Android7.0 PowerManagerService 之亮灭屏（一）

本篇从按下power按键后，按键事件从InputManagerService 传到PhoneWindowManager.java开始分析power 按键做屏幕亮灭过程的分析，关于power 按键的其他行为参考另一篇博文（Android 7.0 Power 按键处理流程）

（注：博客园显示的图片很模糊，上传的为大图，可以图片另存为查看）

言归正传，本篇涉及的几个模块（文件）如下，先做个简单的介绍有个直观大概的了解，方便后面流程细节的理解。

Ø  PowerManagerService.Java：（/frameworks/base/services/core/java/com/android/server/policy/PhoneWindowManager.java）

　　 PMS，是Android系统中的电源处理服务，主要负责电源相关的计算和决策，如是否应该灭屏 或者让屏幕变暗，是否应该让系统休眠等等。

Ø  DisplayPowerController.java：（/frameworks/base/services/core/java/com/android/server/display/DisplayPowerController.java）

　　DPC，管理显示设备（这里指的显示设备是屏幕）状态，主要处理距离传感器（如打电话时候靠近则灭屏，离开时候屏幕亮起）以及亮灭屏动画（包括根据光感传感器计算屏幕目标亮度值）。在DisplayManagerService.java(DMS)中实例化一个对象，以DMS为桥梁与PMS进行交互通过异步回调机制来通知PMS那些发生了改变。同时也与WMS进行交互。

Ø  DisplayPowerState.java：（/frameworks/base/services/core/java/com/android/server/display/DisplayPowerState.java）

　　DPS，管理显示设备的状态仅在DPC中实例化一个对象，是DPC的一部分。

Ø  Notifier.java：（ /frameworks/base/services/core/java/com/android/server/power/Notifier.java）

　　将电源状态的重要变化，通过广播通知出去。

Ø  ColorFade.java：（/frameworks/base/services/core/java/com/android/server/display/ColorFade.java）

　　是负责屏幕由关到开，由开到关的一些GL动画，由DPC进行控制。

Ø  AutomaticBrightnessController.java：（/frameworks/base/services/core/java/com/android/server/display/AutomaticBrightnessController.java）

　　主要处理光传感器，将底层上传的参数进行处理计算，将计算的新的亮度值传给DPC来设定屏幕的亮度值（即根据环境的光线强度来计算屏幕的亮暗程度）。

Ø  RampAnimator.java：（/frameworks/base/services/core/java/com/android/server/display/RampAnimator.java）

　　仅仅是屏幕亮度渐变动画。

一、Power按键的上报与处理

详细见【Android 7.0 Power 按键处理流程】此处仅略微的复习一下，方便了后面的理解。

1）Power按键的上报

在InputManagerService收到power按键事件经过一系列的处理和转换最终将会传递到PhoneWindowManager（PWM）的interceptKeyBeforeQueueing（）函数来做具体的业务逻辑.下图为上报的流程图。

2）power 按键关于量灭屏处理

关于量灭屏的处理主要在interceptKeyBeforeQueueing（）函数中。判断是否是isWakeKey，如果是则在此函数的最后通过调用wakeUp（）函数来具体处理，这就拉开了本文的序幕。

注：此函数很长本文删除无关的部分，仅仅保留部分和量灭屏相关的说明具体处理流程即可。详细参考【Android 7.0 Power 按键处理流程】

A: 按键处理判断是否要量灭屏

public int interceptKeyBeforeQueueing(KeyEvent event, int policyFlags) {
 
        boolean isWakeKey = (policyFlags & WindowManagerPolicy.FLAG_WAKE) != 0
                || event.isWakeKey();
        if (interactive || (isInjected && !isWakeKey)) {
            // When the device is interactive or the key is injected pass the
            // key to the application.
            result = ACTION_PASS_TO_USER;
            isWakeKey = false;
 
            if (interactive) {
                // If the screen is awake, but the button pressed was the one that woke the device
                // then don't pass it to the application
                if (keyCode == mPendingWakeKey && !down) {
                    result = 0;
                }
                // Reset the pending key
                mPendingWakeKey = PENDING_KEY_NULL;
            }
        } else if (!interactive && shouldDispatchInputWhenNonInteractive(event)) {
            // If we're currently dozing with the screen on and the keyguard showing, pass the key
            // to the application but preserve its wake key status to make sure we still move
            // from dozing to fully interactive if we would normally go from off to fully
            // interactive.
            result = ACTION_PASS_TO_USER;
            // Since we're dispatching the input, reset the pending key
            mPendingWakeKey = PENDING_KEY_NULL;
        } else {
            // When the screen is off and the key is not injected, determine whether
            // to wake the device but don't pass the key to the application.
            result = 0;
            if (isWakeKey && (!down || !isWakeKeyWhenScreenOff(keyCode))) {
                isWakeKey = false;
            }
            // Cache the wake key on down event so we can also avoid sending the up event to the app
            if (isWakeKey && down) {
                mPendingWakeKey = keyCode;
            }
        }
 
        // If the key would be handled globally, just return the result, don't worry about special
        // key processing.
        if (isValidGlobalKey(keyCode)
                && mGlobalKeyManager.shouldHandleGlobalKey(keyCode, event)) {
            if (isWakeKey) {
                wakeUp(event.getEventTime(), mAllowTheaterModeWakeFromKey, "android.policy:KEY");
            }
            return result;
        }
 
     ....................
 
            case KeyEvent.KEYCODE_ENDCALL: {
                result &= ~ACTION_PASS_TO_USER;
                if (down) {
                    TelecomManager telecomManager = getTelecommService();
                    boolean hungUp = false;
                    if (telecomManager != null) {
                        hungUp = telecomManager.endCall();
                    }
                    if (interactive && !hungUp) {
                        mEndCallKeyHandled = false;
                        mHandler.postDelayed(mEndCallLongPress,
                                ViewConfiguration.get(mContext).getDeviceGlobalActionKeyTimeout());
                    } else {
                        mEndCallKeyHandled = true;
                    }
                } else {
                    if (!mEndCallKeyHandled) {
                        mHandler.removeCallbacks(mEndCallLongPress);
                        if (!canceled) {
                            if ((mEndcallBehavior
                                    & Settings.System.END_BUTTON_BEHAVIOR_HOME) != 0) {
                                if (goHome()) {
                                    break;
                                }
                            }
                            if ((mEndcallBehavior
                                    & Settings.System.END_BUTTON_BEHAVIOR_SLEEP) != 0) {
                                mPowerManager.goToSleep(event.getEventTime(),
                                        PowerManager.GO_TO_SLEEP_REASON_POWER_BUTTON, 0);
                                isWakeKey = false;
                            }
                        }
                    }
                }
                break;
            }
 
....................
 
        if (useHapticFeedback) {
            performHapticFeedbackLw(null, HapticFeedbackConstants.VIRTUAL_KEY, false);
        }
 
        if (isWakeKey) {
            wakeUp(event.getEventTime(), mAllowTheaterModeWakeFromKey, "android.policy:KEY");
        }
 
        return result;
    }

B：wakeUp处理量灭屏

private boolean wakeUp(long wakeTime, boolean wakeInTheaterMode, String reason) {
    final boolean theaterModeEnabled = isTheaterModeEnabled();
    if (!wakeInTheaterMode && theaterModeEnabled) {
        return false;
    }  
 
    if (theaterModeEnabled) {
        Settings.Global.putInt(mContext.getContentResolver(),
                    Settings.Global.THEATER_MODE_ON, 0);
        }  
 
        mPowerManager.wakeUp(wakeTime, reason);      //调用PowerManagerService亮屏操作
        return true;
    }
}

二、PowerManagerService处理量灭屏过程

从上面的分析可知，在PWM中处理按键事件如果需要唤醒屏幕则会调用PWM的wakeUp（）函数，此函数会调用PMS 的wakeUp（）函数来具体处理。

从上面的分析可知，在PWM中处理按键事件如果需要唤醒屏幕则会调用PWM的wakeUp（）函数，此函数会调用PMS 的wakeUp（）函数来具体处理。

注：限于篇幅本文仅列出重要的函数和调用过程

首先来个概览，了解一下主要完成了如下三件事

1）  由Notifier根据系统的具体状态来发出广播

2）  PMS 通过updatePowerStateLocked（）计算和更新电源的全局状态

3）  PMS将最新的电源状态等传入DPC中，根据距离传感器和光感传感器，计算具体的屏幕亮度和量灭屏动画等

4）  DPC通知PWM绘制keyguard与windows（此时会block等待绘制完成，灭屏时候无需绘制），绘制完成后通知DPC继续

5）  DPC具体调用显示设备开启或关闭屏幕（执行量灭屏的动画效果）

1）PowerManagerService--wakeUpNoUpdateLocked()

PMS首先讲wakefullness状态. 之后发送亮灭屏广播通知其他应用手机处于亮屏还是灭屏状态。

private boolean wakeUpNoUpdateLocked(long eventTime, String reason, int reasonUid,  
        String opPackageName, int opUid) {  
    if (DEBUG_SPEW) {  
        Slog.d(TAG, "wakeUpNoUpdateLocked: eventTime=" + eventTime + ", uid=" + reasonUid);  
    }  
  
    if (eventTime < mLastSleepTime || mWakefulness == WAKEFULNESS_AWAKE  
            || !mBootCompleted || !mSystemReady) {  
        return false;        //判断是否要去亮屏  
     }  
   
     Trace.traceBegin(Trace.TRACE_TAG_POWER, "wakeUp");  
     try {  
         switch (mWakefulness) {  
             case WAKEFULNESS_ASLEEP:  
                 Slog.i(TAG, "Waking up from sleep due to"+opPackageName+" "+reason+" (uid " + reasonUid +")...");  
                 break;  
             case WAKEFULNESS_DREAMING:  
                 Slog.i(TAG, "Waking up from dream due to"+opPackageName+" "+reason+" (uid " + reasonUid +")...");  
                 break;  
             case WAKEFULNESS_DOZING:  
                 Slog.i(TAG, "Waking up from dozing due to"+opPackageName+" "+reason+" (uid " + reasonUid +")...");  
                 break;  
         }  
   
         mLastWakeTime = eventTime;   //设置最后一次唤醒的时间  
         setWakefulnessLocked(WAKEFULNESS_AWAKE, 0);   //Notifier调用onWakefulnessChangeStarted发送亮屏广播  
   
         mNotifier.onWakeUp(reason, reasonUid, opPackageName, opUid);  //调用Notifier通知battery处理  
         userActivityNoUpdateLocked(     //更新最后一次用户事件时间  
                 eventTime, PowerManager.USER_ACTIVITY_EVENT_OTHER, 0, reasonUid);  
     } finally {  
         Trace.traceEnd(Trace.TRACE_TAG_POWER);  
     }  
     return true;  
 }  

1）Notifier 发送量灭屏广播

Notifier发送广播前会与与AMS，WMS，IMS进行交互，通知各模块电源状态的改变，各模块会自行处理电源状态改变通知。

A:onWakefulnessChangeStarted()

public void onWakefulnessChangeStarted(final int wakefulness, int reason) {  
   final boolean interactive = PowerManagerInternal.isInteractive(wakefulness); //亮屏true, 灭屏false  
   if (DEBUG) {  
       Slog.d(TAG, "onWakefulnessChangeStarted: wakefulness=" + wakefulness  
               + ", reason=" + reason + ", interactive=" + interactive);  
   }  
 
   // Tell the activity manager about changes in wakefulness, not just interactivity.  
   // It needs more granularity than other components.  
    mHandler.post(new Runnable() {  
        @Override  
        public void run() {  
            mActivityManagerInternal.onWakefulnessChanged(wakefulness);   //与AMS交互处理  
        }  
    });  
  
    // Handle any early interactive state changes.  
    // Finish pending incomplete ones from a previous cycle.  
    if (mInteractive != interactive) {  
        // Finish up late behaviors if needed.  
        if (mInteractiveChanging) {  
            handleLateInteractiveChange();  
        }  
  
        // Start input as soon as we start waking up or going to sleep.  
        mInputManagerInternal.setInteractive(interactive);    //在IMS中记录现在的屏幕状态  
        mInputMethodManagerInternal.setInteractive(interactive);  
  
        // Notify battery stats.  
        try {  
            mBatteryStats.noteInteractive(interactive);   //唤醒battery状态  
        } catch (RemoteException ex) { }  
  
        // Handle early behaviors.  
        mInteractive = interactive;  
        mInteractiveChangeReason = reason;  
        mInteractiveChanging = true;  
        handleEarlyInteractiveChange();   //初期处理交互模式改变  
    }  
}  

B: handleEarlyInteractiveChange()

当屏幕在wakingup时需要通知window进行更新手势监听，更新方向监听，更新锁屏超时时间 

private void handleEarlyInteractiveChange() {
    synchronized (mLock) {
        if (mInteractive) {
            // Waking up...    //亮屏
            mHandler.post(new Runnable() {
                @Override
                public void run() {
                    EventLog.writeEvent(EventLogTags.POWER_SCREEN_STATE, 1, 0, 0, 0);
                    mPolicy.startedWakingUp();
                 }
             });  
 
             // Send interactive broadcast.
             mPendingInteractiveState = INTERACTIVE_STATE_AWAKE;
             mPendingWakeUpBroadcast = true;
             updatePendingBroadcastLocked();   //更新亮屏广播
         } else {
             // Going to sleep...   //灭屏
             // Tell the policy that we started going to sleep.
             final int why = translateOffReason(mInteractiveChangeReason);
             mHandler.post(new Runnable() {
                 @Override
                 public void run() {
                     mPolicy.startedGoingToSleep(why);
                 }
             });
         }
     } 

(1):updatePendingBroadcastLocked()

    private void updatePendingBroadcastLocked() {
        if (!mBroadcastInProgress
                && mPendingInteractiveState != INTERACTIVE_STATE_UNKNOWN
                && (mPendingWakeUpBroadcast || mPendingGoToSleepBroadcast
                        || mPendingInteractiveState != mBroadcastedInteractiveState)) {
            mBroadcastInProgress = true;
            mSuspendBlocker.acquire();
            Message msg = mHandler.obtainMessage(MSG_BROADCAST);
            msg.setAsynchronous(true);
            mHandler.sendMessage(msg);
        }
    }

(2)sendNextBroadcast()

 private void sendNextBroadcast() {
        final int powerState;
        synchronized (mLock) {
            if (mBroadcastedInteractiveState == INTERACTIVE_STATE_UNKNOWN) {
                // Broadcasted power state is unknown.  Send wake up.
                mPendingWakeUpBroadcast = false;
                mBroadcastedInteractiveState = INTERACTIVE_STATE_AWAKE;
            } else if (mBroadcastedInteractiveState == INTERACTIVE_STATE_AWAKE) {
                // Broadcasted power state is awake.  Send asleep if needed.
                if (mPendingWakeUpBroadcast || mPendingGoToSleepBroadcast
                        || mPendingInteractiveState == INTERACTIVE_STATE_ASLEEP) {
                    mPendingGoToSleepBroadcast = false;
                    mBroadcastedInteractiveState = INTERACTIVE_STATE_ASLEEP;
                } else {
                    finishPendingBroadcastLocked();
                    return;
                }
            } else {
                // Broadcasted power state is asleep.  Send awake if needed.
                if (mPendingWakeUpBroadcast || mPendingGoToSleepBroadcast
                        || mPendingInteractiveState == INTERACTIVE_STATE_AWAKE) {
                    mPendingWakeUpBroadcast = false;
                    mBroadcastedInteractiveState = INTERACTIVE_STATE_AWAKE;
                } else {
                    finishPendingBroadcastLocked();
                    return;
                }
            }
 
            mBroadcastStartTime = SystemClock.uptimeMillis();
            powerState = mBroadcastedInteractiveState;
        }
 
        EventLog.writeEvent(EventLogTags.POWER_SCREEN_BROADCAST_SEND, 1);
 
        if (powerState == INTERACTIVE_STATE_AWAKE) {
            sendWakeUpBroadcast();//这里发送亮屏广播
        } else {
            sendGoToSleepBroadcast();
        }
    }

 （3）sendWakeUpBroadcast()

注意：Notifier 自身也会接收亮屏广播，其受到后会调用finishPendingBroadcastLocked()函数来释放wakeLock

    private void sendWakeUpBroadcast() {
        if (DEBUG) {
            Slog.d(TAG, "Sending wake up broadcast.");
        }
 
        if (ActivityManagerNative.isSystemReady()) {
            mContext.sendOrderedBroadcastAsUser(mScreenOnIntent, UserHandle.ALL, null,
                    mWakeUpBroadcastDone, mHandler, 0, null, null);
        } else {
            EventLog.writeEvent(EventLogTags.POWER_SCREEN_BROADCAST_STOP, 2, 1);
            sendNextBroadcast();
        }
    }