ActivityManagerService 启动

BootRoom -----> Boot

企业微信截图_16467247018996.png

AMS

1. 管理四大组件的生命周期

AMS 启动

SystemServer 在zygote进程启动后，zygote直接fork一个进程，启动SystemServer， SystemServer进入main方法开始执行，在SystemServier的main方法中， 执行了SystemServer.run（）方法。

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

SystemServer.run()

 // Start services.
        try {
            startBootstrapServices();  //启动一些 boot进程 ， 在这里第一次开启了ActivtyManagerService ，这里还会将当前进程设置为System进程
            startCoreServices();  //启动一些核心进程
            startOtherServices(); //启动其他服务
        } catch (Throwable ex) {
            Slog.e("System", "******************************************");
            Slog.e("System", "************ Failure starting system services", ex);
            throw ex;
        }
       Looper.loop(); //启动looper循环，保证当前线程不会停止

进入 startBootstrapService

 private void startBootstrapServices() {
        // Wait for installd to finish starting up so that it has a chance to
        // create critical directories such as /data/user with the appropriate
        // permissions.  We need this to complete before we initialize other services.
        Installer installer = mSystemServiceManager.startService(Installer.class);

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

在SystemServer.run中，最后所有service启动之后：

      mActivityManagerService.systemReady(new Runnable() { //这里会执行一系列方法，通知其他服务，当前系统启动完成
            mSystemServiceManager.startBootPhase(
                        SystemService.PHASE_ACTIVITY_MANAGER_READY);

                try {
                    mActivityManagerService.startObservingNativeCrashes();
                } catch (Throwable e) {
                    reportWtf("observing native crashes", e);
                }

                Slog.i(TAG, "WebViewFactory preparation");
                WebViewFactory.prepareWebViewInSystemServer();

                try {
                    startSystemUi(context);
                } catch (Throwable e) {
                    reportWtf("starting System UI", e);
                }
                try {
                    if (networkScoreF != null) networkScoreF.systemReady();
                } catch (Throwable e) {
                  reportWtf("making Network Score Service ready", e);
                }
          ...  //剩余的就不在进行表述
      }

AMS.systemReady()

AMS.systemReady() 方法中，会调用startHomeActiivtyLocked.();

SystemServer中将当前服务准备完成之后，调用systemReady方法来启动Launcher

来看 startHomeActivityLocked

 boolean startHomeActivityLocked(int userId, String reason) {
         ...
        Intent intent = getHomeIntent(); //获取当前应用的HomeIntent
        ActivityInfo aInfo =
            resolveActivityInfo(intent, STOCK_PM_FLAGS, userId);
        if (aInfo != null) {
            intent.setComponent(new ComponentName(
                    aInfo.applicationInfo.packageName, aInfo.name));
            // Don't do this if the home app is currently being
            // instrumented.
            aInfo = new ActivityInfo(aInfo);
            aInfo.applicationInfo = getAppInfoForUser(aInfo.applicationInfo, userId);
            ProcessRecord app = getProcessRecordLocked(aInfo.processName,
                    aInfo.applicationInfo.uid, true);
            if (app == null || app.instrumentationClass == null) { 
                intent.setFlags(intent.getFlags() | Intent.FLAG_ACTIVITY_NEW_TASK);
                mStackSupervisor.startHomeActivity(intent, aInfo, reason);
            }
        }

        return true;
    }

到这里就属于Activity的启动流程了