoundException e) {
2075 throw new RuntimeException(
2076 "Unable to find android system package", e);
2077 }
2078
2079 // Start watching app ops after we and the package manager are up and running.
2080 mAppOpsService.startWatchingMode(AppOpsManager.OP_RUN_IN_BACKGROUND, null,
2081 new IAppOpsCallback.Stub() {
2082 @Override public void opChanged(int op, int uid, String packageName) {
2083 if (op == AppOpsManager.OP_RUN_IN_BACKGROUND && packageName != null) {
2084 if (mAppOpsService.checkOperation(op, uid, packageName)
2085 != AppOpsManager.MODE_ALLOWED) {
2086 runInBackgroundDisabled(uid);
2087 }
2088 }
2089 }
2090 });
2091 }
setSystemProcess()In the method, firstAMSregister your own serviceServiceManager, and then register权限服务等other system services;- Through the previously created Context, get
PMSthe service, retrieve itframework-res的Application信息, and then configure it into the systemActivityThread; - In order to allow the same management and scheduling system process, an object
AMSabout the system process is also created , and the object stores the relevant information of a process;ProcessRecordProcessRecord - Then save it to
mPidsSelfLocked集合for easy management; AMSSpecifically, how to retrieveframework-res的application信息and configure itActivityThreadin, and the method that needs to continue to beActivityThreadanalyzedinstallSystemApplicationInfo(ApplicationInfo info, ClassLoader classLoader));
Let's continue to look at the methods in the ActivityThread class installSystemApplicationInfo():
2.2.3 ActivityThread的installSystemApplicationInfo
/frameworks/base/core/java/android/app/ActivityThread.java
2417 public void installSystemApplicationInfo(ApplicationInfo info, ClassLoader classLoader) {
2418 synchronized (this) {
2419 getSystemContext().installSystemApplicationInfo(info, classLoader);
2420 getSystemUiContext().installSystemApplicationInfo(info, classLoader);
2421
2422 // give ourselves a default profiler
2423 mProfiler = new Profiler();
2424 }
2425 }
In this method, the methods of SystemContext and SystemUiContext created above are finally called installSystemApplicationInfo().
Then look at installSystemApplicationInfo()the method of ContextImpl:
/frameworks/base/core/java/android/app/ContextImpl.java
......
2427 /**
2428 * System Context to be used for UI. This Context has resources that can be themed.
2429 * Make sure that the created system UI context shares the same LoadedApk as the system context.
2430 * @param systemContext The system context which created by
2431 * {@link #createSystemContext(ActivityThread)}.
2432 * @param displayId The ID of the display where the UI is shown.
2433 */
2434 static ContextImpl createSystemUiContext(ContextImpl systemContext, int displayId) {
2435 final LoadedApk packageInfo = systemContext.mPackageInfo;
2436 ContextImpl context = new ContextImpl(null, systemContext.mMainThread, packageInfo, null,
2437 null, null, 0, null, null);
2438 context.setResources(createResources(null, packageInfo, null, displayId, null,
2439 packageInfo.getCompatibilityInfo()));
2440 context.updateDisplay(displayId);
2441 return context;
2442 }
2443
2444 /**
2445 * The overloaded method of {@link #createSystemUiContext(ContextImpl, int)}.
2446 * Uses {@Code Display.DEFAULT_DISPLAY} as the target display.
2447 */
2448 static ContextImpl createSystemUiContext(ContextImpl systemContext) {
2449 return createSystemUiContext(systemContext, Display.DEFAULT_DISPLAY);
2450 }
......
2581 void installSystemApplicationInfo(ApplicationInfo info, ClassLoader classLoader) {
2582 mPackageInfo.installSystemApplicationInfo(info, classLoader);
2583 }
......
It has the method finally mPackageInfocalled installSystemApplication():
/frameworks/base/core/java/android/app/LoadedApk.java
240 /**
241 * Sets application info about the system package.
242 */
243 void installSystemApplicationInfo(ApplicationInfo info, ClassLoader classLoader) {
244 assert info.packageName.equals("android");
245 mApplicationInfo = info;
246 mDefaultClassLoader = classLoader;
247 mAppComponentFactory = createAppFactory(info, mDefaultClassLoader);
248 mClassLoader = mAppComponentFactory.instantiateClassLoader(mDefaultClassLoader,
249 new ApplicationInfo(mApplicationInfo));
250 }
mPackageInfoIt is passed in when the Context object is created LoadedApk, and the basic information of an application is stored in it;
setSystemProcess()it is mainly to set some information for system integration, where the Application information of the system process is set, and the object of the system process is created and ProcessRecordsaved in In the process collection, it is convenient AMSto manage and schedule;
startBootstrapServices()At this point, the initialization of the startup boot service in our first-stage method AMShas ended. Next, I will continue to look at the initialization of the pair startOtherServices()in the second-stage method to start other servicesAMS .
From the above, we can see the method startOtherServices()called in the method AMS. installSystemProviders()Let's check what this method does:
2.2.4 ActivityManagerService的installSystemProviders
ActivityManagerServiceThe installSystemProviders()method;
there are a lot of configuration information in the Android system that needs to be saved, and these information are saved in SettingsProvider, and this SettingsProvideris also running in SystemServer进程, due to SystemServer进程dependencies SettingsProvider, putting it in a process can reduce the efficiency loss of inter-process communication;
let’s analyze it below The following how will SettingsProvider.apkalso be loaded into SystemServer进程;
/frameworks/base/services/core/java/com/android/server/am/ActivityManagerService.java
7543 public final void installSystemProviders() {
7544 List<ProviderInfo> providers;
7545 synchronized (this) {
// 找到名为"system"的进程，就是setSystemProcess中创建的ProcessRecord对象
7546 ProcessRecord app = mProcessList.mProcessNames.get("system", SYSTEM_UID);
7547 providers = generateApplicationProvidersLocked(app);
7548 if (providers != null) {
7549 for (int i=providers.size()-1; i>=0; i--) {
7550 ProviderInfo pi = (ProviderInfo)providers.get(i);
7551 if ((pi.applicationInfo.flags&ApplicationInfo.FLAG_SYSTEM) == 0) {
7552 Slog.w(TAG, "Not installing system proc provider " + pi.name
7553 + ": not system .apk");
// 移除非系统provider
7554 providers.remove(i);
7555 }
7556 }
7557 }
7558 }
7559 if (providers != null) {
// 安装所有的系统provider
7560 mSystemThread.installSystemProviders(providers);
7561 }
7562
7563 synchronized (this) {
7564 mSystemProvidersInstalled = true;
7565 }
7566 mConstants.start(mContext.getContentResolver());
// 创建核心Settings Observer，用于监听Settings的改变
7567 mCoreSettingsObserver = new CoreSettingsObserver(this);
7568 mActivityTaskManager.installSystemProviders();
// 开发者权限
7569 mDevelopmentSettingsObserver = new DevelopmentSettingsObserver();
7570 SettingsToPropertiesMapper.start(mContext.getContentResolver());
7571 mOomAdjuster.initSettings();
7572
7573 // Now that the settings provider is published we can consider sending
7574 // in a rescue party.
7575 RescueParty.onSettingsProviderPublished(mContext);
7576
7577 //mUsageStatsService.monitorPackages();
7578 }
Find the process object named system, that is SystemServer进程, and then query all related ones according to the process object ContentProvider, call the main thread of the system process ActivityThreadto install all related ones ContentProvider, specifically how to find related ones ContentProviderand how to install them ContentProvideron the main thread of the system.
generateApplicationProvidersLocked()Function: Return a ProviderInfo List.
installSystemProviders()Function: ActivityThread can be regarded as the Android operating environment of the process, so this method means that it is installed for the process ContentProvider.
Then analyze the following two methods;
2.2.5 ActivityManagerService的generateApplicationProvidersLocked()
First look at generateApplicationProvidersLocked()the method:
/frameworks/base/services/core/java/com/android/server/am/ActivityManagerService.java
......
6409 private final List<ProviderInfo> generateApplicationProvidersLocked(ProcessRecord app) {
6410 List<ProviderInfo> providers = null;
6411 try {
// 向PMS查询满足要求的ProviderInfo，最重要的查询条件包括：进程名和进程uid
6412 providers = AppGlobals.getPackageManager()
6413 .queryContentProviders(app.processName, app.uid,
6414 STOCK_PM_FLAGS | PackageManager.GET_URI_PERMISSION_PATTERNS
6415 | MATCH_DEBUG_TRIAGED_MISSING, /*metadastaKey=*/ null)
6416 .getList();
6417 } catch (RemoteException ex) {
6418 }
6419 if (DEBUG_MU) Slog.v(TAG_MU,
6420 "generateApplicationProvidersLocked, app.info.uid = " + app.uid);
6421 int userId = app.userId;
6422 if (providers != null) {
6423 int N = providers.size();
6424 app.pubProviders.ensureCapacity(N + app.pubProviders.size());
6425 for (int i=0; i<N; i++) {
......
// AMS对ContentProvider的管理
6427 ProviderInfo cpi =
6428 (ProviderInfo)providers.get(i);
6429 boolean singleton = isSingleton(cpi.processName, cpi.applicationInfo,
6430 cpi.name, cpi.flags);
6431 if (singleton && UserHandle.getUserId(app.uid) != UserHandle.USER_SYSTEM) {
6432 // This is a singleton provider, but a user besides the
6433 // default user is asking to initialize a process it runs
6434 // in... well, no, it doesn't actually run in this process,
6435 // it runs in the process of the default user. Get rid of it.
6436 providers.remove(i);
6437 N--;
6438 i--;
6439 continue;
6440 }
6441
6442 ComponentName comp = new ComponentName(cpi.packageName, cpi.name);
6443 ContentProviderRecord cpr = mProviderMap.getProviderByClass(comp, userId);
6444 if (cpr == null) {
// ContentProvider在AMS中用ContentProviderRecord来表示
6445 cpr = new ContentProviderRecord(this, cpi, app.info, comp, singleton);
// 保存到AMS的mProvidersByClass中
6446 mProviderMap.putProviderByClass(comp, cpr);
6447 }
6448 if (DEBUG_MU) Slog.v(TAG_MU,
6449 "generateApplicationProvidersLocked, cpi.uid = " + cpr.uid);
// 将信息也保存到ProcessRecord中
6450 app.pubProviders.put(cpi.name, cpr);
6451 if (!cpi.multiprocess || !"android".equals(cpi.packageName)) {
......
// 保存PackageName到ProcessRecord中
6456 app.addPackage(cpi.applicationInfo.packageName,
6457 cpi.applicationInfo.longVersionCode, mProcessStats);
6458 }
6459 notifyPackageUse(cpi.applicationInfo.packageName,
6460 PackageManager.NOTIFY_PACKAGE_USE_CONTENT_PROVIDER);
6461 }
6462 }
6463 return providers;
6464 }
- The method
PMSis to query andSystemServer进程correlate from itProvider, that isSettingsProvder, and then save it to the listAMSofContentProvider; - At the same time, it is also saved in the
ProcessRecordvariable list of the system process object, which ispubProviderssavedAMSin the list because it needs to manage all ;providerAMSContentProvder - Save to the list of process objects
pubProvidersbecause eachContentProviderneeds to correspond to a process;
2.2.6 ActivityThread的installSystemProviders()
Then see how to SettingsProviderinstall it into the main process of the system:
/frameworks/base/core/java/android/app/ActivityThread.java
......
6515 private void installContentProviders(
6516 Context context, List<ProviderInfo> providers) {
6517 final ArrayList<ContentProviderHolder> results = new ArrayList<>();
6518
6519 for (ProviderInfo cpi : providers) {
6520 if (DEBUG_PROVIDER) {
6521 StringBuilder buf = new StringBuilder(128);
6522 buf.append("Pub ");
6523 buf.append(cpi.authority);
6524 buf.append(": ");
6525 buf.append(cpi.name);
6526 Log.i(TAG, buf.toString());
6527 }
// 调用installProvider函数，得到一个ContentProviderHolder对象
6528 ContentProviderHolder cph = installProvider(context, null, cpi,
6529 false /*noisy*/, true /*noReleaseNeeded*/, true /*stable*/);
6530 if (cph != null) {
6531 cph.noReleaseNeeded = true;
// 将返回的cph保存到results数组中
6532 results.add(cph);
6533 }
6534 }
6535
6536 try {
// 调用AMS的publishContentProviders注册这些ContentProvider
6537 ActivityManager.getService().publishContentProviders(
6538 getApplicationThread(), results);
6539 } catch (RemoteException ex) {
6540 throw ex.rethrowFromSystemServer();
6541 }
6542 }
......
7167 public final void installSystemProviders(List<ProviderInfo> providers) {
7168 if (providers != null) {
7169 installContentProviders(mInitialApplication, providers);
7170 }
7171 }
- This method encapsulates the obtained
ContentProvderobject intocontentProviderHolderan object, which is actuallyBinderan object, so that it can be transferred between processes, and then callAMSservice registration across processesProvider; AMSResponsible for managementContentProvider, only other processes that willContentProviderregister withAMSthe service can access;
Then see AMShow to register Provider:
2.2.7 publishContentProviders() of ActivityManagerService register Provider
/frameworks/base/services/core/java/com/android/server/am/ActivityManagerService.java
7342
7343 public final void publishContentProviders(IApplicationThread caller,
7344 List<ContentProviderHolder> providers) {
7345 if (providers == null) {
7346 return;
7347 }
7348
7349 enforceNotIsolatedCaller("publishContentProviders");
7350 synchronized (this) {
7351 final ProcessRecord r = getRecordForAppLocked(caller);
7352 if (DEBUG_MU) Slog.v(TAG_MU, "ProcessRecord uid = " + r.uid);
7353 if (r == null) {
7354 throw new SecurityException(
7355 "Unable to find app for caller " + caller
7356 + " (pid=" + Binder.getCallingPid()
7357 + ") when publishing content providers");
7358 }
7359
7360 final long origId = Binder.clearCallingIdentity();
7361
7362 final int N = providers.size();
7363 for (int i = 0; i < N; i++) {
7364 ContentProviderHolder src = providers.get(i);
7365 if (src == null || src.info == null || src.provider == null) {
7366 continue;
7367 }
7368 ContentProviderRecord dst = r.pubProviders.get(src.info.name);
7369 if (DEBUG_MU) Slog.v(TAG_MU, "ContentProviderRecord uid = " + dst.uid);
7370 if (dst != null) {
7371 ComponentName comp = new ComponentName(dst.info.packageName, dst.info.name);
7372 mProviderMap.putProviderByClass(comp, dst);
7373 String names[] = dst.info.authority.split(";");
7374 for (int j = 0; j < names.length; j++) {
7375 mProviderMap.putProviderByName(names[j], dst);
7376 }
7377
7378 int launchingCount = mLaunchingProviders.size();
7379 int j;
7380 boolean wasInLaunchingProviders = false;
7381 for (j = 0; j < launchingCount; j++) {
7382 if (mLaunchingProviders.get(j) == dst) {
7383 mLaunchingProviders.remove(j);
7384 wasInLaunchingProviders = true;
7385 j--;
7386 launchingCount--;
7387 }
7388 }
7389 if (wasInLaunchingProviders) {
7390 mHandler.removeMessages(CONTENT_PROVIDER_PUBLISH_TIMEOUT_MSG, r);
7391 }
7392 // Make sure the package is associated with the process.
7393 // XXX We shouldn't need to do this, since we have added the package
7394 // when we generated the providers in generateApplicationProvidersLocked().
7395 // But for some reason in some cases we get here with the package no longer
7396 // added... for now just patch it in to make things happy.
7397 r.addPackage(dst.info.applicationInfo.packageName,
7398 dst.info.applicationInfo.longVersionCode, mProcessStats);
7399 synchronized (dst) {
7400 dst.provider = src.provider;
7401 dst.setProcess(r);
7402 dst.notifyAll();
7403 }
7404 updateOomAdjLocked(r, true, OomAdjuster.OOM_ADJ_REASON_GET_PROVIDER);
7405 maybeUpdateProviderUsageStatsLocked(r, src.info.packageName,
7406 src.info.authority);
7407 }
7408 }
7409
7410 Binder.restoreCallingIdentity(origId);
7411 }
7412 }
AMSproviderThe registration service is to find the informationpubProviderssaved in the original process list according to the information passed by the parameters , and then saveContentProviderRecordit as a class and save it as a class.keymProviderMapauthoritykeymProviderMap- That is to say,
AMSa variety of solutions are provided to find oneContentProvider, one is toauthorityfind through, and the other is to specifyCompomentNameto find - At this moment, the position one
SettingsProvideris officially registered inSystemServer进程the middle, so it can be seen thatinstallSystemProviderthe main work of the method is to register it in the system process in a similar way to the ordinary process,SettingsProviderso that the system process can callsettingsthe configuration data
Let's continue to look at the second stage startOtherServices()method to go down, there is a very critical methodsystemReady()
2.2.8 ActivityManagerService的systemReady
/frameworks/base/services/core/java/com/android/server/am/ActivityManagerService.java
8967
8968 public void systemReady(final Runnable goingCallback, TimingsTraceLog traceLog) {
8969 traceLog.traceBegin("PhaseActivityManagerReady");
8970 synchronized(this) {
// 第一次进入mSystemReady为false
8971 if (mSystemReady) {
8972 // If we're done calling all the receivers, run the next "boot phase" passed in
8973 // by the SystemServer
8974 if (goingCallback != null) {
8975 goingCallback.run();
8976 }
8977 return;
8978 }
8979
// 关键服务等待systemReady，继续完成一些初始化或进一步的工作
8980 mLocalDeviceIdleController
8981 = LocalServices.getService(DeviceIdleController.LocalService.class);
// 调用各种服务的Ready方法
8982 mActivityTaskManager.onSystemReady();
8983 // Make sure we have the current profile info, since it is needed for security checks.
8984 mUserController.onSystemReady();
8985 mAppOpsService.systemReady();
8986 mSystemReady = true;
8987 }
8988
8989 try {
//获取设备识别字符串
8990 sTheRealBuildSerial = IDeviceIdentifiersPolicyService.Stub.asInterface(
8991 ServiceManager.getService(Context.DEVICE_IDENTIFIERS_SERVICE))
8992 .getSerial();
8993 } catch (RemoteException e) {
}
8994
// 收集目前已经存在的进程（mPidsSelfLocked中保留了当前正在运行的所有进程信息）
8995 ArrayList<ProcessRecord> procsToKill = null;
8996 synchronized(mPidsSelfLocked) {
8997 for (int i=mPidsSelfLocked.size()-1; i>=0; i--) {
8998 ProcessRecord proc = mPidsSelfLocked.valueAt(i);
// 已启动的进程，若进程没有FLAG_PERSISTENT标志，则会被加入到procsToKill中
8999 if (!isAllowedWhileBooting(proc.info)){
9000 if (procsToKill == null) {
9001 procsToKill = new ArrayList<ProcessRecord>();
9002 }
9003 procsToKill.add(proc);
9004 }
9005 }
9006 }
9007
// 销毁在AMS启动之前存在的进程（关闭procsToKill中的所有进程）
9008 synchronized(this) {
9009 if (procsToKill != null) {
9010 for (int i=procsToKill.size()-1; i>=0; i--) {
9011 ProcessRecord proc = procsToKill.get(i);
9012 Slog.i(TAG, "Removing system update proc: " + proc);
9013 mProcessList.removeProcessLocked(proc, true, false, "system update done");
9014 }
9015 }
9016
9017 // Now that we have cleaned up any update processes, we
9018 // are ready to start launching real processes and know that
9019 // we won't trample on them any more.
// 到这里系统准备完毕
9020 mProcessesReady = true;
9021 }
9022
9023 Slog.i(TAG, "System now ready");
9024 EventLog.writeEvent(EventLogTags.BOOT_PROGRESS_AMS_READY, SystemClock.uptimeMillis());
9025
9026 mAtmInternal.updateTopComponentForFactoryTest();
9027 mAtmInternal.getLaunchObserverRegistry().registerLaunchObserver(mActivityLaunchObserver);
9028
9029 watchDeviceProvisioning(mContext);
9030
// 初始化Settings变量
9031 retrieveSettings();
9032 mUgmInternal.onSystemReady();
9033
9034 final PowerManagerInternal pmi = LocalServices.getService(PowerManagerInternal.class);
9035 if (pmi != null) {
9036 pmi.registerLowPowerModeObserver(ServiceType.FORCE_BACKGROUND_CHECK,
9037 state -> updateForceBackgroundCheck(state.batterySaverEnabled));
9038 updateForceBackgroundCheck(
9039 pmi.getLowPowerState(ServiceType.FORCE_BACKGROUND_CHECK).batterySaverEnabled);
9040 } else {
9041 Slog.wtf(TAG, "PowerManagerInternal not found.");
9042 }
9043
// 运行goingCallback，SystemServer调用时传入的
9044 if (goingCallback != null) goingCallback.run();
9045 // Check the current user here as a user can be started inside goingCallback.run() from
9046 // other system services.
9047 final int currentUserId = mUserController.getCurrentUserId();
9048 Slog.i(TAG, "Current user:" + currentUserId);
// 获取UserId
9049 if (currentUserId != UserHandle.USER_SYSTEM && !mUserController.isSystemUserStarted()) {
9050 // User other than system user has started. Make sure that system user is already
9051 // started before switching user.
9052 throw new RuntimeException("System user not started while current user is:"
9053 + currentUserId);
9054 }
9055 traceLog.traceBegin("ActivityManagerStartApps");
// 给BatteryStatsService发送状态
9056 mBatteryStatsService.noteEvent(BatteryStats.HistoryItem.EVENT_USER_RUNNING_START,
9057 Integer.toString(currentUserId), currentUserId);
9058 mBatteryStatsService.noteEvent(BatteryStats.HistoryItem.EVENT_USER_FOREGROUND_START,
9059 Integer.toString(currentUserId), currentUserId);
// SystemServiceManager设置UserId
9060 mSystemServiceManager.startUser(currentUserId);
9061
9062 synchronized (this) {
9063 // Only start up encryption-aware persistent apps; once user is
9064 // unlocked we'll come back around and start unaware apps
9065 startPersistentApps(PackageManager.MATCH_DIRECT_BOOT_AWARE);
9066
9067 // Start up initial activity.
9068 mBooting = true;
9069 // Enable home activity for system user, so that the system can always boot. We don't
9070 // do this when the system user is not setup since the setup wizard should be the one
9071 // to handle home activity in this case.
9072 if (UserManager.isSplitSystemUser() &&
9073 Settings.Secure.getInt(mContext.getContentResolver(),
9074 Settings.Secure.USER_SETUP_COMPLETE, 0) != 0) {
9075 ComponentName cName = new ComponentName(mContext, SystemUserHomeActivity.class);
9076 try {
9077 AppGlobals.getPackageManager().setComponentEnabledSetting(cName,
9078 PackageManager.COMPONENT_ENABLED_STATE_ENABLED, 0,
9079 UserHandle.USER_SYSTEM);
9080 } catch (RemoteException e) {
9081 throw e.rethrowAsRuntimeException();
9082 }
9083 }
// 调用ActivityTaskManagerService的startHomeOnAllDisplays方法（就是启动Launcher的Activity）
9084 mAtmInternal.startHomeOnAllDisplays(currentUserId, "systemReady");
9085
9086 mAtmInternal.showSystemReadyErrorDialogsIfNeeded();
9087
9088 final int callingUid = Binder.getCallingUid();
9089 final int callingPid = Binder.getCallingPid();
9090 long ident = Binder.clearCallingIdentity();
9091 try {
// 发送一些广播ACTION_USER_STARTED 和 ACTION_USER_STARTING
9092 Intent intent = new Intent(Intent.ACTION_USER_STARTED);
9093 intent.addFlags(Intent.FLAG_RECEIVER_REGISTERED_ONLY
9094 | Intent.FLAG_RECEIVER_FOREGROUND);
9095 intent.putExtra(Intent.EXTRA_USER_HANDLE, currentUserId);
9096 broadcastIntentLocked(null, null, intent,
9097 null, null, 0, null, null, null, OP_NONE,
9098 null, false, false, MY_PID, SYSTEM_UID, callingUid, callingPid,
9099 currentUserId);
9100 intent = new Intent(Intent.ACTION_USER_STARTING);
9101 intent.addFlags(Intent.FLAG_RECEIVER_REGISTERED_ONLY);
9102 intent.putExtra(Intent.EXTRA_USER_HANDLE, currentUserId);
9103 broadcastIntentLocked(null, null, intent,
9104 null, new IIntentReceiver.Stub() {
9105 @Override
9106 public void performReceive(Intent intent, int resultCode, String data,
9107 Bundle extras, boolean ordered, boolean sticky, int sendingUser)
9108 throws RemoteException {
9109 }
9110 }, 0, null, null,
9111 new String[] {
INTERACT_ACROSS_USERS}, OP_NONE,
9112 null, true, false, MY_PID, SYSTEM_UID, callingUid, callingPid,
9113 UserHandle.USER_ALL);
9114 } catch (Throwable t) {
9115 Slog.wtf(TAG, "Failed sending first user broadcasts", t);
9116 } finally {
9117 Binder.restoreCallingIdentity(ident);
9118 }
9119 mAtmInternal.resumeTopActivities(false /* scheduleIdle */);
9120 mUserController.sendUserSwitchBroadcasts(-1, currentUserId);
9121
9122 BinderInternal.nSetBinderProxyCountWatermarks(BINDER_PROXY_HIGH_WATERMARK,
9123 BINDER_PROXY_LOW_WATERMARK);
9124 BinderInternal.nSetBinderProxyCountEnabled(true);
9125 BinderInternal.setBinderProxyCountCallback(
9126 new BinderInternal.BinderProxyLimitListener() {
9127 @Override
9128 public void onLimitReached(int uid) {
9129 Slog.wtf(TAG, "Uid " + uid + " sent too many Binders to uid "
9130 + Process.myUid());
9131 BinderProxy.dumpProxyDebugInfo();
9132 if (uid == Process.SYSTEM_UID) {
9133 Slog.i(TAG, "Skipping kill (uid is SYSTEM)");
9134 } else {
9135 killUid(UserHandle.getAppId(uid), UserHandle.getUserId(uid),
9136 "Too many Binders sent to SYSTEM");
9137 }
9138 }
9139 }, mHandler);
9140
9141 traceLog.traceEnd(); // ActivityManagerStartApps
9142 traceLog.traceEnd(); // PhaseActivityManagerReady
9143 }
9144 }
systemReady()The method is also relatively long and can be roughly divided into:
- The etc object
systemReady()is initialized atdeviceIdleController - Remove and kill processes that should not be started before AMS (processes without the FLAG_PERSISTENT flag will be killed)
- Run goingCallback and execute the callback function passed in as parameters
- Start the Activity of the Launcher, that is, the desktop application
- Start those processes whose persistent configuration is 1
From the above SystemServer, startOtherServices()we know that systemReady()after the method is called back, it also does some logic. The callback function does the following work:
- The main thing is to start systemUI and call the systemReady method of other services
- The SystemReady function completes the necessary work for the system to be ready
- Started HomeActivity and SystemUI
- Then the Android system is all started
3 summary
Let's summarize the start of AMS here:
Zygote进程The first fork after the system startsSystemServer进程SystemServer->run()->createSystemContext():
createdActivityThreadthe object of the system, the operating environmentmSystemContext,systemUiContext.SystemServer->run()->startBootstrapServices()->ActivityManagerService.Lifecycle.startService():
In the boot service startup method, AMS creates and initializes some objects through the constructor ( creation of management and scheduling objectsnew ActivityManagerService()except activity ; creation of related objects such as monitoring of , , , , etc.), start services ( , , , etc. Serve).3大组件内存电池权限性能cpustart()移除进程组启动cpu线程注册权限电池SystemServer->run()->startBootstrapServices()->setSystemServiceManager()、setInstaller()、initPowerManagement()、setSystemProcess():
After AMS is created, a series of related initialization and settings are performed.
setSystemProcess(): Add the information of framework-res.apk toSystemServer进程,LoadedApkand create , add to , and be managed uniformlySystemServer进程.ProcessRecordmPidsSelfLockedAMSSystemServer->run()->startOtherServices():
The follow-up work after AMS is started,systemReady()which is passed in when calling and running the main callgoingCallback.
systemReady()/goingCallback: Various services or processes and other work to be completed after AMS startup is completed and system-related initialization. The desktop applicationsystemReady()is started in the method and finishedsystemuiingoingCallbackthe . When the desktop application is started, send a boot broadcastACTION_BOOT_COMPLETED
So far, the entire AMS startup is complete. In the next chapter, we will explain the startup process of Activity
The AMS startup process diagram is attached below:
