Android14 SystemUI 启动流程（1）

1.从SystemServer启动

  private void run() {
		......
        // Start services.
        try {
            t.traceBegin("StartServices");
            startBootstrapServices(t);
            startCoreServices(t);
            startOtherServices(t);//从这里走
            startApexServices(t);
            // Only update the timeout after starting all the services so that we use
            // the default timeout to start system server.
            updateWatchdogTimeout(t);
        } catch (Throwable ex) {
            Slog.e("System", "******************************************");
            Slog.e("System", "************ Failure starting system services", ex);
            throw ex;
        } finally {
            t.traceEnd(); // StartServices
        }
		......

2.走startOtherServices()

    /**
     * Starts a miscellaneous grab bag of stuff that has yet to be refactored and organized.
     */
    private void startOtherServices(@NonNull TimingsTraceAndSlog t) {
		......
		
        t.traceBegin("StartSystemUI");
        try {
            startSystemUi(context, windowManagerF);
        } catch (Throwable e) {
            reportWtf("starting System UI", e);
        }
	    ......
    }

3.启动SystemUi

    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);
        context.startServiceAsUser(intent, UserHandle.SYSTEM);
        windowManager.onSystemUiStarted();
    }

//frameworks/base/services/core/java/com/android/server/pm/PackageManagerInternalBase.java
    @Override
    @Deprecated
    public final ComponentName getSystemUiServiceComponent() {
        return ComponentName.unflattenFromString(getContext().getResources().getString(
                com.android.internal.R.string.config_systemUIServiceComponent));
    }

    <!-- SystemUi service component -->
    <string name="config_systemUIServiceComponent" translatable="false"
            >com.android.systemui/com.android.systemui.SystemUIService</string>

4.启动SystemUIService服务（SystemUI中）

public class SystemUIService extends Service {

    @Override
    public void onCreate() {
        super.onCreate();
        // Start all of SystemUI
        ((SystemUIApplication) getApplication()).startServicesIfNeeded();
    }
}

    启动实现了CoreStartable的实体类：如CentralSurfacesImpl等等，去start,去onBootCompleted
    /**
     * Makes sure that all the SystemUI services are running. If they are already running, this is a
     * no-op. This is needed to conditinally start all the services, as we only need to have it in
     * the main process.
     * <p>This method must only be called from the main thread.</p>
     */

    public void startServicesIfNeeded() {
        final String vendorComponent = mInitializer.getVendorComponent(getResources());

        // Sort the startables so that we get a deterministic ordering.
        // TODO: make #start idempotent and require users of CoreStartable to call it.
        Map<Class<?>, Provider<CoreStartable>> sortedStartables = new TreeMap<>(
                Comparator.comparing(Class::getName));
        sortedStartables.putAll(mSysUIComponent.getStartables());
        sortedStartables.putAll(mSysUIComponent.getPerUserStartables());
        startServicesIfNeeded(
                sortedStartables, "StartServices", vendorComponent);
    }