StatusBar

在SystemServer中，首先启动了StatusBarManagerService，来提供StatusBar的相关服务：

if (!disableSystemUI) {
    try {
        Slog.i(TAG, "Status Bar");
        statusBar = new StatusBarManagerService(context, wm);
        ServiceManager.addService(Context.STATUS_BAR_SERVICE, statusBar);
    } catch (Throwable e) {
        reportWtf("starting StatusBarManagerService", e);
    }
}

StatusBarManagerService中构造函数中初始化了状态栏要显示的图标名称IconList，注意——这里并未加载实际的图标，真正的图标drawable资源的加载

是在xxx中做的：

framework\base\services\java\com\android\server\StatusBarManagerService.java

public StatusBarManagerService(Context context, WindowManagerService windowManager) {
    mContext = context;
    mWindowManager = windowManager;
    mWindowManager.setOnHardKeyboardStatusChangeListener(this);

    final Resources res = context.getResources();
    mIcons.defineSlots(res.getStringArray(com.android.internal.R.array.config_statusBarIcons));
}

framework\base\core\res\res\values\Config.xml

<!-- Do not translate. Defines the slots for the right-hand side icons.  That is to say, the
         icons in the status bar that are not notifications. -->
    <string-array name="config_statusBarIcons">
       <item><xliff:g id="id">ime</xliff:g></item>
       <item><xliff:g id="id">sync_failing</xliff:g></item>
       <item><xliff:g id="id">sync_active</xliff:g></item>
       <item><xliff:g id="id">location</xliff:g></item>
       <item><xliff:g id="id">bluetooth</xliff:g></item>
       <item><xliff:g id="id">nfc</xliff:g></item>
       <item><xliff:g id="id">tty</xliff:g></item>
       <item><xliff:g id="id">speakerphone</xliff:g></item>
       <item><xliff:g id="id">mute</xliff:g></item>
       <item><xliff:g id="id">volume</xliff:g></item>
       <item><xliff:g id="id">wifi</xliff:g></item>
       <item><xliff:g id="id">cdma_eri</xliff:g></item>
       <item><xliff:g id="id">data_connection</xliff:g></item>
       <item><xliff:g id="id">phone_evdo_signal</xliff:g></item>
       <item><xliff:g id="id">phone_signal</xliff:g></item>
       <item><xliff:g id="id">battery</xliff:g></item>
       <item><xliff:g id="id">alarm_clock</xliff:g></item>
       <item><xliff:g id="id">secure</xliff:g></item>
       <item><xliff:g id="id">clock</xliff:g></item>
    </string-array>

在SystemServer中启动获取的StatusBarManagerService实例，作为NotificationManagerService的构造参数，以便NotificationManager来调用StatusBarManagerService提供的回调来进行添加、更新状态栏通知等操作：

public IBinder addNotification(StatusBarNotification notification)；

public void updateNotification(IBinder key, StatusBarNotification notification)；

public void removeNotification(IBinder key)；

InputMethodManagerService被初始化后，调用immF.systemRunning(statusBarF)时也传递过去，以供输入法来更新状态栏的输入法图标的显示隐藏等状态变化；

其它，诸如BatterService、MountService等相关图标的更新还未发现如何运作，后续更新

SystemServer在将系统的关键服务项启动完成之后，最后通过启动SystemUIService来创建SystemBar。

// We now tell the activity manager it is okay to run third party
// code.  It will call back into us once it has gotten to the state
// where third party code can really run (but before it has actually
// started launching the initial applications), for us to complete our
// initialization.
ActivityManagerService.self().systemReady(new Runnable() {
    public void run() {
        Slog.i(TAG, "Making services ready");

        try {
            ActivityManagerService.self().startObservingNativeCrashes();
        } catch (Throwable e) {
            reportWtf("observing native crashes", e);
        }
        if (!headless) {
            startSystemUi(contextF);
        }

        ......
    }
}

static final void startSystemUi(Context context) {
    Intent intent = new Intent();
    intent.setComponent(new ComponentName("com.android.systemui",
                "com.android.systemui.SystemUIService"));
    //Slog.d(TAG, "Starting service: " + intent);
    context.startServiceAsUser(intent, UserHandle.OWNER);
}

SystemUIService负责启动如下和状态栏各项显示服务相关的service

private final Class<?>[] SERVICES = new Class[] {
    com.android.systemui.recent.Recents.class,
    com.android.systemui.statusbar.SystemBars.class,
    com.android.systemui.usb.StorageNotification.class,
    com.android.systemui.power.PowerUI.class,
    com.android.systemui.media.RingtonePlayer.class,
    com.android.systemui.settings.SettingsUI.class,
};