按鍵先在PhoneWindowManager.java處理。

音量鍵：

case KeyEvent.KEYCODE_VOLUME_DOWN:
            case KeyEvent.KEYCODE_VOLUME_UP:
            case KeyEvent.KEYCODE_VOLUME_MUTE: {
                if (keyCode == KeyEvent.KEYCODE_VOLUME_DOWN) {
                    if (down) {
                        if (interactive && !mScreenshotChordVolumeDownKeyTriggered
                                && (event.getFlags() & KeyEvent.FLAG_FALLBACK) == 0) {
                            mScreenshotChordVolumeDownKeyTriggered = true;
                            mScreenshotChordVolumeDownKeyTime = event.getDownTime();
                            mScreenshotChordVolumeDownKeyConsumed = false;
                            cancelPendingPowerKeyAction();
                            interceptScreenshotChord();
                        }
                    } else {
                        mScreenshotChordVolumeDownKeyTriggered = false;
                        cancelPendingScreenshotChordAction();
                    }
                }
 

if (interactive && !mScreenshotChordPowerKeyTriggered
                && (event.getFlags() & KeyEvent.FLAG_FALLBACK) == 0) {
            mScreenshotChordPowerKeyTriggered = true;
            mScreenshotChordPowerKeyTime = event.getDownTime();
            interceptScreenshotChord();
        }
 

private void interceptScreenshotChord() {
        if (mScreenshotChordEnabled
                && mScreenshotChordVolumeDownKeyTriggered && mScreenshotChordPowerKeyTriggered
                && !mScreenshotChordVolumeUpKeyTriggered) {
            final long now = SystemClock.uptimeMillis();
            if (now <= mScreenshotChordVolumeDownKeyTime + SCREENSHOT_CHORD_DEBOUNCE_DELAY_MILLIS
                    && now <= mScreenshotChordPowerKeyTime
                            + SCREENSHOT_CHORD_DEBOUNCE_DELAY_MILLIS) {
                mScreenshotChordVolumeDownKeyConsumed = true;
                cancelPendingPowerKeyAction();

                mHandler.postDelayed(mScreenshotRunnable, getScreenshotChordLongPressDelay());
            }
        }		
    }
 

為了防止截圖的時候音量下鍵生效出現調節音量的dialog，有

 if (keyCode == KeyEvent.KEYCODE_VOLUME_DOWN
                    && mScreenshotChordVolumeDownKeyConsumed) {
                if (!down) {
                    mScreenshotChordVolumeDownKeyConsumed = false;
                }
                return -1;
            }

在監聽到home鍵的地方加：

if (isScreenOn() && !mBackBtnDownKeyTriggered
                            && (event.getFlags() & KeyEvent.FLAG_FALLBACK) == 0) {
                        mBackBtnDownKeyTriggered = true;
                        mBackkeyTime = event.getDownTime();
                        mBackDownKeyConsumedByScreenshotChord = false;
                        cancelPendingPowerKeyAction();
                        interceptScreenshotChord();
                    }
                }

if (mBackBtnDownKeyTriggered && mScreenshotChordPowerKeyTriggered ) {
            final long now = SystemClock.uptimeMillis();
			//android.util.Log.i("cenon","interceptScreenshotChord  mBackkeyTime="+mBackkeyTime+"  now="+now+" mScreenshotChordPowerKeyTime="+mScreenshotChordPowerKeyTime);
            if (now <= mBackkeyTime+ SCREENSHOT_CHORD_DEBOUNCE_DELAY_MILLIS
                    && now <= mScreenshotChordPowerKeyTime + SCREENSHOT_CHORD_DEBOUNCE_DELAY_MILLIS) {
                //android.util.Log.i("cenon","mScreenshotRunnable post");
                mBackDownKeyConsumedByScreenshotChord = true;
                cancelPendingPowerKeyAction();

                mHandler.postDelayed(mScreenshotRunnable,
                        ViewConfiguration.getGlobalActionKeyTimeout());
            }
        }

if (keyCode == KeyEvent.KEYCODE_HOME
                    && mBackDownKeyConsumedByScreenshotChord 
                    && android.provider.Settings.System.getInt(mContext.getContentResolver(), "home_button_layout_flag", 0) == 0) {//modified by wangyouyou
                if (!down) {
                    mBackDownKeyConsumedByScreenshotChord = false;
                }
                return -1;
            }

其實就是仿造原始碼寫，當然擡手的時候要將相應的boolen值改為false

protected boolean onKeyUp(int featureId, int keyCode, KeyEvent event) {
        final KeyEvent.DispatcherState dispatcher =
                mDecor != null ? mDecor.getKeyDispatcherState() : null;
        if (dispatcher != null) {
            dispatcher.handleUpEvent(event);
        }
        //Log.i(TAG, "Key up: repeat=" + event.getRepeatCount()
        //        + " flags=0x" + Integer.toHexString(event.getFlags()));

        switch (keyCode) {
            case KeyEvent.KEYCODE_VOLUME_UP:
            case KeyEvent.KEYCODE_VOLUME_DOWN: {
                final int flags = /*AudioManager.FLAG_PLAY_SOUND |*/ AudioManager.FLAG_VIBRATE // delete by csc
                        | AudioManager.FLAG_FROM_KEY;
                // If we have a session send it the volume command, otherwise
                // use the suggested stream.
                if (mMediaController != null) {
                    mMediaController.adjustVolume(0, flags);
                } else {
                    MediaSessionLegacyHelper.getHelper(getContext()).sendAdjustVolumeBy(
                            mVolumeControlStreamType, 0, flags);
                }
                return true;
            }
            case KeyEvent.KEYCODE_VOLUME_MUTE: {
                // Similar code is in PhoneFallbackEventHandler in case the window
                // doesn't have one of these.  In this case, we execute it here and
                // eat the event instead, because we have mVolumeControlStreamType
                // and they don't.
                getAudioManager().handleKeyUp(event, mVolumeControlStreamType);
                return true;
            }