[Android14] SystemUI的启动

server/2024/9/22 15:37:36/

1. 什么是System UI

        SystemUI是Android系统级应用，负责反馈系统及应用状态并与用户保持大量的交互。业务主要涉及的组成部分包括状态栏(Status Bar)，通知栏(Notification Panel)，锁屏(Keyguard)，控制中心(Quick Setting)，音量调节（VolumeUI）, 近期任务(Recents)等等。

图例如下所示：

2. 源码位置

package name:    com.android.systemui

SystemUI源码目录位于： framework/base/packages/SystemUI

Application位于:        frameworks\base\packages\SystemUI\SystemUIApplication

Service位于：            frameworks\base\services\java\com\android\server\

3. systemUI 启动流程

SystemServer.run()-> startOtherServices()-> startSystemUi()

SystemServer由ZygoteInit进程创建并启动

frameworks/base/services/java/com/android/server/SystemServer.java/*** The main entry point from zygote.*/public static void main(String[] args) {new SystemServer().run();}private void run() {......// Start services.try {t.traceBegin("StartServices");startBootstrapServices(t);startCoreServices(t);startOtherServices(t);  //在这里会启动startSystemUi()} catch (Throwable ex) {Slog.e("System", "******************************************");Slog.e("System", "************ Failure starting system services", ex);throw ex;} finally {t.traceEnd(); // StartServices}......}/*** Starts a miscellaneous grab bag of stuff that has yet to be refactored and organized.*/private void startOtherServices(@NonNull TimingsTraceAndSlog t) {......try {startSystemUi(context, windowManagerF);} catch (Throwable e) {reportWtf("starting System UI", e);}......}private static void startSystemUi(Context context, WindowManagerService windowManager) {PackageManagerInternal pm = LocalServices.getService(PackageManagerInternal.class);Intent intent = new Intent();intent.setComponent(pm.getSystemUiServiceComponent());  //这里intent.addFlags(Intent.FLAG_DEBUG_TRIAGED_MISSING);//Slog.d(TAG, "Starting service: " + intent);context.startServiceAsUser(intent, UserHandle.SYSTEM);windowManager.onSystemUiStarted();}

注意看这一段 

intent.setComponent(pm.getSystemUiServiceComponent());

pm是PackageManagerInternal实例，它的getSystemUiServiceComponent()方法是一个抽象方法

frameworks/base/services/core/java/android/content/pm/PackageManagerInternal.java/*** @return The SystemUI service component name.*/public abstract ComponentName getSystemUiServiceComponent();

PackageManagerService实现了该方法，如下：

frameworks/base/services/core/java/com/android/server/pm/PackageManagerService.java@Overridepublic ComponentName getSystemUiServiceComponent() {return ComponentName.unflattenFromString(mContext.getResources().getString(com.android.internal.R.string.config_systemUIServiceComponent));}

 com.android.internal.R.string.config_systemUIServiceComponent的值是

frameworks/base/core/res/res/values/config.xml<!-- SystemUi service component --><string name="config_systemUIServiceComponent" translatable="false">com.android.systemui/com.android.systemui.SystemUIService</string>

 unflattenFromString返回的是ComponentName(“com.android.systemui”, “com.android.systemui.SystemUIService”);

unflattenFromString 具体方法如下，很简单，感兴趣的可以看看，不感兴趣的直接跳过就好，这个方法不是重点。

    /*** Recover a ComponentName from a String that was previously created with* {@link #flattenToString()}.  It splits the string at the first '/',* taking the part before as the package name and the part after as the* class name.  As a special convenience (to use, for example, when* parsing component names on the command line), if the '/' is immediately* followed by a '.' then the final class name will be the concatenation* of the package name with the string following the '/'.  Thus* "com.foo/.Blah" becomes package="com.foo" class="com.foo.Blah".** @param str The String that was returned by flattenToString().* @return Returns a new ComponentName containing the package and class* names that were encoded in <var>str</var>** @see #flattenToString()*/public static @Nullable ComponentName unflattenFromString(@NonNull String str) {int sep = str.indexOf('/');if (sep < 0 || (sep+1) >= str.length()) {return null;}String pkg = str.substring(0, sep);String cls = str.substring(sep+1);if (cls.length() > 0 && cls.charAt(0) == '.') {cls = pkg + cls;}return new ComponentName(pkg, cls);}

以上代码功能为通过Intent启动了SystemUIService。

于是走到SystemUIService的onCreate()方法

frameworks/base/packages/SystemUI/src/com/android/systemui/SystemUIService.javapublic void onCreate() {super.onCreate();// Start all of SystemUI((SystemUIApplication) getApplication()).startServicesIfNeeded();......}public void startServicesIfNeeded() {String[] names = SystemUIFactory.getInstance().getSystemUIServiceComponents(getResources());startServicesIfNeeded(/* metricsPrefix= */ "StartServices", names);}

通过工厂模式获得SystemUI组件列表

frameworks/base/packages/SystemUI/src/com/android/systemui/SystemUIFactory.javapublic String[] getSystemUIServiceComponents(Resources resources) {return resources.getStringArray(R.array.config_systemUIServiceComponents);}

 列表如下：

frameworks/base/packages/SystemUI/res/values/config.xml<!-- SystemUI Services: The classes of the stuff to start. --><string-array name="config_systemUIServiceComponents" translatable="false"><item>com.android.systemui.util.NotificationChannels</item><item>com.android.systemui.keyguard.KeyguardViewMediator</item><item>com.android.systemui.recents.Recents</item><item>com.android.systemui.volume.VolumeUI</item><item>com.android.systemui.stackdivider.Divider</item><item>com.android.systemui.statusbar.phone.StatusBar</item><item>com.android.systemui.usb.StorageNotification</item><item>com.android.systemui.power.PowerUI</item><item>com.android.systemui.media.RingtonePlayer</item><item>com.android.systemui.keyboard.KeyboardUI</item><item>com.android.systemui.pip.PipUI</item><item>com.android.systemui.shortcut.ShortcutKeyDispatcher</item><item>@string/config_systemUIVendorServiceComponent</item><item>com.android.systemui.util.leak.GarbageMonitor$Service</item><item>com.android.systemui.LatencyTester</item><item>com.android.systemui.globalactions.GlobalActionsComponent</item><item>com.android.systemui.ScreenDecorations</item><item>com.android.systemui.biometrics.AuthController</item><item>com.android.systemui.SliceBroadcastRelayHandler</item><item>com.android.systemui.SizeCompatModeActivityController</item><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></string-array>

 这个列表是要传到上面的String[] names里的，作为参数，下一步执行startServicesIfNeeded(/* metricsPrefix= */ "StartServices", names);

方法如下：

大致内容就是通过反射获得上面列表的类的构造函数，然后通过构造函数创建上面那些类的实例，然后调用这些类的start方法，启动这些systemuI组件。

private void startServicesIfNeeded(String metricsPrefix, String[] services) {if (mServicesStarted) {return;}mServices = new SystemUI[services.length];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);log.traceBegin(metricsPrefix);final int N = services.length;for (int i = 0; i < N; i++) {String clsName = services[i];  //获取类名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);  //获取构造函数obj = (SystemUI) constructor.newInstance(this); //通过构造函数获取实例}mServices[i] = obj; //把实例放入到mServices数组中} catch (ClassNotFoundException| NoSuchMethodException| IllegalAccessException| InstantiationException| InvocationTargetException ex) {throw new RuntimeException(ex);}if (DEBUG) Log.d(TAG, "running: " + mServices[i]);mServices[i].start(); //执行start方法log.traceEnd();// Warn if initialization of component takes too longti = 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();log.traceEnd();mServicesStarted = true;}

SystemUI的启动就是这样。剩下的就是启动具体组件了，例如com.android.systemui.statusbar.phone.StatusBar。

StatusBar也就是状态栏，想看状态栏怎么启动的可以跟到它的start方法，这篇就先到这里。

 

 

 

 

 


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