Android 相关启动执行流程

Android相关流程图

init:

1. 挂载和创建系统文件
2. 解析rc文件
3. 进入无限循环
   1. 执行action -- zygote启动
   2. 检测并重启进程
   3. 接收子进程的SIGCHLD信号，执行响应的方法

zygote：

1. native
   1. 初始化Android运行环境
   2. 注册jni
   3. 执行ZygoteInit.main 方法 进入Java层
2. Java
   1. 创建 socket
   2. 执行预加载
   3. 通过fork创建 SystemServer 进程
   4. 进入循环：等待AMS的通知，创建对应的进程

SystemServer
nice-name 给进程的名称

pid = Zygote.forkSystemServer

//启动 SystemServer.main
return handleSystemServerProcess(parsedArgs);
    //开启Binder线程池
    ZygoteInit.nativeZygoteInit();
        gCurRuntime->onZygoteInit();
             sp<ProcessState> proc = ProcessState::self();
                proc->startThreadPool();
    // 运行 SystemServer.main
    RuntimeInit.applicationInit
        // 通过反射执行 SystemServer.main
        mMethod.invoke(null, new Object[] { mArgs }); 

SystemServer进程:

1. createSystemContext();
   //执行systemMain()@ActivityThread,在systemMain方法中

   1. new ActivityThread()，执行attach()@ActivityThread
      //在attach方法中
   2. new Instrumentation(),
   3. ContextImpl context = ContextImpl.createAppContext(
      this, getSystemContext().mPackageInfo);
   4. Application mInitialApplication = context.mPackageInfo.makeApplication(true, null);

2. mSystemServiceManager = new SystemServiceManager(mSystemContext); // 系统服务

   1. startService --> service.onStart(); // 继承自 SystemService 的服务

3. startBootstrapServices(t); // 引导服务 --AMS
   //android 10开始 多了个 ATMS(ActivityTaskManagerService)

   1. mService = new ActivityTaskManagerService(context);

      mService.start();

       ServiceManager.addService(name, service,resumeTopActivityInnerLocked allowIsolated, dumpPriority);
      

   2. 创建 AMS -- 其他三个服务，持有 ATMS
      mService = new ActivityManagerService(context, sAtm);

      mService.start();

4. startCoreServices(t); // 核心服务

5. startOtherServices(t); // 其他服务 -- WMS

   mActivityManagerService.systemReady // 启动Launcher

   startSystemUi(context, windowManagerF); // 启动 SystemUI

mActivityManagerService.systemReady -->

mActivityTaskManager.onSystemReady@ActivityTaskManagerService -->

mAtmInternal.resumeTopActivities@ActivityTaskManagerService -->

mRootWindowContainer.resumeFocusedStacksTopActivities()@RootWindowContainer -->

resumeFocusedStacksTopActivities@RootWindowContainer -->

targetStack.resumeTopActivityUncheckedLocked@ActivityStack

--> resumeTopActivityInnerLocked@ActivityStack -->

resumeNextFocusableActivityWhenStackIsEmpty@ActivityStack

--> mRootWindowContainer.resumeHomeActivity@RootWindowContainer -->

startHomeOnTaskDisplayArea@RootWindowContainer -->

resolveHomeActivity@RootWindowContainer -->

mService.getActivityStartController().startHomeActivity@ActivityStartController obtainStarter@ActivityStartController -->

execute@ActivityStarter -->

executeRequest@ActivityStarter -->

startActivityInner@ActivityStarter

这里调用了startActivity()方法来启动Launcher，最终会进入Launcher的onCreate()方法，Launcher启动完成。

mSystemServiceManager.startBootPhase // 状态设置

SystemServiceManager:管理服务的生命周期

ServerManager：管理Binder服务的

ServiceManager.getService(Context.ACTIVITY_TASK_SERVICE);

publishBinderService(Context.ACTIVITY_TASK_SERVICE, mService);

ServiceManager.addService(name, service, allowIsolated, dumpPriority); // 注册Binder服务

Activity启动流程：

startActivity@Activity --> startActivityForResult@Activity

--> mInstrumentation.execStartActivity@Instrumentation -->

ActivityTaskManager.getService().startActivity@ActivityTaskManagerService

--> startActivityAsUser@ActivityTaskManagerService

--> execute@ActivityStarter -->

executeRequest@ActivityStarter -->

startActivityUnchecked@ActivityStarter -->

startActivityInner@ActivityStarter -->

resumeFocusedStacksTopActivities@RootWindowContainer -->

resumeTopActivityUncheckedLocked@ActivityStack -->

resumeTopActivityInnerLocked@ActivityStack -->

startSpecificActivity@ActivityStackSupervisor -->

realStartActivityLocked@ActivityStackSupervisor -->

scheduleTransaction@ClientLifecycleManager -->

schedule@ClientTransaction -->

scheduleTransaction@ApplicationThread -->

scheduleTransaction@Activity -->

execute@TransactionExecutor -->

executeCallbacks@TransactionExecutor -->

execute@LaunchActivityItem -->

handleLaunchActivity@ActivityThread -->

performLaunchActivity@ActivityThread -->

createBaseContextForActivity@ActivityThread 、mInstrumentation.newActivity、makeApplication@LoadApk -->

attach@Activity、callActivityOnCreate@Instrumentation -->

onCreate@Activity

小结

1. 调用从system_server进程传过来的ClientTransaction.CallBack类中的execute方法，其继续调用ActivityThread.handleLaunchActivity方法来启动Activity。
2. ActivityThread.handleLaunchActivity调用performLaunchActivity方法启动Activity
3. performLaunchActivity先获取启动Activity的ActivityInfo，而后创建一个LoadedApk和上下文ContextImpl。在通过反射去创建此Activity对象，并执行Activity的onCreate方法。

SystemServer执行流程图：

image.png

Activity启动：

image.png

Android 启动流程时序图：

image.png

Activity生命周期管理类图：

image.png

下图是ATMS处理startActivity过程，并回调启动进程的ApplicationThread:

22650779-eabf22046e2f33d4.png

下图为Android 30 之后，ActivityThread启动Activity过程的时序图：

22650779-72d2d3d9acda317d.png