Android 8.0 电池图标 显示分析

        frameworks/base/packages/SystemUI/src/com/android/systemui/BatteryMeterView.java 显示电池图标变化状态，setImageDrawable(mDrawable) 就是设置的电池图标。

    public BatteryMeterView(Context context, AttributeSet attrs, int defStyle) {
        super(context, attrs, defStyle);

        setOrientation(LinearLayout.HORIZONTAL);
        setGravity(Gravity.CENTER_VERTICAL | Gravity.START);

        TypedArray atts = context.obtainStyledAttributes(attrs,                 R.styleable.BatteryMeterView,
                defStyle, 0);
        final int frameColor = atts.getColor(R.styleable.BatteryMeterView_frameColor,
                context.getColor(R.color.meter_background_color));
        mDrawable = new BatteryMeterDrawableBase(context, frameColor);
        atts.recycle();
        mSettingObserver = new SettingObserver(new Handler(context.getMainLooper()));

        mSlotBattery = context.getString(
                com.android.internal.R.string.status_bar_battery);
        mBatteryIconView = new ImageView(context);
        //设置图标，矢量图
        mBatteryIconView.setImageDrawable(mDrawable);

.......
            }
        };
    }

监听电池变化，当电池发生变化时，实现 BatteryController.BatteryStateChangeCallback

  @Override
    //电池状态的变化，充放电，电量
    public void onBatteryLevelChanged(int level, boolean pluggedIn, boolean charging) {
        //显示电量等级
        mDrawable.setBatteryLevel(level);
        //是否充电状态，充电状态图标会有闪电的标记
        mDrawable.setCharging(pluggedIn);
        mLevel = level;
        updatePercentText();
        setContentDescription(
                getContext().getString(charging ? R.string.accessibility_battery_level_charging
                        : R.string.accessibility_battery_level, level));
    }