Android6.0 亮屏灭屏流程（DisplayPowerControler、WMS）（二）亮度设置

上一篇博客我们主要分析了在setScreenState中调用PhoneWindowManager的一些流程，在setScreenState中先是调用了DisplayPowerState的setScreenState函数。上篇博客我们没有分析，这篇博客我们先从这个函数开始分析，主要分析下亮度的设置流程。

 

    public void setScreenState(int state) {
        if (mScreenState != state) {
            if (DEBUG) {
                Slog.d(TAG, "setScreenState: state=" + state);
            }

            mScreenState = state;
            mScreenReady = false;
            scheduleScreenUpdate();
        }
    }

 

 

 



scheduleScreenUpdate主要通过消息方式，最后调用到下面函数。当我们屏幕刚要点亮，这个时候mScreenBrightness为0，所以这个时候调用mPhotonicModulator.setState设置state是点亮，但是brightness是0的。

    private final Runnable mScreenUpdateRunnable = new Runnable() {
        @Override
        public void run() {
            mScreenUpdatePending = false;

            int brightness = mScreenState != Display.STATE_OFF
                    && mColorFadeLevel > 0f ? mScreenBrightness : 0;
            if (mPhotonicModulator.setState(mScreenState, brightness)) {
                if (DEBUG) {
                    Slog.d(TAG, "Screen ready");
                }
                mScreenReady = true;
                invokeCleanListenerIfNeeded();
            } else {
                if (DEBUG) {
                    Slog.d(TAG, "Screen not ready");
                }
            }
        }
    };

 

DisplayPowerState的设置亮度状态逻辑分析

mPhotonicModulator.setState应该要PhotonicModulator的run函数结合一起看。

        public boolean setState(int state, int backlight) {
            synchronized (mLock) {
                boolean stateChanged = state != mPendingState;
                boolean backlightChanged = backlight != mPendingBacklight;
                if (stateChanged || backlightChanged) {
                    if (DEBUG) {
                        Slog.d(TAG, "Requesting new screen state: state="
                                + Display.stateToString(state) + ", backlight=" + backlight);
                    }

                    mPendingState = state;
                    mPendingBacklight = backlight;

                    boolean changeInProgress = mStateChangeInProgress || mBacklightChangeInProgress;
                    mStateChangeInProgress = stateChanged;
                    mBacklightChangeInProgress = backlightChanged;

                    if (!changeInProgress) {
                        Slog.d(TAG,"notify set backlight thread run");
                        mLock.notifyAll();
                    }
                }
                return !mStateChangeInProgress;
            }
        }

两者结合看先setState设置了状态，只有状态改变时，我们才能重新设置状态（设置到mpendingState和mPendingBacklight）。而在run函数中，当设置的状态mPendingState、mPendingBacklight和mActualState、mActualBacklight（真正设置到背光的状态、亮度）不一样时，才会调用mBlanker.requestDisplayState设置亮度。否则状态没有改变，就会把mStateChangeInProgress 和mBacklightChangeInProgress 设置为false，然后线程就wait住。

而此时setState重新设置下来的话，这个时候把亮度和状态设置到mPendingState 和mPendingBacklight 。然后这时mStateChangeInProgress 和 mBacklightChangeInProgress都是false。这样就可以调用mLock的notifyAll函数重新唤醒线程，这样就把把前面setState设置下来的mPendingState和mPendingBacklight再通过mBlanker.requestDisplayState设置到背光设备中去。

        @Override
        public void run() {
            for (;;) {
                // Get pending change.
                final int state;
                final boolean stateChanged;
                final int backlight;
                final boolean backlightChanged;
                synchronized (mLock) {
                    state = mPendingState;
                    stateChanged = (state != mActualState);
                    backlight = mPendingBacklight;
                    backlightChanged = (backlight != mActualBacklight);
                    if (!stateChanged) {
                        // State changed applied, notify outer class.
                        postScreenUpdateThreadSafe();
                        mStateChangeInProgress = false;
                    }
                    if (!backlightChanged) {
                        mBacklightChangeInProgress = false;