Android系统之System Server大纲

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发布于 2024-07-02 08:27:40

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发布于 2024-07-02 08:27:40

前言

System Server是android 基本服务的提供者，是android系统运行的最基本需求，所有server运行在一个叫system_process的进程中，system_process进程是android java虚拟机跑的第一个进程，从Zygote 创建而来，是andorid系统最重要的java虚拟机。可以说，整个android系统的业务都是围绕system server而展开，所以，当system_process死掉了，手机必须重启。

System server概要

System server主要包含以下服务：

1、 EntropyService，熵服务，用于产生随机数；

2、 PowerManagerService，电源管理服务；

3、 ActivityMangerService Activity，管理服务；

4、 TelephonyRegistry，电话服务，电话底层通知服务；

5、 PackageManagerService，程序包管理服务；

6、 AccountManagerService，联系人账户管理服务；

7、 ContentService，内容提供器服务，提供跨进程数据交换；

8、 LightService，光感应传感器服务；

9、 BatteryService，电池服务；

10、 VibrateService，震动器服务；

11、 AlarmManagerService，闹钟服务；

12、 WindowManagerService，窗口管理服务；

13、 BluetoothService，蓝牙服务；

14、 InputMethodManagerService，输入法服务；

15、 AccessibilityManagerService，辅助器管理程序服务；

16、 DevicePolicyManagerService，提供系统级别的设置及属性；

17、 StatusBarManagerService，状态栏管理服务；

18、 ClipboardService，粘贴板服务；

19、 NetworkManagerService，网络管理服务；

20、 TextServicesManagerService，用户管理服务；

21、 NetworkStatsService，手机网络状态服务；

22、 NetworkPolicyManagerService，low-level网络策略服务；

23、 WifiP2pService，Wifi点对点服务；

24、 WifiService，Wifi服务；

25、 ConnectivityService，网络连接状态服务；

26、 MountService，磁盘加载服务；

27、 NotificationManagerService，通知管理服务；

28、 DeviceStorageMonitorService，存储设备容量监听服务；

29、 LocationManagerService，位置管理服务；

30、 CountryDetectorService，检查用户当前所在国家服务；

31、 SearchManagerService，搜索管理服务；

32、 DropBoxManagerService，系统日志文件管理服务；

33、 WallpaperManagerService，壁纸管理服务；

34、 AudioService，AudioFlinger上层封装音频管理服务；

35、 UsbService，USB Host 和 device管理服务；

36、 UiModeManagerService，UI模式管理服务；

37、 BackupManagerService，备份服务；

38、 AppWidgetService，应用桌面部件服务；

39、 RecognitionManagerService，身份识别服务；

40、 DiskStatsService，磁盘统计服务；

41、 SamplingProfilerService，性能统计服务；

42、 NetworkTimeUpdateService，网络时间更新服务；

43、 InputManagerService，输入管理服务；

44、 FingerprintService，指纹服务；

45、 DreamManagerService， dreams服务；

46、 HdmiControlService， HDMI控制服务；

47、 SsvService，SIM卡状态和转换服务；

以上所列系统服务不代表最新Android系统的所有系统服务。

System server启动的入口

这些服务那么重要，它们什么时候启动？都做了些什么事情？等等这些问题是本文以及大纲下面的文章将会一一道来。

了解这些系统服务之前，先来了解一个重量级的超级类SystemServer.java，这个类在AOSP中的路径是：frameworks/base/services/java/com/android/server/SystemServer.java，在上文中提到，从Zygote创建system_process进程时，便实例化了该类。熟悉java的开发者都知道，启动某个java程序时，最先调用的就是声明了main()方法的类。所以SystemServer.java被实例化后，便调用了main()方法。首先看看SystemServer.java的构造方法：

public SystemServer() {
    // Check for factory test mode.
    mFactoryTestMode = FactoryTest.getMode();
}

构造方法里面只做了从属性系统中读取了工厂测试模式，这个不在本文以及本大纲的文章中赘述的内容，这里就不在叙述了。

下面直接进入main()方法：

public static void main(String[] args) {
    new SystemServer().run();
}

直接调用了类内的run()方法，继续跟踪：

private void run() {
    try {
        // AndroidRuntime using the same set of system properties, but only the system_server
        // Initialize the system context.
        createSystemContext();

        // Create the system service manager.
        mSystemServiceManager = new SystemServiceManager(mSystemContext);
        LocalServices.addService(SystemServiceManager.class, mSystemServiceManager);
    } finally {
        Trace.traceEnd(Trace.TRACE_TAG_SYSTEM_SERVER);
    }

    // Start services.
    try {
        Trace.traceBegin(Trace.TRACE_TAG_SYSTEM_SERVER, "StartServices");
        startBootstrapServices();
        startCoreServices();
        startOtherServices();
    } catch (Throwable ex) {
        Slog.e("System", "******************************************");
        Slog.e("System", "************ Failure starting system services", ex);
        throw ex;
    } finally {
        Trace.traceEnd(Trace.TRACE_TAG_SYSTEM_SERVER);
    }
    .....
}

上述代码中，首先创建一个system context，这个对象在整个system server中使用非常频繁。接着创建一个SystemServiceManager.java的实例，顾名思义就是SystemService的管理者，管理所有的SystemService。代码中把接着创建一个SystemServiceManager的实例通过LocalServices.addService(SystemServiceManager.class, mSystemServiceManager)语句设置到LocalService中，LocalServices的功能类似SystemServiceManager，不同点在于LocalServices专门用来管理system_process进程中的SystemService，也就没有真正的跨进程通信，也就没有Binder对象。

System server启动的过程

接着就是启动各种系统服务，在这里分三种类型的SystemService，依次启动，分别对应三个方法：

        startBootstrapServices();
        startCoreServices();
        startOtherServices();

这三个方法的顺序不能混乱，一定要按照上述顺序依次执行，先看startBootstrapServices()中启动了那些系统服务

private void startBootstrapServices() {
    Installer installer = mSystemServiceManager.startService(Installer.class);

    // Activity manager runs the show.
    mActivityManagerService = mSystemServiceManager.startService(
            ActivityManagerService.Lifecycle.class).getService();
    mActivityManagerService.setSystemServiceManager(mSystemServiceManager);
    mActivityManagerService.setInstaller(installer);


    mPowerManagerService = mSystemServiceManager.startService(PowerManagerService.class);

    Trace.traceBegin(Trace.TRACE_TAG_SYSTEM_SERVER, "InitPowerManagement");
    mActivityManagerService.initPowerManagement();
    Trace.traceEnd(Trace.TRACE_TAG_SYSTEM_SERVER);

    // Manages LEDs and display backlight so we need it to bring up the display.
    mSystemServiceManager.startService(LightsService.class);

    // Display manager is needed to provide display metrics before package manager
    // starts up.
    mDisplayManagerService = mSystemServiceManager.startService(DisplayManagerService.class);

    // We need the default display before we can initialize the package manager.
    mSystemServiceManager.startBootPhase(SystemService.PHASE_WAIT_FOR_DEFAULT_DISPLAY);

    ......

    // Start the package manager.
    .....

    traceBeginAndSlog("StartUserManagerService");
    mSystemServiceManager.startService(UserManagerService.LifeCycle.class);
    ......
}

上述代码可以看到，这里启动了

Installer
ActivityManagerService.Lifecycle
PowerManagerService
LightsService
DisplayManagerService
UserManagerService

启动这些SystemService都是通过SystemServiceManager的startService()的方式启动，启动完成后会回调SystemService的onStart()方法。继续看第二个方法startCoreServices()启动了那些系统服务

private void startCoreServices() {
    // Tracks the battery level.  Requires LightService.
    mSystemServiceManager.startService(BatteryService.class);

    // Tracks application usage stats.
    mSystemServiceManager.startService(UsageStatsService.class);
    mActivityManagerService.setUsageStatsManager(
            LocalServices.getService(UsageStatsManagerInternal.class));

    // Tracks whether the updatable WebView is in a ready state and watches for update installs.
    mWebViewUpdateService = mSystemServiceManager.startService(WebViewUpdateService.class);
}

startCoreServices()中启动了

BatteryService
UsageStatsService
WebViewUpdateService

上文中提到，startBootstrapServices()必须在startCoreServices()前面执行，这里就能找到一个原因，startCoreServices()中用到mActivityManagerService对象，而该对象在startBootstrapServices()中被实例化，如果先调用startCoreServices()，mActivityManagerService对象便会发生NullPointerException的RuntimeException异常。

接着就是startOtherServices()中启动的service了，先看代码

private void startOtherServices() {
    try {
        ServiceManager.addService("scheduling_policy", new SchedulingPolicyService());

        mSystemServiceManager.startService(TelecomLoaderService.class);

        traceBeginAndSlog("StartTelephonyRegistry");
        telephonyRegistry = new TelephonyRegistry(context);
        ServiceManager.addService("telephony.registry", telephonyRegistry);
        Trace.traceEnd(Trace.TRACE_TAG_SYSTEM_SERVER);

        mEntropyMixer = new EntropyMixer(context);

        mContentResolver = context.getContentResolver();

        mSystemServiceManager.startService(CameraService.class);

        mSystemServiceManager.startService(ACCOUNT_SERVICE_CLASS);

        mSystemServiceManager.startService(CONTENT_SERVICE_CLASS);

        mActivityManagerService.installSystemProviders();

        vibrator = new VibratorService(context);
        ServiceManager.addService("vibrator", vibrator);

        consumerIr = new ConsumerIrService(context);
        ServiceManager.addService(Context.CONSUMER_IR_SERVICE, consumerIr);

        mSystemServiceManager.startService(AlarmManagerService.class);

        final Watchdog watchdog = Watchdog.getInstance();
        watchdog.init(context, mActivityManagerService);

        traceBeginAndSlog("StartInputManagerService");
        inputManager = new InputManagerService(context);
        Trace.traceEnd(Trace.TRACE_TAG_SYSTEM_SERVER);

        wm = WindowManagerService.main(context, inputManager,
                mFactoryTestMode != FactoryTest.FACTORY_TEST_LOW_LEVEL,
                !mFirstBoot, mOnlyCore);
        ServiceManager.addService(Context.WINDOW_SERVICE, wm);
        ServiceManager.addService(Context.INPUT_SERVICE, inputManager);

        mSystemServiceManager.startService(VrManagerService.class);

        mActivityManagerService.setWindowManager(wm);

        inputManager.setWindowManagerCallbacks(wm.getInputMonitor());
        inputManager.start();

        // TODO: Use service dependencies instead.
        mDisplayManagerService.windowManagerAndInputReady();

        .....
            mSystemServiceManager.startService(BluetoothService.class);
        .....

        mSystemServiceManager.startService(MetricsLoggerService.class);

        mSystemServiceManager.startService(PinnerService.class);
    } catch (RuntimeException e) {
    }
    // Bring up services needed for UI.
    if (mFactoryTestMode != FactoryTest.FACTORY_TEST_LOW_LEVEL) {
        mSystemServiceManager.startService(InputMethodManagerService.Lifecycle.class);

        traceBeginAndSlog("StartAccessibilityManagerService");
        try {
            ServiceManager.addService(Context.ACCESSIBILITY_SERVICE,
                    new AccessibilityManagerService(context));
        } catch (Throwable e) {
        }
    }
    if (mFactoryTestMode != FactoryTest.FACTORY_TEST_LOW_LEVEL) {
        if (!disableStorage &&
            !"0".equals(SystemProperties.get("system_init.startmountservice"))) {
            try {
                mSystemServiceManager.startService(MOUNT_SERVICE_CLASS);
                mountService = IMountService.Stub.asInterface(
                        ServiceManager.getService("mount"));
            } catch (Throwable e) {
                reportWtf("starting Mount Service", e);
            }
        }
    }
    mSystemServiceManager.startService(UiModeManagerService.class);
    .....

    if (mFactoryTestMode != FactoryTest.FACTORY_TEST_LOW_LEVEL) {
        if (!disableNonCoreServices) {
            try {
                mSystemServiceManager.startService(LOCK_SETTINGS_SERVICE_CLASS);
                lockSettings = ILockSettings.Stub.asInterface(
                        ServiceManager.getService("lock_settings"));
            } catch (Throwable e) {
            }

            if (!SystemProperties.get(PERSISTENT_DATA_BLOCK_PROP).equals("")) {
                mSystemServiceManager.startService(PersistentDataBlockService.class);
            }

            mSystemServiceManager.startService(DeviceIdleController.class);
            mSystemServiceManager.startService(DevicePolicyManagerService.Lifecycle.class);
        }

        if (!disableSystemUI) {
            try {
                statusBar = new StatusBarManagerService(context, wm);
                ServiceManager.addService(Context.STATUS_BAR_SERVICE, statusBar);
            } catch (Throwable e) {
            }
        }

        if (!disableNonCoreServices) {
            try {
                ServiceManager.addService(Context.CLIPBOARD_SERVICE,
                        new ClipboardService(context));
            } catch (Throwable e) {
            }
        }

        if (!disableNetwork) {
            try {
                networkManagement = NetworkManagementService.create(context);
                ServiceManager.addService(Context.NETWORKMANAGEMENT_SERVICE, networkManagement);
            } catch (Throwable e) {
            }
        }

        if (!disableNonCoreServices && !disableTextServices) {
            mSystemServiceManager.startService(TextServicesManagerService.Lifecycle.class);
        }

        if (!disableNetwork) {
            traceBeginAndSlog("StartNetworkScoreService");
            try {
                networkScore = new NetworkScoreService(context);
                ServiceManager.addService(Context.NETWORK_SCORE_SERVICE, networkScore);
            } catch (Throwable e) {
            }
            try {
                networkStats = NetworkStatsService.create(context, networkManagement);
                ServiceManager.addService(Context.NETWORK_STATS_SERVICE, networkStats);
            } catch (Throwable e) {
            }

            try {
                networkPolicy = new NetworkPolicyManagerService(
                        context, mActivityManagerService,
                        (IPowerManager)ServiceManager.getService(Context.POWER_SERVICE),
                        networkStats, networkManagement);
                ServiceManager.addService(Context.NETWORK_POLICY_SERVICE, networkPolicy);
            } catch (Throwable e) {
            }

            if (context.getPackageManager().hasSystemFeature(PackageManager.FEATURE_WIFI_NAN)) {
                mSystemServiceManager.startService(WIFI_NAN_SERVICE_CLASS);
            } else {
                Slog.i(TAG, "No Wi-Fi NAN Service (NAN support Not Present)");
            }
            mSystemServiceManager.startService(WIFI_P2P_SERVICE_CLASS);
            mSystemServiceManager.startService(WIFI_SERVICE_CLASS);
            mSystemServiceManager.startService(
                        "com.android.server.wifi.scanner.WifiScanningService");

            if (!disableRtt) {
                mSystemServiceManager.startService("com.android.server.wifi.RttService");
            }

            if (mPackageManager.hasSystemFeature(PackageManager.FEATURE_ETHERNET) ||
                mPackageManager.hasSystemFeature(PackageManager.FEATURE_USB_HOST)) {
                mSystemServiceManager.startService(ETHERNET_SERVICE_CLASS);
            }

            traceBeginAndSlog("StartConnectivityService");
            try {
                connectivity = new ConnectivityService(
                        context, networkManagement, networkStats, networkPolicy);
                ServiceManager.addService(Context.CONNECTIVITY_SERVICE, connectivity);
                networkStats.bindConnectivityManager(connectivity);
                networkPolicy.bindConnectivityManager(connectivity);
            } catch (Throwable e) {
            }

            try {
                serviceDiscovery = NsdService.create(context);
                ServiceManager.addService(
                        Context.NSD_SERVICE, serviceDiscovery);
            } catch (Throwable e) {
                reportWtf("starting Service Discovery Service", e);
        }

        if (!disableNonCoreServices) {
            try {
                ServiceManager.addService(Context.UPDATE_LOCK_SERVICE,
                        new UpdateLockService(context));
            } catch (Throwable e) {
            }
        }

        if (!disableNonCoreServices) {
            mSystemServiceManager.startService(RecoverySystemService.class);
        }
        ......

        mSystemServiceManager.startService(NotificationManagerService.class);
        notification = INotificationManager.Stub.asInterface(
                ServiceManager.getService(Context.NOTIFICATION_SERVICE));
        networkPolicy.bindNotificationManager(notification);

        mSystemServiceManager.startService(DeviceStorageMonitorService.class);

        if (!disableLocation) {
            try {
                location = new LocationManagerService(context);
                ServiceManager.addService(Context.LOCATION_SERVICE, location);
            } catch (Throwable e) {
            }
            try {
                countryDetector = new CountryDetectorService(context);
                ServiceManager.addService(Context.COUNTRY_DETECTOR, countryDetector);
            } catch (Throwable e) {
            }
        }

        if (!disableNonCoreServices && !disableSearchManager) {
            traceBeginAndSlog("StartSearchManagerService");
            try {
                mSystemServiceManager.startService(SEARCH_MANAGER_SERVICE_CLASS);
            } catch (Throwable e) {
            }
        }

        mSystemServiceManager.startService(DropBoxManagerService.class);

        if (!disableNonCoreServices && context.getResources().getBoolean(
                    R.bool.config_enableWallpaperService)) {
            mSystemServiceManager.startService(WALLPAPER_SERVICE_CLASS);
        }

        mSystemServiceManager.startService(AudioService.Lifecycle.class);

        if (!disableNonCoreServices) {
            mSystemServiceManager.startService(DockObserver.class);

            if (context.getPackageManager().hasSystemFeature(PackageManager.FEATURE_WATCH)) {
                mSystemServiceManager.startService(THERMAL_OBSERVER_CLASS);
            }
        }
        try {
            // Listen for wired headset changes
            inputManager.setWiredAccessoryCallbacks(
                    new WiredAccessoryManager(context, inputManager));
        } catch (Throwable e) {
        }

        if (!disableNonCoreServices) {
            if (mPackageManager.hasSystemFeature(PackageManager.FEATURE_MIDI)) {
                // Start MIDI Manager service
                mSystemServiceManager.startService(MIDI_SERVICE_CLASS);
            }

            if (mPackageManager.hasSystemFeature(PackageManager.FEATURE_USB_HOST)
                    || mPackageManager.hasSystemFeature(
                            PackageManager.FEATURE_USB_ACCESSORY)) {
                mSystemServiceManager.startService(USB_SERVICE_CLASS);
            }

            if (!disableSerial) {
                try {
                    // Serial port support
                    serial = new SerialService(context);
                    ServiceManager.addService(Context.SERIAL_SERVICE, serial);
                } catch (Throwable e) {
                }
            }

                    "StartHardwarePropertiesManagerService");
            try {
                hardwarePropertiesService = new HardwarePropertiesManagerService(context);
                ServiceManager.addService(Context.HARDWARE_PROPERTIES_SERVICE,
                        hardwarePropertiesService);
            } catch (Throwable e) {
                Slog.e(TAG, "Failure starting HardwarePropertiesManagerService", e);
            }
        }

        mSystemServiceManager.startService(TwilightService.class);

        mSystemServiceManager.startService(JobSchedulerService.class);

        mSystemServiceManager.startService(SoundTriggerService.class);

        if (!disableNonCoreServices) {
            if (mPackageManager.hasSystemFeature(PackageManager.FEATURE_BACKUP)) {
                mSystemServiceManager.startService(BACKUP_MANAGER_SERVICE_CLASS);
            }

            if (mPackageManager.hasSystemFeature(PackageManager.FEATURE_APP_WIDGETS)
                || context.getResources().getBoolean(R.bool.config_enableAppWidgetService)) {
                mSystemServiceManager.startService(APPWIDGET_SERVICE_CLASS);
            }

            if (mPackageManager.hasSystemFeature(PackageManager.FEATURE_VOICE_RECOGNIZERS)) {
                mSystemServiceManager.startService(VOICE_RECOGNITION_MANAGER_SERVICE_CLASS);
            }

            if (GestureLauncherService.isGestureLauncherEnabled(context.getResources())) {
                Slog.i(TAG, "Gesture Launcher Service");
                mSystemServiceManager.startService(GestureLauncherService.class);
            }
            mSystemServiceManager.startService(SensorNotificationService.class);
            mSystemServiceManager.startService(ContextHubSystemService.class);
        }

        try {
            ServiceManager.addService("diskstats", new DiskStatsService(context));
        } catch (Throwable e) {
        }

        if (!disableSamplingProfiler) {
            traceBeginAndSlog("StartSamplingProfilerService");
            try {
                ServiceManager.addService("samplingprofiler",
                            new SamplingProfilerService(context));
            } catch (Throwable e) {
            }
        }

        if (!disableNetwork && !disableNetworkTime) {
            traceBeginAndSlog("StartNetworkTimeUpdateService");
            try {
                networkTimeUpdater = new NetworkTimeUpdateService(context);
                ServiceManager.addService("network_time_update_service", networkTimeUpdater);
            } catch (Throwable e) {
            }
        }

        traceBeginAndSlog("StartCommonTimeManagementService");
        try {
            commonTimeMgmtService = new CommonTimeManagementService(context);
            ServiceManager.addService("commontime_management", commonTimeMgmtService);
        } catch (Throwable e) {
        }
        Trace.traceEnd(Trace.TRACE_TAG_SYSTEM_SERVER);

        if (!disableNetwork) {
            try {
                CertBlacklister blacklister = new CertBlacklister(context);
            } catch (Throwable e) {
            }
        }

        if (!disableNonCoreServices) {
            mSystemServiceManager.startService(DreamManagerService.class);
        }

        if (!disableNonCoreServices && ZygoteInit.PRELOAD_RESOURCES) {
            traceBeginAndSlog("StartAssetAtlasService");
            try {
                atlas = new AssetAtlasService(context);
                ServiceManager.addService(AssetAtlasService.ASSET_ATLAS_SERVICE, atlas);
            } catch (Throwable e) {
            }
        }

        if (!disableNonCoreServices) {
            ServiceManager.addService(GraphicsStatsService.GRAPHICS_STATS_SERVICE,
                    new GraphicsStatsService(context));
        }

        if (mPackageManager.hasSystemFeature(PackageManager.FEATURE_PRINTING)) {
            mSystemServiceManager.startService(PRINT_MANAGER_SERVICE_CLASS);
        }

        mSystemServiceManager.startService(RestrictionsManagerService.class);

        mSystemServiceManager.startService(MediaSessionService.class);

        if (mPackageManager.hasSystemFeature(PackageManager.FEATURE_HDMI_CEC)) {
            mSystemServiceManager.startService(HdmiControlService.class);
        }

        if (mPackageManager.hasSystemFeature(PackageManager.FEATURE_LIVE_TV)) {
            mSystemServiceManager.startService(TvInputManagerService.class);
        }

        if (mPackageManager.hasSystemFeature(PackageManager.FEATURE_PICTURE_IN_PICTURE)) {
            mSystemServiceManager.startService(MediaResourceMonitorService.class);
        }

        if (mPackageManager.hasSystemFeature(PackageManager.FEATURE_LEANBACK)) {
            mSystemServiceManager.startService(TvRemoteService.class);
        }

        if (!disableNonCoreServices) {
            traceBeginAndSlog("StartMediaRouterService");
            try {
                mediaRouter = new MediaRouterService(context);
                ServiceManager.addService(Context.MEDIA_ROUTER_SERVICE, mediaRouter);
            } catch (Throwable e) {
            }

            if (!disableTrustManager) {
                mSystemServiceManager.startService(TrustManagerService.class);
            }

            if (mPackageManager.hasSystemFeature(PackageManager.FEATURE_FINGERPRINT)) {
                mSystemServiceManager.startService(FingerprintService.class);
            }
        }
        // LauncherAppsService uses ShortcutService.
        mSystemServiceManager.startService(ShortcutService.Lifecycle.class);

        mSystemServiceManager.startService(LauncherAppsService.class);
    }

    if (!disableNonCoreServices && !disableMediaProjection) {
        mSystemServiceManager.startService(MediaProjectionManagerService.class);
    }

    if (context.getPackageManager().hasSystemFeature(PackageManager.FEATURE_WATCH)) {
        mSystemServiceManager.startService(WEAR_BLUETOOTH_SERVICE_CLASS);
    }
    mmsService = mSystemServiceManager.startService(MmsServiceBroker.class);

    // It is now time to start up the app processes...

    try {
        vibrator.systemReady();
    } catch (Throwable e) {
    }

    if (lockSettings != null) {
        try {
            lockSettings.systemReady();
        } catch (Throwable e) {
        }
    }

    // Needed by DevicePolicyManager for initialization
    mSystemServiceManager.startBootPhase(SystemService.PHASE_LOCK_SETTINGS_READY);

    mSystemServiceManager.startBootPhase(SystemService.PHASE_SYSTEM_SERVICES_READY);

    Trace.traceBegin(Trace.TRACE_TAG_SYSTEM_SERVER, "MakeWindowManagerServiceReady");
    try {
        wm.systemReady();
    } catch (Throwable e) {
    }
    try {
        // TODO: use boot phase
        mPowerManagerService.systemReady(mActivityManagerService.getAppOpsService());
    } catch (Throwable e) {
    }

    try {
        mPackageManagerService.systemReady();
    } catch (Throwable e) {
    }

    try {
        // TODO: use boot phase and communicate these flags some other way
        mDisplayManagerService.systemReady(safeMode, mOnlyCore);
    } catch (Throwable e) {
    }
    mActivityManagerService.systemReady(new Runnable() {
        @Override
        public void run() {
            try {
                startSystemUi(context);
            } catch (Throwable e) {
            }
            "MakeNetworkManagementServiceReady");
            try {
                if (networkManagementF != null) networkManagementF.systemReady();
            } catch (Throwable e) {
                reportWtf("making Network Managment Service ready", e);
            }
            "MakeNetworkStatsServiceReady");
            try {
                if (networkStatsF != null) networkStatsF.systemReady();
            } catch (Throwable e) {
            }
            try {
                if (networkPolicyF != null) networkPolicyF.systemReady();
            } catch (Throwable e) {
                reportWtf("making Network Policy Service ready", e);
            }
            "MakeConnectivityServiceReady");
            try {
                if (connectivityF != null) connectivityF.systemReady();
            } catch (Throwable e) {
            }
            Watchdog.getInstance().start();

            try {
                if (locationF != null) locationF.systemRunning();
            } catch (Throwable e) {
            }
            try {
                if (countryDetectorF != null) countryDetectorF.systemRunning();
            } catch (Throwable e) {
            }
            try {
                if (networkTimeUpdaterF != null) networkTimeUpdaterF.systemRunning();
            } catch (Throwable e) {
            }
            try {
                if (commonTimeMgmtServiceF != null) {
                    commonTimeMgmtServiceF.systemRunning();
                }
            } catch (Throwable e) {
            }
            try {
                if (atlasF != null) atlasF.systemRunning();
            } catch (Throwable e) {
            }
            try {
                // TODO(BT) Pass parameter to input manager
                if (inputManagerF != null) inputManagerF.systemRunning();
            } catch (Throwable e) {
            }
            try {
                if (telephonyRegistryF != null) telephonyRegistryF.systemRunning();
            } catch (Throwable e) {
                reportWtf("Notifying TelephonyRegistry running", e);
            }
            try {
                if (mediaRouterF != null) mediaRouterF.systemRunning();
            } catch (Throwable e) {
            }

            try {
                if (mmsServiceF != null) mmsServiceF.systemRunning();
            } catch (Throwable e) {
            }

            try {
                if (networkScoreF != null) networkScoreF.systemRunning();
            } catch (Throwable e) {
            }
        }
    });
}

这个方法中启动的service非常多，代码量非常巨大，所以可见，这个方法对于Android系统而言，不言也可知其重要性。由于代码量巨大，将startOtherServices()分成三部分解说：

1.startOtherServices()中启动了那些服务

SchedulingPolicyService
TelecomLoaderService
TelephonyRegistry
CameraService
AccountManagerService LifecycleContentServiceLifecycle
VibratorService
ConsumerIrService
AlarmManagerService
InputManagerService
WindowManagerService
VrManagerService
MetricsLoggerService
PinnerService
InputMethodManagerService
AccessibilityManagerService
MountService

LifecycleUiModeManagerServiceLockSettingsService

Lifecycle

PersistentDataBlockService
DeviceIdleController
DevicePolicyManagerService
StatusBarManagerService
ClipboardService
NetworkManagementService
TextServicesManagerService
NetworkScoreService
NetworkStatsService
NetworkPolicyManagerService
WifiNanService
WifiP2pService
WifiService
WifiScanningService
RttService
EthernetService
ConnectivityService
NsdService
UpdateLockService
RecoverySystemService
NotificationManagerService
DeviceStorageMonitorService
LocationManagerService
CountryDetectorService
SearchManagerService

LifecycleDropBoxManagerServiceWallpaperManagerService

Lifecycle

AudioService.Lifecycle
DockObserver
ThermalObserver
MidiService

LifecycleUsbService

Lifecycle

SerialService
HardwarePropertiesManagerService
TwilightService
JobSchedulerService
SoundTriggerService
BackupManagerService$Lifecycle
AppWidgetService
VoiceInteractionManagerService
GestureLauncherService
SensorNotificationService
ContextHubSystemService
DiskStatsService
SamplingProfilerService
NetworkTimeUpdateService
CommonTimeManagementService
DreamManagerService
AssetAtlasService
GraphicsStatsService
PrintManagerService
RestrictionsManagerService
MediaSessionService
HdmiControlService
TvInputManagerService
MediaResourceMonitorService
TvRemoteService
MediaRouterService
TrustManagerService ShortcutService.Lifecycle LauncherAppsService MediaProjectionManagerService WearBluetoothService MmsServiceBroke

所列的这些服务，不一定全部都启动，系统会依照一些配置，选择性启动某些服务。如，因为Android系统会用于众多设备，手机，电视等等，当Android安装到电视设备是，TvInputManagerService、TvRemoteService这些service才会被启动，相反，手机设备时，这两个服务就不会被启动了。

2.不同的启动服务的方式

不知读者是否注意到，在startOtherServices()中存在和startBootstrapServices()、startCoreServices()中不同的启动service的方法，在startBootstrapServices()、startCoreServices()中见到SystemServiceManager.startService()和LocalServices.addService()的方式，而startOtherServices()中又多了ServiceManager.addService()，这三种方式有什么不同呢？

类型不同

SystemServiceManager.startService()和LocalServices.addService()启动的系统服务是SystemService的子类，启动这些服务后会回调SystemService的onStart()方法。ServiceManager.addService()启动的系统服务是实现了Android IPC 的Binder的子类，这些服务启动后会调用systemReady()或systemRunning()方法。
SystemServiceManager.startService()和ServiceManager.addService()中启动的服务需要Binder对象，而LocalServices.addService()却没有Binder对象。
SystemServiceManager.startService()中启动的是需要关心lifecycle events的服务，而ServiceManager.addService()和LocalServices.addService()不关心lifecycle events。
ServiceManager.addService()启动的服务本身是实现Binder通信的子类，而一般SystemServiceManager.startService()启动的服务是某个服务的内部类且这个内部类是SystemService的子类，如BackupManagerService$Lifecycle，在启动这个Lifecycle的内部类服务时，当回调onStart()方法时通过SystemService的publishBinderService()方法应用某个服务的Binder对象，且这个Binder的实现类也是某个服务的内部类。也就是说需要启动服务，而这个服务需要关心lifecycle events，所以不能通过ServiceManager.addService()的方式启动，然后在这个服务中声明一个实现了SystemService的子类Lifecycle，来接受lifecycle events，通过SystemServiceManager.startService()的方式启动这个服务，在SystemService的回调方法onStart()中应用这个服务的Binder对象。所以通过SystemServiceManager.startService()启动的服务，实际是启动了一个即需要关心lifecycle events，也需要像ServiceManager.addService()那样需要Binder对象的服务。

所以，其实在startBootstrapServices()中就已经通过ServiceManager.addService()的方式启动了一些特别特别重要的服务，如

private void startBootstrapServices() {
    mPackageManagerService = PackageManagerService.main(mSystemContext, installer,
        mFactoryTestMode != FactoryTest.FACTORY_TEST_OFF, mOnlyCore);
}


public static PackageManagerService main(Context context, Installer installer,
    boolean factoryTest, boolean onlyCore) {
    ......
    ServiceManager.addService("package", m);
    return m;
}

3.通过ServiceManager.addService()启动的服务，会调用服务的systemReady()或systemRunning()方法，初始化一些需要在系统服务启动后的其它代码。如启动SystemUI。

全部启动所需要的服务以后，SystemServer便要进入了接受Message的循环中，等待Message的事件

本文参与腾讯云自媒体同步曝光计划，分享自作者个人站点/博客。

原始发表：2024-07-01，如有侵权请联系 cloudcommunity@tencent.com 删除

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