How Android handles KEY_POWER?

最新推荐文章于 2024-10-22 17:49:52 发布

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最新推荐文章于 2024-10-22 17:49:52 发布

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Within axp202 device driver, the driver sends KEY_POWER to Android when user press POWER button on board, no matter what a long OR short press.
But Android responds differently:
long press: pop up a POWER OFF dialogue box.

short press: go to sleep directly.

WHY?

       Enable DEBUG in driver:
       short press:       interrupt -- short press -- rising edge -- falling edge -- timer handler
       long press:       interrupt -- long press -- falling edge -- timer handler

       The difference lies in there is no rising edge within 'long press' procedure,
       And,
       In Android, (frameworks/base/policy/src/com/android/internal/policy/impl/PhoneWindowManager.java)

   public int interceptKeyBeforeQueueing(KeyEvent event,
                                                                                   int policyFlags,
                                                                                   boolean isScreenOn) {
    ......
    switch (keyCode) {
    ......
    case KeyEvent.KEYCODE_POWER: {
        if (down) { // 如果是按下键
                if (isScreenOn && !mPowerKeyTriggered
                    && (event.getFlags() & KeyEvent.FLAG_FALLBACK) == 0) {
                    mPowerKeyTriggered = true; // 按键触发为true
                    mPowerKeyTime = event.getDownTime(); // 记录事件时间
                    cancelPendingRingerChordAction(); // 结束音量长按事件
                    interceptScreenshotChord(); // 判断是否是截屏处理
        }

        // 当电话铃响起时，则会静音，而正在通话时，则会挂掉电话
        ITelephony telephonyService = getTelephonyService();
        boolean hungUp = false;
        if (telephonyService != null) {
               ......
        }

        ......

        // 延迟固定时间触发长按事件，长按事件主要是弹出全局对话框
        interceptPowerKeyDown(!isScreenOn || hungUp
                           || mVolumeDownKeyTriggered || mVolumeUpKeyTriggered);
        }
        else { //进入sleep模式
        mPowerKeyTriggered = false;
        cancelPendingScreenshotChordAction();
        if (interceptPowerKeyUp(canceled || mPendingPowerKeyUpCanceled)) {
            result = (result & ~ACTION_POKE_USER_ACTIVITY) | ACTION_GO_TO_SLEEP;
        }


        CONCLUSION:   The dirver always sends KEY_POWER to system no matter what
                               the user's activity (long/short press) is. The system will
                               handle the event according to key code (KEY_POWER) as well
                               as key status (up/down).