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1 前言
ATMS 即 ActivityTaskManagerService，用于管理 Activity 及其容器（任务、堆栈、显示等）。ATMS 在 Android 10 中才出现，由原来的 AMS（ActivityManagerService）分离而来，承担了 AMS 的部分职责。因此，在 AMS初始化过程中（AMS启动流程），也伴随着了 ATMS 的初始化。
（1）ATMS 创建流程
SystemServer：依次调用 main()、run()、startBootstrapServices()，再调用 SystemServiceManager 的 startService() 方法，并将 Lifecyle.class 传入；
SystemServiceManager ：startService() 方法通过反射调用 Lifecyle 的构造方法，生成 Lifecyle 对象；
Lifecyle：构造方法中调用 ATMS 的构造方法创建 ATMS 对象，并通过 getService() 方法返回 ATMS 对象。
（2）ATMS 初始化
如图，ATMS 在初始化时创建了图中蓝色类的对象。
2 ATMS 启动流程
（1）main
/frameworks/base/services/java/com/android/server/SystemServer.java
public static void main(String[] args) { new SystemServer().run();}（2）run
/frameworks/base/services/java/com/android/server/SystemServer.java
private void run() {try {...// 创建LooperLooper.prepareMainLooper();// 加载libandroid_servers.soSystem.loadLibrary("android_servers");// 创建系统的 Context：ContextImpl.createSystemContext(new ActivityThread())createSystemContext();// 创建 SystemServiceManagermSystemServiceManager = new SystemServiceManager(mSystemContext);LocalServices.addService(SystemServiceManager.class, mSystemServiceManager);...}...try {//启动引导服务，ActivityManagerService、ActivityTaskManagerService、PackageManagerService、PowerManagerService、DisplayManagerService 等startBootstrapServices(); //启动核心服务，BatteryService、UsageStatusService 等startCoreServices(); //启动其他服务，InputManagerService、WindowManagerService、CameraService、AlarmManagerService 等startOtherServices(); ...}...// 开启消息循环Looper.loop();}（3）startBootstrapServices
/frameworks/base/services/java/com/android/server/SystemServer.java
private void startBootstrapServices() {... //启动 ATMSActivityTaskManagerService atm = mSystemServiceManager.startService(ActivityTaskManagerService.Lifecycle.class).getService(); //启动 AMS，并将 ATMS 注入mActivityManagerService = ActivityManagerService.Lifecycle.startService(mSystemServiceManager, atm);...}（4）startService
/frameworks/base/services/core/java/com/android/server/SystemServiceManager.java
public <T extends SystemService> T startService(Class<T> serviceClass) {try {final String name = serviceClass.getName();...final T service;try { //通过反射调用 serviceClass 的构造方法 创建 Lifecycle 对象Constructor<T> constructor = serviceClass.getConstructor(Context.class);service = constructor.newInstance(mContext);}...startService(service);return service;}...}public void startService(SystemService service) {mServices.add(service); //mServices: ArrayList<SystemService>...try {service.onStart(); //调用 Lifecycle 的 onStart 方法}...}（5）ATMS.Lifecycle
/frameworks/base/services/core/java/com/android/server/wm/ActivityTaskManagerService.Lifecycle.java
public static final class Lifecycle extends SystemService {private final ActivityTaskManagerService mService;public Lifecycle(Context context) {//被 SystemServiceManager 的 startService() 方法调用super(context);mService = new ActivityTaskManagerService(context);}public void onStart() { //添加 ATMS 服务，方便跨进程调用：ServiceManager.addService(Context.ACTIVITY_TASK_SERVICE, mService, false, DUMP_FLAG_PRIORITY_DEFAULT)publishBinderService(Context.ACTIVITY_TASK_SERVICE, mService);mService.start(); //调用 ATMS 的 start() 方法}...public ActivityTaskManagerService getService() {return mService;}}注意：onStart() 方法中调用 ATMS 的 start() 方法初始化（下文还会介绍）。 已通过 ServiceManager.addService() 将 Context.ACTIVITY_TASK_SERVICE 与 ATMS 绑定，因此在其他进程中可以通过如下方式获取 ATMS。
IBinder b = ServiceManager.getService(Context.ACTIVITY_TASK_SERVICE); IActivityTaskManager atm = IActivityTaskManager.Stub.asInterface(b);3 ATMS 初始化
（1）ATMS 的构造方法
/frameworks/base/services/core/java/com/android/server/wm/ActivityTaskManagerService.java
public ActivityTaskManagerService(Context context) {mContext = context;...mSystemThread = ActivityThread.currentActivityThread();mUiContext = mSystemThread.getSystemUiContext(); //ContextImpl.createSystemUiContext(getSystemContext())mLifecycleManager = new ClientLifecycleManager();mInternal = new LocalService(); //ActivityTaskManagerInternal 的子类...}（2）start
start() 方法被 Lifecycle 的 onStart() 方法调用，onStart() 方法又被 SystemServiceManager 的 startService() 方法调用。
/frameworks/base/services/core/java/com/android/server/wm/ActivityTaskManagerService.java
private void start() {LocalServices.addService(ActivityTaskManagerInternal.class, mInternal);}mInternal 属于 LocalService 类（ActivityTaskManagerInternal 的子类），在 ATMS 的构造方法中创建。
（3）initialize
在 AMS 的构造方法中，调用了 ATMS 的 initialize() 方法进一步初始化。
/frameworks/base/services/core/java/com/android/server/am/ActivityManagerService.java
public ActivityManagerService(Context systemContext, ActivityTaskManagerService atm) {...mHandlerThread = new ServiceThread(TAG, THREAD_PRIORITY_FOREGROUND, false); ... mUserController = new UserController(this);mPendingIntentController = new PendingIntentController(mHandlerThread.getLooper(), mUserController);...mIntentFirewall = new IntentFirewall(new IntentFirewallInterface(), mHandler);mActivityTaskManager = atm;//进一步初始化 ATMSmActivityTaskManager.initialize(mIntentFirewall, mPendingIntentController, DisplayThread.get().getLooper());...}/frameworks/base/services/core/java/com/android/server/wm/ActivityTaskManagerService.java
public void initialize(IntentFirewall intentFirewall, PendingIntentController intentController, Looper looper) {mH = new H(looper);mUiHandler = new UiHandler();mIntentFirewall = intentFirewall;...mPendingIntentController = intentController;mTempConfig.setToDefaults(); //定义时即被创建：mTempConfig = new Configuration()...//new ActivityStackSupervisor(this, mH.getLooper())mStackSupervisor = createStackSupervisor(); mRootActivityContainer = new RootActivityContainer(this);mRootActivityContainer.onConfigurationChanged(mTempConfig);...mLockTaskController = new LockTaskController(mContext, mStackSupervisor, mH);mActivityStartController = new ActivityStartController(this);mRecentTasks = createRecentTasks(); //new RecentTasks(this, mStackSupervisor)mStackSupervisor.setRecentTasks(mRecentTasks);...}（4）onActivityManagerInternalAdded
在 AMS 的 start() 方法中，调用了 ATMS 的 onActivityManagerInternalAdded() 方法进一步初始化。
/frameworks/base/services/core/java/com/android/server/am/ActivityManagerService.java
private void start() {...LocalServices.addService(ActivityManagerInternal.class, new LocalService()); //调用 ATMS 的 onActivityManagerInternalAdded 方法进一步初始化mActivityTaskManager.onActivityManagerInternalAdded();mUgmInternal.onActivityManagerInternalAdded();mPendingIntentController.onActivityManagerInternalAdded();...}/frameworks/base/services/core/java/com/android/server/wm/ActivityTaskManagerService.java
public void onActivityManagerInternalAdded() {synchronized (mGlobalLock) {mAmInternal = LocalServices.getService(ActivityManagerInternal.class);mUgmInternal = LocalServices.getService(UriGrantsManagerInternal.class);}}（5）ActivityStartController
ActivityStartController 作为 ATMS 的一个重要成员，控制了 Activity 的启动，因此我们继续跟进 ActivityStartController 的构造方法。
/frameworks/base/services/core/java/com/android/server/am/ActivityStartController.java
ActivityStartController(ActivityTaskManagerService service) {this(service, service.mStackSupervisor,new DefaultFactory(service, service.mStackSupervisor,new ActivityStartInterceptor(service, service.mStackSupervisor)));}ActivityStartController(ActivityTaskManagerService service, ActivityStackSupervisor supervisor,Factory factory) {mService = service;mSupervisor = supervisor;mHandler = new StartHandler(mService.mH.getLooper());mFactory = factory;mFactory.setController(this);...}（6）DefaultFactory
DefaultFactory 是 ActivityStarter 的静态内部类，负责 ActivityStarter 的创建和回收。因此我们继续跟进 DefaultFactory 类。
/frameworks/base/services/core/java/com/android/server/wm/ActivityStarter.DefaultFactory.java
static class DefaultFactory implements Factory {...private ActivityStartController mController;private ActivityTaskManagerService mService;private ActivityStackSupervisor mSupervisor;private ActivityStartInterceptor mInterceptor;//MAX_STARTER_COUNT = 3private SynchronizedPool<ActivityStarter> mStarterPool = new SynchronizedPool<>(MAX_STARTER_COUNT);DefaultFactory(ActivityTaskManagerService service, ActivityStackSupervisor supervisor, ActivityStartInterceptor interceptor) {mService = service;mSupervisor = supervisor;mInterceptor = interceptor;}public ActivityStarter obtain() {ActivityStarter starter = mStarterPool.acquire();if (starter == null) {starter = new ActivityStarter(mController, mService, mSupervisor, mInterceptor);}return starter;}@Overridepublic void recycle(ActivityStarter starter) {mStarterPool.release(starter);}}关于“Android framework ATMS启动流程是什么”的内容就介绍到这里了，感谢大家的阅读。如果想了解更多行业相关的知识，可以关注编程网行业资讯频道，小编每天都会为大家更新不同的知识点。
