Android SystemUI分析之状态栏字体和图标颜色随背景而改变

Android版本： 8.1

切换桌面的时候我们可以看到，状态栏的数字和icon图标都变成颜色，假如我们开发的时候也要添加一个新的view到状态栏，就需要实现同样的方法。

实现这个功能，需要实现DarkReceiver这个接口。

    interface DarkReceiver {
        void onDarkChanged(Rect area, float darkIntensity, int tint);
    }

onDarkChanged就是在当背景色改变时，对应发生的监听回调。
下面开始看源码是怎么操作的

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当Window 界面切换的时候，会调用setSystemUiVisibility
传到StatusBar里，

@Override // CommandQueue
    public void setSystemUiVisibility(int vis, int fullscreenStackVis, int dockedStackVis,
            int mask, Rect fullscreenStackBounds, Rect dockedStackBounds) {
        。。。//最后调用了mLightBarController
        mLightBarController.onSystemUiVisibilityChanged(fullscreenStackVis, dockedStackVis,
                mask, fullscreenStackBounds, dockedStackBounds, sbModeChanged, mStatusBarMode);
    }

setSystemUiVisibility最后调用了mLightBarController，这里的mLightBarController是LightBarController

onSystemUiVisibilityChanged

public void onSystemUiVisibilityChanged(int fullscreenStackVis, int dockedStackVis,
            int mask, Rect fullscreenStackBounds, Rect dockedStackBounds, boolean sbModeChanged,
            int statusBarMode) {
        int oldFullscreen = mFullscreenStackVisibility;
        int newFullscreen = (oldFullscreen & ~mask) | (fullscreenStackVis & mask);
        int diffFullscreen = newFullscreen ^ oldFullscreen;
        int oldDocked = mDockedStackVisibility;
        int newDocked = (oldDocked & ~mask) | (dockedStackVis & mask);
        int diffDocked = newDocked ^ oldDocked;
        if ((diffFullscreen & View.SYSTEM_UI_FLAG_LIGHT_STATUS_BAR) != 0
                || (diffDocked & View.SYSTEM_UI_FLAG_LIGHT_STATUS_BAR) != 0
                || sbModeChanged
                || !mLastFullscreenBounds.equals(fullscreenStackBounds)
                || !mLastDockedBounds.equals(dockedStackBounds)) {

            mFullscreenLight = isLight(newFullscreen, statusBarMode,
                    View.SYSTEM_UI_FLAG_LIGHT_STATUS_BAR);
            mDockedLight = isLight(newDocked, statusBarMode, View.SYSTEM_UI_FLAG_LIGHT_STATUS_BAR);
            updateStatus(fullscreenStackBounds, dockedStackBounds);
        }

        mFullscreenStackVisibility = newFullscreen;
        mDockedStackVisibility = newDocked;
        mLastStatusBarMode = statusBarMode;
        mLastFullscreenBounds.set(fullscreenStackBounds);
        mLastDockedBounds.set(dockedStackBounds);
    }

如果参数比较有改变，则会走向updateStatus

private void updateStatus(Rect fullscreenStackBounds, Rect dockedStackBounds) {
        boolean hasDockedStack = !dockedStackBounds.isEmpty();

        // If both are light or fullscreen is light and there is no docked stack, all icons get
        // dark.
        if ((mFullscreenLight && mDockedLight) || (mFullscreenLight && !hasDockedStack)) {
            mStatusBarIconController.setIconsDarkArea(null);
            mStatusBarIconController.getTransitionsController().setIconsDark(true, animateChange());

        }

        // If no one is light or the fullscreen is not light and there is no docked stack,
        // all icons become white.
        else if ((!mFullscreenLight && !mDockedLight) || (!mFullscreenLight && !hasDockedStack)) {
            mStatusBarIconController.getTransitionsController().setIconsDark(
                    false, animateChange());
        }

        // Not the same for every stack, magic!
        else {
            Rect bounds = mFullscreenLight ? fullscreenStackBounds : dockedStackBounds;
            if (bounds.isEmpty()) {
                mStatusBarIconController.setIconsDarkArea(null);
            } else {
                mStatusBarIconController.setIconsDarkArea(bounds);
            }
            mStatusBarIconController.getTransitionsController().setIconsDark(true, animateChange());
        }
    }

最终都会走向mStatusBarIconController。

private final DarkIconDispatcher mStatusBarIconController;

这里的DarkIconDispatcher是个接口，实际对象是他的继承者DarkIconDispatcherImpl
这里的setIconsDarkArea

    public void setIconsDarkArea(Rect darkArea) {
        if (darkArea == null && mTintArea.isEmpty()) {
            return;
        }
        if (darkArea == null) {
            mTintArea.setEmpty();
        } else {
            mTintArea.set(darkArea);
        }
        applyIconTint();
    }

    private void applyIconTint() {
        for (int i = 0; i < mReceivers.size(); i++) {
            mReceivers.valueAt(i).onDarkChanged(mTintArea, mDarkIntensity, mIconTint);
        }
    }

然后就是更新所有Receivers，通知onDarkChanged。

前面getTransitionsController,

    public LightBarTransitionsController getTransitionsController() {
        return mTransitionsController;
    }

LightBarTransitionsController

   mTransitionsController = new LightBarTransitionsController(context,
           this::setIconTintInternal);

最终调用的setIconTintInternal，

    private void setIconTintInternal(float darkIntensity) {
        mDarkIntensity = darkIntensity;
        mIconTint = (int) ArgbEvaluator.getInstance().evaluate(darkIntensity,
                mLightModeIconColorSingleTone, mDarkModeIconColorSingleTone);
        applyIconTint();
    }

也是通知其他Receivers去更新。

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接着我们看看所有的mReceivers。

    public void addDarkReceiver(DarkReceiver receiver) {
        mReceivers.put(receiver, receiver);
        receiver.onDarkChanged(mTintArea, mDarkIntensity, mIconTint);
    }

所有Receivers都是调用addDarkReceiver实现的。
分别有

1. 时钟图标 Dependency.get(DarkIconDispatcher.class).addDarkReceiver(this);
2. 电池图标 Dependency.get(DarkIconDispatcher.class).addDarkReceiver(mBattery);
3. 信号栏图标 Dependency.get(DarkIconDispatcher.class).addDarkReceiver(mSignalClusterView);
4. 通知栏图标 Dependency.get(DarkIconDispatcher.class).addDarkReceiver(mNotificationIconAreaController);

对应着状态栏里所有的图标显示。

比如，当回调的时候，看看mBattery，

public class BatteryMeterView extends LinearLayout implements
        BatteryStateChangeCallback, Tunable, DarkReceiver, ConfigurationListener 

BatteryMeterView 实现了DarkReceiver接口，
所以注册addDarkReceiver之后，回调的时候会调用BatteryMeterView 的onDarkChanged

    @Override
    public void onDarkChanged(Rect area, float darkIntensity, int tint) {
        mDarkIntensity = darkIntensity;
        float intensity = DarkIconDispatcher.isInArea(area, this) ? darkIntensity : 0;
        int foreground = getColorForDarkIntensity(intensity, mLightModeFillColor,
                mDarkModeFillColor);
        int background = getColorForDarkIntensity(intensity, mLightModeBackgroundColor,
                mDarkModeBackgroundColor);
        mDrawable.setColors(foreground, background);
        setTextColor(foreground);
    }

最后切换图标染色，实现不同的颜色转换。

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总结：

假如我们自己开发需要加入状态栏图标，随背景转换颜色，需要自定义view里实现DarkReceiver这个接口，然后实现onDarkChanged，在这里更改颜色背景即可。