Android7.0 PowerManagerService(4) Power按键流程

按键的处理主要由InputManagerService负责，属于Android输入系统的流程。在这篇博客里，我们只关注与Power键相关的内容。InputManagerService处理的按键事件，最终将会传递到PhoneWindowManager的interceptKeyBeforeQueueing函数。
我们就从这个函数开始，逐步进行分析。

public int interceptKeyBeforeQueueing(KeyEvent event, int policyFlags) {if (!mSystemBooted) {// If we have not yet booted, don't let key events do anything.return 0;}//表示屏幕是否点亮final boolean interactive = (policyFlags & FLAG_INTERACTIVE) != 0;final boolean down = event.getAction() == KeyEvent.ACTION_DOWN;final boolean canceled = event.isCanceled();//按键对应的编码final int keyCode = event.getKeyCode();.................switch (keyCode) {...........case KeyEvent.KEYCODE_POWER: {result &= ~ACTION_PASS_TO_USER;isWakeKey = false; // wake-up will be handled separatelyif (down) {//处理按下Power键interceptPowerKeyDown(event, interactive);} else {//处理松开Power键interceptPowerKeyUp(event, interactive, canceled);}break;}}..............if (isWakeKey) {//按power键时，isWakeKey置为false，于是不会调用wakeUp函数wakeUp(event.getEventTime(), mAllowTheaterModeWakeFromKey, "android.policy:KEY");}return result;
}

接下来，我们分别看一下interceptPowerKeyDown和interceptPowerKeyUp函数。

一、interceptPowerKeyDown

interceptPowerKeyDown用于处理按下Power键(还未松手释放)对应的事件。

private void interceptPowerKeyDown(KeyEvent event, boolean interactive) {// Hold a wake lock until the power key is released.// mPowerKeyWakeLock为PARTIAL_WAKE_LOCK级别的锁if (!mPowerKeyWakeLock.isHeld()) {//将调用到PMS的acquire WakeLock流程mPowerKeyWakeLock.acquire();}// Cancel multi-press detection timeout.//处理多次按power键的场景//每次power up时，发送MSG_POWER_DELAYED_PRESS的延迟消息//如果延迟消息被处理，说明一次完整的Power键处理结束（按下去，弹起来）//在延迟消息被处理前，再次按power键，就检测到多次点击了//实际上，原生终端不支持该场景if (mPowerKeyPressCounter != 0) {mHandler.removeMessages(MSG_POWER_DELAYED_PRESS);}// Detect user pressing the power button in panic when an application has// taken over the whole screen.// 从注释来看及mHiddenNavPanic的代码，觉得像是处理“误触”的boolean panic = mImmersiveModeConfirmation.onPowerKeyDown(interactive,SystemClock.elapsedRealtime(), isImmersiveMode(mLastSystemUiFlags));if (panic) {mHandler.post(mHiddenNavPanic);}// Latch power key state to detect screenshot chord.// 如果当前是亮屏状态，且满足触发截屏的条件，触发截屏功能if (interactive && !mScreenshotChordPowerKeyTriggered&& (event.getFlags() & KeyEvent.FLAG_FALLBACK) == 0) {mScreenshotChordPowerKeyTriggered = true;mScreenshotChordPowerKeyTime = event.getDownTime();interceptScreenshotChord();}// Stop ringing or end call if configured to do so when power is pressed.TelecomManager telecomManager = getTelecommService();boolean hungUp = false;if (telecomManager != null) {if (telecomManager.isRinging()) {// Pressing Power while there's a ringing incoming// call should silence the ringer.//如果有电话拨入，且电话铃声响起，按Power键，设置电话响铃静音telecomManager.silenceRinger();} else if ((mIncallPowerBehavior& Settings.Secure.INCALL_POWER_BUTTON_BEHAVIOR_HANGUP) != 0&& telecomManager.isInCall() && interactive) {// Otherwise, if "Power button ends call" is enabled,// the Power button will hang up any current active call.//如果正在接听电话，且配置了Power键挂断电话的话，按Power按键挂断正在接听的电话hungUp = telecomManager.endCall();}}GestureLauncherService gestureService = LocalServices.getService(GestureLauncherService.class);boolean gesturedServiceIntercepted = false;if (gestureService != null) {//手势对应的服务，尝试拦截处理Power键动作事件gesturedServiceIntercepted = gestureService.interceptPowerKeyDown(event, interactive,mTmpBoolean);if (mTmpBoolean.value && mGoingToSleep) {mCameraGestureTriggeredDuringGoingToSleep = true;}}// If the power key has still not yet been handled, then detect short// press, long press, or multi press and decide what to do.// Power键事件的处理，就像处理屏幕上的点击事件一样，也依赖于事件分发机制// 如果已经被消耗掉了，就不会再被继续处理mPowerKeyHandled = hungUp || mScreenshotChordVolumeDownKeyTriggered|| mScreenshotChordVolumeUpKeyTriggered || gesturedServiceIntercepted;//Power键事件未被消耗掉if (!mPowerKeyHandled) {//屏幕还是亮的if (interactive) {// When interactive, we're already awake.// Wait for a long press or for the button to be released to decide what to do.//1、 判断是否支持长按的行为if (hasLongPressOnPowerBehavior()) {//2、 亮屏时，长按Power键将触发MSG_POWER_LONG_PRESS消息Message msg = mHandler.obtainMessage(MSG_POWER_LONG_PRESS);msg.setAsynchronous(true);mHandler.sendMessageDelayed(msg,ViewConfiguration.get(mContext).getDeviceGlobalActionKeyTimeout());}} else {//此时屏幕是熄灭状态//3、先唤醒系统，这个会调用到PMS的wakeUpwakeUpFromPowerKey(event.getDownTime());//支持熄屏长按，mSupportLongPressPowerWhenNonInteractive读资源文件得到，默认为falseif (mSupportLongPressPowerWhenNonInteractive && hasLongPressOnPowerBehavior()) {Message msg = mHandler.obtainMessage(MSG_POWER_LONG_PRESS);msg.setAsynchronous(true);mHandler.sendMessageDelayed(msg,ViewConfiguration.get(mContext).getDeviceGlobalActionKeyTimeout());mBeganFromNonInteractive = true;} else {//默认返回1final int maxCount = getMaxMultiPressPowerCount();if (maxCount <= 1) {//息屏时，按下power键（不弹起），仅消耗掉该事件mPowerKeyHandled = true;} else {mBeganFromNonInteractive = true;}}}}
}

1、hasLongPressOnPowerBehavior
hasLongPressOnPowerBehavior负责判断终端是否支持长按的行为：

private boolean hasLongPressOnPowerBehavior() {return getResolvedLongPressOnPowerBehavior() != LONG_PRESS_POWER_NOTHING;
}private int getResolvedLongPressOnPowerBehavior() {//取决与系统属性"factory.long_press_power_off"，此处默认为falseif (FactoryTest.isLongPressOnPowerOffEnabled()) {return LONG_PRESS_POWER_SHUT_OFF_NO_CONFIRM;}return mLongPressOnPowerBehavior;
}

从上面的代码可以看出，终端是否支持长按行为，最终将由mLongPressOnPowerBehavior决定。

.........
mLongPressOnPowerBehavior = mContext.getResources().getInteger(com.android.internal.R.integer.config_longPressOnPowerBehavior);
.........

mLongPressOnPowerBehavior将在PhoneWindowManager初始化时，通过读取资源文件得到，一般情况下应该为1。
于是，hasLongPressOnPowerBehavior的值返回true，即终端支持Power键长按。

2、MSG_POWER_LONG_PRESS的处理
从上面的代码，我们知道亮屏时按Power键，会触发延迟的MSG_POWER_LONG_PRESS消息。
如果在MSG_POWER_LONG_PRESS超时前，Power键未被释放掉，那么此次操作被定义为长按Power键。

MSG_POWER_LONG_PRESS对应的处理函数为powerLongPress：

private void powerLongPress() {//也是由资源文件得到，默认为1，即LONG_PRESS_POWER_GLOBAL_ACTIONSfinal int behavior = getResolvedLongPressOnPowerBehavior();switch (behavior) {case LONG_PRESS_POWER_NOTHING:break;case LONG_PRESS_POWER_GLOBAL_ACTIONS:mPowerKeyHandled = true;//感觉这里是：终端对接收的事件处理后，给用户一个反馈信息//performHapticFeedbackLw主要进行震动反馈，例如按键后，终端震动一下//不同的事件，定义了不同的震动模式if (!performHapticFeedbackLw(null, HapticFeedbackConstants.LONG_PRESS, false)) {//如果没有震动反馈，这里尝试进行声音的反馈，例如响一下按键音performAuditoryFeedbackForAccessibilityIfNeed();}//弹出选择关机还是重启的对话框showGlobalActionsInternal();break;.........}
}

3、wakeUpFromPowerKey
在息屏的状态下按下Power键，将调用wakeUpFromPowerKey函数唤醒系统：

private void wakeUpFromPowerKey(long eventTime) {//从config.xml来看，mAllowTheaterModeWakeFromPowerKey默认为truewakeUp(eventTime, mAllowTheaterModeWakeFromPowerKey, "android.policy:POWER");
}private boolean wakeUp(long wakeTime, boolean wakeInTheaterMode, String reason) {//取数据库的值final boolean theaterModeEnabled = isTheaterModeEnabled();//按Power键时，条件返回falseif (!wakeInTheaterMode && theaterModeEnabled) {return false;}//看来唤醒时，将退出剧院模式if (theaterModeEnabled) {Settings.Global.putInt(mContext.getContentResolver(),Settings.Global.THEATER_MODE_ON, 0);}//最终将调用到PMS的wakeUp函数mPowerManager.wakeUp(wakeTime, reason);return true;
}

我们跟进一下PMS的wakeUp函数：

public void wakeUp(long eventTime, String reason, String opPackageName) {..........try {wakeUpInternal(eventTime, reason, uid, opPackageName, uid);} finally {...............}
}private void wakeUpInternal(long eventTime, String reason, int uid, String opPackageName,int opUid) {synchronized (mLock) {//更新Wakefullness的状态为WAKEFULNESS_AWAKE，记录一次UserActivityif (wakeUpNoUpdateLocked(eventTime, reason, uid, opPackageName, opUid)) {//如之前博客所述，对整个电源状态进行一次调整，将在需要时点亮屏幕updatePowerStateLocked();}}
}

二、interceptPowerKeyUp
interceptPowerKeyUp处理松开Power键后的流程：

private void interceptPowerKeyUp(KeyEvent event, boolean interactive, boolean canceled) {//事件被取消，或者在按下Power键时，该事件已被消耗掉//那么就不用继续处理final boolean handled = canceled || mPowerKeyHandled;mScreenshotChordPowerKeyTriggered = false;//退出截屏cancelPendingScreenshotChordAction();//取消MSG_POWER_LONG_PRESS事件，即在一定事件内Power键弹起，则表示这一次不是长按Power键cancelPendingPowerKeyAction();//从之前的代码，我们知道除了特殊功能外//灭屏按Power键或亮屏长按时，均会消耗掉Power事件//因此，只有亮屏短按Power键需要进行处理if (!handled) {// Figure out how to handle the key now that it has been released.// 记录短按的次数mPowerKeyPressCounter += 1;final int maxCount = getMaxMultiPressPowerCount();final long eventTime = event.getDownTime();if (mPowerKeyPressCounter < maxCount) {// This could be a multi-press.  Wait a little bit longer to confirm.// Continue holding the wake lock.// 与之前interceptPowerKeyDown，处理Power键被多次按下场景对应// 每次被按下，均发送MSG_POWER_DELAYED_PRESS消息// 实际上maxCount为1，该不会进入该分支Message msg = mHandler.obtainMessage(MSG_POWER_DELAYED_PRESS,interactive ? 1 : 0, mPowerKeyPressCounter, eventTime);msg.setAsynchronous(true);mHandler.sendMessageDelayed(msg, ViewConfiguration.getDoubleTapTimeout());return;}//1、No other actions.  Handle it immediately.powerPress(eventTime, interactive, mPowerKeyPressCounter);}// 2、Done.  Reset our state.finishPowerKeyPress();
}

1、powerPress
我们跟进一下powerPress函数：

private void powerPress(long eventTime, boolean interactive, int count) {if (mScreenOnEarly && !mScreenOnFully) {Slog.i(TAG, "Suppressed redundant power key press while "+ "already in the process of turning the screen on.");return;}if (count == 2) {//原生不进入powerMultiPressAction(eventTime, interactive, mDoublePressOnPowerBehavior);} else if (count == 3) {//原生不进入powerMultiPressAction(eventTime, interactive, mTriplePressOnPowerBehavior);} else if (interactive && !mBeganFromNonInteractive) {//亮屏时，将进入该分支//mShortPressOnPowerBehavior被配置为1switch (mShortPressOnPowerBehavior) {case SHORT_PRESS_POWER_NOTHING:break;case SHORT_PRESS_POWER_GO_TO_SLEEP://最终调用到PMS的goToSleep函数mPowerManager.goToSleep(eventTime,PowerManager.GO_TO_SLEEP_REASON_POWER_BUTTON, 0);break;...............}}
}

从上面的代码可以看出，在亮屏状态下，短按一下Power键，最终将调用到PMS的goToSleep函数，使终端进入到休眠状态，与实际情况一致。
我们跟进一下PMS的goToSleep函数：

public void goToSleep(long eventTime, int reason, int flags) {............try {goToSleepInternal(eventTime, reason, flags, uid);} finally {...............}
}private void goToSleepInternal(long eventTime, int reason, int flags, int uid) {synchronized (mLock) {//没有触发用户事件，将mWakefullness置为WAKEFULNESS_DOZINGif (goToSleepNoUpdateLocked(eventTime, reason, flags, uid)) {//执行整体的电源状态更新，将熄灭屏幕updatePowerStateLocked();}
}

2、finishPowerKeyPress

每当处理一次完整的Power键按下、弹出操作后，interceptPowerKeyUp调用finishPowerKeyPress进行最后的状态复位操作：

private void finishPowerKeyPress() {mBeganFromNonInteractive = false;mPowerKeyPressCounter = 0;if (mPowerKeyWakeLock.isHeld()) {mPowerKeyWakeLock.release();}
}

从代码可以看出，主要的工作其实就是将状态变量恢复为初始值，同时释放掉最初申请的锁。

三、总结

整个Power按键的主要处理流程如上图所示。结合手机的实际情况，整个逻辑还是非常好理解的。

原文地址：http://blog.csdn.net/gaugamela/article/details/52912382

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