Android開發四大元件原始碼解讀簡單梳理

1. Activity啟動流程

   //主程序-main
   Activity.startActivity()
   mInstrumentation.execStartActivity()
   ActivityTaskManager.getService().startActivity()
   	- final IBinder b = ServiceManager.getService(Context.ACTIVITY_TASK_SERVICE);
       - return IActivityTaskManager.Stub.asInterface(b);
   //準備Stack有關的，新的binder程序-AMS
   ActivityTaskManagerService.startActivity()
   getActivityStartController().obtainStarter()...execute();//...組裝Request()，接著執行
   ActivityStarter.executeRequest(Request request);//啟動器執行Request,新增Activity到ActivityStack
   	- ActivityRecord r = new ActivityRecord()
   	- startActivityUnchecked()
   	- startActivityInner() 
   	- addOrReparentStartingActivity();//parent.addChild(mStartActivity)新增Activity到ActivityStack
   	- mTargetStack.getStack().moveToFront("reuseOrNewTask", targetTask);
   ActivityStack.startActivityLocked()	//執行stack邏輯，比如判斷是否顯示前一個Activity視窗過程等等
   ActivityRecord.showStartingWindow()	//執行當前Activity的show window邏輯
   
   //可能需要新程序，比如第一次啟動程序還不存在
   ActivityStarter.startActivityInner()
   	RootWindowContainer.resumeFocusedStacksTopActivities()
   		//如果新程序,則增加下面三個邏輯非同步建立程序
   		- ActivityStack.resumeTopActivityUncheckedLocked()
   		- ActivityStack.resumeTopActivityInnerLocked
   		- mAtmService.startProcessAsync(); //mAtmService是ActivityTaskManagerService
   		- ActivityManagerInternal::startProcess	//建立程序
   		- ActivityManagerService::LocalService::startProcess()	//最好還是回到AMS內部類
   		- ProcessList.startProcessLocked()
   		- ProcessList.startProcess()
   		- Process.start(entryPoint,...) //entryPoint就是“android.app.ActivityThread ”
   	mSupervisor.mRecentTasks.add(mStartActivity.getTask());//最後新增到最近任務列表
   
   //準備視窗有關的，這裡東西比較多，也比較底層，涉及到Display、Surface、WmService等等
   ActivityTaskManagerService.continueWindowLayout()
   DisplayContent、DisplayManagerService
   mWmService.mDisplayManagerInternal.performTraversal(mDisplayTransaction);
   
   //Activity生命週期有關的，底層Binder-AMS傳送各種和生命週期有關的Transaction與主執行緒ActivityThread互動
   ClientTransactionHandler.scheduleTransaction()
   ActivityThread(extends ClientTransactionHandler).sendMessage()
   	- ActivityThread.mH.sendMessage(msg);
   	- mTransactionExecutor.execute(transaction);//LaunchActivityItem
   LaunchActivityItem.execute()
   	- client.handleLaunchActivity(r, pendingActions, null);
   	- ActivityThread.performLaunchActivity()
    
   

2. Service啟動流程

   //main
   Context.startService()
   ContextImpl.startServiceCommon()
   //AMS
   ActivityManager.getService().startService()
   ActivityManagerService.startService()
   ActiveServices.startServiceLocked()	//ActiveServices管理Service啟動關閉，前後臺，啟動是否超時等等
   	- startServiceInnerLocked
   	- bringUpServiceLocked
   	- realStartServiceLocked
   	- app.thread.scheduleCreateService()//ApplicationThread
   //main
   ApplicationThread.scheduleCreateService()
   	- sendMessage(H.CREATE_SERVICE, s);
   	- ActivityThread.handleCreateService()
    
   

3. Broadcast接收與傳送廣播流程

   //main
   Context.registerReceiver()
   ContextImpl.registerReceiverInternal()
   LoadedApk.getReceiverDispatcher()	//獲取Dispatcher，儲存Receiver
   	- ReceiverDispatcher.performReceive()
   //AMS
   ActivityManager.getService().registerReceiverWithFeature()
   	- rl = new ReceiverList(this, callerApp, callingPid, callingUid, userId, receiver);
   	- mRegisteredReceivers.put(receiver.asBinder(), rl);	//AMS的mRegisteredReceivers儲存封裝的接收者列表
   	- BroadcastFilter bf = new BroadcastFilter(filter, rl, callerPackage, ...);
   	- rl.add(bf);
   
   //main
   Context.sendBroadcast
   ContextImpl.sendBroadcast
   //AMS
   ActivityManager.getService().broadcastIntentWithFeature()
   ActivityManagerService.broadcastIntentWithFeature()
   ActivityManagerService.broadcastIntentLocked()
   	- BroadcastRecord r = new BroadcastRecord()
   	- queue.enqueueOrderedBroadcastLocked(r);
   	- ActivityManagerService持有三類廣播，前臺廣播，後臺廣播，離線廣播
   		BroadcastQueue mFgBroadcastQueue;	//是否為前臺廣播通過Intent的flag指定
       	BroadcastQueue mBgBroadcastQueue;	//預設是後臺廣播
       	BroadcastQueue mOffloadBroadcastQueue;	//比如BOOT_COMPLETED廣播
       	mStickyBroadcasts //粘性廣播使用SparseArray儲存
   BroadcastQueue.scheduleBroadcastsLocked()	//Handler轉發一次
   BroadcastQueue.processNextBroadcast()
   BroadcastQueue.deliverToRegisteredReceiverLocked()
   BroadcastQueue.performReceiveLocked()
   	- app.thread.scheduleRegisteredReceiver()
   LoadedApk.performReceive()
   	- Handler.post(args.getRunnable())
   	- receiver.onReceive(mContext, intent);
   
    
   

4. ContentProvider初始化流程

   //main
   ActivityThread.main(String[] args)
   ActivityThread.attach(false, startSeq)
   	- mgr = ActivityManager.getService(); mgr.attachApplication(mAppThread, startSeq);
   //AMS
   ActivityManagerService.attachApplication(IApplicationThread thread, long startSeq)
   ActivityManagerService.attachApplicationLocked(IApplicationThread thread,...)
   	- generateApplicationProvidersLocked()//通過PMS獲取xml註冊的ContentProvider元件
   	- thread.bindApplication(processName, appInfo, providerList)//將解析的provider資訊傳遞給主程序
   //main
   ActivityThread.bindApplication()
   	- sendMessage(H.BIND_APPLICATION, data);
   ActivityThread.handleBindApplication(data);
   ActivityThread.installContentProviders(app, data.providers)
   	- for (ProviderInfo cpi : providers)
   	- installProvider(context, null, cpi,false, true, true);
   ContentProvider.attachInfo()
   	- ContentProvider.this.onCreate();	//ContentProvider的初始化是在Application之前哦。。。
   
   //main
   ContentResolver.insert()
   ContentProvider.acquireProvider()
   ActivityThread.acquireExistingProvider()//獲取ContentProviderProxy代理類
   ContentProviderProxy.insert()	//binder通訊mRemote.transact -> onTransact
   ContentProviderNative.insert()