android状态栏电池颜色？

android 8.0状态栏电池图标，低电量时变色，在哪实现的？

/frameworks/base/packages/SystemUI/src/com/android/systemui/statusbar/policy/BatteryControllerImpl.java
在Intent.ACTION_BATTERY_CHANGED broadcast处理中调用fireBatteryLevelChanged()方法
fireBatteryLevelChanged中会回掉BatteryStateChangeCallback
frameworks/base/packages/SystemUI/src/com/android/systemui/BatteryMeterView.java中实现了BatteryStateChangeCallback， 并向BatteryControllerImpl注册了，mBatteryController.addCallback(this);

 public void onAttachedToWindow() {
        super.onAttachedToWindow();
        mBatteryController = Dependency.get(BatteryController.class);
        mBatteryController.addCallback(this);
        mUser = ActivityManager.getCurrentUser();
        getContext().getContentResolver().registerContentObserver(
                Settings.System.getUriFor(SHOW_BATTERY_PERCENT), false, mSettingObserver, mUser);
        updateShowPercent();
        Dependency.get(TunerService.class).addTunable(this, StatusBarIconController.ICON_BLACKLIST);
        Dependency.get(ConfigurationController.class).addCallback(this);
        mUserTracker.startTracking();
    }

看下BatteryMeterView中的BatteryStateChangeCallback实现就知道了

图标布局在 {croot}/frameworks/base/packages/SystemUI/res/layout/battery_detail.xml 状态更新应该在{croot}/frameworks/base/packages/SystemUI/src/com/android/systemui/statusbar/phone