SystemUI 有哪内容

从表面上看， 我们看到的状态栏、通知栏、下拉菜单、导航栏、锁屏、最近任务、低电提示等系统页面都是 SystemUI 的。SystemUI，在源码目录中位于： framework/base/packages 目录下， 可见 SystemUI 和 framework 是关联的， SystemUI 依赖了很多内部 API ， 系统资源， SystemUI 编译是要依赖系统源码的。

SystemUI 也是一个应用，不过这个应用特殊之处在于他没有启动图标、也没有入口 Activity 。他的入口程序是一个服务:SystemUIService。 这个服务会被系统服务拉起来， 这个服务起来， SystemUI 应用进程就创建起来了，具体启动过程后面会分析。除了 SystemUIService ， SystemUI 还有很多服务， 例如： 负责锁屏的KeyguardService、负责最近任务的 RecentsSystemUserService、负责壁纸的 ImageWallpaper 、负责截屏的TakeScreenshotService 等。

下面是PhoneStatusBarView的view 树形图：

PanelHolder

PanelHolder是用户下拉 status bar 后得到的 view。它主要包含 QuickSettings 和 Notification panel 两个部分。PanelHolder是一个继承自FrameLayout的自定义view,它的内容是通过include status_bar_expanded.xml进行填充的。PanelHolder的布局比较复杂，为了提高view的重用性大量的使用了include标签。下面是PanelHolder的view树形图, 只给出了了主要的view：

架构关系

在系统服务中，有一个服务是专门为 SystemUI 的状态栏服务的， 这个服务就是 StatusbarManagerService （简称：SMS），和这个服务关系比较密切的服务是 WindowManagerService（简称：WMS）， SMS 主要管控的是状态栏、导航栏， 例如：我们可以设置全屏、沉浸式状态栏都是 SMS 在起作用。

services组件启动时配置列表 : (R.array.config_systemUIServiceComponents)

所有 SystemUIService 都是继承自 SystemUI.class , SystemUI.class 是一个抽象类

<item>com.android.systemui.util.NotificationChannels</item> 通知信息 
<item>com.android.systemui.keyguard.KeyguardViewMediator</item> 锁屏 
<item>com.android.systemui.recents.Recents</item> 近期列表
Android 10之后近期列表的显示被移到Launcher里面了。在Launcher3的一个 类中TouchInteractionService.java   IBinder mMyBinder = new IOverviewProxy.Stub() 通过AIDL的方法与systemUI通信
————————————————
<item>com.android.systemui.volume.VolumeUI</item> 声音UI显示 
<item>com.android.systemui.statusbar.phone.StatusBar</item> 状态栏及下拉面板
<item>com.android.systemui.usb.StorageNotification</item> usb通知管理 
<item>com.android.systemui.power.PowerUI</item>  电源UI显示管理
<item>com.android.systemui.media.RingtonePlayer</item> 播放铃声 
<item>com.android.systemui.keyboard.KeyboardUI</item>键盘UI 
<item>com.android.systemui.shortcut.ShortcutKeyDispatcher</item>快捷方式  
<item>@string/config_systemUIVendorServiceComponent</item>厂商相关定制 
<item>com.android.systemui.util.leak.GarbageMonitor$Service</item>垃圾监测器  
<item>com.android.systemui.LatencyTester</item> 延迟测试仪 
<item>com.android.systemui.globalactions.GlobalActionsComponent</item>  关机界面的显示、全局控制
<item>com.android.systemui.ScreenDecorations</item>屏幕装饰  
<item>com.android.systemui.biometrics.AuthController</item>生物识别  
<item>com.android.systemui.SliceBroadcastRelayHandler</item> 切片广播 
<item>com.android.systemui.statusbar.notification.InstantAppNotifier</item>  
<item>com.android.systemui.theme.ThemeOverlayController</item>  
<item>com.android.systemui.accessibility.WindowMagnification</item>  
<item>com.android.systemui.accessibility.SystemActions</item>  
<item>com.android.systemui.toast.ToastUI</item>  Toast
<item>com.android.systemui.wmshell.WMShell</item> 

一、SystemUI的启动流程

1、SystemServer

SystemServer启动后，会在Main Thread启动ActivityManagerService，当ActivityManagerService systemReady后，会去启动SystemUIService。

/frameworks/base/services/java/com/android/server/SystemServer.java

①main

    /**
     * The main entry point from zygote.
     */
    public static void main(String[] args) {
        new SystemServer().run();
    }

②run

    private void run() {
        t.traceBegin("InitBeforeStartServices");
        ....
       // Create the system service manager.
            mSystemServiceManager = new SystemServiceManager(mSystemContext);
            mSystemServiceManager.setStartInfo(mRuntimeRestart,
                    mRuntimeStartElapsedTime, mRuntimeStartUptime);
            LocalServices.addService(SystemServiceManager.class, mSystemServiceManager);
        ....
       }

③mActivityManagerService.systemReady

mActivityManagerService.systemReady(() -> {
    //准备好服务
    Slog.i(TAG, "Making services ready");
    ....
            //跟踪开启系统界面
            t.traceBegin("StartSystemUI");
            try {
                //开启系统界面
                startSystemUi(context, windowManagerF);
            } catch (Throwable e) {
                reportWtf("starting System UI", e);
            }
            t.traceEnd();
    ....
}

④startSystemUi

    private static void startSystemUi(Context context, WindowManagerService windowManager) {
        PackageManagerInternal pm = LocalServices.getService(PackageManagerInternal.class);
        Intent intent = new Intent();
        intent.setComponent(pm.getSystemUiServiceComponent());
        intent.addFlags(Intent.FLAG_DEBUG_TRIAGED_MISSING);
        //Slog.d(TAG, "Starting service: " + intent);
        //通过startServiceAsUser，SystemUIService就启动了，即SystemUI进程开机启动
        context.startServiceAsUser(intent, UserHandle.SYSTEM);
        windowManager.onSystemUiStarted();
    }

2、systemUIService

在SystemUIService的onCreate方法中会调用SystemUIApplication的startServicesIfNeeded方法，这个方法会调用 startServicesIfNeeded(SERVICES)方法启动一系列服务

    @Override
    public void onCreate() {
        super.onCreate();

        // Start all of SystemUI
        ((SystemUIApplication) getApplication()).startServicesIfNeeded();

3、SystemUIApplication

/frameworks/base/packages/SystemUI/src/com/android/systemui/SystemUIApplication.java

①startServicesIfNeeded()

public void startServicesIfNeeded() {
    //获取所有的服务的路径，所有SERVICES统一继承了SystemUI类：
    String[] names = SystemUIFactory.getInstance().getSystemUIServiceComponents(getResources());
    startServicesIfNeeded(/* metricsPrefix= */ "StartServices", names);
}

②startServicesIfNeeded(String metricsPrefix, String[] services)

在重载方法中将每一个名称通过反射来得到实例对象,然后依次调用每一个SystemUI的子类的start方法启动每一个模块。

private void startServicesIfNeeded(String metricsPrefix, String[] services) {
    if (mServicesStarted) {
        return;
    }
    mServices = new SystemUI[services.length];

    //检查一下，也许在我们开始之前很久它就已经完成了
    if (!mBootCompleteCache.isBootComplete()) {
        // check to see if maybe it was already completed long before we began
        // see ActivityManagerService.finishBooting()
        if ("1".equals(SystemProperties.get("sys.boot_completed"))) {
            mBootCompleteCache.setBootComplete();
            if (DEBUG) {
                Log.v(TAG, "BOOT_COMPLETED was already sent");
            }
        }
    }

    final DumpManager dumpManager = mRootComponent.createDumpManager();

    Log.v(TAG, "Starting SystemUI services for user " +
            Process.myUserHandle().getIdentifier() + ".");
    TimingsTraceLog log = new TimingsTraceLog("SystemUIBootTiming",
            Trace.TRACE_TAG_APP);
    //开始追踪
    log.traceBegin(metricsPrefix);
    final int N = services.length;
    //遍历services这个数组
    for (int i = 0; i < N; i++) {
        String clsName = services[i];
        if (DEBUG) Log.d(TAG, "loading: " + clsName);
        log.traceBegin(metricsPrefix + clsName);
        long ti = System.currentTimeMillis();
        try {
            SystemUI obj = mComponentHelper.resolveSystemUI(clsName);
            if (obj == null) {
                Constructor constructor = Class.forName(clsName).getConstructor(Context.class);
                obj = (SystemUI) constructor.newInstance(this);
            }
            mServices[i] = obj;
        } catch (ClassNotFoundException
                | NoSuchMethodException
                | IllegalAccessException
                | InstantiationException
                | InvocationTargetException ex) {
            throw new RuntimeException(ex);
        }

        if (DEBUG) Log.d(TAG, "running: " + mServices[i]);
        //依次调用service的start方法启动服务
        mServices[i].start();
        log.traceEnd();

        // Warn if initialization of component takes too long
        //如果组件初始化时间过长，则发出警告
        ti = System.currentTimeMillis() - ti;
        if (ti > 1000) {
            Log.w(TAG, "Initialization of " + clsName + " took " + ti + " ms");
        }
        if (mBootCompleteCache.isBootComplete()) {
            mServices[i].onBootCompleted();
        }

        dumpManager.registerDumpable(mServices[i].getClass().getName(), mServices[i]);
    }
    mRootComponent.getInitController().executePostInitTasks();
    //结束追踪
    log.traceEnd();

    mServicesStarted = true;
}

4、SystemUI

/**
 * @see SystemUIApplication#startServicesIfNeeded()
 *系统界面应用  如果需要，启动服务
 */
public abstract class SystemUI implements Dumpable {
    protected final Context mContext;

    public SystemUI(Context context) {
        mContext = context;
    }

    public abstract void start();

    protected void onConfigurationChanged(Configuration newConfig) {
    }

    @Override
    public void dump(@NonNull FileDescriptor fd, @NonNull PrintWriter pw, @NonNull String[] args) {
    }

    protected void onBootCompleted() {
    }

    public static void overrideNotificationAppName(Context context, Notification.Builder n,
            boolean system) {
        final Bundle extras = new Bundle();
        String appName = system
                ? context.getString(com.android.internal.R.string.notification_app_name_system)
                : context.getString(com.android.internal.R.string.notification_app_name_settings);
        extras.putString(Notification.EXTRA_SUBSTITUTE_APP_NAME, appName);

        n.addExtras(extras);
    }
}

二、状态栏

1、SystemBars

SystemBars加载基本全部SystemUI的界面显示，由前面可知调用的start方法实际上是每一个继承于SytemUI的子类中的方法

①start

②createStatusBarFromConfig

从string资源文件里面读取class name，通过java的反射机制实例化对象，然后调用start()方法启动，class name的值如下图：

    private void createStatusBarFromConfig() {
        ......
        String clsName = mContext.getString(R.string.config_statusBarComponent);
        ......
        try {
            cls = mContext.getClassLoader().loadClass(clsName);
        } catch (Throwable t) {
            throw andLog("Error loading status bar component: " + clsName, t);
        }
        try {
            mStatusBar = (BaseStatusBar) cls.newInstance();
        } catch (Throwable t) {
            throw andLog("Error creating status bar component: " + clsName, t);
        }
        ......
        mStatusBar.start();
        ......
    }

③String

    <!-- Component to be used as the status bar service.  Must implement the IStatusBar
     interface.  This name is in the ComponentName flattened format (package/class)  -->
    <string name="config_statusBarComponent" translatable="false">com.android.systemui.statusbar.phone.StatusBar</string>

2、StatusBar

①createAndAddWindows

    public void createAndAddWindows(@Nullable RegisterStatusBarResult result) {
        //创建状态栏
        makeStatusBarView(result);
        mNotificationShadeWindowController.attach();
        //创建状态栏的窗口
        mStatusBarWindowController.attach();
    }

②makeStatusBarView

protected void makeStatusBarView(@Nullable RegisterStatusBarResult result) {
    final Context context = mContext;
    .....
    FragmentHostManager.get(mPhoneStatusBarWindow)
            .addTagListener(CollapsedStatusBarFragment.TAG, (tag, fragment) -> {
                //CollapsedStatusBarFragment 替换 status_bar_container(状态栏通知显示区域)
                CollapsedStatusBarFragment statusBarFragment =
                        (CollapsedStatusBarFragment) fragment;

                PhoneStatusBarView oldStatusBarView = mStatusBarView;
                mStatusBarView = (PhoneStatusBarView) statusBarFragment.getView();
                //传递statusBar处理下拉事件
                mStatusBarView.setBar(this);
                //传递 NotificationPanelView 显示下拉UI控制
                mStatusBarView.setPanel(mNotificationPanelViewController);
                mStatusBarView.setScrimController(mScrimController);
                //初始化通知栏区域
                statusBarFragment.initNotificationIconArea(mNotificationIconAreaController);
                ......
                    
            }).getFragmentManager()
            .beginTransaction()
            .replace(R.id.status_bar_container, new CollapsedStatusBarFragment(),
                    CollapsedStatusBarFragment.TAG)
            .commit();
    .....

2、CollapsedStatusBarFragment

①onCreateView

    @Override
    public View onCreateView(LayoutInflater inflater, @Nullable ViewGroup container,
            Bundle savedInstanceState) {
        return inflater.inflate(R.layout.status_bar, container, false);
    }

②initNotificationIconArea

public void initNotificationIconArea(NotificationIconAreaController
        notificationIconAreaController) {
    //notification_icon_area是在status_bar.xml的布局，它是属于通知Notification    
    //获取到 notification_icon_area，FrameLayout转为ViewGroup，
    ViewGroup notificationIconArea = mStatusBar.findViewById(R.id.notification_icon_area);
    //调用 notificationIconAreaController 获取通知要显示的view(LinearLayout)
    //在4中跟进
    mNotificationIconAreaInner =
            notificationIconAreaController.getNotificationInnerAreaView();
    //如果已经有显示的view，通过 view 父布局将其自身remove，然后再重新addView。
    //最后将 mNotificationIconAreaInner 显示出来(设置透明度为1，visibility为VISIBLE)
    if (mNotificationIconAreaInner.getParent() != null) {
        ((ViewGroup) mNotificationIconAreaInner.getParent())
                .removeView(mNotificationIconAreaInner);
    }
    notificationIconArea.addView(mNotificationIconAreaInner);

    //与上面一样
    ViewGroup statusBarCenteredIconArea = mStatusBar.findViewById(R.id.centered_icon_area);
    mCenteredIconArea = notificationIconAreaController.getCenteredNotificationAreaView();
    if (mCenteredIconArea.getParent() != null) {
        ((ViewGroup) mCenteredIconArea.getParent())
                .removeView(mCenteredIconArea);
    }
    statusBarCenteredIconArea.addView(mCenteredIconArea);

    //默认为显示，直到我们知道其他情况
    // Default to showing until we know otherwise.
    showNotificationIconArea(false);
}

③showNotificationIconArea

当状态栏下拉时，状态栏中的图标icon会慢慢的变成透明和不可见，就是通过hideSystemIconArea(true), hideNotificationIconArea(true）

//当状态栏下拉时，设置状态栏中的图标icon会慢慢的变成透明和不可见    
public void hideNotificationIconArea(boolean animate) {
        animateHide(mNotificationIconAreaInner, animate);
        animateHide(mCenteredIconArea, animate);
    }
//设置状态栏图标透明度为1，visibility为VISIBLE
    public void showNotificationIconArea(boolean animate) {
        animateShow(mNotificationIconAreaInner, animate);
        animateShow(mCenteredIconArea, animate);
    }

    public void hideOperatorName(boolean animate) {
        if (mOperatorNameFrame != null) {
            animateHide(mOperatorNameFrame, animate);
        }
    }

    public void showOperatorName(boolean animate) {
        if (mOperatorNameFrame != null) {
            animateShow(mOperatorNameFrame, animate);
        }

④animateShow

    private void animateShow(View v, boolean animate) {
        v.animate().cancel();
        //(设置透明度为1，visibility为VISIBLE)
        v.setVisibility(View.VISIBLE);
        if (!animate) {
            v.setAlpha(1f);
            return;
        }
        .....
    }

⑤animateHiddenState

//将视图动画化为 INVISIBLE 或 GONE    
private void animateHiddenState(final View v, int state, boolean animate) {
        v.animate().cancel();
        if (!animate) {
            v.setAlpha(0f);
            v.setVisibility(state);
            return;
        }

        v.animate()
                .alpha(0f)
                .setDuration(160)
                .setStartDelay(0)
                .setInterpolator(Interpolators.ALPHA_OUT)
                .withEndAction(() -> v.setVisibility(state));
    }

3、status_bar.xml

<?xml version="1.0" encoding="utf-8"?>
<!--
**
** Copyright 2006, The Android Open Source Project
**
** Licensed under the Apache License, Version 2.0 (the "License");
** you may not use this file except in compliance with the License.
** You may obtain a copy of the License at
**
**     http://www.apache.org/licenses/LICENSE-2.0
**
** Unless required by applicable law or agreed to in writing, software
** distributed under the License is distributed on an "AS IS" BASIS,
** WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
** See the License for the specific language governing permissions and
** limitations under the License.
*/
-->

<!--    android:background="@drawable/status_bar_closed_default_background" -->
<com.android.systemui.statusbar.phone.PhoneStatusBarView
    xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:systemui="http://schemas.android.com/apk/res/com.android.systemui"
    android:layout_width="match_parent"
    android:layout_height="@dimen/status_bar_height"
    android:id="@+id/status_bar"
    android:orientation="vertical"
    android:focusable="false"
    android:descendantFocusability="afterDescendants"
    android:accessibilityPaneTitle="@string/status_bar"
    >

    <!-- add for KGDAANWIKFRA-135 -->
    <View
        android:layout_width="match_parent"
        android:layout_height="@dimen/status_bar_height"
        android:id="@+id/status_bar_dark_view"
        android:background="#ff000000"
        android:visibility="gone" />
    //<!--通知灯，默认gone-->
    <ImageView
        android:id="@+id/notification_lights_out"
        android:layout_width="@dimen/status_bar_icon_size"
        android:layout_height="match_parent"
        android:paddingStart="@dimen/status_bar_padding_start"
        android:paddingBottom="2dip"
        android:src="@drawable/ic_sysbar_lights_out_dot_small"
        android:scaleType="center"
        android:visibility="gone"
        />
    //<!--状态栏内容-->
    <LinearLayout android:id="@+id/status_bar_contents"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:paddingStart="@dimen/status_bar_padding_start"
        android:paddingEnd="@dimen/status_bar_padding_end"
        android:paddingTop="@dimen/status_bar_padding_top"
        android:orientation="horizontal"
        >
        <FrameLayout
            android:layout_height="match_parent"
            android:layout_width="0dp"
            android:layout_weight="1">

            <include layout="@layout/heads_up_status_bar_layout" />

            <!-- The alpha of the left side is controlled by PhoneStatusBarTransitions, and the
             individual views are controlled by StatusBarManager disable flags DISABLE_CLOCK and
             DISABLE_NOTIFICATION_ICONS, respectively -->
            <LinearLayout
                android:id="@+id/status_bar_left_side"
                android:layout_height="match_parent"
                android:layout_width="match_parent"
                android:clipChildren="false"
            >
                <ViewStub
                    android:id="@+id/operator_name"
                    android:layout_width="wrap_content"
                    android:layout_height="match_parent"
                    android:layout="@layout/operator_name" />

                <com.android.systemui.statusbar.policy.Clock
                    android:id="@+id/clock"
                    android:layout_width="wrap_content"
                    android:layout_height="match_parent"
                    android:textAppearance="@style/TextAppearance.StatusBar.Clock"
                    android:singleLine="true"
                    android:paddingStart="@dimen/status_bar_left_clock_starting_padding"
                    android:paddingEnd="@dimen/status_bar_left_clock_end_padding"
                    android:gravity="center_vertical|start"
                />

                //<!--通知图标区域-->
                <com.android.systemui.statusbar.AlphaOptimizedFrameLayout
                    android:id="@+id/notification_icon_area"
                    android:layout_width="0dp"
                    android:layout_height="match_parent"
                    android:layout_weight="1"
                    android:orientation="horizontal"
                    android:clipChildren="false"/>

            </LinearLayout>
        </FrameLayout>

        <!-- Space should cover the notch (if it exists) and let other views lay out around it -->
        <android.widget.Space
            android:id="@+id/cutout_space_view"
            android:layout_width="0dp"
            android:layout_height="match_parent"
            android:gravity="center_horizontal|center_vertical"
        />

        //居中的图标区域        
        <com.android.systemui.statusbar.AlphaOptimizedFrameLayout
            android:id="@+id/centered_icon_area"
            android:layout_width="wrap_content"
            android:layout_height="match_parent"
            android:orientation="horizontal"
            android:clipChildren="false"
            android:gravity="center_horizontal|center_vertical"/>

        <com.android.keyguard.AlphaOptimizedLinearLayout android:id="@+id/system_icon_area"
            android:layout_width="0dp"
            android:layout_height="match_parent"
            android:layout_weight="1"
            android:orientation="horizontal"
            android:gravity="center_vertical|end"
            >
            //<!--系统图标-->
            <include layout="@layout/system_icons" />
        </com.android.keyguard.AlphaOptimizedLinearLayout>
    </LinearLayout>
    //<!--紧急密码管理员文本-->
    <ViewStub
        android:id="@+id/emergency_cryptkeeper_text"
        android:layout_width="wrap_content"
        android:layout_height="match_parent"
        android:layout="@layout/emergency_cryptkeeper_text"
    />

</com.android.systemui.statusbar.phone.PhoneStatusBarView>

4、NotificationIconAreaController

①getNotificationInnerAreaView

    /**
     * Returns the view that represents the notification area.+
     * 返回表示通知区域的视图。
     */
    public View getNotificationInnerAreaView() {
        return mNotificationIconArea;
    }

②initializeNotificationAreaViews

/**
 * Initializes the views that will represent the notification area.
 * 初始化将表示通知区域的视图。
 */
protected void initializeNotificationAreaViews(Context context) {
    reloadDimens(context);
    
    LayoutInflater layoutInflater = LayoutInflater.from(context);
    //通知图标区域布局
    mNotificationIconArea = inflateIconArea(layoutInflater);
    //通知图标
    mNotificationIcons = mNotificationIconArea.findViewById(R.id.notificationIcons);
    //获取通知滚动布局
    mNotificationScrollLayout = mStatusBar.getNotificationScrollLayout();
    //中心图标区域布局
    mCenteredIconArea = layoutInflater.inflate(R.layout.center_icon_area, null);
    //居中的图标
    mCenteredIcon = mCenteredIconArea.findViewById(R.id.centeredIcon);

    initAodIcons();
}

③inflateIconArea

    protected View inflateIconArea(LayoutInflater inflater) {
        return inflater.inflate(R.layout.notification_icon_area, null);
    }

三、status icon加载流程

1、 status_bar.xml

        <com.android.systemui.statusbar.AlphaOptimizedFrameLayout
            android:id="@+id/centered_icon_area"
            android:layout_width="wrap_content"
            android:layout_height="match_parent"
            android:orientation="horizontal"
            android:clipChildren="false"
            android:gravity="center_horizontal|center_vertical"/>

        <com.android.keyguard.AlphaOptimizedLinearLayout android:id="@+id/system_icon_area"
            android:layout_width="0dp"
            android:layout_height="match_parent"
            android:layout_weight="1"
            android:orientation="horizontal"
            android:gravity="center_vertical|end"
            >
            <!--系统图标-->
            <include layout="@layout/system_icons" />
        </com.android.keyguard.AlphaOptimizedLinearLayout>

2、system_icons.xml

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
              xmlns:systemui="http://schemas.android.com/apk/res-auto"
    android:id="@+id/system_icons"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:gravity="center_vertical">
    //StatusIconContainer继承AlphaOptimizedLinearLayout
    <com.android.systemui.statusbar.phone.StatusIconContainer android:id="@+id/statusIcons"
        android:layout_width="0dp"
        android:layout_weight="1"
        android:layout_height="match_parent"
        android:paddingEnd="@dimen/signal_cluster_battery_padding"
        android:gravity="center_vertical"
        android:orientation="horizontal"/>

    <com.android.systemui.BatteryMeterView android:id="@+id/battery"
        android:layout_height="match_parent"
        android:layout_width="wrap_content"
        android:clipToPadding="false"
        android:clipChildren="false"
        systemui:textAppearance="@style/TextAppearance.StatusBar.Clock" />
</LinearLayout>

3、AlphaOptimizedLinearLayout

    //该方法用来标记当前view是否存在过度绘制，存在返回ture，不存在返回false，
    //api里面默认返回为true，status icon不存在过度绘制。
    @Override
    public boolean hasOverlappingRendering() {
        return false;
    }

4、CollapsedStatusBarFragment

    @Override
    public void onViewCreated(View view, @Nullable Bundle savedInstanceState) {
        super.onViewCreated(view, savedInstanceState);
        mStatusBar = (PhoneStatusBarView) view;
        if (savedInstanceState != null && savedInstanceState.containsKey(EXTRA_PANEL_STATE)) {
            mStatusBar.restoreHierarchyState(
                    savedInstanceState.getSparseParcelableArray(EXTRA_PANEL_STATE));
        }
        // TINNO BEGIN, add for KGDAANWIKFRA-135
        if (Utils.TINNO_NOTCH_SCREEN) {
            mStatusBarDarkView = mStatusBar.findViewById(R.id.status_bar_dark_view);
            toggleStatusBarDarkView();
            mLastOrientation = getContext().getResources().getConfiguration().orientation;
        }
        // TINNO END
        //DarkIconManager初始化
        mDarkIconManager = new DarkIconManager(view.findViewById(R.id.statusIcons),
                Dependency.get(CommandQueue.class));
        
        mDarkIconManager.setShouldLog(true);
        Dependency.get(StatusBarIconController.class).addIconGroup(mDarkIconManager);
        mSystemIconArea = mStatusBar.findViewById(R.id.system_icon_area);
        mClockView = mStatusBar.findViewById(R.id.clock);
        showSystemIconArea(false);
        showClock(false);
        initEmergencyCryptkeeperText();
        initOperatorName();
    }

4、StatusBarIconController

①DarkIconManager

    /**
     * Version of ViewGroup that observes state from the DarkIconDispatcher.
     */
    public static class DarkIconManager extends IconManager {
        private final DarkIconDispatcher mDarkIconDispatcher;
        private int mIconHPadding;

        public DarkIconManager(LinearLayout linearLayout, CommandQueue commandQueue) {
            super(linearLayout, commandQueue);
            mIconHPadding = mContext.getResources().getDimensionPixelSize(
                    R.dimen.status_bar_icon_padding);
            mDarkIconDispatcher = Dependency.get(DarkIconDispatcher.class);
        }
        //每个icon应该就是对应着代表顺序的index和数据类型为String的slot
        @Override
        protected void onIconAdded(int index, String slot, boolean blocked,
                StatusBarIconHolder holder) {
            StatusIconDisplayable view = addHolder(index, slot, blocked, holder);
            mDarkIconDispatcher.addDarkReceiver((DarkReceiver) view);
        }
        .....

        //onSetIcon可能就是刷新icon状态的
        @Override
        public void onSetIcon(int viewIndex, StatusBarIcon icon) {
            super.onSetIcon(viewIndex, icon);
            mDarkIconDispatcher.applyDark((DarkReceiver) mGroup.getChildAt(viewIndex));
        }
        .....

    }

②IconManager

public static class IconManager implements DemoMode {
    .....
    protected void onIconAdded(int index, String slot, boolean blocked,
        StatusBarIconHolder holder) {
        
        addHolder(index, slot, blocked, holder);
    }    
    
    protected StatusIconDisplayable addHolder(int index, String slot, boolean blocked,
        StatusBarIconHolder holder) {
        switch (holder.getType()) {
            case TYPE_ICON:
                return addIcon(index, slot, blocked, holder.getIcon());
    
            case TYPE_WIFI:
                return addSignalIcon(index, slot, holder.getWifiState());
    
            case TYPE_MOBILE:
                return addMobileIcon(index, slot, holder.getMobileState());
        }
        return null;
    }
    
    @VisibleForTesting
    protected StatusBarIconView addIcon(int index, String slot, boolean blocked,
            StatusBarIcon icon) {
        
            StatusBarIconView view = onCreateStatusBarIconView(slot, blocked);
            view.set(icon);
            mGroup.addView(view, index, onCreateLayoutParams());
            return view;
    }
        .....
}

5、StatusBarIconControllerImpl

//继承StatusBarIconList
public class StatusBarIconControllerImpl extends StatusBarIconList implements Tunable,
        ConfigurationListener, Dumpable, CommandQueue.Callbacks, StatusBarIconController {   
    ......        
    @Inject
    public StatusBarIconControllerImpl(Context context, CommandQueue commandQueue) {
        //config_statusBarIcons
        super(context.getResources().getStringArray(
                com.android.internal.R.array.config_statusBarIcons));
        Dependency.get(ConfigurationController.class).addCallback(this);
     .....
    }
}

6、StatusBarIconList

在初始化的时候就已经定义好了所有的slots，然后从framework中加载出来，index就是string-array中的顺序。

public class StatusBarIconList {
    private ArrayList<Slot> mSlots = new ArrayList<>();

    public StatusBarIconList(String[] slots) {
        final int N = slots.length;
        for (int i=0; i < N; i++) {
            mSlots.add(new Slot(slots[i], null));
        }
    }

7、config_statusBarIcons

<string-array name="config_statusBarIcons">
        <item><xliff:g id="id">@string/status_bar_rotate</xliff:g></item>
        <item><xliff:g id="id">@string/status_bar_headset</xliff:g></item>
        <item><xliff:g id="id">@string/status_bar_data_saver</xliff:g></item>
        <item><xliff:g id="id">@string/status_bar_managed_profile</xliff:g></item>
        <item><xliff:g id="id">@string/status_bar_ime</xliff:g></item>
        <item><xliff:g id="id">@string/status_bar_sync_failing</xliff:g></item>
        <item><xliff:g id="id">@string/status_bar_sync_active</xliff:g></item>
        <item><xliff:g id="id">@string/status_bar_cast</xliff:g></item>
        <item><xliff:g id="id">@string/status_bar_hotspot</xliff:g></item>
        <item><xliff:g id="id">@string/status_bar_location</xliff:g></item>
        <item><xliff:g id="id">@string/status_bar_bluetooth</xliff:g></item>
        <item><xliff:g id="id">@string/status_bar_nfc</xliff:g></item>
        <item><xliff:g id="id">@string/status_bar_tty</xliff:g></item>
        <item><xliff:g id="id">@string/status_bar_speakerphone</xliff:g></item>
        <item><xliff:g id="id">@string/status_bar_zen</xliff:g></item>
        <item><xliff:g id="id">@string/status_bar_mute</xliff:g></item>
        <item><xliff:g id="id">@string/status_bar_volume</xliff:g></item>
        <item><xliff:g id="id">@string/status_bar_vpn</xliff:g></item>
        <item><xliff:g id="id">@string/status_bar_ethernet</xliff:g></item>
        <item><xliff:g id="id">@string/status_bar_wifi</xliff:g></item>
        <item><xliff:g id="id">@string/status_bar_mobile</xliff:g></item>
        <item><xliff:g id="id">@string/status_bar_airplane</xliff:g></item>
        <item><xliff:g id="id">@string/status_bar_cdma_eri</xliff:g></item>
        <item><xliff:g id="id">@string/status_bar_data_connection</xliff:g></item>
        <item><xliff:g id="id">@string/status_bar_phone_evdo_signal</xliff:g></item>
        <item><xliff:g id="id">@string/status_bar_phone_signal</xliff:g></item>
        <item><xliff:g id="id">@string/status_bar_battery</xliff:g></item>
        <item><xliff:g id="id">@string/status_bar_alarm_clock</xliff:g></item>
        <item><xliff:g id="id">@string/status_bar_secure</xliff:g></item>
        <item><xliff:g id="id">@string/status_bar_clock</xliff:g></item>
    </string-array>
 
    <string translatable="false" name="status_bar_rotate">rotate</string>
    <string translatable="false" name="status_bar_headset">headset</string>
    <string translatable="false" name="status_bar_data_saver">data_saver</string>
    <string translatable="false" name="status_bar_managed_profile">managed_profile</string>
    <string translatable="false" name="status_bar_ime">ime</string>
    <string translatable="false" name="status_bar_sync_failing">sync_failing</string>
    <string translatable="false" name="status_bar_sync_active">sync_active</string>
    <string translatable="false" name="status_bar_cast">cast</string>
    <string translatable="false" name="status_bar_hotspot">hotspot</string>
    <string translatable="false" name="status_bar_location">location</string>
    <string translatable="false" name="status_bar_bluetooth">bluetooth</string>
    <string translatable="false" name="status_bar_nfc">nfc</string>
    <string translatable="false" name="status_bar_tty">tty</string>
    <string translatable="false" name="status_bar_speakerphone">speakerphone</string>
    <string translatable="false" name="status_bar_zen">zen</string>
    <string translatable="false" name="status_bar_mute">mute</string>
    <string translatable="false" name="status_bar_volume">volume</string>
    <string translatable="false" name="status_bar_wifi">wifi</string>
    <string translatable="false" name="status_bar_cdma_eri">cdma_eri</string>
    <string translatable="false" name="status_bar_data_connection">data_connection</string>
    <string translatable="false" name="status_bar_phone_evdo_signal">phone_evdo_signal</string>
    <string translatable="false" name="status_bar_phone_signal">phone_signal</string>
    <string translatable="false" name="status_bar_battery">battery</string>
    <string translatable="false" name="status_bar_alarm_clock">alarm_clock</string>
    <string translatable="false" name="status_bar_secure">secure</string>
    <string translatable="false" name="status_bar_clock">clock</string>
    <string translatable="false" name="status_bar_mobile">mobile</string>
    <string translatable="false" name="status_bar_vpn">vpn</string>
    <string translatable="false" name="status_bar_ethernet">ethernet</string>
    <string translatable="false" name="status_bar_airplane">airplane</string>

好了，到这里我们的第一部分初始化流程就讲完了

四、状态显示流程

由上面的初始化流程我们可以知道，每个icon都对应了slot，slot数量比较多，我们就挑一个常见的Headset讲下，其他的流程都是大致一样的。

1、PhoneStatusBarPolicy

初始化注册了大量的监听

①init

//  初始化headset的slot
mSlotHeadset = resources.getString(com.android.internal.R.string.status_bar_headset);
/** Initialize the object after construction. */
public void init() {
    // listen for broadcasts
    IntentFilter filter = new IntentFilter();
    //  注册headset状态变化的action
    filter.addAction(AudioManager.ACTION_HEADSET_PLUG);
    
    filter.addAction(Intent.ACTION_SIM_STATE_CHANGED);
    filter.addAction(TelecomManager.ACTION_CURRENT_TTY_MODE_CHANGED);
    filter.addAction(Intent.ACTION_MANAGED_PROFILE_AVAILABLE);
    filter.addAction(Intent.ACTION_MANAGED_PROFILE_UNAVAILABLE);
    filter.addAction(Intent.ACTION_MANAGED_PROFILE_REMOVED);
    mBroadcastDispatcher.registerReceiverWithHandler(mIntentReceiver, filter, mHandler);
    Observer<Integer> observer = ringer -> mHandler.post(this::updateVolumeZen);

    mRingerModeTracker.getRingerMode().observeForever(observer);
    mRingerModeTracker.getRingerModeInternal().observeForever(observer);
    ....
    }

②BroadcastReceiver

    private BroadcastReceiver mIntentReceiver = new BroadcastReceiver() {
        @Override
        public void onReceive(Context context, Intent intent) {
            String action = intent.getAction();
            switch (action) {
                case Intent.ACTION_SIM_STATE_CHANGED:
                    // Avoid rebroadcast because SysUI is direct boot aware.
                    if (intent.getBooleanExtra(Intent.EXTRA_REBROADCAST_ON_UNLOCK, false)) {
                        break;
                    }
                    break;
                case TelecomManager.ACTION_CURRENT_TTY_MODE_CHANGED:
                    updateTTY(intent.getIntExtra(TelecomManager.EXTRA_CURRENT_TTY_MODE,
                            TelecomManager.TTY_MODE_OFF));
                    break;
                case Intent.ACTION_MANAGED_PROFILE_AVAILABLE:
                case Intent.ACTION_MANAGED_PROFILE_UNAVAILABLE:
                case Intent.ACTION_MANAGED_PROFILE_REMOVED:
                    updateManagedProfile();
                    break;
                //监听ACTION_HEADSET_PLUG
                case AudioManager.ACTION_HEADSET_PLUG:
                    updateHeadsetPlug(context, intent);
                    break;
            }
        }
    };

③updateHeadsetPlug

完成icon添加和状态监听，然后当收到对应的action变化的时候，更新headset icon

    private void updateHeadsetPlug(Context context, Intent intent) {
        boolean connected = intent.getIntExtra("state", 0) != 0;
        boolean hasMic = intent.getIntExtra("microphone", 0) != 0;
        if (connected) {
            String contentDescription = mResources.getString(hasMic
                    ? R.string.accessibility_status_bar_headset
                    : R.string.accessibility_status_bar_headphones);
            //setIcon负责设置icon
            mIconController.setIcon(mSlotHeadset, hasMic ? R.drawable.stat_sys_headset_mic
                    : R.drawable.stat_sys_headset, contentDescription);
            //setIconVisibility则根据connected状态设置icon的可见性
            mIconController.setIconVisibility(mSlotHeadset, true);
        } else {
            /*UNISOC: Add for bug 1130932 {@ */
            AudioManager audioManager = (AudioManager) context.getSystemService(Context.AUDIO_SERVICE);
            if (!audioManager.isWiredHeadsetOn()) {
                //setIconVisibility则根据connected状态设置icon的可见性
                mIconController.setIconVisibility(mSlotHeadset, false);
            }
            /* @} */
        }
    }

2、StatusBarIconControllerImpl

①setIcon

@Override
public void setIcon(String slot, int resourceId, CharSequence contentDescription) {
    //根据slot找到对应的index
    int index = getSlotIndex(slot);
    //用index取得对应的icon
    StatusBarIconHolder holder = getIcon(index, 0);
    if (holder == null) {
        //第一次的时候，icon == null，所以通过new StatusBarIcon创建一个
        StatusBarIcon icon = new StatusBarIcon(UserHandle.SYSTEM, mContext.getPackageName(),
                Icon.createWithResource(
                        mContext, resourceId), 0, 0, contentDescription);
        holder = StatusBarIconHolder.fromIcon(icon);
        //然后调用此方法
        setIcon(index, holder);
    } else {
        holder.getIcon().icon = Icon.createWithResource(mContext, resourceId);
        holder.getIcon().contentDescription = contentDescription;
        handleSet(index, holder);
    }
}


@Override
public void setIcon(int index, @NonNull StatusBarIconHolder holder) {
    boolean isNew = getIcon(index, holder.getTag()) == null;
    super.setIcon(index, holder);

    if (isNew) {
        addSystemIcon(index, holder);
    } else {
        handleSet(index, holder);
    }
}

private void addSystemIcon(int index, StatusBarIconHolder holder) {
    String slot = getSlotName(index);
    int viewIndex = getViewIndex(index, holder.getTag());
    boolean blocked = mIconBlacklist.contains(slot);
    //onIconAdded-》初始化流程里面StatusBarIconController中添加icon的入口
    //到这里setIcon就添加完毕了
    mIconGroups.forEach(l -> l.onIconAdded(viewIndex, slot, blocked, holder));
}

②setIconVisibility

public void setIconVisibility(String slot, boolean visibility) {
    int index = getSlotIndex(slot);
    StatusBarIconHolder holder = getIcon(index, 0);
    if (holder == null || holder.isVisible() == visibility) {
        return;
    }
    holder.setVisible(visibility);
    //icon已经创建成功了，icon非空，并且第一次是icon.visible != visibility的
    //就会顺利的走到handleSet(index, icon)
    handleSet(index, holder);
}

private void handleSet(int index, StatusBarIconHolder holder) {
    int viewIndex = getViewIndex(index, holder.getTag());
    //初始化流程里面StatusBarIconController中setIcon的地方
    //到这里setIconVisibility也设置完毕了
    mIconGroups.forEach(l -> l.onSetIconHolder(viewIndex, holder));
}

五、创建状态栏的窗口

1、StatusBarWindowController

mStatusBarWindowController.attach()

    /**
     * Adds the status bar view to the window manager.
     */
    public void attach() {
        // Now that the status bar window encompasses the sliding panel and its
        // translucent backdrop, the entire thing is made TRANSLUCENT and is
        // hardware-accelerated.
        mLp = new WindowManager.LayoutParams(
                ViewGroup.LayoutParams.MATCH_PARENT,
                mBarHeight,
                WindowManager.LayoutParams.TYPE_STATUS_BAR,
                WindowManager.LayoutParams.FLAG_NOT_FOCUSABLE
                        | WindowManager.LayoutParams.FLAG_SPLIT_TOUCH
                        | WindowManager.LayoutParams.FLAG_DRAWS_SYSTEM_BAR_BACKGROUNDS,
                PixelFormat.TRANSLUCENT);
        mLp.privateFlags |= PRIVATE_FLAG_COLOR_SPACE_AGNOSTIC;
        mLp.token = new Binder();
        mLp.gravity = Gravity.TOP;
        mLp.setFitInsetsTypes(0 /* types */);
        mLp.setTitle("StatusBar");
        mLp.packageName = mContext.getPackageName();
        mLp.layoutInDisplayCutoutMode = LAYOUT_IN_DISPLAY_CUTOUT_MODE_ALWAYS;

        //WindowManager中添加view
        //mStatusBarView = mSuperStatusBarViewFactory.getStatusBarWindowView();
        //private final SuperStatusBarViewFactory mSuperStatusBarViewFactory;
        mWindowManager.addView(mStatusBarView, mLp);
        mLpChanged.copyFrom(mLp);
    }

2、SuperStatusBarViewFactory

    /**
     * Gets the inflated {@link StatusBarWindowView} from {@link R.layout#super_status_bar}.
     * Returns a cached instance, if it has already been inflated.
     */
    public StatusBarWindowView getStatusBarWindowView() {
        if (mStatusBarWindowView != null) {
            return mStatusBarWindowView;
        }

        //由其可知加载的布局来自于super_status_bar
        mStatusBarWindowView =
                (StatusBarWindowView) mInjectionInflationController.injectable(
                LayoutInflater.from(mContext)).inflate(R.layout.super_status_bar,
                /* root= */ null);
        if (mStatusBarWindowView == null) {
            throw new IllegalStateException(
                    "R.layout.super_status_bar could not be properly inflated");
        }
        return mStatusBarWindowView;
    }

3、super_status_bar.xml

从前面可知这里会用CollapsedStatusBarFragment 替换 status_bar_container(状态栏通知显示区域)，完成图标的显示

<!-- This is the status bar window. -->
<com.android.systemui.statusbar.phone.StatusBarWindowView
    xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:sysui="http://schemas.android.com/apk/res-auto"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:fitsSystemWindows="true">

    <LinearLayout
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:orientation="vertical"
    >
        <FrameLayout
            android:id="@+id/status_bar_container"
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:visibility="gone"
        />

        <FrameLayout
            android:id="@+id/car_top_navigation_bar_container"
            android:layout_width="match_parent"
            android:layout_height="wrap_content"/>
    </LinearLayout>

</com.android.systemui.statusbar.phone.StatusBarWindowView>