Android 7.0 Power 按键处理流程

Android 7.0  Power 按键处理流程

Power按键的处理逻辑由PhoneWindowManager来完成，本文只关注PhoneWindowManager中与Power键相关的内容，其他系统按键的处理类似也是在PhoneWindowManager中处理的。理解了power按键的处理再看其他系统按键的逻辑会容易的多也简单的多。

一、Power按键的上报

Power按键的上报流程与其余的按键处理流程一致，在按下power按键后驱动上报按键经InputManagerService处理按键事件，最终将会传递到PhoneWindowManager的interceptKeyBeforeQueueing函数来做具体的业务逻辑。（具体处理 Input system 做详细介绍）本篇侧重power的业务逻辑处理，这里简单介绍下power 按键的上报流程如下图：

1-4：在power 按键按下时驱动会上报按键事件，EventHub读取到事件后转给InputReader来做处理。

5-9：InputReader根据上报的事件类型（此处是按键事件），交给KeyBoardInputMapper来做按键映射，根据驱动上报的按键值来映射为android framework的按键值（即KeyEvent.KEYCODE_POWER 和相应的flag），并通知上层。

10-16：经过层调用最后到PhoneWindowManager的interceptKeyBeforeQueueing（）函数来做具体的业务处理。这是本文的重点，下面具体分析。

17-18：通过PowerManagerService来唤醒系统。

二、Power 按键处理

PhoneWindowManager的interceptKeyBeforeQueueing（）函数处理具体的业务逻辑，从这个函数开始进行分析。

按键的事件分为按下和抬起两个，framework的处理也是分为按下和抬起来不同的事件分别由不同的函数来处理。

public int interceptKeyBeforeQueueing(KeyEvent event, int policyFlags) {
    if (!mSystemBooted) {
        // If we have not yet booted, don't let key events do anything.
        return ;
    }
    //是否点亮屏幕
    final boolean interactive = (policyFlags & FLAG_INTERACTIVE) != ;
    final boolean down = event.getAction() == KeyEvent.ACTION_DOWN;
    final boolean canceled = event.isCanceled();
    //获取按键对应的android framework层的按键编码
    final int keyCode = event.getKeyCode();
    .................
    switch (keyCode) {
        ...........
        case KeyEvent.KEYCODE_POWER: {
            result &= ~ACTION_PASS_TO_USER;
            isWakeKey = false; // wake-up will be handled separately
            if (down) {
                //处理Power键按下
                interceptPowerKeyDown(event, interactive);
            } else {
                //处理Power键松开
                interceptPowerKeyUp(event, interactive, canceled);
            }
             break;
        }
    }
    ..............
    if (isWakeKey) {
        //按power键时，isWakeKey置为false，于是不会调用wakeUp函数，即不会唤醒系统点亮屏幕
        wakeUp(event.getEventTime(), mAllowTheaterModeWakeFromKey, "android.policy:KEY");
    }
    return result;
}

扩展：由上可知 isWakeKey 用来控制是否唤醒系统并点亮屏幕，如果需要添加按键需要实现点亮屏幕功能，可以在此处理 ^_^。

接下来，我们分别看一下interceptPowerKeyDown和interceptPowerKeyUp函数。

1、Power按键按下（interceptPowerKeyDown）

interceptPowerKeyDown（）用于处理按下Power键(还未抬起)对应的事件。

A: Power按键按下处理时序图

处理流程：

1）  判断是否power按键与音量按键“同时”按下需要做截屏动作，是则触发截屏。

2）  是否为响铃或通话状态，是则执行与之相关配置的动作（默认响铃会静音，如果设置按power挂断电话则挂断）。

3）  判断是否为长按，是则根据配置执行长按行为的动作。

B: 代码分析

private void interceptPowerKeyDown(KeyEvent event, boolean interactive) {
    // Hold a wake lock until the power key is released.
    // mPowerKeyWakeLock为PARTIAL_WAKE_LOCK级别的锁
    if (!mPowerKeyWakeLock.isHeld()) {
        //将调用到PMS的acquire WakeLock流程
        mPowerKeyWakeLock.acquire();
    }
    // Cancel multi-press detection timeout.
    //处理多次按power键的场景
    //每次power up时，发送MSG_POWER_DELAYED_PRESS的延迟消息
    //如果延迟消息被处理，说明一次完整的Power键处理结束（按下去，弹起来）
    if (mPowerKeyPressCounter != ) {
        mHandler.removeMessages(MSG_POWER_DELAYED_PRESS);

    }

    // Detect user pressing the power button in panic when an application has
    // taken over the whole screen.

    boolean panic = mImmersiveModeConfirmation.onPowerKeyDown(interactive,
        SystemClock.elapsedRealtime(), isImmersiveMode(mLastSystemUiFlags));
    if (panic) {
        mHandler.post(mHiddenNavPanic);
    }

    // Latch power key state to detect screenshot chord.
    //屏状态，满足触发截屏的条件则触发截屏功能

    if (interactive && !mScreenshotChordPowerKeyTriggered
            && (event.getFlags() & KeyEvent.FLAG_FALLBACK) == ) {
        mScreenshotChordPowerKeyTriggered = true;
        mScreenshotChordPowerKeyTime = event.getDownTime();
        //触发截屏功能
        interceptScreenshotChord();
    }

    // Stop ringing or end call if configured to do so when power is pressed.

    TelecomManager telecomManager = getTelecommService();
    boolean hungUp = false;
    if (telecomManager != null) {
        if (telecomManager.isRinging()) {
            // Pressing Power while there's a ringing incoming
            // call should silence the ringer.
            //有电话拨入且响铃状态，默认设置静音
            telecomManager.silenceRinger();
        } else if ((mIncallPowerBehavior &Settings.Secure.INCALL_POWER_BUTTON_BEHAVIOR_HANGUP) != && telecomManager.isInCall() && interactive) {

            // Otherwise, if "Power button ends call" is enabled,
            // the Power button will hang up any current active call.
            //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
            hungUp = telecomManager.endCall();
        }
    }

    GestureLauncherService gestureService = LocalServices.getService(
            GestureLauncherService.class);
    boolean gesturedServiceIntercepted = false;
    if (gestureService != null) {
        //手势对应的服务，尝试拦截处理Power键动作事件
        gesturedServiceIntercepted = gestureService.interceptPowerKeyDown(event, interactive,mTmpBoolean);

        if (mTmpBoolean.value && mGoingToSleep) {
            mCameraGestureTriggeredDuringGoingToSleep = true;
        }
    }

    // If the power key has still not yet been handled, then detect short
    // press, long press, or multi press and decide what to do.
    mPowerKeyHandled = hungUp ||mScreenshotChordVolumeDownKeyTriggered||mScreenshotChordVolumeUpKeyTriggered || gesturedServiceIntercepted;

    //Power键事件未被消耗掉
    if (!mPowerKeyHandled) {
       //屏幕还是亮的
        if (interactive) {
            // When interactive, we're already awake.
            // Wait for a long press or for the button to be released to decide what to do.
            //1、 判断是否支持长按的行为
            if (hasLongPressOnPowerBehavior()) {
            //2、 亮屏状态，长按Power键将触发MSG_POWER_LONG_PRESS消息

                Message msg = mHandler.obtainMessage(MSG_POWER_LONG_PRESS);

                msg.setAsynchronous(true);
                mHandler.sendMessageDelayed(msg,
                        ViewConfiguration.get(mContext).getDeviceGlobalActionKeyTimeout());

            }

        } else {
            //3、灭屏状态先唤醒系统，这个会调用到PMS的wakeUp
            wakeUpFromPowerKey(event.getDownTime());

            //支持熄屏长按，mSupportLongPressPowerWhenNonInteractive读资源文件得到，默认为false

            if (mSupportLongPressPowerWhenNonInteractive && hasLongPressOnPowerBehavior()) {

                Message msg = mHandler.obtainMessage(MSG_POWER_LONG_PRESS);

                msg.setAsynchronous(true);
                mHandler.sendMessageDelayed(msg,                   ViewConfiguration.get(mContext).getDeviceGlobalActionKeyTimeout());

                mBeganFromNonInteractive = true;

            } else {

                //默认返回1

                final int maxCount = getMaxMultiPressPowerCount();

                if (maxCount <= ) {

                    //息屏时，按下power键（不弹起），仅消耗掉该事件

                    mPowerKeyHandled = true;

                } else {
                    mBeganFromNonInteractive = true;

                }
            }
        }
    }
}

1）是否支持长按hasLongPressOnPowerBehavior （）

hasLongPressOnPowerBehavior负责判断终端是否支持长按的行为，通过读取系统的配置文件来判断。

private boolean hasLongPressOnPowerBehavior() {

    return getResolvedLongPressOnPowerBehavior() != LONG_PRESS_POWER_NOTHING;

}

private int getResolvedLongPressOnPowerBehavior() {
    //取决与系统属性"factory.long_press_power_off"，此处默认为false
    if (FactoryTest.isLongPressOnPowerOffEnabled()) {
        return LONG_PRESS_POWER_SHUT_OFF_NO_CONFIRM;
    }
    return mLongPressOnPowerBehavior;
}

从上面的代码可以看出，终端是否支持长按行为，最终将由mLongPressOnPowerBehavior决定。
.........
mLongPressOnPowerBehavior = mContext.getResources().getInteger(      com.android.internal.R.integer.config_longPressOnPowerBehavior);

.........

mLongPressOnPowerBehavior将在PhoneWindowManager初始化时，通过读取资源文件（定义在frameworks/base/res/res/values/config.xm 中）得到，一般情况下应该为1。 于是，hasLongPressOnPowerBehavior的值返回true，即终端支持Power键长按。

config.xm 中定义的power按键的长按、短按、双击 、三联按的行为

2）长按MSG_POWER_LONG_PRESS的处理

从上面的代码，在亮屏时按Power键，会触发延迟的MSG_POWER_LONG_PRESS消息。 如果在MSG_POWER_LONG_PRESS超时前，Power键未被释放掉，那么此次操作被定义为长按Power键。

MSG_POWER_LONG_PRESS对应的处理函数为powerLongPress：

private void powerLongPress() {
    //也是由资源文件得到，默认为1，即LONG_PRESS_POWER_GLOBAL_ACTIONS

    final int behavior = getResolvedLongPressOnPowerBehavior();
    switch (behavior) {
        case LONG_PRESS_POWER_NOTHING:
            break;
        case LONG_PRESS_POWER_GLOBAL_ACTIONS:
            mPowerKeyHandled = true;
            //performHapticFeedbackLw进行震动反馈，不同的事件，定义了不同的震动模式
            if (!performHapticFeedbackLw(null, HapticFeedbackConstants.LONG_PRESS, false)) {
                //如果没有震动反馈，尝试声音反馈，例如响一下按键音
                performAuditoryFeedbackForAccessibilityIfNeed();
            }
            //弹出选择关机还是重启的对话框
            showGlobalActionsInternal();
            break;
        case LONG_PRESS_POWER_SHUT_OFF:
        case LONG_PRESS_POWER_SHUT_OFF_NO_CONFIRM:
            mPowerKeyHandled = true;
            performHapticFeedbackLw(null, HapticFeedbackConstants.LONG_PRESS, false);
            //弹出系统关机界面
     sendCloseSystemWindows(SYSTEM_DIALOG_REASON_GLOBAL_ACTIONS);
            //调关机接口
            mWindowManagerFuncs.shutdown(behavior == LONG_PRESS_POWER_SHUT_OFF);
            break;
        .........
    }
}

3）唤醒系统点亮屏幕wakeUpFromPowerKey （）

在息屏的状态下按下Power键，将调用wakeUpFromPowerKey函数唤醒系统：

private void wakeUpFromPowerKey(long eventTime) {
    //从config.xml读mAllowTheaterModeWakeFromPowerKey默认为true
    wakeUp(eventTime, mAllowTheaterModeWakeFromPowerKey, "android.policy:POWER");

}

private boolean wakeUp(long wakeTime, boolean wakeInTheaterMode, String reason) {
    //取数据库的值
    final boolean theaterModeEnabled = isTheaterModeEnabled();
    //按Power键时，条件返回false
    if (!wakeInTheaterMode && theaterModeEnabled) {
        return false;
    }

    if (theaterModeEnabled) {
        Settings.Global.putInt(mContext.getContentResolver(),
                Settings.Global.THEATER_MODE_ON, );
    }
    //最终将调用到PMS的wakeUp函数
    mPowerManager.wakeUp(wakeTime, reason);
    return true;
}

我们跟进一下PMS的wakeUp函数：

public void wakeUp(long eventTime, String reason, String opPackageName) {
    ..........

    try {
        wakeUpInternal(eventTime, reason, uid, opPackageName, uid);

    } finally {
        ...............
    }
}

private void wakeUpInternal(long eventTime, String reason, int uid, String opPackageName,
        int opUid) {
    synchronized (mLock) {
        //更新Wakefullness的状态为WAKEFULNESS_AWAKE，记录一次UserActivity
        if (wakeUpNoUpdateLocked(eventTime, reason, uid, opPackageName, opUid)) {
            //如之前博客所述，对整个电源状态进行一次调整，将在需要时点亮屏幕
            updatePowerStateLocked();
        }
    }
}

2、Power抬起（interceptPowerKeyUp ）

A: Power抬起 时序图

interceptPowerKeyUp处理松开Power键后的流程：

B: Power抬起代码分析

private void interceptPowerKeyUp(KeyEvent event, boolean interactive, boolean canceled) {
    //事件被取消，或者在按下Power键时，该事件已被消耗掉
    //那么就不用继续处理
    final boolean handled = canceled || mPowerKeyHandled;
    mScreenshotChordPowerKeyTriggered = false;
    //退出截屏
    cancelPendingScreenshotChordAction();
    //取消MSG_POWER_LONG_PRESS事件，即在一定事件内Power键弹起，则表示这一次不是长按Power键

    cancelPendingPowerKeyAction();
    //从之前的代码，我们知道除了特殊功能外灭屏按Power键或亮屏长按时，均会消耗掉Power事件因此，只有亮屏短按Power键需要进行处理
    if (!handled) {
        // Figure out how to handle the key now that it has been released.

        mPowerKeyPressCounter += ;
        final int maxCount = getMaxMultiPressPowerCount();
        final long eventTime = event.getDownTime();
        if (mPowerKeyPressCounter < maxCount) {
            // This could be a multi-press.  Wait a little bit longer to confirm.
            // Continue holding the wake lock.
            // 与之前interceptPowerKeyDown，处理Power键被多次按下场景对应
            // 每次被按下，均发送MSG_POWER_DELAYED_PRESS消息
            // 实际上maxCount为1，不会进入该分支
            Message msg = mHandler.obtainMessage(MSG_POWER_DELAYED_PRESS,
                interactive ?  : , mPowerKeyPressCounter, eventTime);
            msg.setAsynchronous(true);
            mHandler.sendMessageDelayed(msg, ViewConfiguration.getDoubleTapTimeout());

           return;
        }
        //1、No other actions.  Handle it immediately.
        powerPress(eventTime, interactive, mPowerKeyPressCounter);
    }

    // 2、Done.  Reset our state.
    finishPowerKeyPress();
}

1）powerPress

powerPress函数根据屏幕状态和配置的条件，如果亮屏状态下短按power按键则调用PMS的goToSleep（）函数，执行灭屏并将系统休眠。

private void powerPress(long eventTime, boolean interactive, int count) {

if (mScreenOnEarly && !mScreenOnFully) {
Slog.i(TAG, "Suppressed redundant power key press while "
+ "already in the process of turning the screen on.");
return;
}

if (count == ) {
//原生不进入
powerMultiPressAction(eventTime, interactive, mDoublePressOnPowerBehavior);
} else if (count == ) {

//原生不进入
powerMultiPressAction(eventTime, interactive, mTriplePressOnPowerBehavior);
} else if (interactive && !mBeganFromNonInteractive) {
//亮屏时，将进入该分支
//mShortPressOnPowerBehavior被配置为1
switch (mShortPressOnPowerBehavior) {
case SHORT_PRESS_POWER_NOTHING:
break;
case SHORT_PRESS_POWER_GO_TO_SLEEP:
//最终调用到PMS的goToSleep函数
mPowerManager.goToSleep(eventTime,
PowerManager.GO_TO_SLEEP_REASON_POWER_BUTTON, );
break;
...............
}
}
}

在亮屏状态下，短按一下Power键，最终将调用到PMS的goToSleep函数，使终端进入到休眠状态，与实际情况一致。 

PMS的goToSleep函数

public void goToSleep(long eventTime, int reason, int flags) {
    ............

    try {
        goToSleepInternal(eventTime, reason, flags, uid);

    } finally {
        ...............

    }
}

private void goToSleepInternal(long eventTime, int reason, int flags, int uid) {

    synchronized (mLock) {

    //没有触发用户事件，将mWakefullness置为WAKEFULNESS_DOZING

    if (goToSleepNoUpdateLocked(eventTime, reason, flags, uid)) {

        //执行整体的电源状态更新，将熄灭屏幕

        updatePowerStateLocked();

    }

}

2）finishPowerKeyPress

每当处理一次完整的Power键按下、弹出操作后，interceptPowerKeyUp调用finishPowerKeyPress进行最后的状态复位操作：

private void finishPowerKeyPress() {

    mBeganFromNonInteractive = false;
    mPowerKeyPressCounter = ;
    if (mPowerKeyWakeLock.isHeld()) {
        mPowerKeyWakeLock.release();
    }
}

从代码可以看出，主要的工作其实就是将状态变量恢复为初始值，同时释放掉最初申请的锁。

三、Power按键处理总流程

按键处理的总流程如下图：