ActivityManagerService 启动流程

它是在SyetemServer进程中启动的：
文件所在目录: frameworks/base/services/java/com/android/server/SystemServer.java

SyetemServer run

   private void run() {
        Looper.prepareMainLooper();

        // Initialize native services.
        System.loadLibrary("android_servers");

        // Create the system service manager.
        mSystemServiceManager = new SystemServiceManager(mSystemContext);

        // Start services.

        // 引导服务
        startBootstrapServices();
        // 核心服务
        startCoreServices();
        // 其他服务
        startOtherServices();
        
        // Loop forever.
        Looper.loop();
    }

SyetemServer 启动了一堆服务，这些服务由 mSystemServiceManager进行创建、启动和生命周期管理。
ActivityManagerService 则由此创建：

 /**
     * Starts the small tangle of critical services that are needed to get
     * the system off the ground.  These services have complex mutual dependencies
     * which is why we initialize them all in one place here.  Unless your service
     * is also entwined in these dependencies, it should be initialized in one of
     * the other functions.
     */
    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);

        // Set up the Application instance for the system process and get started.
        mActivityManagerService.setSystemProcess();

        // The sensor service needs access to package manager service, app ops
        // service, and permissions service, therefore we start it after them.
        startSensorService();
    }

注意1：mSystemServiceManager的startService(Class<T> serviceClass)，包含了创建，注册，启动service的过程：

  /**
     * Creates and starts a system service. The class must be a subclass of
     * {@link com.android.server.SystemService}.
     *
     * @param serviceClass A Java class that implements the SystemService interface.
     * @return The service instance, never null.
     * @throws RuntimeException if the service fails to start.
     */
    @SuppressWarnings("unchecked")
    public <T extends SystemService> T startService(Class<T> serviceClass) {
        try {
            final String name = serviceClass.getName();
            Slog.i(TAG, "Starting " + name);
            Trace.traceBegin(Trace.TRACE_TAG_SYSTEM_SERVER, "StartService " + 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();
            } catch (RuntimeException ex) {
                throw new RuntimeException("Failed to start service " + name
                        + ": onStart threw an exception", ex);
            }
            return service;
        } finally {
            Trace.traceEnd(Trace.TRACE_TAG_SYSTEM_SERVER);
        }
    }

注意2：mActivityManagerService.setSystemProcess():

public void setSystemProcess() {
        try {
            ServiceManager.addService(Context.ACTIVITY_SERVICE, this, true);
            ServiceManager.addService(ProcessStats.SERVICE_NAME, mProcessStats);
            ServiceManager.addService("meminfo", new MemBinder(this));
            ServiceManager.addService("gfxinfo", new GraphicsBinder(this));
            ServiceManager.addService("dbinfo", new DbBinder(this));
            if (MONITOR_CPU_USAGE) {
                ServiceManager.addService("cpuinfo", new CpuBinder(this));
            }
            ServiceManager.addService("permission", new PermissionController(this));
            ServiceManager.addService("processinfo", new ProcessInfoService(this));

            ApplicationInfo info = mContext.getPackageManager().getApplicationInfo(
                    "android", STOCK_PM_FLAGS | MATCH_SYSTEM_ONLY);
            mSystemThread.installSystemApplicationInfo(info, getClass().getClassLoader());

         
        } catch (PackageManager.NameNotFoundException e) {
            throw new RuntimeException(
                    "Unable to find android system package", e);
        }
    }

Activity 启动流程

Activity 启动流程

PlantUML 文件记录

1. Activity 成长路程

@startuml Activity 成长路程
Activity->Activity:startActivity
Activity->Activity:startActivityForResult
Activity->Activity:startActivityForResult

Activity->Instrumentation:execStartActivity

Instrumentation->ActivityManagerService:startActivity
ActivityManagerService->ActivityManagerService:startActivityAsUser
ActivityManagerService->ActivityStarter:startActivityMayWait
ActivityStarter->ActivityStarter:startActivityLocked
ActivityStarter->ActivityStarter:startActivityUnchecked

ActivityStarter->ActivityStack:startActivityLocked
ActivityStarter->ActivityStackSupervisor:resumeFocusedStackTopActivityLocked
ActivityStackSupervisor->ActivityStack:resumeTopActivityUncheckedLocked
ActivityStack->ActivityStack:resumeTopActivityInnerLocked
ActivityStack->ActivityStackSupervisor:startSpecificActivityLocked
ActivityStackSupervisor->ActivityStackSupervisor:realStartActivityLocked
ActivityStackSupervisor->ApplicationThread:scheduleLaunchActivity


ApplicationThread->ActivityThread:sendMessage(H.LAUNCH_ACTIVITY)
ActivityThread->ActivityThread:handleLaunchActivity
ActivityThread->ActivityThread:performLaunchActivity
ActivityThread->Instrumentation:callActivityOnCreate

Instrumentation->Instrumentation:prePerformCreate
Instrumentation->Activity:performCreate
Activity->Activity:onCreate

ActivityThread->ActivityThread:handleResumeActivity
ActivityThread->ActivityThread:performResumeActivity
ActivityThread->Activity:performResume
Activity->Activity:performRestart
Activity->Instrumentation:callActivityOnRestart
Instrumentation->Activity:onRestart
Activity->Instrumentation:callActivityOnResume
Instrumentation->Activity:onResume

ActivityThread->Activity:makeVisibale



@enduml

参考