一、概念
Android10（API29）开始，ActivityTaskManagerService 接管 ActivityManagerService。
二、启动ATMS过程
三、启动APP & 跳转Activity过程
3.1 Activity → ATMS
启动一个 APP 或跳转一个 Activity 都是调用的 startActivity()，进而调用 startActivityForResult()。
3.1.1 Activity
Activity{public void startActivity(Intent intent, @Nullable Bundle options) {startActivityForResult(intent, -1, options);}public void startActivityForResult(@RequiresPermission Intent intent, int requestCode, @Nullable Bundle options) {//委托给Instrumentation来启动Instrumentation.ActivityResult ar = mInstrumentation.execStartActivity(this, mMainThread.getApplicationThread(), mToken, this, intent, requestCode, options);mMainThread.sendActivityResult(mToken, mEmbeddedID, requestCode, ar.getResultCode(), ar.getResultData());}
}3.1.2 Instrumentation
Instrumentation{public ActivityResult execStartActivity(Context who, IBinder contextThread, IBinder token, String target, Intent intent, int requestCode, Bundle options) {//获取一个Binder，它是ActivityTaskManagerService的proxy，然后调用startActivity()进行跨进程通信int result = ActivityTaskManager.getService().startActivity(whoThread,who.getOpPackageName(), who.getAttributionTag(), intent,intent.resolveTypeIfNeeded(who.getContentResolver()), token, target,requestCode, 0, null, options);}
}ActivityTaskManager{public static IActivityTaskManager getService() {return IActivityTaskManagerSingleton.get();}//一种单例模式private static final Singleton<IActivityTaskManager> IActivityTaskManagerSingleton = new Singleton<IActivityTaskManager>() {@Overrideprotected IActivityTaskManager create() {//获取ATMS的代理对象Binderfinal IBinder b = ServiceManager.getService(Context.ACTIVITY_TASK_SERVICE);return IActivityTaskManager.Stub.asInterface(b);}};
}3.2 ATMS → PMS
ActivityTaskManagerService{public final int startActivity(IApplicationThread caller, String callingPackage, String callingFeatureId, Intent intent, String resolvedType, IBinder resultTo, String resultWho, int requestCode, int startFlags, ProfilerInfo profilerInfo, Bundle bOptions) {return startActivityAsUser(caller, callingPackage, callingFeatureId, intent, resolvedType, resultTo, resultWho, requestCode, startFlags, profilerInfo, bOptions, UserHandle.getCallingUserId());}private int startActivityAsUser(IApplicationThread caller, String callingPackage, @Nullable String callingFeatureId, Intent intent, String resolvedType, IBinder resultTo, String resultWho, int requestCode, int startFlags, ProfilerInfo profilerInfo, Bundle bOptions, int userId, boolean validateIncomingUser) {//获取ActivityStarter实例，去执行execute方法return getActivityStartController().obtainStarter(intent, "startActivityAsUser").setCaller(caller)....execute();}
}ActivityStarter{int execute() {if (mRequest.activityInfo == null) {mRequest.resolveActivity(mSupervisor);}}static class Request {void resolveActivity(ActivityTaskSupervisor supervisor) {//AndroidManifest中intent标签resolveInfo = supervisor.resolveIntent(intent, resolvedType, userId, 0, computeResolveFilterUid(callingUid, realCallingUid, filterCallingUid));//转为Activity标签activityInfo = supervisor.resolveActivity(intent, resolveInfo, startFlags, profilerInfo);}}
}
ActivityTaskSupervisor{ResolveInfo resolveIntent(Intent intent, String resolvedType, int userId, int flags, int filterCallingUid) {//通过ATMS获取抽象类PackageManagerInternal//PMS内部类PackageManagerInternalImpl实现了它（内部类持有外部类，就可以调用PMS的方法了）//resolveIntent()会将从PMS的mPackages中查询到的ActivityInfo赋值给ResultInfomService.getPackageManagerInternalLocked().resolveIntent(intent, resolvedType, modifiedFlags, privateResolveFlags, userId, true, filterCallingUid);}//将获取的ResultInfo转为ActivityInfoActivityInfo resolveActivity(Intent intent, String resolvedType, int startFlags, ProfilerInfo profilerInfo, int userId, int filterCallingUid) {final ResolveInfo rInfo = resolveIntent(intent, resolvedType, userId, 0, filterCallingUid);return resolveActivity(intent, rInfo, startFlags, profilerInfo);}
}
