从InputManagerService分析我们知道，当按下手机的Power键之后，按键事件会传到InputDispatcher 的notifyKey 方法，然后调用到调用了NativeInputManager的interceptKeyBeforeQueueing函数，最终在这个函数中会调用到PhoneWindowManager中的interceptKeyBeforeQueueing函数，以上主要属于InputManagerService的范畴，Power按键流程我们从PhoneWindowManager 的interceptKeyBeforeQueueing 方法开始分析。
方法interceptKeyBeforeQueueing关键步骤：
第一步：初始化关键变量
if (!mSystemBooted) {
return 0;
}
final boolean interactive = (policyFlags & FLAG_INTERACTIVE) != 0;
final boolean down = event.getAction() == KeyEvent.ACTION_DOWN;
final boolean canceled = event.isCanceled();
final int keyCode = event.getKeyCode();
final boolean isInjected = (policyFlags & WindowManagerPolicy.FLAG_INJECTED) != 0;首先判断系统是否启动完成，然后就是初始化一些关键变量
Interactive 表示屏幕是否点亮，这个变量表示PowerManagerService关于屏幕的状态
Down 表示是否是ActionDown事件
Canceled 事件是否取消
keyCode 按键编码
第二步，根据interative的状态的处理一些基本逻辑
if (interactive || (isInjected && !isWakeKey)) {
//事件传递给用户
result = ACTION_PASS_TO_USER;
isWakeKey = false;
} else if (!interactive && shouldDispatchInputWhenNonInteractive()) {
result = ACTION_PASS_TO_USER;
} else {
result = 0;
if (isWakeKey && (!down || !isWakeKeyWhenScreenOff(keyCode))) {
isWakeKey = false;
}
}
if (isValidGlobalKey(keyCode)
&& mGlobalKeyManager.shouldHandleGlobalKey(keyCode, event)) {
if (isWakeKey) {
//直接唤醒系统
wakeUp(event.getEventTime(), mAllowTheaterModeWakeFromKey, " android.policy:KEY");
}
return result;
}第三步，处理Power按键的事件
case KeyEvent.KEYCODE_POWER: {
result &= ~ACTION_PASS_TO_USER;
isWakeKey = false; // wake-up will be handled separately
if (down) {
Power键按下
interceptPowerKeyDown(event, interactive);
} else {
Power键释放
interceptPowerKeyUp(event, interactive, canceled);
}
break;
}首先是Power按键的事件的话，不再分发到应用，如果是ActionDown事件执行InterceptPowerKeyDown()方法，如果是ActionUP事件则执行InterceptPowerKeyUp()方法
下一步继续分析interceptPowerKeyDown方法
private void interceptPowerKeyDown(KeyEvent event, boolean interactive) {
if (!mPowerKeyWakeLock.isHeld()) {
mPowerKeyWakeLock.acquire();
}获取Power按键的锁，直到释放Power键
……
if (interactive && !mScreenshotChordPowerKeyTriggered
&& (event.getFlags() & KeyEvent.FLAG_FALLBACK) == 0) {
mScreenshotChordPowerKeyTriggered = true;
mScreenshotChordPowerKeyTime = event.getDownTime();
interceptScreenshotChord();
}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
TelecomManager telecomManager = getTelecommService();
boolean hungUp = false;
if (telecomManager != null) {
if (telecomManager.isRinging()) {
telecomManager.silenceRinger();
} else if ((mIncallPowerBehavior
& Settings.Secure.INCALL_POWER_BUTTON_BEHAVIOR_HANGUP) != 0
&& telecomManager.isInCall() && interactive) {
hungUp = telecomManager.endCall();
}
}如果有电话拨入，且电话铃声响起的话，这个时候按Power键，设置电话响铃静音
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
……
mPowerKeyHandled = hungUp || mScreenshotChordVolumeDownKeyTriggered
|| mScreenshotChordVolumeUpKeyTriggered || gesturedServiceIntercepted;如果按Power按键执行了截图功能或者电话静音或者挂断电话等功能后，Power事件不在传递，表示已经消耗掉了Power事件
if (!mPowerKeyHandled) {如果未消耗掉Power事件，继续执行此处逻辑
分为两种情况
1， 当前是亮屏状态
2， 当前是灭屏状态
if (interactive) {
//是否支持长按功能
if (hasLongPressOnPowerBehavior()) {
Message msg = mHandler.obtainMessage(MSG_POWER_LONG_PRESS);
msg.setAsynchronous(true);
//发送MSG_POWER_LONG_PRESS消息，有Handler来处理
mHandler.sendMessageDelayed(msg,
ViewConfiguration.get(mContext).getDeviceGlobalActionKeyTimeout());
}
} else {
//当前灭屏状态，此时按Power键，先唤醒系统
wakeUpFromPowerKey(event.getDownTime());
//是否支持灭屏下的长按功能
if (mSupportLongPressPowerWhenNonInteractive && hasLongPressOnPowerBehavior()) {
Message msg = mHandler.obtainMessage(MSG_POWER_LONG_PRESS);
msg.setAsynchronous(true);
mHandler.sendMessageDelayed(msg,
ViewConfiguration.get(mContext).getDeviceGlobalActionKeyTimeout());
mBeganFromNonInteractive = true;
} else {
final int maxCount = getMaxMultiPressPowerCount();
if (maxCount <= 1) {
mPowerKeyHandled = true;
} else {
mBeganFromNonInteractive = true;
}
}
}
}
}当前亮屏状态
首先判断是否支持长按的行为
先来看看hasLongPressOnPowerBehavior函数
private boolean hasLongPressOnPowerBehavior() {
return getResolvedLongPressOnPowerBehavior() != LONG_PRESS_POWER_NOTHING;
}再来看看getResolvedLongPressOnPowerBehavior函数
private int getResolvedLongPressOnPowerBehavior() {
if (FactoryTest.isLongPressOnPowerOffEnabled()) {
return LONG_PRESS_POWER_SHUT_OFF_NO_CONFIRM;
}
return mLongPressOnPowerBehavior;
}由于systemProperty中的factory.long_press_power_off" 配置为0，所以不支持灭屏长按功能，。因此只要看mLongPressOnPowerBehavior这个变量
mLongPreesOnPowerBehavior 默认配置获取为
mLongPressOnPowerBehavior = mContext.getResources().getInteger(
com.android.internal.R.integer.config_longPressOnPowerBehavior);config_longPressOnPowerBehavior 默认值为1，所以 mLongPressOnPowerBehavior = 1， 最后hasLongPressOnPowerBehavior返回 true
if (hasLongPressOnPowerBehavior()) {
Message msg = mHandler.obtainMessage(MSG_POWER_LONG_PRESS);
msg.setAsynchronous(true);
mHandler.sendMessageDelayed(msg,
ViewConfiguration.get(mContext).getDeviceGlobalActionKeyTimeout());
}当hasLongPressOnPowerBehavior返回true，则发送MSG_POWER_LONG_PRESS的Handler消息，Handler处理消息调用 powerLongPress()方法，接着我们来看下Handler处理消息的逻辑
private void powerLongPress() {
final int behavior = getResolvedLongPressOnPowerBehavior();
switch (behavior) {
case LONG_PRESS_POWER_NOTHING:
break;
case LONG_PRESS_POWER_GLOBAL_ACTIONS:
mPowerKeyHandled = true;
if (!performHapticFeedbackLw(null, HapticFeedbackConstants.LONG_PRESS, false)) {
performAuditoryFeedbackForAccessibilityIfNeed();
}
showGlobalActionsInternal();
break;
……由以上的分析指导getResolvedLongPressOnPowerBehavior的值为1，所以执行case LONG_PRESS_POWER_GLOBAL_ACTIONS,
将mPowerKeyHandled的值设置为true，表示处理了PowerDown事件，showGlobalActionsInternal()方法弹出关机，重启对话框
1. 当屏幕是灭屏状态
首先执行wakeUpFromPowerKey方法，唤醒手机系统，最终调用mPowerManager.wakeUp(wakeTime, reason)来唤醒手机
然后mSupportLongPressPowerWhenNonInteractive默认不支持，所以默认执行
final int maxCount = getMaxMultiPressPowerCount();
if (maxCount <= 1) {
mPowerKeyHandled = true;
} else {
mBeganFromNonInteractive = true;
}getMaxMultiPressPowerCount() ==1，默认不支持对此按键，所以将mPowerKeyHandled设置为true，表示处理了PowerDown事件
2，处理PowerUp事件
PowerUp事件也分为两种情况，分别对应PowerDown的亮屏和灭屏两种情况private void interceptPowerKeyUp(KeyEvent event, boolean interactive, boolean canceled) {
final boolean handled = canceled || mPowerKeyHandled;
……
if (!handled) {
mPowerKeyPressCounter += 1;
final int maxCount = getMaxMultiPressPowerCount();
final long eventTime = event.getDownTime();
if (mPowerKeyPressCounter < maxCount) {
Message msg = mHandler.obtainMessage(MSG_POWER_DELAYED_PRESS,
interactive ? 1 : 0, mPowerKeyPressCounter, eventTime);
msg.setAsynchronous(true);
mHandler.sendMessageDelayed(msg, ViewConfiguration.getDoubleTapTimeout());
return;
}
powerPress(eventTime, interactive, mPowerKeyPressCounter);
}
finishPowerKeyPress();
}在灭屏的时候，和亮屏长按的时候mPowerKeyHandled最后设置为true，即handle为true，直接执行finishPowerKeyPress方法，释放mPowerKeyWakeLock
在亮屏短按的时候，handled为false，由以上分析，手机默认不支持多次按键所以maxCount为1，mPowerKeyPressCounter=1，所以直接执行powerPress方法
private void powerPress(long eventTime, boolean interactive, int count) {
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:
mPowerManager.goToSleep(eventTime,
PowerManager.GO_TO_SLEEP_REASON_POWER_BUTTON, 0);
break;
case SHORT_PRESS_POWER_REALLY_GO_TO_SLEEP:
mPowerManager.goToSleep(eventTime,
PowerManager.GO_TO_SLEEP_REASON_POWER_BUTTON,
PowerManager.GO_TO_SLEEP_FLAG_NO_DOZE);
break;
case SHORT_PRESS_POWER_REALLY_GO_TO_SLEEP_AND_GO_HOME:
mPowerManager.goToSleep(eventTime,
PowerManager.GO_TO_SLEEP_REASON_POWER_BUTTON,
PowerManager.GO_TO_SLEEP_FLAG_NO_DOZE);
launchHomeFromHotKey();
break;
case SHORT_PRESS_POWER_GO_HOME:
launchHomeFromHotKey(true /* awakenFromDreams */, false
break;
}
}
}由于mPowerKeyPressCounter 为1，所以执行case SHORT_PRESS_POWER_GO_TO_SLEEP,调用mPowerManager.goToSleep休眠系统
Power按键流程总结
Power按键
1.亮屏 down
长按 弹出关闭重启对话框
短按 不做处理
亮屏 up
长按 不做处理
短按 调用goToSleep休眠系统
2. 灭屏 down
调用wakeup 唤醒系统
灭屏 up
不做处理