Android getSystemService 源码分析

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前言

一直用，但是具体在代码中是如何实现的并知道。

 ActivityManager am = (ActivityManager)getSystemService(Context.ACTIVITY_SERVICE);

以获得AM为类，进行跟踪framework流程

activity.java

    @Override    protected void onCreate(Bundle savedInstanceState) {        super.onCreate(savedInstanceState);        setContentView(R.layout.activity_main);        ActivityManager am = (ActivityManager)getSystemService(Context.ACTIVITY_SERVICE);    }

Activity.java

    @Override    public Object getSystemService(@ServiceName @NonNull String name) {        if (getBaseContext() == null) {            throw new IllegalStateException(                    "System services not available to Activities before onCreate()");        }        if (WINDOW_SERVICE.equals(name)) {            return mWindowManager;        } else if (SEARCH_SERVICE.equals(name)) {            ensureSearchManager();            return mSearchManager;        }        return super.getSystemService(name);    }

ContextThemeWrapper.java

    @Override public Object getSystemService(String name) {        if (LAYOUT_INFLATER_SERVICE.equals(name)) {            if (mInflater == null) {                mInflater = LayoutInflater.from(getBaseContext()).cloneInContext(this);            }            return mInflater;        }        return getBaseContext().getSystemService(name);    }

Context.java

    public abstract Object getSystemService(@ServiceName @NonNull String name);

最终我们发现这个方法是Context中的一个抽象接口。
我们知道Context类是一个abstract类。它的具体实现是在ContextImpl类中。
于是我们在ComtextImpl中找到

    @Override    public Object getSystemService(String name) {        return SystemServiceRegistry.getSystemService(this, name);    }

SystemServiceRegistry.java
顾名思义SystemServiceRegistry这个类是为了实现系统服务注册的。
SystemServiceRegistry 这个类中有一些静态代码块，就是为了注册系统服务的；

    static {        registerService(Context.ACCESSIBILITY_SERVICE, AccessibilityManager.class,                new CachedServiceFetcher<AccessibilityManager>() {            @Override            public AccessibilityManager createService(ContextImpl ctx) {                return AccessibilityManager.getInstance(ctx);            }});        registerService(Context.CAPTIONING_SERVICE, CaptioningManager.class,                new CachedServiceFetcher<CaptioningManager>() {            @Override            public CaptioningManager createService(ContextImpl ctx) {                return new CaptioningManager(ctx);            }});        registerService(Context.ACCOUNT_SERVICE, AccountManager.class,                new CachedServiceFetcher<AccountManager>() {            @Override            public AccountManager createService(ContextImpl ctx) {                IBinder b = ServiceManager.getService(Context.ACCOUNT_SERVICE);                IAccountManager service = IAccountManager.Stub.asInterface(b);                return new AccountManager(ctx, service);            }});        registerService(Context.ACTIVITY_SERVICE, ActivityManager.class,                new CachedServiceFetcher<ActivityManager>() {            @Override            public ActivityManager createService(ContextImpl ctx) {                return new ActivityManager(ctx.getOuterContext(), ctx.mMainThread.getHandler());            }});        registerService(Context.ALARM_SERVICE, AlarmManager.class,                new CachedServiceFetcher<AlarmManager>() {            @Override            public AlarmManager createService(ContextImpl ctx) {                IBinder b = ServiceManager.getService(Context.ALARM_SERVICE);                IAlarmManager service = IAlarmManager.Stub.asInterface(b);                return new AlarmManager(service, ctx);            }});        registerService(Context.AUDIO_SERVICE, AudioManager.class,                new CachedServiceFetcher<AudioManager>() {            @Override            public AudioManager createService(ContextImpl ctx) {                return new AudioManager(ctx);            }});        registerService(Context.MEDIA_ROUTER_SERVICE, MediaRouter.class,                new CachedServiceFetcher<MediaRouter>() {            @Override            public MediaRouter createService(ContextImpl ctx) {                return new MediaRouter(ctx);            }});        registerService(Context.BLUETOOTH_SERVICE, BluetoothManager.class,                new CachedServiceFetcher<BluetoothManager>() {            @Override            public BluetoothManager createService(ContextImpl ctx) {                return new BluetoothManager(ctx);            }});        registerService(Context.HDMI_CONTROL_SERVICE, HdmiControlManager.class,                new StaticServiceFetcher<HdmiControlManager>() {            @Override            public HdmiControlManager createService() {                IBinder b = ServiceManager.getService(Context.HDMI_CONTROL_SERVICE);                return new HdmiControlManager(IHdmiControlService.Stub.asInterface(b));            }});        registerService(Context.CLIPBOARD_SERVICE, ClipboardManager.class,                new CachedServiceFetcher<ClipboardManager>() {            @Override            public ClipboardManager createService(ContextImpl ctx) {                return new ClipboardManager(ctx.getOuterContext(),                        ctx.mMainThread.getHandler());            }});        // The clipboard service moved to a new package.  If someone asks for the old        // interface by class then we want to redirect over to the new interface instead        // (which extends it).        SYSTEM_SERVICE_NAMES.put(android.text.ClipboardManager.class, Context.CLIPBOARD_SERVICE);        registerService(Context.CONNECTIVITY_SERVICE, ConnectivityManager.class,                new StaticOuterContextServiceFetcher<ConnectivityManager>() {            @Override            public ConnectivityManager createService(Context context) {                IBinder b = ServiceManager.getService(Context.CONNECTIVITY_SERVICE);                IConnectivityManager service = IConnectivityManager.Stub.asInterface(b);                return new ConnectivityManager(context, service);            }});        registerService(Context.COUNTRY_DETECTOR, CountryDetector.class,                new StaticServiceFetcher<CountryDetector>() {            @Override            public CountryDetector createService() {                IBinder b = ServiceManager.getService(Context.COUNTRY_DETECTOR);                return new CountryDetector(ICountryDetector.Stub.asInterface(b));            }});        registerService(Context.DEVICE_POLICY_SERVICE, DevicePolicyManager.class,                new CachedServiceFetcher<DevicePolicyManager>() {            @Override            public DevicePolicyManager createService(ContextImpl ctx) {                return DevicePolicyManager.create(ctx, ctx.mMainThread.getHandler());            }});        registerService(Context.DOWNLOAD_SERVICE, DownloadManager.class,                new CachedServiceFetcher<DownloadManager>() {            @Override            public DownloadManager createService(ContextImpl ctx) {                return new DownloadManager(ctx.getContentResolver(), ctx.getPackageName());            }});        registerService(Context.BATTERY_SERVICE, BatteryManager.class,                new StaticServiceFetcher<BatteryManager>() {            @Override            public BatteryManager createService() {                return new BatteryManager();            }});        registerService(Context.NFC_SERVICE, NfcManager.class,                new CachedServiceFetcher<NfcManager>() {            @Override            public NfcManager createService(ContextImpl ctx) {                return new NfcManager(ctx);            }});        registerService(Context.DROPBOX_SERVICE, DropBoxManager.class,                new StaticServiceFetcher<DropBoxManager>() {            @Override            public DropBoxManager createService() {                IBinder b = ServiceManager.getService(Context.DROPBOX_SERVICE);                IDropBoxManagerService service = IDropBoxManagerService.Stub.asInterface(b);                if (service == null) {                    // Don't return a DropBoxManager that will NPE upon use.                    // This also avoids caching a broken DropBoxManager in                    // getDropBoxManager during early boot, before the                    // DROPBOX_SERVICE is registered.                    return null;                }                return new DropBoxManager(service);            }});        registerService(Context.INPUT_SERVICE, InputManager.class,                new StaticServiceFetcher<InputManager>() {            @Override            public InputManager createService() {                return InputManager.getInstance();            }});        registerService(Context.DISPLAY_SERVICE, DisplayManager.class,                new CachedServiceFetcher<DisplayManager>() {            @Override            public DisplayManager createService(ContextImpl ctx) {                return new DisplayManager(ctx.getOuterContext());            }});        registerService(Context.INPUT_METHOD_SERVICE, InputMethodManager.class,                new StaticServiceFetcher<InputMethodManager>() {            @Override            public InputMethodManager createService() {                return InputMethodManager.getInstance();            }});        registerService(Context.TEXT_SERVICES_MANAGER_SERVICE, TextServicesManager.class,                new StaticServiceFetcher<TextServicesManager>() {            @Override            public TextServicesManager createService() {                return TextServicesManager.getInstance();            }});        registerService(Context.KEYGUARD_SERVICE, KeyguardManager.class,                new StaticServiceFetcher<KeyguardManager>() {            @Override            public KeyguardManager createService() {                return new KeyguardManager();            }});        registerService(Context.LAYOUT_INFLATER_SERVICE, LayoutInflater.class,                new CachedServiceFetcher<LayoutInflater>() {            @Override            public LayoutInflater createService(ContextImpl ctx) {                return new PhoneLayoutInflater(ctx.getOuterContext());            }});        registerService(Context.LOCATION_SERVICE, LocationManager.class,                new CachedServiceFetcher<LocationManager>() {            @Override            public LocationManager createService(ContextImpl ctx) {                IBinder b = ServiceManager.getService(Context.LOCATION_SERVICE);                return new LocationManager(ctx, ILocationManager.Stub.asInterface(b));            }});        registerService(Context.NETWORK_POLICY_SERVICE, NetworkPolicyManager.class,                new CachedServiceFetcher<NetworkPolicyManager>() {            @Override            public NetworkPolicyManager createService(ContextImpl ctx) {                return new NetworkPolicyManager(ctx, INetworkPolicyManager.Stub.asInterface(                        ServiceManager.getService(Context.NETWORK_POLICY_SERVICE)));            }});        registerService(Context.NOTIFICATION_SERVICE, NotificationManager.class,                new CachedServiceFetcher<NotificationManager>() {            @Override            public NotificationManager createService(ContextImpl ctx) {                final Context outerContext = ctx.getOuterContext();                return new NotificationManager(                    new ContextThemeWrapper(outerContext,                            Resources.selectSystemTheme(0,                                    outerContext.getApplicationInfo().targetSdkVersion,                                    com.android.internal.R.style.Theme_Dialog,                                    com.android.internal.R.style.Theme_Holo_Dialog,                                    com.android.internal.R.style.Theme_DeviceDefault_Dialog,                                    com.android.internal.R.style.Theme_DeviceDefault_Light_Dialog)),                    ctx.mMainThread.getHandler());            }});        registerService(Context.NSD_SERVICE, NsdManager.class,                new CachedServiceFetcher<NsdManager>() {            @Override            public NsdManager createService(ContextImpl ctx) {                IBinder b = ServiceManager.getService(Context.NSD_SERVICE);                INsdManager service = INsdManager.Stub.asInterface(b);                return new NsdManager(ctx.getOuterContext(), service);            }});        registerService(Context.POWER_SERVICE, PowerManager.class,                new CachedServiceFetcher<PowerManager>() {            @Override            public PowerManager createService(ContextImpl ctx) {                IBinder b = ServiceManager.getService(Context.POWER_SERVICE);                IPowerManager service = IPowerManager.Stub.asInterface(b);                if (service == null) {                    Log.wtf(TAG, "Failed to get power manager service.");                }                return new PowerManager(ctx.getOuterContext(),                        service, ctx.mMainThread.getHandler());            }});        registerService(Context.SEARCH_SERVICE, SearchManager.class,                new CachedServiceFetcher<SearchManager>() {            @Override            public SearchManager createService(ContextImpl ctx) {                return new SearchManager(ctx.getOuterContext(),                        ctx.mMainThread.getHandler());            }});        registerService(Context.SENSOR_SERVICE, SensorManager.class,                new CachedServiceFetcher<SensorManager>() {            @Override            public SensorManager createService(ContextImpl ctx) {                return new SystemSensorManager(ctx.getOuterContext(),                  ctx.mMainThread.getHandler().getLooper());            }});        registerService(Context.STATUS_BAR_SERVICE, StatusBarManager.class,                new CachedServiceFetcher<StatusBarManager>() {            @Override            public StatusBarManager createService(ContextImpl ctx) {                return new StatusBarManager(ctx.getOuterContext());            }});        registerService(Context.STORAGE_SERVICE, StorageManager.class,                new CachedServiceFetcher<StorageManager>() {            @Override            public StorageManager createService(ContextImpl ctx) {                return new StorageManager(ctx, ctx.mMainThread.getHandler().getLooper());            }});        registerService(Context.TELEPHONY_SERVICE, TelephonyManager.class,                new CachedServiceFetcher<TelephonyManager>() {            @Override            public TelephonyManager createService(ContextImpl ctx) {                return new TelephonyManager(ctx.getOuterContext());            }});        registerService(Context.TELEPHONY_SUBSCRIPTION_SERVICE, SubscriptionManager.class,                new CachedServiceFetcher<SubscriptionManager>() {            @Override            public SubscriptionManager createService(ContextImpl ctx) {                return new SubscriptionManager(ctx.getOuterContext());            }});        registerService(Context.CARRIER_CONFIG_SERVICE, CarrierConfigManager.class,                new CachedServiceFetcher<CarrierConfigManager>() {            @Override            public CarrierConfigManager createService(ContextImpl ctx) {                return new CarrierConfigManager();            }});        registerService(Context.TELECOM_SERVICE, TelecomManager.class,                new CachedServiceFetcher<TelecomManager>() {            @Override            public TelecomManager createService(ContextImpl ctx) {                return new TelecomManager(ctx.getOuterContext());            }});        registerService(Context.UI_MODE_SERVICE, UiModeManager.class,                new CachedServiceFetcher<UiModeManager>() {            @Override            public UiModeManager createService(ContextImpl ctx) {                return new UiModeManager();            }});        registerService(Context.USB_SERVICE, UsbManager.class,                new CachedServiceFetcher<UsbManager>() {            @Override            public UsbManager createService(ContextImpl ctx) {                IBinder b = ServiceManager.getService(Context.USB_SERVICE);                return new UsbManager(ctx, IUsbManager.Stub.asInterface(b));            }});        registerService(Context.SERIAL_SERVICE, SerialManager.class,                new CachedServiceFetcher<SerialManager>() {            @Override            public SerialManager createService(ContextImpl ctx) {                IBinder b = ServiceManager.getService(Context.SERIAL_SERVICE);                return new SerialManager(ctx, ISerialManager.Stub.asInterface(b));            }});        registerService(Context.VIBRATOR_SERVICE, Vibrator.class,                new CachedServiceFetcher<Vibrator>() {            @Override            public Vibrator createService(ContextImpl ctx) {                return new SystemVibrator(ctx);            }});        registerService(Context.WALLPAPER_SERVICE, WallpaperManager.class,                new CachedServiceFetcher<WallpaperManager>() {            @Override            public WallpaperManager createService(ContextImpl ctx) {                return new WallpaperManager(ctx.getOuterContext(),                        ctx.mMainThread.getHandler());            }});        registerService(Context.WIFI_SERVICE, WifiManager.class,                new CachedServiceFetcher<WifiManager>() {            @Override            public WifiManager createService(ContextImpl ctx) {                IBinder b = ServiceManager.getService(Context.WIFI_SERVICE);                IWifiManager service = IWifiManager.Stub.asInterface(b);                return new WifiManager(ctx.getOuterContext(), service);            }});        registerService(Context.WIFI_PASSPOINT_SERVICE, WifiPasspointManager.class,                new CachedServiceFetcher<WifiPasspointManager>() {            @Override            public WifiPasspointManager createService(ContextImpl ctx) {                IBinder b = ServiceManager.getService(Context.WIFI_PASSPOINT_SERVICE);                IWifiPasspointManager service = IWifiPasspointManager.Stub.asInterface(b);                return new WifiPasspointManager(ctx.getOuterContext(), service);            }});        registerService(Context.WIFI_P2P_SERVICE, WifiP2pManager.class,                new StaticServiceFetcher<WifiP2pManager>() {            @Override            public WifiP2pManager createService() {                IBinder b = ServiceManager.getService(Context.WIFI_P2P_SERVICE);                IWifiP2pManager service = IWifiP2pManager.Stub.asInterface(b);                return new WifiP2pManager(service);            }});        registerService(Context.WIFI_SCANNING_SERVICE, WifiScanner.class,                new CachedServiceFetcher<WifiScanner>() {            @Override            public WifiScanner createService(ContextImpl ctx) {                IBinder b = ServiceManager.getService(Context.WIFI_SCANNING_SERVICE);                IWifiScanner service = IWifiScanner.Stub.asInterface(b);                return new WifiScanner(ctx.getOuterContext(), service);            }});        registerService(Context.WIFI_RTT_SERVICE, RttManager.class,                new CachedServiceFetcher<RttManager>() {            @Override            public RttManager createService(ContextImpl ctx) {                IBinder b = ServiceManager.getService(Context.WIFI_RTT_SERVICE);                IRttManager service = IRttManager.Stub.asInterface(b);                return new RttManager(ctx.getOuterContext(), service);            }});        registerService(Context.ETHERNET_SERVICE, EthernetManager.class,                new CachedServiceFetcher<EthernetManager>() {            @Override            public EthernetManager createService(ContextImpl ctx) {                IBinder b = ServiceManager.getService(Context.ETHERNET_SERVICE);                IEthernetManager service = IEthernetManager.Stub.asInterface(b);                return new EthernetManager(ctx.getOuterContext(), service);            }});        registerService(Context.WINDOW_SERVICE, WindowManager.class,                new CachedServiceFetcher<WindowManager>() {            @Override            public WindowManager createService(ContextImpl ctx) {                return new WindowManagerImpl(ctx.getDisplay());            }});        registerService(Context.USER_SERVICE, UserManager.class,                new CachedServiceFetcher<UserManager>() {            @Override            public UserManager createService(ContextImpl ctx) {                IBinder b = ServiceManager.getService(Context.USER_SERVICE);                IUserManager service = IUserManager.Stub.asInterface(b);                return new UserManager(ctx, service);            }});        registerService(Context.APP_OPS_SERVICE, AppOpsManager.class,                new CachedServiceFetcher<AppOpsManager>() {            @Override            public AppOpsManager createService(ContextImpl ctx) {                IBinder b = ServiceManager.getService(Context.APP_OPS_SERVICE);                IAppOpsService service = IAppOpsService.Stub.asInterface(b);                return new AppOpsManager(ctx, service);            }});        registerService(Context.CAMERA_SERVICE, CameraManager.class,                new CachedServiceFetcher<CameraManager>() {            @Override            public CameraManager createService(ContextImpl ctx) {                return new CameraManager(ctx);            }});        registerService(Context.LAUNCHER_APPS_SERVICE, LauncherApps.class,                new CachedServiceFetcher<LauncherApps>() {            @Override            public LauncherApps createService(ContextImpl ctx) {                IBinder b = ServiceManager.getService(Context.LAUNCHER_APPS_SERVICE);                ILauncherApps service = ILauncherApps.Stub.asInterface(b);                return new LauncherApps(ctx, service);            }});        registerService(Context.RESTRICTIONS_SERVICE, RestrictionsManager.class,                new CachedServiceFetcher<RestrictionsManager>() {            @Override            public RestrictionsManager createService(ContextImpl ctx) {                IBinder b = ServiceManager.getService(Context.RESTRICTIONS_SERVICE);                IRestrictionsManager service = IRestrictionsManager.Stub.asInterface(b);                return new RestrictionsManager(ctx, service);            }});        registerService(Context.PRINT_SERVICE, PrintManager.class,                new CachedServiceFetcher<PrintManager>() {            @Override            public PrintManager createService(ContextImpl ctx) {                IBinder iBinder = ServiceManager.getService(Context.PRINT_SERVICE);                IPrintManager service = IPrintManager.Stub.asInterface(iBinder);                return new PrintManager(ctx.getOuterContext(), service, UserHandle.myUserId(),                        UserHandle.getAppId(Process.myUid()));            }});        registerService(Context.CONSUMER_IR_SERVICE, ConsumerIrManager.class,                new CachedServiceFetcher<ConsumerIrManager>() {            @Override            public ConsumerIrManager createService(ContextImpl ctx) {                return new ConsumerIrManager(ctx);            }});        registerService(Context.MEDIA_SESSION_SERVICE, MediaSessionManager.class,                new CachedServiceFetcher<MediaSessionManager>() {            @Override            public MediaSessionManager createService(ContextImpl ctx) {                return new MediaSessionManager(ctx);            }});        registerService(Context.TRUST_SERVICE, TrustManager.class,                new StaticServiceFetcher<TrustManager>() {            @Override            public TrustManager createService() {                IBinder b = ServiceManager.getService(Context.TRUST_SERVICE);                return new TrustManager(b);            }});        registerService(Context.FINGERPRINT_SERVICE, FingerprintManager.class,                new CachedServiceFetcher<FingerprintManager>() {            @Override            public FingerprintManager createService(ContextImpl ctx) {                IBinder binder = ServiceManager.getService(Context.FINGERPRINT_SERVICE);                IFingerprintService service = IFingerprintService.Stub.asInterface(binder);                return new FingerprintManager(ctx.getOuterContext(), service);            }});        registerService(Context.TV_INPUT_SERVICE, TvInputManager.class,                new StaticServiceFetcher<TvInputManager>() {            @Override            public TvInputManager createService() {                IBinder iBinder = ServiceManager.getService(Context.TV_INPUT_SERVICE);                ITvInputManager service = ITvInputManager.Stub.asInterface(iBinder);                return new TvInputManager(service, UserHandle.myUserId());            }});        registerService(Context.NETWORK_SCORE_SERVICE, NetworkScoreManager.class,                new CachedServiceFetcher<NetworkScoreManager>() {            @Override            public NetworkScoreManager createService(ContextImpl ctx) {                return new NetworkScoreManager(ctx);            }});        registerService(Context.USAGE_STATS_SERVICE, UsageStatsManager.class,                new CachedServiceFetcher<UsageStatsManager>() {            @Override            public UsageStatsManager createService(ContextImpl ctx) {                IBinder iBinder = ServiceManager.getService(Context.USAGE_STATS_SERVICE);                IUsageStatsManager service = IUsageStatsManager.Stub.asInterface(iBinder);                return new UsageStatsManager(ctx.getOuterContext(), service);            }});        registerService(Context.NETWORK_STATS_SERVICE, NetworkStatsManager.class,                new CachedServiceFetcher<NetworkStatsManager>() {            @Override            public NetworkStatsManager createService(ContextImpl ctx) {                return new NetworkStatsManager(ctx.getOuterContext());            }});        registerService(Context.JOB_SCHEDULER_SERVICE, JobScheduler.class,                new StaticServiceFetcher<JobScheduler>() {            @Override            public JobScheduler createService() {                IBinder b = ServiceManager.getService(Context.JOB_SCHEDULER_SERVICE);                return new JobSchedulerImpl(IJobScheduler.Stub.asInterface(b));            }});        registerService(Context.PERSISTENT_DATA_BLOCK_SERVICE, PersistentDataBlockManager.class,                new StaticServiceFetcher<PersistentDataBlockManager>() {            @Override            public PersistentDataBlockManager createService() {                IBinder b = ServiceManager.getService(Context.PERSISTENT_DATA_BLOCK_SERVICE);                IPersistentDataBlockService persistentDataBlockService =                        IPersistentDataBlockService.Stub.asInterface(b);                if (persistentDataBlockService != null) {                    return new PersistentDataBlockManager(persistentDataBlockService);                } else {                    // not supported                    return null;                }            }});        registerService(Context.MEDIA_PROJECTION_SERVICE, MediaProjectionManager.class,                new CachedServiceFetcher<MediaProjectionManager>() {            @Override            public MediaProjectionManager createService(ContextImpl ctx) {                return new MediaProjectionManager(ctx);            }});        registerService(Context.APPWIDGET_SERVICE, AppWidgetManager.class,                new CachedServiceFetcher<AppWidgetManager>() {            @Override            public AppWidgetManager createService(ContextImpl ctx) {                IBinder b = ServiceManager.getService(Context.APPWIDGET_SERVICE);                return new AppWidgetManager(ctx, IAppWidgetService.Stub.asInterface(b));            }});        registerService(Context.MIDI_SERVICE, MidiManager.class,                new CachedServiceFetcher<MidiManager>() {            @Override            public MidiManager createService(ContextImpl ctx) {                IBinder b = ServiceManager.getService(Context.MIDI_SERVICE);                if (b == null) {                    return null;                }                return new MidiManager(IMidiManager.Stub.asInterface(b));            }});        registerService(Context.RADIO_SERVICE, RadioManager.class,                new CachedServiceFetcher<RadioManager>() {            @Override            public RadioManager createService(ContextImpl ctx) {                return new RadioManager(ctx);            }});//SPRD: add for heartbeat powerguru serviceif (PowerGuru.isEnabled()) {        registerService(Context.POWERGURU_SERVICE,PowerGuru.class,            new CachedServiceFetcher<PowerGuru>() {        public PowerGuru createService(ContextImpl ctx) {            IBinder b = ServiceManager.getService(Context.POWERGURU_SERVICE);            IPowerGuru service = IPowerGuru.Stub.asInterface(b);            return new PowerGuru(service, ctx);        }});    }    }

找到对AM注册的代码块

        registerService(Context.ACTIVITY_SERVICE, ActivityManager.class,                new CachedServiceFetcher<ActivityManager>() {            @Override            public ActivityManager createService(ContextImpl ctx) {                return new ActivityManager(ctx.getOuterContext(), ctx.mMainThread.getHandler());            }});

   /**     * Override this class when the system service constructor needs a     * ContextImpl and should be cached and retained by that context.     */    static abstract class CachedServiceFetcher<T> implements ServiceFetcher<T> {        private final int mCacheIndex;        public CachedServiceFetcher() {            mCacheIndex = sServiceCacheSize++;        }        @Override        @SuppressWarnings("unchecked")        public final T getService(ContextImpl ctx) {            final Object[] cache = ctx.mServiceCache;            synchronized (cache) {                // Fetch or create the service.                Object service = cache[mCacheIndex];                if (service == null) {                    service = createService(ctx);                    cache[mCacheIndex] = service;                }                return (T)service;            }        }        public abstract T createService(ContextImpl ctx);    }

            @Override            public ActivityManager createService(ContextImpl ctx) {                return new ActivityManager(ctx.getOuterContext(), ctx.mMainThread.getHandler());            }});

最终调用

new ActivityManager(ctx.getOuterContext(), ctx.mMainThread.getHandler());

总结

上面代码贴的有点乱

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