按键处理属于本书后续将会分析的输入系统的范围，此处摘出和Power键相关的代码进行分析，代码如下： **com_android_server_InputManager.cpp::handleInterceptActions** ~~~ voidNativeInputManager::handleInterceptActions(jint wmActions, nsecs_t when, uint32_t& policyFlags) { //按下Power键并松开后，将设置wmActions为WM_ACTION_GO_TO_SLEEP，表示需要休眠 if(wmActions & WM_ACTION_GO_TO_SLEEP) { //利用JNI调用PMS的goToSleep函数 android_server_PowerManagerService_goToSleep(when); } //一般的输入事件将触发userActivity函数被调用，此时将唤醒手机 if(wmActions & WM_ACTION_POKE_USER_ACTIVITY) { //利用JNI调用PMS的userActivity函数。相关内容在前一节已经分析过了 android_server_PowerManagerService_userActivity(when, POWER_MANAGER_BUTTON_EVENT); } ......//其他处理 } ~~~ 由以上代码中的注释可知，当按下Power键并松开时[^write]，将触发PMS的goToSleep函数被调用。下面来看goToSleep函数的代码： **PowerManagerService.java::goToSleep** ~~~ public void goToSleep(long time) { goToSleepWithReason(time,WindowManagerPolicy.OFF_BECAUSE_OF_USER); } public void goToSleepWithReason(long time, intreason) { mContext.enforceCallingOrSelfPermission(//检查调用进程是否有DEVICE_POWER权限 android.Manifest.permission.DEVICE_POWER,null); synchronized (mLocks) { goToSleepLocked(time, reason);//调用goToSleepLocked函数 } } ~~~ **PowerManagerService.java::goToSleepLocked** ~~~ private void goToSleepLocked(long time, intreason) { if(mLastEventTime <= time) { mLastEventTime = time; mWakeLockState = SCREEN_OFF; int N= mLocks.size(); intnumCleared = 0; boolean proxLock = false; for(int i=0; i<N; i++) { WakeLock wl = mLocks.get(i); if(isScreenLock(wl.flags)) { if(((wl.flags & LOCK_MASK) == PowerManager.PROXIMITY_SCREEN_OFF_WAKE_LOCK) && reason == WindowManagerPolicy.OFF_BECAUSE_OF_PROX_SENSOR) { proxLock = true;//判断goToSleep的原因是否与接近传感器有关 } else{ mLocks.get(i).activated = false;//禁止和屏幕相关的WakeLock numCleared++; } }// isScreenLock判断结束 }//for循环结束 if(!proxLock) { mProxIgnoredBecauseScreenTurnedOff = true; } mStillNeedSleepNotification = true; mUserState = SCREEN_OFF; setPowerState(SCREEN_OFF, false, reason);//关闭屏幕 cancelTimerLocked();//从mHandler中撤销mTimeoutTask任务 } } ~~~ 掌握了前面的基础知识就会感到Power键的处理流程真的是很简单，读者是否也有同感呢？ [^write]: 必须在一定时间内完成按下和松开Power键的操作，否则系统会认为是关机操作。详情将在卷Ⅲ输入系统一章的分析。