Android 省电模式

Posted by Vector Blog on March 21, 2017

流程分析

UI入口为 : Settings -> Battery -> Battery saver, 通过一个 switch 控件来控制开关

./packages/apps/Settings/src/com/android/settings/fuelgauge/BatterySaverSettings.java

    public void onSwitchChanged(Switch switchView, boolean isChecked) {
        mHandler.removeCallbacks(mStartMode);
        if (isChecked) {
            //private static final long WAIT_FOR_SWITCH_ANIM = 500;
            mHandler.postDelayed(mStartMode, WAIT_FOR_SWITCH_ANIM);
        } else {
            if (DEBUG) Log.d(TAG, "Stopping low power mode from settings");
            trySetPowerSaveMode(false);
        }
    }

其中 postdelayed 的声明如下:

public final boolean postDelayed (Runnable r, long delayMillis)

其中参数Runnable r在Handler对象所运行的线程中执行。 所以这里会开一个新线程 mStartMode ：

    private final Runnable mStartMode = new Runnable() {
        @Override
        public void run() {
            AsyncTask.execute(new Runnable() {
                @Override
                public void run() {
                    if (DEBUG) Log.d(TAG, "Starting low power mode from settings");
                    trySetPowerSaveMode(true);
                }
            });
        }
    };

    private void trySetPowerSaveMode(boolean mode) {
        if (!mPowerManager.setPowerSaveMode(mode)) {
            if (DEBUG) Log.d(TAG, "Setting mode failed, fallback to current value");
            //创建一个线程来设置switch控件
            mHandler.post(mUpdateSwitch);
        }
        // TODO: Remove once broadcast is in place.
        ConditionManager.get(getContext()).getCondition(BatterySaverCondition.class).refreshState();
    }

//其中 mPowerManager 为获取的系统电源管理powermanagerservice 的代理类
mPowerManager = (PowerManager) mContext.getSystemService(Context.POWER_SERVICE);

./frameworks/base/core/java/android/os/PowerManager.java

    public boolean setPowerSaveMode(boolean mode) {
        try {
            //final IPowerManager mService 
            return mService.setPowerSaveMode(mode);
        } catch (RemoteException e) {
            throw e.rethrowFromSystemServer();
        }
    }

./frameworks/base/services/core/java/com/android/server/power/PowerManagerService.java

        public boolean setPowerSaveMode(boolean mode) {
               ......
                return setLowPowerModeInternal(mode);

=>
    private boolean setLowPowerModeInternal(boolean mode) {
        synchronized (mLock) {
            //充电时不允许开启省电模式
            if (mIsPowered) {
                return false;
            }
            Settings.Global.putInt(mContext.getContentResolver(),
                    Settings.Global.LOW_POWER_MODE, mode ? 1 : 0);
            mLowPowerModeSetting = mode;

            if (mAutoLowPowerModeConfigured && mBatteryLevelLow) {
                if (mode && mAutoLowPowerModeSnoozing) {
                    mAutoLowPowerModeSnoozing = false;
                } else if (!mode && !mAutoLowPowerModeSnoozing) {
                    mAutoLowPowerModeSnoozing = true;
                }
            }

            updateLowPowerModeLocked();
            return true;
        }
    }

=>
    private void updateLowPowerModeLocked() {
        if ((mIsPowered || !mBatteryLevelLow && !mBootCompleted) && mLowPowerModeSetting) {
            // 当设备正在(充电或者非低电量且非boot completed 阶段）且已经开启省电模式， 关闭省电模式
            Settings.Global.putInt(mContext.getContentResolver(),
                    Settings.Global.LOW_POWER_MODE, 0);
            mLowPowerModeSetting = false;
        }
        //一下变量分别为 当前没有充电，自动开启省电模式，电量低于省电模式的电量触发点时user没有关闭省电模式，电池电量低
        final boolean autoLowPowerModeEnabled = !mIsPowered && mAutoLowPowerModeConfigured
                && !mAutoLowPowerModeSnoozing && mBatteryLevelLow;
        final boolean lowPowerModeEnabled = mLowPowerModeSetting || autoLowPowerModeEnabled;

        if (mLowPowerModeEnabled != lowPowerModeEnabled) {
            mLowPowerModeEnabled = lowPowerModeEnabled;
            //qcom平台上会调用 device/qcom/common/power 内的 POWER_HARDWARE_MODULE_ID module，其中并不会处理 POWER_HINT_LOW_POWER
            powerHintInternal(POWER_HINT_LOW_POWER, lowPowerModeEnabled ? 1 : 0);           
            postAfterBootCompleted(new Runnable() {
                @Override
                public void run() {
                    // 发送 ACTION_POWER_SAVE_MODE_CHANGING 的broadcast 
                    Intent intent = new Intent(PowerManager.ACTION_POWER_SAVE_MODE_CHANGING)
                            .putExtra(PowerManager.EXTRA_POWER_SAVE_MODE, mLowPowerModeEnabled)
                            .addFlags(Intent.FLAG_RECEIVER_REGISTERED_ONLY);	//只有动态注册的receiver才能接收到
                    mContext.sendBroadcast(intent);
                    ArrayList<PowerManagerInternal.LowPowerModeListener> listeners;
                    synchronized (mLock) {
                        listeners = new ArrayList<PowerManagerInternal.LowPowerModeListener>(
                                mLowPowerModeListeners);
                    }
                    for (int i=0; i<listeners.size(); i++) {
                        listeners.get(i).onLowPowerModeChanged(lowPowerModeEnabled);
                    }
                    intent = new Intent(PowerManager.ACTION_POWER_SAVE_MODE_CHANGED);
                    intent.addFlags(Intent.FLAG_RECEIVER_REGISTERED_ONLY);
                    mContext.sendBroadcast(intent);
                    // Send internal version that requires signature permission.
                    mContext.sendBroadcastAsUser(new Intent(
                            PowerManager.ACTION_POWER_SAVE_MODE_CHANGED_INTERNAL), UserHandle.ALL,
                            Manifest.permission.DEVICE_POWER);
                }
            });
        }
    }

可以看到这里主要是启动了一个线程， 该线程中主要做了3个事情：
1.发送 ACTION_POWER_SAVE_MODE_CHANGING broadcast 2.调用其他地方注册的 onLowPowerModeChanged
3.发送 ACTION_POWER_SAVE_MODE_CHANGED_INTERNAL broadcast

ACTION_POWER_SAVE_MODE_CHANGING

1./packages/apps/Settings/src/com/android/settings/fuelgauge/BatterySaverSettings.java

            if (action.equals(ACTION_POWER_SAVE_MODE_CHANGING)) {
                mHandler.post(mUpdateSwitch);	//更新Settings 中省电模式switch控件状态
            }
  1. /frameworks/base/packages/SystemUI/src/com/android/systemui/statusbar/policy/BatteryControllerImpl.java
        } else if (action.equals(PowerManager.ACTION_POWER_SAVE_MODE_CHANGING)) {
            setPowerSave(intent.getBooleanExtra(PowerManager.EXTRA_POWER_SAVE_MODE, false));
        }
=>
        firePowerSaveChanged();

    private void firePowerSaveChanged() {
        synchronized (mChangeCallbacks) {
            final int N = mChangeCallbacks.size();
            for (int i = 0; i < N; i++) {
                mChangeCallbacks.get(i).onPowerSaveChanged(mPowerSave);	//调用onPowerSaveChanged， 主要用于更新UI, 如电池颜色等
            }
        }
    }

onLowPowerModeChanged

  1. /frameworks/base/services/core/java/com/android/server/VibratorService.java
    在systemReady 中register LowPowerModeObserver, 主要作用是取消震动效果
    2./frameworks/base/services/core/java/com/android/server/wm/WindowManagerService.java
    取消动画效果 3./frameworks/base/services/core/java/com/android/server/net/NetworkPolicyManagerService.java
                        public void onLowPowerModeChanged(boolean enabled) {
                            if (LOGD) Slog.d(TAG, "onLowPowerModeChanged(" + enabled + ")");
                            synchronized (mUidRulesFirstLock) {
                                if (mRestrictPower != enabled) {
                                    mRestrictPower = enabled;
                                    updateRulesForRestrictPowerUL();
                                }
                            }
                        }
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