Android backlight

Android backlight 
Android backlight
Android backlight
frameworks\base\services\core\java\com\android\server\power\PowerManagerService.java
public final class PowerManagerService extends SystemService
        implements Watchdog.Monitor {
    ...



public void systemReady(IAppOpsService appOps) {








    synchronized (mLock) {








        mSettingsObserver = new SettingsObserver(mHandler);


        ....








        // Register for broadcasts from other components of the system.









        IntentFilter filter = new IntentFilter();








        filter.addAction(Intent.ACTION_BATTERY_CHANGED);








        filter.setPriority(IntentFilter.SYSTEM_HIGH_PRIORITY);








        mContext.registerReceiver(new BatteryReceiver(), filter, null, mHandler);










        filter = new IntentFilter();








        filter.addAction(Intent.ACTION_DREAMING_STARTED);








        filter.addAction(Intent.ACTION_DREAMING_STOPPED);








        mContext.registerReceiver(new DreamReceiver(), filter, null, mHandler);
















        filter = new IntentFilter();








        filter.addAction(Intent.ACTION_USER_SWITCHED);








        mContext.registerReceiver(new UserSwitchedReceiver(), filter, null, mHandler);
















        filter = new IntentFilter();








        filter.addAction(Intent.ACTION_DOCK_EVENT);








        mContext.registerReceiver(new DockReceiver(), filter, null, mHandler);
















        // Register for settings changes.









        final ContentResolver resolver = mContext.getContentResolver();








        ...








        resolver.registerContentObserver(Settings.System.getUriFor(








                Settings.System.SCREEN_BRIGHTNESS),








                false, mSettingsObserver, UserHandle.USER_ALL);








        resolver.registerContentObserver(Settings.System.getUriFor(








                Settings.System.SCREEN_BRIGHTNESS_MODE),








                false, mSettingsObserver, UserHandle.USER_ALL);








        ...








    }








}








以上无论是 receiver 还是  mSettingsObserver ,当收到“信号”，都会间接调用到 updatePowerStateLocked 





private void updatePowerStateLocked() {
    if (!mSystemReady || mDirty == 0) {
        return;
    }
    if (!Thread.holdsLock(mLock)) {
        Slog.wtf(TAG, "Power manager lock was not held when calling updatePowerStateLocked");
    }

    Trace.traceBegin(Trace.TRACE_TAG_POWER, "updatePowerState");
    try {
        // Phase 0: Basic state updates.
        updateIsPoweredLocked(mDirty);
        updateStayOnLocked(mDirty);

        // Phase 1: Update wakefulness.
        // Loop because the wake lock and user activity computations are influenced
        // by changes in wakefulness.
        final long now = SystemClock.uptimeMillis();
        int dirtyPhase2 = 0;
        for (;;) {
            int dirtyPhase1 = mDirty;
            dirtyPhase2 |= dirtyPhase1;
            mDirty = 0;

            updateWakeLockSummaryLocked(dirtyPhase1);
            updateUserActivitySummaryLocked(now, dirtyPhase1);
            if (!updateWakefulnessLocked(dirtyPhase1)) {
                break;
            }
        }

        // Phase 2: Update display power state.
        boolean displayBecameReady = updateDisplayPowerStateLocked(dirtyPhase2);

        // Phase 3: Update dream state (depends on display ready signal).
        updateDreamLocked(dirtyPhase2, displayBecameReady);

        // Phase 4: Send notifications, if needed.
        if (mDisplayReady) {
            finishInteractiveStateChangeLocked();
        }

        // Phase 5: Update suspend blocker.
        // Because we might release the last suspend blocker here, we need to make sure
        // we finished everything else first!
        updateSuspendBlockerLocked();
    } finally {
        Trace.traceEnd(Trace.TRACE_TAG_POWER);
    }
}




对于背光，调用 updateDisplayPowerStateLocked(dirtyPhase2);





private boolean updateDisplayPowerStateLocked(int dirty) {
    final boolean oldDisplayReady = mDisplayReady;
        ...
        if (autoBrightness) {
        ...
        }
        screenBrightness = Math.max(Math.min(screenBrightness,
                mScreenBrightnessSettingMaximum), mScreenBrightnessSettingMinimum);
        screenAutoBrightnessAdjustment = Math.max(Math.min(
                screenAutoBrightnessAdjustment, 1.0f), -1.0f);
        mDisplayPowerRequest.screenBrightness = screenBrightness;
        mDisplayPowerRequest.screenAutoBrightnessAdjustment =
                screenAutoBrightnessAdjustment;
        mDisplayPowerRequest.useAutoBrightness = autoBrightness;

        mDisplayPowerRequest.useProximitySensor = shouldUseProximitySensorLocked();

        mDisplayPowerRequest.lowPowerMode = mLowPowerModeEnabled;

        if (mDisplayPowerRequest.policy == DisplayPowerRequest.POLICY_DOZE) {
            mDisplayPowerRequest.dozeScreenState = mDozeScreenStateOverrideFromDreamManager;
            mDisplayPowerRequest.dozeScreenBrightness =
                    mDozeScreenBrightnessOverrideFromDreamManager;
        } else {
            mDisplayPowerRequest.dozeScreenState = Display.STATE_UNKNOWN;
            mDisplayPowerRequest.dozeScreenBrightness = PowerManager.BRIGHTNESS_DEFAULT;
        }

        mDisplayReady = mDisplayManagerInternal.requestPowerState(mDisplayPowerRequest,
                mRequestWaitForNegativeProximity);
        mRequestWaitForNegativeProximity = false;

    }
    return mDisplayReady && !oldDisplayReady;
}


public abstract boolean requestPowerState(DisplayPowerRequest request,boolean waitForNegativeProximity); 


虚函数，子类中实现在：


frameworks\base\services\core\java\com\android\server\display\DisplayManagerService.java





public boolean requestPowerState(DisplayPowerRequest request,
        boolean waitForNegativeProximity) {
    return mDisplayPowerController.requestPowerState(request,
            waitForNegativeProximity);
}


public boolean requestPowerState(DisplayPowerRequest request,
        boolean waitForNegativeProximity) {
    ...
    synchronized (mLock) {
        boolean changed = false;
     ...

        if (changed) {
            mDisplayReadyLocked = false;
        }

        if (changed && !mPendingRequestChangedLocked) {
            mPendingRequestChangedLocked = true;
            sendUpdatePowerStateLocked();
        }

        return mDisplayReadyLocked;
    }
}


private void sendUpdatePowerStateLocked() {
    if (!mPendingUpdatePowerStateLocked) {
        mPendingUpdatePowerStateLocked = true;
        Message msg = mHandler.obtainMessage(MSG_UPDATE_POWER_STATE);
        msg.setAsynchronous(true);
        mHandler.sendMessage(msg);
    }
}


前面学习过线程间通信，将调用到 mHandler 里的 handleMessage 函数


public void handleMessage(Message msg) {
    switch (msg.what) {
        case MSG_UPDATE_POWER_STATE:
            updatePowerState();
            break;
    ...
    }
}


private void updatePowerState() {














// Animate the screen brightness when the screen is on or dozing.





// Skip the animation when the screen is off or suspended.
if (state == Display.STATE_ON || state == Display.STATE_DOZE) {
    animateScreenBrightness(brightness,
            slowChange ? BRIGHTNESS_RAMP_RATE_SLOW : BRIGHTNESS_RAMP_RATE_FAST);
} else {
    animateScreenBrightness(brightness, 0);
}





private void animateScreenBrightness(int target, int rate) {

    if (mScreenBrightnessRampAnimator.animateTo(target, rate)) {

    }
}




public boolean animateTo(int target, int rate) {
    // Immediately jump to the target the first time.
    if (mFirstTime || rate <= 0) {
        if (mFirstTime || target != mCurrentValue) {
       ...
            mProperty.setValue(mObject, target);
       ...
            return true;
        }
        return false;
    }


public void setValue(DisplayPowerState object, int value) {
    object.setScreenBrightness(value);
}


public void setScreenBrightness(int brightness) {
    if (mScreenBrightness != brightness) {
        if (DEBUG) {
            Slog.d(TAG, "setScreenBrightness: brightness=" + brightness);
        }

        mScreenBrightness = brightness;
        if (mScreenState != Display.STATE_OFF) {
            mScreenReady = false;
            scheduleScreenUpdate();
        }
    }
}


private void scheduleScreenUpdate() {
    if (!mScreenUpdatePending) {
        mScreenUpdatePending = true;
        postScreenUpdateThreadSafe();
    }
}


private void postScreenUpdateThreadSafe() {
    mHandler.removeCallbacks(mScreenUpdateRunnable);
    mHandler.post(mScreenUpdateRunnable);
}


还是前面学习的线程间通信,调用 mScreenUpdateRunnable 中的 run 函数


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)) {
        ...
    }
};


public boolean setState(int state, int backlight) {
    synchronized (mLock) {
        if (state != mPendingState || backlight != mPendingBacklight) {

            mPendingState = state;
            mPendingBacklight = backlight;

            if (!mChangeInProgress) {
                mChangeInProgress = true;
                mLock.notifyAll();
            }
        }
        return !mChangeInProgress;
    }
}


唤醒 mLock 休眠的地方：


private final class PhotonicModulator extends Thread {










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 && !backlightChanged) {








                // All changed applied, notify outer class and wait for more.









                mChangeInProgress = false;








                postScreenUpdateThreadSafe();








                try {








                    mLock.wait();//休眠








                } catch (InterruptedException ex) { }








                continue;








            }








            mActualState = state;








            mActualBacklight = backlight;








        }
















        // Apply pending change.









        if (DEBUG) {








            Slog.d(TAG, "Updating screen state: state="









                    + Display.stateToString(state) + ", backlight=" + backlight);








        }








        boolean suspending = Display.isSuspendedState(state);








        if (stateChanged && !suspending) {








            requestDisplayState(state);








        }








        if (backlightChanged) {








            setBrightness(backlight);//设置背光








        }








        if (stateChanged && suspending) {








            requestDisplayState(state);








        }








    }








}





}


private void setBrightness(int backlight) {
    Trace.traceBegin(Trace.TRACE_TAG_POWER, "setBrightness(" + backlight + ")");
    try {
        mBacklight.setBrightness(backlight);
    } finally {
        Trace.traceEnd(Trace.TRACE_TAG_POWER);
    }
}


frameworks\base\services\core\java\com\android\server\lights\LightsService.java





public void setBrightness(int brightness) {
    setBrightness(brightness, BRIGHTNESS_MODE_USER);
}


public void setBrightness(int brightness, int brightnessMode) {
    synchronized (this) {
        int color = brightness & 0x000000ff;
        color = 0xff000000 | (color << 16) | (color << 8) | color;
        setLightLocked(color, LIGHT_FLASH_NONE, 0, 0, brightnessMode);
    }
}


private void setLightLocked(int color, int mode, int onMS, int offMS, int brightnessMode) {
    if (color != mColor || mode != mMode || onMS != mOnMS || offMS != mOffMS) {
        if (DEBUG) Slog.v(TAG, "setLight #" + mId + ": color=#"
                + Integer.toHexString(color));
        mColor = color;
        mMode = mode;
        mOnMS = onMS;
        mOffMS = offMS;
        Trace.traceBegin(Trace.TRACE_TAG_POWER, "setLight(" + mId + ", " + color + ")");
        try {
            setLight_native(mNativePointer, mId, color, mode, onMS, offMS, brightnessMode);
        } finally {
            Trace.traceEnd(Trace.TRACE_TAG_POWER);
        }
    }
}


frameworks\base\services\core\jni\com_android_server_lights_LightsService.cpp





static JNINativeMethod method_table[] = {
    { "init_native", "()J", (void*)init_native },
    { "finalize_native", "(J)V", (void*)finalize_native },
    { "setLight_native", "(JIIIIII)V", (void*)setLight_native },
};


static void setLight_native(JNIEnv *env, jobject clazz, jlong ptr,
        jint light, jint colorARGB, jint flashMode, jint onMS, jint offMS, jint brightnessMode)
{
    Devices* devices = (Devices*)ptr;
    light_state_t state;

    if (light < 0 || light >= LIGHT_COUNT || devices->lights[light] == NULL) {
        return ;
    }

    memset(&state, 0, sizeof(light_state_t));
    state.color = colorARGB;
    state.flashMode = flashMode;
    state.flashOnMS = onMS;
    state.flashOffMS = offMS;
    state.brightnessMode = brightnessMode;

    {
        ALOGD_IF_SLOW(50, "Excessive delay setting light");
        devices->lights[light]->set_light(devices->lights[light], &state);
    }
}


...


这一部分的分析参考之前的文章


由以上代码分析可知，最初的地方注册了一个 ContentObserver 




        resolver.registerContentObserver(Settings.System.getUriFor(


                Settings.System.SCREEN_BRIGHTNESS),


                false, mSettingsObserver, UserHandle.USER_ALL);


我们只需要改变这个东西，它就会帮我们去一层层调用去改变背光


app:


设置背光：


android.provider.Settings.System.putInt(getContentResolver(),
        android.provider.Settings.System.SCREEN_BRIGHTNESS,
        brightness);


获取背光当前值：


android.provider.Settings.System.getInt(getContentResolver(),
        android.provider.Settings.System.SCREEN_BRIGHTNESS);


安卓中自带的背光设置代码在：


frameworks\base\packages\SystemUI\src\com\android\systemui\settings\BrightnessDialog.java







 
                    
            
                

                  
 
        

	 
        

            

                                            

        

        
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