Activity
startActivity()
>startActivityForResult()

Instrumentation
execStartActivity()

ActivityTaskManager
getService() //获取到的是 ActivityTaskManagerService 对象

ActivityTaskManagerService
startActivity()
>startActivityAsUser()
>>getActivityStartController() 获取到的是 ActivityStartController 对象

ActivityStartController
obtainStarter()
其中通过DefaultFactory创建了ActivityStarter对象,详见注释2

ActivityStarter
setIntent()
setReson
… //建造者模式, 众多属性赋值
execute()¹ //!!!关键执行方法
包含了activityInfo的赋值逻辑,详见注释1
>executeRequest()
>>startActivityUnchecked()
>>>startActivityInner()

RootWindowContainer
resumeFocusedStacksTopActivities()

ActivityStack
resumeTopActivityUncheckedLocked()
>resumeTopActivityInnerLocked()

ActivityStackSupervisor
startSpecificActivity()
>realStartActivityLocked()
>>clientTransaction.addCallback(LaunchActivityItem.obtain()) ² //此处将启动信息进行封装
>>goto:next

ClientLifecycleManager
scheduleTransaction()

ClientTransaction
schedule()

ApplicationThread
scheduleTransaction()

ClientTransactionHandler
scheduleTransaction()

ActivityThread
sendMessage()
>H.sendMessage() ³

TransactionExecutor
execute()
>executeCallbacks() : goto:case1
>executeLifecycleState(transaction) : goto:case2

__________case1:start
LaunchActivityItem
execute()

ActivityThread
handleLaunchActivity()
>performLaunchActivity() //关键方法,生成了ContextImpl和Activity,并使其绑定

Instrumentation
callActivityOnCreate()

Activity
performCreate()
>onCreate() //生命周期方法
case1:end

__________case2:start
TransactionExecutor
executeLifecycleState()

ResumeActivityItem
execute()

ActivityThread
handleResumeActivity()
>performResumeActivity()

Activity
performResume()
>goto:case3
>goto:case4
case2:end

__________case3:start
Activity
performRestart()
>performStart()

Instrumentation
callActivityOnStart()

Activity
onStart() //生命周期方法
case3:end

__________case4:start
Instrumentation
callActivityOnResume()
Activity
onResume() //生命周期方法
case4:end

---

注释1
activityInfo赋值

execute(){
	...
	//因为在建造者模式下,并没有给activityInfo赋值,所以此处为null
	if (mRequest.activityInfo == null) {
	     mRequest.resolveActivity(mSupervisor);
	 }
	...
}

Request为ActivityStarter的内部类
Request.resolveActivity(){
	...
	//从intent中收集信息,内部最终会调用 PackageManagerService.resolveIntent()方法,解析出对应的信息
	resolveInfo = supervisor.resolveIntent(intent, resolvedType, userId,
                    0 /* matchFlags */,
                    computeResolveFilterUid(callingUid, realCallingUid, filterCallingUid));
	...
	// supervisor来源见下文
   activityInfo = supervisor.resolveActivity(intent, resolveInfo, startFlags,profilerInfo);
   ...
}

探究 ActivityStarter对象 的 supervisor属性 的来历

1. supervisor属性在ActivityStarter对象创建时传入,且由DefaultFactory工厂创建

   类:ActivityStarter.DefaultFactory
   public ActivityStarter obtain() {
       ActivityStarter starter = mStarterPool.acquire();
       if (starter == null) {
       	//在此构造方法中传入了mSupervisor对象
           starter = new ActivityStarter(mController, mService, mSupervisor, mInterceptor);
       }
       return starter;
   }
   

2. DefaultFactory的mSupervisor属性在构造方法赋值

   DefaultFactory(ActivityTaskManagerService service,ActivityStackSupervisor supervisor, ActivityStartInterceptor interceptor) {
            ...
            mSupervisor = supervisor;
            ...
   }
   

3. DefaultFactory对象创建发生在ActivityStartController构造方法中

   ActivityStartController(ActivityTaskManagerService service) {
        this(service, service.mStackSupervisor,
        		 //service.mStackSupervisor即为mSupervisor 
                new DefaultFactory(service, service.mStackSupervisor,
                    new ActivityStartInterceptor(service, service.mStackSupervisor)));
    }
   
    @VisibleForTesting
    ActivityStartController(ActivityTaskManagerService service, ActivityStackSupervisor supervisor,
            Factory factory) {
        ...
        mFactory = factory;
        ...
    }
   

4. ActivityStartController的创建发生在ActivityTaskManagerService的initialize方法中

   public void initialize(IntentFirewall intentFirewall, PendingIntentController intentController,Looper looper) {
   	...
   	mStackSupervisor = createStackSupervisor();
       ...
       mActivityStartController = new ActivityStartController(this);
       ...
   }
   

5. 结合3和4,所有我们最开始要找的supervisor属性即是ActivityTaskManagerService的mStackSupervisor属性,它的赋值同样在initialize方法中

   public void initialize(IntentFirewall intentFirewall, PendingIntentController intentController,
           Looper looper) {
       ...
       mStackSupervisor = createStackSupervisor();
       ...
   }
       
   protected ActivityStackSupervisor createStackSupervisor() {
           final ActivityStackSupervisor supervisor = new ActivityStackSupervisor(this, mH.getLooper());
           supervisor.initialize();
           return supervisor;
   }
   

6. 从而我们得出结论, ActivityStarter对象的supervisor属性,它的实例指向了ActivityStackSupervisor对象

注释2

ActivityStarter obtainStarter(Intent intent, String reason) {
    return mFactory  //mFactory 为 DefaultFactory对象,它在ActivityStartController构造方法中被传入
    	.obtain()    //此处生成ActivityStarter对象
    	.setIntent(intent).setReason(reason);   //建造者模式给ActivityStarter添加属性
}

---

1. 其返回值用于 checkStartActivityResult (Instrumentation) 查验结果,例如activity未在清单文件中注册等 ↩︎

2. 此处会整合信息存入LaunchActivityItem,并添加进入 ClientTransaction 的 mActivityCallbacks 数组 ↩︎

3. H类为ActivityThread的内部类,为Handler实例
   发送的message的标识: msg.what = ActivityThread.H.EXECUTE_TRANSACTION ↩︎