一.灭屏简述
先来讲灭屏，灭屏的方式一般有如下几种：
1.用户按Power键灭屏；
2.手机自动放置一段时间后超时灭屏；
3.Sensor灭屏。
灭屏的原因在PowerManager类中的sleepReasonToString方法有列出常见的：
/**
* @hide
*/
public static String sleepReasonToString(int sleepReason) {
switch (sleepReason) {
case GO_TO_SLEEP_REASON_APPLICATION: return "application";
case GO_TO_SLEEP_REASON_DEVICE_ADMIN: return "device_admin";
case GO_TO_SLEEP_REASON_TIMEOUT: return "timeout";
case GO_TO_SLEEP_REASON_LID_SWITCH: return "lid_switch";
case GO_TO_SLEEP_REASON_POWER_BUTTON: return "power_button";
case GO_TO_SLEEP_REASON_HDMI: return "hdmi";
case GO_TO_SLEEP_REASON_SLEEP_BUTTON: return "sleep_button";
case GO_TO_SLEEP_REASON_ACCESSIBILITY: return "accessibility";
case GO_TO_SLEEP_REASON_FORCE_SUSPEND: return "force_suspend";
default: return Integer.toString(sleepReason);
}
}
当触发灭屏的时候，其实是调用的PowerManager中的goToSleep方法。
这个方法共有两个：一个是只传参发出睡眠请求的时间time；另一是传三个参数：睡眠请求的时间time、灭屏原因reason、WakeLock的flag：
public void goToSleep(long time) {
goToSleep(time, GO_TO_SLEEP_REASON_APPLICATION, 0);
}
@UnsupportedAppUsage
public void goToSleep(long time, int reason, int flags) {
try {
mService.goToSleep(time, reason, flags);
} catch (RemoteException e) {
throw e.rethrowFromSystemServer();
}
}
最终调用到PowerManagerSevice的goToSleep方法上：
@Override // Binder call
public void goToSleep(long eventTime, int reason, int flags) {
if (eventTime > SystemClock.uptimeMillis()) {
throw new IllegalArgumentException("event time must not be in the future");
}
// 检查DEVICE_POWER权限
mContext.enforceCallingOrSelfPermission(
android.Manifest.permission.DEVICE_POWER, null);
// 线程id
final int uid = Binder.getCallingUid();
final long ident = Binder.clearCallingIdentity();
try {
goToSleepInternal(eventTime, reason, flags, uid);
} finally {
Binder.restoreCallingIdentity(ident);
}
}
接着看goToSleepInternal的实现：
private void goToSleepInternal(long eventTime, int reason, int flags, int uid) {
// 加上锁
synchronized (mLock) {
// 判断goToSleepNoUpdateLocked的返回值
if (goToSleepNoUpdateLocked(eventTime, reason, flags, uid)) {
// 更新Powerstate
updatePowerStateLocked();
}
}
}
先看goToSleepNoUpdateLocked：
@SuppressWarnings("deprecation")
private boolean goToSleepNoUpdateLocked(long eventTime, int reason, int flags, int uid) {
if (DEBUG_SPEW) {
Slog.d(TAG, "goToSleepNoUpdateLocked: eventTime=" + eventTime
+ ", reason=" + reason + ", flags=" + flags + ", uid=" + uid);
}
if (eventTime < mLastWakeTime
|| mWakefulness == WAKEFULNESS_ASLEEP
|| mWakefulness == WAKEFULNESS_DOZING
|| !mBootCompleted || !mSystemReady) {
return false;
}
Trace.traceBegin(Trace.TRACE_TAG_POWER, "goToSleep");
try {
// 获取灭屏的原因
reason = Math.min(PowerManager.GO_TO_SLEEP_REASON_MAX,
Math.max(reason, PowerManager.GO_TO_SLEEP_REASON_MIN));
Slog.i(TAG, "Going to sleep due to " + PowerManager.sleepReasonToString(reason)
+ " (uid " + uid + ")...");
mLastSleepTime = eventTime;
mLastSleepReason = reason;
mSandmanSummoned = true;
// 通知设备更改唤醒状态
setWakefulnessLocked(WAKEFULNESS_DOZING, reason, eventTime);
// Report the number of wake locks that will be cleared by going to sleep.
// 报告将通过睡眠清除的唤醒锁的数量
int numWakeLocksCleared = 0;
final int numWakeLocks = mWakeLocks.size();
for (int i = 0; i < numWakeLocks; i++) {
final WakeLock wakeLock = mWakeLocks.get(i);
switch (wakeLock.mFlags & PowerManager.WAKE_LOCK_LEVEL_MASK) {
case PowerManager.FULL_WAKE_LOCK:
case PowerManager.SCREEN_BRIGHT_WAKE_LOCK:
case PowerManager.SCREEN_DIM_WAKE_LOCK:
numWakeLocksCleared += 1;
break;
}
}
EventLogTags.writePowerSleepRequested(numWakeLocksCleared);
// Skip dozing if requested.
// 跳过dozing状态
if ((flags & PowerManager.GO_TO_SLEEP_FLAG_NO_DOZE) != 0) {
// 调用reallyGoToSleepNoUpdateLocked函数
reallyGoToSleepNoUpdateLocked(eventTime, uid);
}
} finally {
Trace.traceEnd(Trace.TRACE_TAG_POWER);
}
return true;
}
最后来看PowerManagerService的核心方法updatePowerStateLocked方法，关键的地方Google都有注释说明了，来看源码实现：
private void updatePowerStateLocked() {
if (!mSystemReady || mDirty == 0) {
return;
}
if (!Thread.holdsLock(mLock)) {
Slog.wtf(TAG, "Power manager lock was not held when calling updatePowerStateLocked");
}
Trace.traceBegin(Trace.TRACE_TAG_POWER, "updatePowerState");
try {
// Phase 0: Basic state updates.
// 阶段0：基础状态的更新
// 更新mIsPowered的值,ture表示设备插入电源
updateIsPoweredLocked(mDirty);
// 更新mStayOn的值，true表示设备应保持打开状态
updateStayOnLocked(mDirty);
// 更新屏幕亮度
updateScreenBrightnessBoostLocked(mDirty);
// Phase 1: Update wakefulness.
// Loop because the wake lock and user activity computations are influenced
// by changes in wakefulness.
// 阶段1：更新唤醒状态
final long now = SystemClock.uptimeMillis();
int dirtyPhase2 = 0;
// 死循环
for (;;) {
int dirtyPhase1 = mDirty;
dirtyPhase2 |= dirtyPhase1;
mDirty = 0;
// 更新mWakeLockSummary的值以汇总所有活动唤醒锁的状态
updateWakeLockSummaryLocked(dirtyPhase1);
// 更新mUserActivitySummary的值以汇总请求的用户
updateUserActivitySummaryLocked(now, dirtyPhase1);
// 更新设备的唤醒状态，如果返回true表示wakefulness有变化
if (!updateWakefulnessLocked(dirtyPhase1)) {
break;
}
}
// Phase 2: Lock profiles that became inactive/not kept awake.
// 阶段2：锁定已停用/未唤醒的配置文件
// 检查配置文件超时并通知应锁定的配置文件
updateProfilesLocked(now);
// Phase 3: Update display power state.
// 阶段3：更新显示状态
// 异步更新显示状态
// 更新完成之后，mDisplayReady将设置为true。方法返回为true，表示显示准备就绪
final boolean displayBecameReady = updateDisplayPowerStateLocked(dirtyPhase2);
// Phase 4: Update dream state (depends on display ready signal).
// 阶段4：更新dream状态（取决于显示就绪信号）
// 异步更新
updateDreamLocked(dirtyPhase2, displayBecameReady);
// Phase 5: Send notifications, if needed.
// 阶段5：如果需要发送通知
finishWakefulnessChangeIfNeededLocked();
// Phase 6: Update suspend blocker.
// Because we might release the last suspend blocker here, we need to make sure
// we finished everything else first!
// 更新暂停阻止程序
// 更新使CPU保持活动状态的暂停阻塞程序
updateSuspendBlockerLocked();
} finally {
Trace.traceEnd(Trace.TRACE_TAG_POWER);
}
}
二.常见的灭屏方式
1.Power键灭屏
Power键的按键实现从native层到java层的整个流程我们后续会介绍。这里从java层之上开始看。
流程图如下：
具体的代码实现分析如下：
InputManagerService类中interceptKeyBeforeQueueing方法：
// Native callback.
private int interceptKeyBeforeQueueing(KeyEvent event, int policyFlags) {
return mWindowManagerCallbacks.interceptKeyBeforeQueueing(event, policyFlags);
}
调用WindowManagerCallbacks接口的interceptKeyBeforeQueueing方法，来看接口实现类InputMonitor：
@Override
public int interceptKeyBeforeQueueing(KeyEvent event, int policyFlags) {
return mService.mPolicy.interceptKeyBeforeQueueing(event, policyFlags);
}
调用的接口WindowManagerPolicy的interceptKeyBeforeQueueing方法，来看实现类是PhoneWindowManager类：
@Override
public int interceptKeyBeforeQueueing(KeyEvent event, int policyFlags) {
if (!mSystemBooted) {
// If we have not yet booted, don't let key events do anything.
return 0;
}
......
// Handle special keys.
switch (keyCode) {
case KeyEvent.KEYCODE_BACK: {
if (down) {
interceptBackKeyDown();
} else {
boolean handled = interceptBackKeyUp(event);
// Don't pass back press to app if we've already handled it via long press
if (handled) {
result &= ~ACTION_PASS_TO_USER;
}
}
break;
}
......
case KeyEvent.KEYCODE_POWER: {
EventLogTags.writeInterceptPower(
KeyEvent.actionToString(event.getAction()),
mPowerKeyHandled ? 1 : 0, mPowerKeyPressCounter);
// Any activity on the power button stops the accessibility shortcut
cancelPendingAccessibilityShortcutAction();
result &= ~ACTION_PASS_TO_USER;
isWakeKey = false; // wake-up will be handled separately
if (down) {
interceptPowerKeyDown(event, interactive);
} else {
interceptPowerKeyUp(event, interactive, canceled);
}
break;
}
......
return result;
}
根据按键的key值为KEYCODE_POWER ，调用到interceptPowerKeyUp方法：
private void interceptPowerKeyUp(KeyEvent event, boolean interactive, boolean canceled) {
......
if (!handled) {
......
// No other actions. Handle it immediately.
powerPress(eventTime, interactive, mPowerKeyPressCounter);
}
// Done. Reset our state.
finishPowerKeyPress();
}
这里会调用powerPress方法：
private void powerPress(long eventTime, boolean interactive, int count) {
if (mDefaultDisplayPolicy.isScreenOnEarly() && !mDefaultDisplayPolicy.isScreenOnFully()) {
Slog.i(TAG, "Suppressed redundant power key press while "
+ "already in the process of turning the screen on.");
return;
}
Slog.d(TAG, "powerPress: eventTime=" + eventTime + " interactive=" + interactive
+ " count=" + count + " beganFromNonInteractive=" + mBeganFromNonInteractive +
" mShortPressOnPowerBehavior=" + mShortPressOnPowerBehavior);
if (count == 2) {
powerMultiPressAction(eventTime, interactive, mDoublePressOnPowerBehavior);
} else if (count == 3) {
powerMultiPressAction(eventTime, interactive, mTriplePressOnPowerBehavior);
} else if (interactive && !mBeganFromNonInteractive) {
switch (mShortPressOnPowerBehavior) {
case SHORT_PRESS_POWER_NOTHING:
break;
case SHORT_PRESS_POWER_GO_TO_SLEEP:
goToSleepFromPowerButton(eventTime, 0);
break;
case SHORT_PRESS_POWER_REALLY_GO_TO_SLEEP:
goToSleepFromPowerButton(eventTime, PowerManager.GO_TO_SLEEP_FLAG_NO_DOZE);
break;
case SHORT_PRESS_POWER_REALLY_GO_TO_SLEEP_AND_GO_HOME:
if (goToSleepFromPowerButton(eventTime,
PowerManager.GO_TO_SLEEP_FLAG_NO_DOZE)) {
launchHomeFromHotKey(DEFAULT_DISPLAY);
}
break;
case SHORT_PRESS_POWER_GO_HOME:
shortPressPowerGoHome();
break;
case SHORT_PRESS_POWER_CLOSE_IME_OR_GO_HOME: {
if (mDismissImeOnBackKeyPressed) {
if (mInputMethodManagerInternal == null) {
mInputMethodManagerInternal =
LocalServices.getService(InputMethodManagerInternal.class);
}
if (mInputMethodManagerInternal != null) {
mInputMethodManagerInternal.hideCurrentInputMethod();
}
} else {
shortPressPowerGoHome();
}
break;
}
}
}
}
判断mShortPressOnPowerBehavior的值，这个值获取是从config.xml(frameworks/base/core/res/res/values/config.xml)中的config_shortPressOnPowerBehavior：
<!-- Control the behavior when the user short presses the power button.
0 - Nothing
1 - Go to sleep (doze)
2 - Really go to sleep (don't doze)
3 - Really go to sleep and go home (don't doze)
4 - Go to home
5 - Dismiss IME if shown. Otherwise go to home
-->
<integer name="config_shortPressOnPowerBehavior">1</integer>
所以值为1，那么switch语句中就会走SHORT_PRESS_POWER_GO_TO_SLEEP，调用goToSleepFromPowerButton方法：
private boolean goToSleepFromPowerButton(long eventTime, int flags) {
// Before we actually go to sleep, we check the last wakeup reason.
// If the device very recently woke up from a gesture (like user lifting their device)
// then ignore the sleep instruction. This is because users have developed
// a tendency to hit the power button immediately when they pick up their device, and we
// don't want to put the device back to sleep in those cases.
// 检查上一次唤醒的原因
final PowerManager.WakeData lastWakeUp = mPowerManagerInternal.getLastWakeup();
if (lastWakeUp != null && lastWakeUp.wakeReason == PowerManager.WAKE_REASON_GESTURE) {
final int gestureDelayMillis = Settings.Global.getInt(mContext.getContentResolver(),
Settings.Global.POWER_BUTTON_SUPPRESSION_DELAY_AFTER_GESTURE_WAKE,
POWER_BUTTON_SUPPRESSION_DELAY_DEFAULT_MILLIS);
final long now = SystemClock.uptimeMillis();
if (mPowerButtonSuppressionDelayMillis > 0
&& (now < lastWakeUp.wakeTime + mPowerButtonSuppressionDelayMillis)) {
Slog.i(TAG, "Sleep from power button suppressed. Time since gesture: "
+ (now - lastWakeUp.wakeTime) + "ms");
return false;
}
}
goToSleep(eventTime, PowerManager.GO_TO_SLEEP_REASON_POWER_BUTTON, flags);
return true;
}
接着调用goToSleep方法：
private void goToSleep(long eventTime, int reason, int flags) {
mRequestedOrGoingToSleep = true;
mPowerManager.goToSleep(eventTime, reason, flags);
}
这里看到传入的reason是GO_TO_SLEEP_REASON_POWER_BUTTON，最终就调用到了PowerManager中的goToSleep方法。之后的调用流程和上面是一样的。
2.超时灭屏
系统在设置中有一个Screen Timeout选项，可以设置系统的灭屏时间。当灭屏时间到达之后，底层会去将屏幕置暗。这块流程我们暂不讨论，看屏幕置暗之后的流程：
从上面的描述中可以知道，当PowerManagerService启动之后最终会调用到核心函数updatePowerStateLocked上，这个函数是会实时监控屏幕亮度等信息的。这里会调用到一个关键函数updateUserActivitySummaryLocked（该函数更新mUserActivitySummary的值，以总结用户请求的状态，例如屏幕是亮还是暗）。
共有四种屏幕状态：Awake（唤醒）、Dream（屏保）、Doze（Doze）、Asleep（睡眠）
流程图如下：
代码实现如下：
private void updateUserActivitySummaryLocked(long now, int dirty) {
// Update the status of the user activity timeout timer.
if ((dirty & (DIRTY_WAKE_LOCKS | DIRTY_USER_ACTIVITY
| DIRTY_WAKEFULNESS | DIRTY_SETTINGS)) != 0) {
mHandler.removeMessages(MSG_USER_ACTIVITY_TIMEOUT);
long nextTimeout = 0;
// 判断mWakefulness处于AWAKE或DREAMING或DOZING
if (mWakefulness == WAKEFULNESS_AWAKE
|| mWakefulness == WAKEFULNESS_DREAMING
|| mWakefulness == WAKEFULNESS_DOZING) {
// 取超时时间和config_minimumScreenOffTimeout(10s)的最大值，为-1
final long sleepTimeout = getSleepTimeoutLocked();
// 获取屏幕灭屏超时时间，该值即设置中的屏幕超时时间设置值
final long screenOffTimeout = getScreenOffTimeoutLocked(sleepTimeout);
// 获取屏幕置暗时间，为6000ms
final long screenDimDuration = getScreenDimDurationLocked(screenOffTimeout);
final boolean userInactiveOverride = mUserInactiveOverrideFromWindowManager;
final long nextProfileTimeout = getNextProfileTimeoutLocked(now);
mUserActivitySummary = 0;
// 赋值对应的mUserActivitySummary值(0/2/4)
if (mLastUserActivityTime >= mLastWakeTime) {
nextTimeout = mLastUserActivityTime
+ screenOffTimeout - screenDimDuration;
if (now < nextTimeout) {
mUserActivitySummary = USER_ACTIVITY_SCREEN_BRIGHT;
} else {
nextTimeout = mLastUserActivityTime + screenOffTimeout;
if (now < nextTimeout) {
mUserActivitySummary = USER_ACTIVITY_SCREEN_DIM;
}
}
}
if (mUserActivitySummary == 0
&& mLastUserActivityTimeNoChangeLights >= mLastWakeTime) {
nextTimeout = mLastUserActivityTimeNoChangeLights + screenOffTimeout;
if (now < nextTimeout) {
if (mDisplayPowerRequest.policy == DisplayPowerRequest.POLICY_BRIGHT
|| mDisplayPowerRequest.policy == DisplayPowerRequest.POLICY_VR) {
mUserActivitySummary = USER_ACTIVITY_SCREEN_BRIGHT;
} else if (mDisplayPowerRequest.policy == DisplayPowerRequest.POLICY_DIM) {
mUserActivitySummary = USER_ACTIVITY_SCREEN_DIM;
}
}
}
if (mUserActivitySummary == 0) {
if (sleepTimeout >= 0) {
final long anyUserActivity = Math.max(mLastUserActivityTime,
mLastUserActivityTimeNoChangeLights);
if (anyUserActivity >= mLastWakeTime) {
nextTimeout = anyUserActivity + sleepTimeout;
if (now < nextTimeout) {
mUserActivitySummary = USER_ACTIVITY_SCREEN_DREAM;
}
}
} else {
mUserActivitySummary = USER_ACTIVITY_SCREEN_DREAM;
nextTimeout = -1;
}
}
if (mUserActivitySummary != USER_ACTIVITY_SCREEN_DREAM && userInactiveOverride) {
if ((mUserActivitySummary &
(USER_ACTIVITY_SCREEN_BRIGHT | USER_ACTIVITY_SCREEN_DIM)) != 0) {
// Device is being kept awake by recent user activity
if (nextTimeout >= now && mOverriddenTimeout == -1) {
// Save when the next timeout would have occurred
mOverriddenTimeout = nextTimeout;
}
}
mUserActivitySummary = USER_ACTIVITY_SCREEN_DREAM;
nextTimeout = -1;
}
if ((mUserActivitySummary & USER_ACTIVITY_SCREEN_BRIGHT) != 0
&& (mWakeLockSummary & WAKE_LOCK_STAY_AWAKE) == 0) {
nextTimeout = mAttentionDetector.updateUserActivity(nextTimeout);
}
if (nextProfileTimeout > 0) {
nextTimeout = Math.min(nextTimeout, nextProfileTimeout);
}
if (mUserActivitySummary != 0 && nextTimeout >= 0) {
scheduleUserInactivityTimeout(nextTimeout);
}
} else {
mUserActivitySummary = 0;
}
if (DEBUG_SPEW) {
Slog.d(TAG, "updateUserActivitySummaryLocked: mWakefulness="
+ PowerManagerInternal.wakefulnessToString(mWakefulness)
+ ", mUserActivitySummary=0x" + Integer.toHexString(mUserActivitySummary)
+ ", nextTimeout=" + TimeUtils.formatUptime(nextTimeout));
}
}
}
这里会调用到scheduleUserInactivityTimeout方法：
private void scheduleUserInactivityTimeout(long timeMs) {
final Message msg = mHandler.obtainMessage(MSG_USER_ACTIVITY_TIMEOUT);
msg.setAsynchronous(true);
mHandler.sendMessageAtTime(msg, timeMs);
}
发送一个MSG_USER_ACTIVITY_TIMEOUT广播：
private final class PowerManagerHandler extends Handler {
public PowerManagerHandler(Looper looper) {
super(looper, null, true /*async*/);
}
@Override
public void handleMessage(Message msg) {
switch (msg.what) {
case MSG_USER_ACTIVITY_TIMEOUT:
handleUserActivityTimeout();
break;
....
}
}
接着会调用到handleUserActivityTimeout方法：
private void handleUserActivityTimeout() { // runs on handler thread
synchronized (mLock) {
if (DEBUG_SPEW) {
Slog.d(TAG, "handleUserActivityTimeout");
}
mDirty |= DIRTY_USER_ACTIVITY;
updatePowerStateLocked();
}
}
这时又会调用到updatePowerStateLocked方法，直接看关键代码：
// Phase 1: Update wakefulness.
// Loop because the wake lock and user activity computations are influenced
// by changes in wakefulness.
final long now = SystemClock.uptimeMillis();
int dirtyPhase2 = 0;
for (;;) {
int dirtyPhase1 = mDirty;
dirtyPhase2 |= dirtyPhase1;
mDirty = 0;
updateWakeLockSummaryLocked(dirtyPhase1);
updateUserActivitySummaryLocked(now, dirtyPhase1);
if (!updateWakefulnessLocked(dirtyPhase1)) {
break;
}
}
看updateWakefulnessLocked的实现：
private boolean updateWakefulnessLocked(int dirty) {
boolean changed = false;
if ((dirty & (DIRTY_WAKE_LOCKS | DIRTY_USER_ACTIVITY | DIRTY_BOOT_COMPLETED
| DIRTY_WAKEFULNESS | DIRTY_STAY_ON | DIRTY_PROXIMITY_POSITIVE
| DIRTY_DOCK_STATE)) != 0) {
if (mWakefulness == WAKEFULNESS_AWAKE && isItBedTimeYetLocked()) {
if (DEBUG_SPEW) {
Slog.d(TAG, "updateWakefulnessLocked: Bed time...");
}
final long time = SystemClock.uptimeMillis();
if (shouldNapAtBedTimeLocked()) {
changed = napNoUpdateLocked(time, Process.SYSTEM_UID);
} else {
changed = goToSleepNoUpdateLocked(time,
PowerManager.GO_TO_SLEEP_REASON_TIMEOUT, 0, Process.SYSTEM_UID);
}
}
}
return changed;
}
这里要看下shouldNapAtBedTimeLocked方法的返回值，这个返回值是和手机中设置的屏保等值有关联的。这时我们返回false，走到goToSleepNoUpdateLocked：
@SuppressWarnings("deprecation")
private boolean goToSleepNoUpdateLocked(long eventTime, int reason, int flags, int uid) {
if (DEBUG_SPEW) {
Slog.d(TAG, "goToSleepNoUpdateLocked: eventTime=" + eventTime
+ ", reason=" + reason + ", flags=" + flags + ", uid=" + uid);
}
if (eventTime < mLastWakeTime
|| mWakefulness == WAKEFULNESS_ASLEEP
|| mWakefulness == WAKEFULNESS_DOZING
|| !mBootCompleted || !mSystemReady) {
return false;
}
Trace.traceBegin(Trace.TRACE_TAG_POWER, "goToSleep");
try {
reason = Math.min(PowerManager.GO_TO_SLEEP_REASON_MAX,
Math.max(reason, PowerManager.GO_TO_SLEEP_REASON_MIN));
Slog.i(TAG, "Going to sleep due to " + PowerManager.sleepReasonToString(reason)
+ " (uid " + uid + ")...");
mLastSleepTime = eventTime;
mLastSleepReason = reason;
mSandmanSummoned = true;
setWakefulnessLocked(WAKEFULNESS_DOZING, reason, eventTime);
// Report the number of wake locks that will be cleared by going to sleep.
int numWakeLocksCleared = 0;
final int numWakeLocks = mWakeLocks.size();
for (int i = 0; i < numWakeLocks; i++) {
final WakeLock wakeLock = mWakeLocks.get(i);
switch (wakeLock.mFlags & PowerManager.WAKE_LOCK_LEVEL_MASK) {
case PowerManager.FULL_WAKE_LOCK:
case PowerManager.SCREEN_BRIGHT_WAKE_LOCK:
case PowerManager.SCREEN_DIM_WAKE_LOCK:
numWakeLocksCleared += 1;
break;
}
}
EventLogTags.writePowerSleepRequested(numWakeLocksCleared);
// Skip dozing if requested.
if ((flags & PowerManager.GO_TO_SLEEP_FLAG_NO_DOZE) != 0) {
reallyGoToSleepNoUpdateLocked(eventTime, uid);
}
} finally {
Trace.traceEnd(Trace.TRACE_TAG_POWER);
}
return true;
}
这里后面就会调用到reallyGoToSleepNoUpdateLocked。逻辑就和power键灭屏类似。
3.Psensor灭屏
Proximity Sensor（近距离传感器）。手机通话过程中（比如QQ、微信语音等），当手机靠近人脸的时候，屏幕会去灭屏，这样就能保证用户不会触碰到屏幕导致误操作，还能起到省电的作用。这里是需要kernel层和java层的交互的，主要涉及kernel sensor、PowerManagerService、DisplayManagerService等。
PhotonicModulator是DisplayPowerState的内部类，是一个线程，用来异步更新screen和backlight
private final class PhotonicModulator extends Thread {
private static final int INITIAL_SCREEN_STATE = Display.STATE_OFF; // unknown, assume off
private static final int INITIAL_BACKLIGHT = -1; // unknown
private final Object mLock = new Object();
.......
@Override
public void run() {
for (;;) {
// Get pending change.
final int state;
final boolean stateChanged;
final int backlight;
final boolean backlightChanged;
synchronized (mLock) {
state = mPendingState;
stateChanged = (state != mActualState);
backlight = mPendingBacklight;
backlightChanged = (backlight != mActualBacklight);
if (!stateChanged) {
// State changed applied, notify outer class.
postScreenUpdateThreadSafe();
mStateChangeInProgress = false;
}
if (!backlightChanged) {
mBacklightChangeInProgress = false;
}
if (!stateChanged && !backlightChanged) {
try {
mLock.wait();
} catch (InterruptedException ex) { }
continue;
}
mActualState = state;
mActualBacklight = backlight;
}
// Apply pending change.
if (DEBUG) {
Slog.d(TAG, "Updating screen state: state="
+ Display.stateToString(state) + ", backlight=" + backlight);
}
mBlanker.requestDisplayState(state, backlight);
}
}
}
在方法最后调用mBlanker.requestDisplayState函数，DisplayBlanker是一个接口，requestDisplayState接口方法。实现是在DisplayManagerService中：
private final class LocalService extends DisplayManagerInternal {
@Override
public void initPowerManagement(final DisplayPowerCallbacks callbacks, Handler handler,
SensorManager sensorManager) {
synchronized (mSyncRoot) {
DisplayBlanker blanker = new DisplayBlanker() {
@Override
public void requestDisplayState(int state, int brightness) {
// The order of operations is important for legacy reasons.
if (state == Display.STATE_OFF) {
requestGlobalDisplayStateInternal(state, brightness);
}
callbacks.onDisplayStateChange(state);
if (state != Display.STATE_OFF) {
requestGlobalDisplayStateInternal(state, brightness);
}
}
};
mDisplayPowerController = new DisplayPowerController(
mContext, callbacks, handler, sensorManager, blanker);
}
mHandler.sendEmptyMessage(MSG_LOAD_BRIGHTNESS_CONFIGURATION);
}
}
接着看DisplayManagerInternal的定义：
/**
* Asynchronous callbacks from the power controller to the power manager service.
*/
public interface DisplayPowerCallbacks {
void onStateChanged();
void onProximityPositive();
void onProximityNegative();
void onDisplayStateChange(int state); // one of the Display state constants
void acquireSuspendBlocker();
void releaseSuspendBlocker();
}
而在PowerManagerService中是有实现这个接口的：
private final DisplayManagerInternal.DisplayPowerCallbacks mDisplayPowerCallbacks =
new DisplayManagerInternal.DisplayPowerCallbacks() {
private int mDisplayState = Display.STATE_UNKNOWN;
@Override
public void onStateChanged() {
synchronized (mLock) {
mDirty |= DIRTY_ACTUAL_DISPLAY_POWER_STATE_UPDATED;
updatePowerStateLocked();
}
}
@Override
public void onProximityPositive() {
synchronized (mLock) {
mProximityPositive = true;
mDirty |= DIRTY_PROXIMITY_POSITIVE;
updatePowerStateLocked();
}
}
@Override
public void onProximityNegative() {
synchronized (mLock) {
mProximityPositive = false;
mDirty |= DIRTY_PROXIMITY_POSITIVE;
userActivityNoUpdateLocked(SystemClock.uptimeMillis(),
PowerManager.USER_ACTIVITY_EVENT_OTHER, 0, Process.SYSTEM_UID);
updatePowerStateLocked();
}
}
@Override
public void onDisplayStateChange(int state) {
// This method is only needed to support legacy display blanking behavior
// where the display's power state is coupled to suspend or to the power HAL.
// The order of operations matters here.
synchronized (mLock) {
if (mDisplayState != state) {
mDisplayState = state;
if (state == Display.STATE_OFF) {
if (!mDecoupleHalInteractiveModeFromDisplayConfig) {
setHalInteractiveModeLocked(false);
}
if (!mDecoupleHalAutoSuspendModeFromDisplayConfig) {
setHalAutoSuspendModeLocked(true);
}
} else {
if (!mDecoupleHalAutoSuspendModeFromDisplayConfig) {
setHalAutoSuspendModeLocked(false);
}
if (!mDecoupleHalInteractiveModeFromDisplayConfig) {
setHalInteractiveModeLocked(true);
}
}
}
}
}
......
};
onDisplayStateChange方法：
@Override
public void onDisplayStateChange(int state) {
// This method is only needed to support legacy display blanking behavior
// where the display's power state is coupled to suspend or to the power HAL.
// The order of operations matters here.
synchronized (mLock) {
if (mDisplayState != state) {
mDisplayState = state;
if (state == Display.STATE_OFF) {
if (!mDecoupleHalInteractiveModeFromDisplayConfig) {
setHalInteractiveModeLocked(false);
}
if (!mDecoupleHalAutoSuspendModeFromDisplayConfig) {
setHalAutoSuspendModeLocked(true);
}
} else {
if (!mDecoupleHalAutoSuspendModeFromDisplayConfig) {
setHalAutoSuspendModeLocked(false);
}
if (!mDecoupleHalInteractiveModeFromDisplayConfig) {
setHalInteractiveModeLocked(true);
}
}
}
}
}
setHalInteractiveModeLocked是一个native方法，
Dialer中实现Psensor的亮灭屏的控制是通过ProximitySensor类。
位置在：/packages/apps/Dialer/java/com/android/incallui/ProximitySensor.java，初始化等方法就不去具体关注，只看他控制Psensor的关键方法updateProximitySensorMode：
private synchronized void updateProximitySensorMode() {
Trace.beginSection("ProximitySensor.updateProximitySensorMode");
final int audioRoute = audioModeProvider.getAudioState().getRoute();
boolean screenOnImmediately =
(CallAudioState.ROUTE_WIRED_HEADSET == audioRoute
|| CallAudioState.ROUTE_SPEAKER == audioRoute
|| CallAudioState.ROUTE_BLUETOOTH == audioRoute
|| isAttemptingVideoCall
|| isVideoCall
|| isRttCall);
// We do not keep the screen off when the user is outside in-call screen and we are
// horizontal, but we do not force it on when we become horizontal until the
// proximity sensor goes negative.
final boolean horizontal = (orientation == AccelerometerListener.ORIENTATION_HORIZONTAL);
screenOnImmediately |= !uiShowing && horizontal;
// We do not keep the screen off when dialpad is visible, we are horizontal, and
// the in-call screen is being shown.
// At that moment we're pretty sure users want to use it, instead of letting the
// proximity sensor turn off the screen by their hands.
screenOnImmediately |= dialpadVisible && horizontal;
LogUtil.i(
"ProximitySensor.updateProximitySensorMode",
"screenOnImmediately: %b, dialPadVisible: %b, "
+ "offHook: %b, horizontal: %b, uiShowing: %b, audioRoute: %s",
screenOnImmediately,
dialpadVisible,
isPhoneOffhook,
orientation == AccelerometerListener.ORIENTATION_HORIZONTAL,
uiShowing,
CallAudioState.audioRouteToString(audioRoute));
if (isPhoneOffhook && !screenOnImmediately) {
LogUtil.v("ProximitySensor.updateProximitySensorMode", "turning on proximity sensor");
// Phone is in use! Arrange for the screen to turn off
// automatically when the sensor detects a close object.
turnOnProximitySensor();
} else {
LogUtil.v("ProximitySensor.updateProximitySensorMode", "turning off proximity sensor");
// Phone is either idle, or ringing. We don't want any special proximity sensor
// behavior in either case.
turnOffProximitySensor(screenOnImmediately);
}
Trace.endSection();
}
对应的控制Psensor的方法为turnOnProximitySensor/turnOffProximitySensor：
private void turnOnProximitySensor() {
if (proximityWakeLock != null) {
if (!proximityWakeLock.isHeld()) {
LogUtil.i("ProximitySensor.turnOnProximitySensor", "acquiring wake lock");
proximityWakeLock.acquire();
} else {
LogUtil.i("ProximitySensor.turnOnProximitySensor", "wake lock already acquired");
}
}
}
private void turnOffProximitySensor(boolean screenOnImmediately) {
if (proximityWakeLock != null) {
if (proximityWakeLock.isHeld()) {
LogUtil.i("ProximitySensor.turnOffProximitySensor", "releasing wake lock");
int flags = (screenOnImmediately ? 0 : PowerManager.RELEASE_FLAG_WAIT_FOR_NO_PROXIMITY);
proximityWakeLock.release(flags);
} else {
LogUtil.i("ProximitySensor.turnOffProximitySensor", "wake lock already released");
}
}
}
这两个函数就是根据isHeld方法的返回值来判断当前是否有进程持wake 锁，没有的话就会去申请（acquire）/释放（release）锁。
另proximityWakeLock的初始赋值在ProximitySensor的初始化中，申请了一个PROXIMITY_SCREEN_OFF_WAKE_LOCK类型的wakeLock（在wakeLock章节中已介绍了这个锁是当传感器激活时，关闭屏幕；物体移开后不久，屏幕再次打开）：
public ProximitySensor(
@NonNull Context context,
@NonNull AudioModeProvider audioModeProvider,
@NonNull AccelerometerListener accelerometerListener) {
Trace.beginSection("ProximitySensor.Constructor");
powerManager = (PowerManager) context.getSystemService(Context.POWER_SERVICE);
if (powerManager.isWakeLockLevelSupported(PowerManager.PROXIMITY_SCREEN_OFF_WAKE_LOCK)) {
proximityWakeLock =
powerManager.newWakeLock(PowerManager.PROXIMITY_SCREEN_OFF_WAKE_LOCK, TAG);
} else {
LogUtil.i("ProximitySensor.constructor", "Device does not support proximity wake lock.");
proximityWakeLock = null;
}
接着就会调用到PowerManagerService中去了，在申请和释放wakelock的时候，最终会调用到核心函数updatePowerStateLocked，其中第三步是更新显示状态：
// Phase 3: Update display power state.
final boolean displayBecameReady = updateDisplayPowerStateLocked(dirtyPhase2);
来看updateDisplayPowerStateLocked的实现：
private boolean updateDisplayPowerStateLocked(int dirty) {
final boolean oldDisplayReady = mDisplayReady;
if ((dirty & (DIRTY_WAKE_LOCKS | DIRTY_USER_ACTIVITY | DIRTY_WAKEFULNESS
| DIRTY_ACTUAL_DISPLAY_POWER_STATE_UPDATED | DIRTY_BOOT_COMPLETED
| DIRTY_SETTINGS | DIRTY_SCREEN_BRIGHTNESS_BOOST | DIRTY_VR_MODE_CHANGED |
DIRTY_QUIESCENT)) != 0) {
mDisplayPowerRequest.policy = getDesiredScreenPolicyLocked();
// Determine appropriate screen brightness and auto-brightness adjustments.
.......
// Update display power request.
.......
mDisplayReady = mDisplayManagerInternal.requestPowerState(mDisplayPowerRequest,
mRequestWaitForNegativeProximity);
mRequestWaitForNegativeProximity = false;
......
}
return mDisplayReady && !oldDisplayReady;
}
mDisplayPowerController对象，查看DisplayPowerController的requestPowerState方法：
public boolean requestPowerState(DisplayPowerRequest request,
boolean waitForNegativeProximity) {
if (DEBUG) {
Slog.d(TAG, "requestPowerState: "
+ request + ", waitForNegativeProximity=" + waitForNegativeProximity);
}
synchronized (mLock) {
boolean changed = false;
......
if (changed && !mPendingRequestChangedLocked) {
mPendingRequestChangedLocked = true;
sendUpdatePowerStateLocked();
}
return mDisplayReadyLocked;
}
}
这里会执行sendUpdatePowerStateLocked方法：
private void sendUpdatePowerStateLocked() {
if (!mPendingUpdatePowerStateLocked) {
mPendingUpdatePowerStateLocked = true;
Message msg = mHandler.obtainMessage(MSG_UPDATE_POWER_STATE);
mHandler.sendMessage(msg);
}
}
通过发送一个MSG_UPDATE_POWER_STATE消息：
private final class DisplayControllerHandler extends Handler {
public DisplayControllerHandler(Looper looper) {
super(looper, null, true /*async*/);
}
@Override
public void handleMessage(Message msg) {
switch (msg.what) {
case MSG_UPDATE_POWER_STATE:
updatePowerState();
break;
执行updatePowerState方法：
private void updatePowerState() {
// Update the power state request.
final boolean mustNotify;
final int previousPolicy;
boolean mustInitialize = false;
int brightnessAdjustmentFlags = 0;
mBrightnessReasonTemp.set(null);
.......
// Apply the proximity sensor.
if (mProximitySensor != null) {
// 如果当前不是灭屏状态
if (mPowerRequest.useProximitySensor && state != Display.STATE_OFF) {
// 注册PSensor监听，Enable PSensor
setProximitySensorEnabled(true);
// 默认mScreenOffBecauseOfProximity为false，同时当前PSensor处于被遮挡状态
if (!mScreenOffBecauseOfProximity
&& mProximity == PROXIMITY_POSITIVE) {
mScreenOffBecauseOfProximity = true;
// 回调PowerManagerService的onProximityPositive方法上
sendOnProximityPositiveWithWakelock();
}
} else if (mWaitingForNegativeProximity
&& mScreenOffBecauseOfProximity
&& mProximity == PROXIMITY_POSITIVE
&& state != Display.STATE_OFF) {
// 通话过程中设备PSensor被遮挡，屏幕关闭
setProximitySensorEnabled(true);
} else {
setProximitySensorEnabled(false);
mWaitingForNegativeProximity = false;
}
if (mScreenOffBecauseOfProximity
&& mProximity != PROXIMITY_POSITIVE) {
mScreenOffBecauseOfProximity = false;
sendOnProximityNegativeWithWakelock();
}
} else {
mWaitingForNegativeProximity = false;
}
if (mScreenOffBecauseOfProximity) {
state = Display.STATE_OFF;
}
.......
}
截取方法中涉及到Psensor的部分，可以看到会调用到setProximitySensorEnabled方法：
private void setProximitySensorEnabled(boolean enable) {
if (enable) {
if (!mProximitySensorEnabled) {
// Register the listener.
// Proximity sensor state already cleared initially.
mProximitySensorEnabled = true;
mSensorManager.registerListener(mProximitySensorListener, mProximitySensor,
SensorManager.SENSOR_DELAY_NORMAL, mHandler);
}
} else {
if (mProximitySensorEnabled) {
// Unregister the listener.
// Clear the proximity sensor state for next time.
mProximitySensorEnabled = false;
mProximity = PROXIMITY_UNKNOWN;
mPendingProximity = PROXIMITY_UNKNOWN;
mHandler.removeMessages(MSG_PROXIMITY_SENSOR_DEBOUNCED);
mSensorManager.unregisterListener(mProximitySensorListener);
clearPendingProximityDebounceTime(); // release wake lock (must be last)
}
}
}
这里会去注册一个mProximitySensorListener的监听。当Psensor的状态发生了变化，就会回调Listener的onSensorChanged方法：
private final SensorEventListener mProximitySensorListener = new SensorEventListener() {
@Override
public void onSensorChanged(SensorEvent event) {
if (mProximitySensorEnabled) {
final long time = SystemClock.uptimeMillis();
// 从Event中获取distance值，这个值与driver上报有关，不同设备有可能不同
// distance = 1 接近 ；distance = 2 远离
final float distance = event.values[0];
boolean positive = distance >= 0.0f && distance < mProximityThreshold;
handleProximitySensorEvent(time, positive);
}
}
......
}
执行到handleProximitySensorEvent方法：
private void handleProximitySensorEvent(long time, boolean positive) {
if (mProximitySensorEnabled) {
if (mPendingProximity == PROXIMITY_NEGATIVE && !positive) {
return; // no change
}
if (mPendingProximity == PROXIMITY_POSITIVE && positive) {
return; // no change
}
// Only accept a proximity sensor reading if it remains
// stable for the entire debounce delay. We hold a wake lock while
// debouncing the sensor.
mHandler.removeMessages(MSG_PROXIMITY_SENSOR_DEBOUNCED);
if (positive) {
mPendingProximity = PROXIMITY_POSITIVE;
setPendingProximityDebounceTime(
time + PROXIMITY_SENSOR_POSITIVE_DEBOUNCE_DELAY); // acquire wake lock
} else {
mPendingProximity = PROXIMITY_NEGATIVE;
setPendingProximityDebounceTime(
time + PROXIMITY_SENSOR_NEGATIVE_DEBOUNCE_DELAY); // acquire wake lock
}
// Debounce the new sensor reading.
debounceProximitySensor();
}
}
而debounceProximitySensor方法又会回到updatePowerState方法的调用：
private void debounceProximitySensor() {
if (mProximitySensorEnabled
&& mPendingProximity != PROXIMITY_UNKNOWN
&& mPendingProximityDebounceTime >= 0) {
final long now = SystemClock.uptimeMillis();
if (mPendingProximityDebounceTime <= now) {
// Sensor reading accepted. Apply the change then release the wake lock.
mProximity = mPendingProximity;
updatePowerState();
clearPendingProximityDebounceTime(); // release wake lock (must be last)
} else {
// Need to wait a little longer.
// Debounce again later. We continue holding a wake lock while waiting.
Message msg = mHandler.obtainMessage(MSG_PROXIMITY_SENSOR_DEBOUNCED);
mHandler.sendMessageAtTime(msg, mPendingProximityDebounceTime);
}
}
}
这时回到updatePowerState方法上，关注sendOnProximityPositiveWithWakelock方法：
private void sendOnProximityPositiveWithWakelock() {
mCallbacks.acquireSuspendBlocker();
mHandler.post(mOnProximityPositiveRunnable);
}
private final Runnable mOnProximityPositiveRunnable = new Runnable() {
@Override
public void run() {
mCallbacks.onProximityPositive();
mCallbacks.releaseSuspendBlocker();
}
};
这个回调方法会在PowerManagerService中实现的。而最终的最终会调用到PowerManagerService的核心函数updatePowerStateLocked方法上。
当PSensor完成了屏幕的关闭/点亮之后就会去执行updateSuspendBlockerLocked方法：
private void updateSuspendBlockerLocked() {
final boolean needWakeLockSuspendBlocker = ((mWakeLockSummary & WAKE_LOCK_CPU) != 0);
final boolean needDisplaySuspendBlocker = needDisplaySuspendBlockerLocked();
final boolean autoSuspend = !needDisplaySuspendBlocker;
final boolean interactive = mDisplayPowerRequest.isBrightOrDim();
// Disable auto-suspend if needed.
// FIXME We should consider just leaving auto-suspend enabled forever since
// we already hold the necessary wakelocks.
if (!autoSuspend && mDecoupleHalAutoSuspendModeFromDisplayConfig) {
setHalAutoSuspendModeLocked(false);
}
// First acquire suspend blockers if needed.
// acquire WakeLock，系统中如果有WakeLock没有释放则无法进入深度睡眠
if (needWakeLockSuspendBlocker && !mHoldingWakeLockSuspendBlocker) {
mWakeLockSuspendBlocker.acquire();
mHoldingWakeLockSuspendBlocker = true;
}
if (needDisplaySuspendBlocker && !mHoldingDisplaySuspendBlocker) {
mDisplaySuspendBlocker.acquire();
mHoldingDisplaySuspendBlocker = true;
}
// Inform the power HAL about interactive mode.
// Although we could set interactive strictly based on the wakefulness
// as reported by isInteractive(), it is actually more desirable to track
// the display policy state instead so that the interactive state observed
// by the HAL more accurately tracks transitions between AWAKE and DOZING.
// Refer to getDesiredScreenPolicyLocked() for details.
if (mDecoupleHalInteractiveModeFromDisplayConfig) {
// When becoming non-interactive, we want to defer sending this signal
// until the display is actually ready so that all transitions have
// completed. This is probably a good sign that things have gotten
// too tangled over here...
if (interactive || mDisplayReady) {
setHalInteractiveModeLocked(interactive);
}
}
// Then release suspend blockers if needed.
// release WakeLock，释放系统的WakeLock以使系统可以正常进入休眠
if (!needWakeLockSuspendBlocker && mHoldingWakeLockSuspendBlocker) {
mWakeLockSuspendBlocker.release();
mHoldingWakeLockSuspendBlocker = false;
}
if (!needDisplaySuspendBlocker && mHoldingDisplaySuspendBlocker) {
mDisplaySuspendBlocker.release();
mHoldingDisplaySuspendBlocker = false;
}
// Enable auto-suspend if needed.
if (autoSuspend && mDecoupleHalAutoSuspendModeFromDisplayConfig) {
setHalAutoSuspendModeLocked(true);
}
}
而acquire/release会去调用到native中的方法：
@Override
public void acquire() {
synchronized (this) {
mReferenceCount += 1;
if (mReferenceCount == 1) {
if (DEBUG_SPEW) {
Slog.d(TAG, "Acquiring suspend blocker \"" + mName + "\".");
}
Trace.asyncTraceBegin(Trace.TRACE_TAG_POWER, mTraceName, 0);
mNativeWrapper.nativeAcquireSuspendBlocker(mName);
}
}
}
@Override
public void release() {
synchronized (this) {
mReferenceCount -= 1;
if (mReferenceCount == 0) {
if (DEBUG_SPEW) {
Slog.d(TAG, "Releasing suspend blocker \"" + mName + "\".");
}
mNativeWrapper.nativeReleaseSuspendBlocker(mName);
Trace.asyncTraceEnd(Trace.TRACE_TAG_POWER, mTraceName, 0);
} else if (mReferenceCount < 0) {
Slog.wtf(TAG, "Suspend blocker \"" + mName
+ "\" was released without being acquired!", new Throwable());
mReferenceCount = 0;
}
}
}
jni层：com_android_server_power_PowerManagerService.cpp中的实现：
static void nativeAcquireSuspendBlocker(JNIEnv *env, jclass /* clazz */, jstring nameStr) {
ScopedUtfChars name(env, nameStr);
acquire_wake_lock(PARTIAL_WAKE_LOCK, name.c_str());
}
static void nativeReleaseSuspendBlocker(JNIEnv *env, jclass /* clazz */, jstring nameStr) {
ScopedUtfChars name(env, nameStr);
release_wake_lock(name.c_str());
}
综上，PowerManagerService的灭屏相关知识就讲到这。
