Android8.0 Activity 启动流程

参考别人的分享，总结了一下代码的调用流程，做了一下笔记

startActivity() -> startActivityForResult() -> mInstrumentation.execStartActivity() -> 
ActivityManager.getService().startActivity()，会通过Binder机制，调用到ActivityManagerService
的startActivity()方法。

ActivityManagerService{
	
	startActivity() -> startActivityAsUser() -> ActivityStarter.startActivityMayWait()

}

ActivityStarter{
	
	startActivityMayWait() -> startActivityLocked() -> startActivity() ->
    经辗转调用ActivityStackSupervisor.realStartActivityLocked() -> 
    IApplicationThread.scheduleLaunchActivity() 通过Binder机制，调用到
    ApplicationThread.schedulelaunchActivity()

}

看一下 ActivityThread.ApplicationThread.schedulelaunchActivity()

schedulelaunchActivity() -> 通过Handler机制，发送消息sendMessage(H.LAUNCH_ACTIVITY, r) 
-> handleLaunchActivity()
-> performLaunchActivity(){

	mInstrumentation.newActivity() 使用类加载器，类名通过反射，创建Activity对象
	
	makeApplication(){
		
		Instrumentation.newApplication() 使用类加载器，类名通过反射，创建Application对象
		
		callApplicationOnCreate() -> app.onCreate()
		
	}
	
	activity.attach() 创建了窗口对象PhoneWindow
	
	Instrumentation.callActivityOnCreate() -> activity.performCreate() ->
    调用Activity的onCreate()

}

调用Activity的onCreate() 一个Activity 也就启动了。