PMS/AMS启动流程

1. zygote进程启动SystemServer进程(如何启动有待进一步研究)

2.在SystemServer.java的main()函数中启动SystemServer进程

    /**
     * The main entry point from zygote.
     */
    public static void main(String[] args) {
        new SystemServer().run();
    }

3. 在SystemServer.java的run()(430)方法中启动启动服务、核心服务和其他服务

 590           startBootstrapServices(t);
 591           startCoreServices(t);
 592           startOtherServices(t);

4. 在SystemServer.java的startBootstrapServices()(704)方法中启动了PMS(PMS做了哪些事情，后续分析)

  //848行，通过PackageManagerService.main()函数启动PMS(实际上其并不是一个进程，没有纯main()方法，它的main方法是有参数的)
        t.traceBegin("StartPackageManagerService");
        try {
            Watchdog.getInstance().pauseWatchingCurrentThread("packagemanagermain");
            mPackageManagerService = PackageManagerService.main(mSystemContext, installer,
                    mFactoryTestMode != FactoryTest.FACTORY_TEST_OFF, mOnlyCore);
        } finally {
            Watchdog.getInstance().resumeWatchingCurrentThread("packagemanagermain");
        }

通过PackageManagerService.main()函数启动PMS(实际上其并不是一个进程，没有纯main()方法)，例如Systemserver.java就是开启了一个进程，看看其main方法，由zygote进程开启

    /**
     * The main entry point from zygote.
     */
    public static void main(String[] args) {
        new SystemServer().run();
    }

5. 在SystemServer.java的startBootstrapServices()(704)方法中启动了AMS

//755行
//通过ActivityManagerService.Lifecycle.startService()方法，并传入ActivityTaskManagerService实例
        // Activity manager runs the show.
        t.traceBegin("StartActivityManager");
        // 通过SystemServiceManager.startService反射ActivityTaskManagerService.java的构造方法，并实例化
        ActivityTaskManagerService atm = mSystemServiceManager.startService(
                ActivityTaskManagerService.Lifecycle.class).getService();
        
//ActivityManagerService通过自己的Lifecycle.startService方法实例化，实际上也是通过SystemServiceManager反射实例化的
        mActivityManagerService = ActivityManagerService.Lifecycle.startService(
                mSystemServiceManager, atm);
        mActivityManagerService.setSystemServiceManager(mSystemServiceManager);
        mActivityManagerService.setInstaller(installer);
        mWindowManagerGlobalLock = atm.getGlobalLock();
        t.traceEnd();

6. SystemServiceManager.java中startService()(136)反射实例化的代码

    public <T extends SystemService> T startService(Class<T> serviceClass) {
        try {
            final String name = serviceClass.getName();
           ...
            final T service;
            try {
                Constructor<T> constructor = serviceClass.getConstructor(Context.class);
                service = constructor.newInstance(mContext);
   
            }

            startService(service);
            return service;
        } finally {
            Trace.traceEnd(Trace.TRACE_TAG_SYSTEM_SERVER);
        }
    }

7. ActivityManagerService和ActivityTaskManagerService的关系
   在实例化并开始AMS服务时，将ATMS传入到了AMS中，AMS代理了ATMS,工作都是由ATMS完成
   类似：

    @Override
    public int startActivity(IApplicationThread caller, String callingPackage,
            Intent intent, String resolvedType, IBinder resultTo, String resultWho, int requestCode,
            int startFlags, ProfilerInfo profilerInfo, Bundle bOptions) {
        return mActivityTaskManager.startActivity(caller, callingPackage, null, intent,
                resolvedType, resultTo, resultWho, requestCode, startFlags, profilerInfo, bOptions);
    }