android手機中power鍵按下後控制著螢幕的喚醒與休眠，可以說是最重要的按鍵。它的運轉流程跟以下幾個檔案有關

InputDispatcher.cpp

void InputDispatcher::notifyKey(const NotifyKeyArgs* args)

com_android_server_input_InputManagerService.cpp

void NativeInputManager::interceptKeyBeforeQueueing(const KeyEvent* keyEvent,
        uint32_t& policyFlags) 

void NativeInputManager::handleInterceptActions(jint wmActions, nsecs_t when,
        uint32_t& policyFlags) 

PhoneWindowManager.java

   public int interceptKeyBeforeQueueing(KeyEvent event, int policyFlags, boolean isScreenOn)

com_android_server_power_PowerManagerService.cpp

  void android_server_PowerManagerService_goToSleep(nsecs_t eventTime) 

  void android_server_PowerManagerService_wakeUp(nsecs_t eventTime)

PowerManagerService.java.

   private void wakeUpFromNative(long eventTime)

   private void goToSleepFromNative(long eventTime, int reason)

按以上排列的順序一路走下來，然後在PowerManagerService中設定相關標誌位，開關螢幕