Android SystemService的启动流程

       SystemServer.java(由init进程起来)之后会调用:


    // Initialize the system context.
    createSystemContext();<strong>//方法一 
    // Create the system service manager.
    mSystemServiceManager = new SystemServiceManager(mSystemContext);
    LocalServices.addService(SystemServiceManager.class, mSystemServiceManager);
    


    //ActivityManagerService 启动
    mActivityManagerService = mSystemServiceManager.startService(//方法二
    ActivityManagerService.Lifecycle.class).getService();
    mActivityManagerService.setSystemServiceManager(mSystemServiceManager);
    
    //方法一
    private void createSystemContext() {
        ActivityThread activityThread = ActivityThread.systemMain();
        mSystemContext = activityThread.getSystemContext();
        mSystemContext.setTheme(android.R.style.Theme_DeviceDefault_Light_DarkActionBar);
    }




    //方法二
    public <T extends SystemService> T startService(Class<T> serviceClass) {
        final String name = serviceClass.getName();
        Slog.i(TAG, "Starting " + name);
        // Create the service.
        if (!SystemService.class.isAssignableFrom(serviceClass)) {
            throw new RuntimeException("Failed to create " + name
                    + ": service must extend " + SystemService.class.getName());
        }
        final T service;
        try {
            Constructor<T> constructor = serviceClass.getConstructor(Context.class);
            service = constructor.newInstance(mContext);
        } catch (InstantiationException ex) {
            throw new RuntimeException("Failed to create service " + name
                    + ": service could not be instantiated", ex);
        } catch (IllegalAccessException ex) {
            throw new RuntimeException("Failed to create service " + name
                    + ": service must have a public constructor with a Context argument", ex);
        } catch (NoSuchMethodException ex) {
            throw new RuntimeException("Failed to create service " + name
                    + ": service must have a public constructor with a Context argument", ex);
        } catch (InvocationTargetException ex) {
            throw new RuntimeException("Failed to create service " + name
                    + ": service constructor threw an exception", ex);
        }
        // Register it.
        mServices.add(service);
        // Start it.
        try {
            service.onStart();//方法三，很关键的方法，会把自己添加到SystemManager中
        } catch (RuntimeException ex) {
            throw new RuntimeException("Failed to start service " + name
                    + ": onStart threw an exception", ex);
        }
        return service;
    }


    //方法三
    @Override
    public void onStart() {
        publishBinderService(Context.FINGERPRINT_SERVICE, new FingerprintServiceWrapper());//方法四
        IFingerprintDaemon daemon = getFingerprintDaemon();
        if (DEBUG) Slog.v(TAG, "Fingerprint HAL id: " + mHalDeviceId);
        listenForUserSwitches();
    }




    //方法四
    /**
     * Publish the service so it is accessible to other services and apps.
     */
    protected final void publishBinderService(String name, IBinder service,
            boolean allowIsolated) {
        ServiceManager.addService(name, service, allowIsolated);
    }




    //authenticate()为什么要用mhander.post 调用startAuthentication()方法，不可以直接调用
    mHandler.post(new Runnable() {
        @Override
        public void run() {
            startAuthentication(token, opId, effectiveGroupId, receiver, flags, restricted);
        }
    });