Activity启动流程
目的:
- 理清activity的生命周期管理与AMS之间的关系
一、理清activity的生命周期管理与AMS之间的关系
1、Launcher通知AMS启动某个activity:
Launcher中:应用程序中开启一个activity通过startActivitySafely()—->startActivity(),如果是程序内部启动那么直接调用Activity中的startActivity(),被启动的activity的参数包含在intent中,intent中的参数来自于.xml
文件,—>startActivityForResult()—-> mInstrumentation.execStartActivity(this, mMainThread.getApplicationThread(), mToken, this,intent, requestCode, options),其中Instrumentation是用来监控应用程序与系统之间的交互,其中mMainThread是ActivityThread类的实例,.getApplicationThread()用于获取内部的ApplicationThread的Binder对象(此处有疑问??);—–>ActivityManagerNative.getDefault()
.startActivity(), .getDefault()通过ServerManager获取AMS的代理对象”activity”,代码如下:
//ActivityManagerNative.java
private static final Singleton<IActivityManager> gDefault = new Singleton<IActivityManager>() {
protected IActivityManager create() {
IBinder b = ServiceManager.getService("activity"); //获取代理对象
if (false) {
Log.v("ActivityManager", "default service binder = " + b);
}
IActivityManager am = asInterface(b);
if (false) {
Log.v("ActivityManager", "default service = " + am);
}
return am;
}
};
接着调用他的方法startActivity()通知AMS启动相应的Activity,这里已经是binder通讯了。
startActivitySafely() <-----------------Launcher中,如果是在Launcher中点击,从这一步开始
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startActivity() <-----------------Activity中,如果是程序中调用,从这一步开始
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startActivityForResult() <-----------------Activity中
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mInstrumentation.execStartActivity() <----------Instrumentation中
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ActivityManagerNative.getDefault().startActivity()<----------AMS的proxy
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...binder... Launcher--->AMS: Launcher请求启动activity
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startActivity() ---------->通知AMS的Stub中startActivity(),即ActivityManagerService.java中的
至此Launcher中暂时结束!即Launcher进程会——>请求AMS启动一个activity,具体是哪一个activity,看intent
2、AMS保存将要启动的mainactivity,并且AMS处理Launcher向AMS发送的binder消息:START_ACTIVITY_TRANSACTION
startActivity() ------->AMS
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startActivityAsUser() ------->AMS
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mStackSupervisor.startActivityMayWait() ------->ActivityStackSupervisor.java
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startActivityLocked() ------->ActivityStackSupervisor.java
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startActivityUncheckedLocked()
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resumeTopActivitiesLocked(targetStack, null, options) ----->ActivityStack.java
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startPausingLocked() ----->ActivityStack.java
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prev.app.thread.schedulePauseActivity() ----->ActivityStack.java Proxy
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...binder... AMS--->Launcher: AMS请求Launcher Pause
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schedulePauseActivity() ------>ActivityThread.java Stub
//ActivityThread.java
public final void schedulePauseActivity(IBinder token, boolean finished,
boolean userLeaving, int configChanges, boolean dontReport) {
sendMessage(
finished ? H.PAUSE_ACTIVITY_FINISHING : H.PAUSE_ACTIVITY,
token,
(userLeaving ? 1 : 0) | (dontReport ? 2 : 0),
configChanges);
}
- mStackSupervisor.startActivityMayWait()中还会用binder和PMS通讯,解析intent中的界面内容,以便显示
- mStackSupervisor是ActivityStackSupervisor的成员变量,用于描述Activity组件堆栈(疑问???)
- startPausingLocked()中又会涉及到一个binder通讯,这个是AMS向Launcher组件所在的应用程序进程发送通讯SCHEDULE_PAUSE_ACTIVITY_TRANSACTION:需要Pause掉Launcher了
至此AMS暂时结束,即AMS向Launcher组件所在的应用程序进程发送了SCHEDULE_PAUSE_ACTIVITY_TRANSACTION进程间通讯请求,请求内容是告诉Launcher组件Pause吧。当然其中会有一些列的异步超时处理。
- startPausingLocked()中又会涉及到一个binder通讯,这个是AMS向Launcher组件所在的应用程序进程发送通讯SCHEDULE_PAUSE_ACTIVITY_TRANSACTION:需要Pause掉Launcher了
3、Launcher收到Pause请求后的动作,并回复AMS(通过AMS的proxy)
schedulePauseActivity() ------>ActivityThread.java Stub
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sendMessage() ------>ActivityThread.java 果然这里是消息处理机制实现
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handleMessage(Message msg) ------>ActivityThread.java
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handlePauseActivity()
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performPauseActivity(token, finished, r.isPreHoneycomb()); ------>ActivityThread.java
ActivityManagerNative.getDefault().activityPaused(token) ------>ActivityThread.java AMS proxy
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...binder... Launcher--->AMS : Launcher告知AMS,Launcher已经Pause
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activityPaused(token) ------>AMS Stub
- activityPaused()获取AMS的proxy,用于回复AMS:告诉AMS,Launcher已经进入Pause状态了;AMS你可以继续启动Activity了。
- performPauseActivity()—>mInstrumentation.callActivityOnPause(r.activity)—>activity.performPause() —> onPause() 这应该就是与APP继承的 onPause()一致的。
疑问:
- 至此Launcher已经Paused了,并通过binder进程间通讯发送了ACTIVITY_PAUSED_TRANSACTION告知AMS。
4、AMS中处理Launcher发来的Paused通讯请求,并做相应处理
activityPaused(token) ------>AMS Stub
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activityPausedLocked() ------>ActivityStack.java
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completePauseLocked(true)
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finishCurrentActivityLocked()
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resumeTopActivityLocked()
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resumeTopActivityInnerLocked()
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startSpecificActivityLocked() ------->ActivityStackSupervisor.java
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startProcessLocked() ------->AMS
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startProcessLocked() ------->重载的函数, AMS (如果进程不在的话)
//AMS startProcessLocked()
checkTime(startTime, "startProcess: asking zygote to start proc");
Process.ProcessStartResult startResult = Process.start(entryPoint,
app.processName, uid, uid, gids, debugFlags, mountExternal,
app.info.targetSdkVersion, app.info.seinfo, requiredAbi, instructionSet,
app.info.dataDir, entryPointArgs);
checkTime(startTime, "startProcess: returned from zygote!");
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try {
return startViaZygote(processClass, niceName, uid, gid, gids,
debugFlags, mountExternal, targetSdkVersion, seInfo,
abi, instructionSet, appDataDir, zygoteArgs);
}
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zygoteSendArgsAndGetResult(openZygoteSocketIfNeeded(abi), argsForZygote)
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通知zygote孵化出新的虚拟机应用程序,并返回PID给AMS,新的应用程序启动起来之后就会进入ActivityThread的main方法中。
至此,AMS就调用Process类创建了一个新的应用程序。并且,该进程的入口函数为main函数,接下来就是新的应用程序进程的工作了。
5、新的应用程序启动之后,会向AMS发送一个启动完成的进程间通讯。
main() ------->ActivityThread.java
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Looper.prepareMainLooper() ------->创建消息循环队列,是当前应用进程进入消息循环队列中
ActivityThread thread = new ActivityThread() 创建一个ActivityThread对象
attach(boolean system) ------->ActivityThread.java
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final IActivityManager mgr = ActivityManagerNative.getDefault();//获取AMS的proxy
mgr.attachApplication(mAppThread) ----->AMS proxy,调用IActivityManager的接口通讯函数
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...binder... ActivityThread--->AMS: APP进程告知AMS启动进程完成
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attachApplication(IApplicationThread thread) ----->AMS Stub
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Looper.loop()
至此,新的应用程序进程通过调用,thread.attach(false)调用attach()函数来向AMS的proxy发送一个进程间通讯回复ATTACH_APPLICATION_TRANSACTION:告诉AMS新的应用程序已经启动完成。
6、 AMS将2步中保存的MainActivity信息,发送给第4步中创建的新应用程序,,以便它可以将MainActivity启动起来
attachApplication(IApplicationThread thread) ----->AMS Stub
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attachApplicationLocked(IApplicationThread thread, int pid) ----->AMS
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attachApplicationLocked(ProcessRecord app) ----->ActivityStackSupervisor.java 重载
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realStartActivityLocked(hr, app, true, true) ----->ActivityStackSupervisor.java
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app.thread.scheduleLaunchActivity() ----->ActivityThread proxy
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...binder... AMS--->ActivityThread: AMS将MainActivity信息发送新进程
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scheduleLaunchActivity() ----->ActivityThread Stub
至此,AMS向ActivityThread发送进程间通讯SCHEDULE_LAUNCH_ACTIVITY_TRANSACTION
7、应用程序中执行最后工作
scheduleLaunchActivity() ----->ActivityThread Stub
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sendMessage(H.LAUNCH_ACTIVITY, r)
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handleMessage(Message msg)
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handleLaunchActivity(r, null)
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Activity a = performLaunchActivity(r, customIntent)
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mInstrumentation.callActivityOnCreate(activity, r.state) ------->Instrumentation.java
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activity.performCreate(icicle)
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onCreate(icicle) ------>Activity.java
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protected void onCreate(@Nullable Bundle savedInstanceState)
APP中继承的OnCreate()就被调用起来了,最后一步将Activity对象activity启动起来了
注意:
1、mainActivity组件是由Launcher组件启动的,Launcher组件又是通过AMS来启动mainActivity的,因此会涉及到三个进程之间的binder通讯
2、AMS启动是和PMS一样,都在systemServer进程中启动起来的,startBootstrapServices()函数中。
3、还得理清楚ActivityManagerService.java,ActivityManagerNative.java,IActivityManager.java之间的关系
- ActivityManagerService.java毋庸置疑肯定是Activity栈管理实现
- ActivityManagerNative.java根据代码看,应该是BnXXXX和BpXXXX,也就是binder本地和代理,ActivityManagerService里面才是真正的物理实现。所有的通讯都是通过ActivityManagerNative处理的
- IActivityManager.java当然是接口类,ActivityManagerNative实现IActivityManager。
总结,问题:
- 目前只看到onCreate() 被调用的地方,其他的生命周期onRestart(),onStart(), onResume() ,onPause() ,onStop() ,onDestroy() 是怎么被AMS调用转换的???
解:都在ActivityThread(UI主线程)管理的,当发生生命周期变换时,最终都会call到Activity.java中去,而这个文件正是APP中继承的Activity。
应用进程启动时会先创建Application对象,并执行Application对象的生命周期方法,然后才启动应用的组件。
ActivityThread —> performPauseActivity() —> callActivityOnPause()—>performPause()—>onPause()
ActivityThread —> performResumeActivity() –> performResume()—>onResume()
- 目前只看到onCreate() 被调用的地方,其他的生命周期onRestart(),onStart(), onResume() ,onPause() ,onStop() ,onDestroy() 是怎么被AMS调用转换的???
private void handleLaunchActivity(ActivityClientRecord r, Intent customIntent, String reason) {
// If we are getting ready to gc after going to the background, well
// we are back active so skip it.
unscheduleGcIdler();
mSomeActivitiesChanged = true;
if (r.profilerInfo != null) {
mProfiler.setProfiler(r.profilerInfo);
mProfiler.startProfiling();
}
// Make sure we are running with the most recent config.
handleConfigurationChanged(null, null);
// Initialize before creating the activity
WindowManagerGlobal.initialize();
Activity a = performLaunchActivity(r, customIntent);
if (a != null) {
r.createdConfig = new Configuration(mConfiguration);
reportSizeConfigurations(r);
Bundle oldState = r.state;
handleResumeActivity(r.token, false, r.isForward,
!r.activity.mFinished && !r.startsNotResumed, r.lastProcessedSeq, reason); // launch之后紧接着调用ResumeActivity
if (!r.activity.mFinished && r.startsNotResumed) {
performPauseActivityIfNeeded(r, reason);
if (r.isPreHoneycomb()) {
r.state = oldState;
}
}
}
}
…
- ActivityStack堆栈组件???
解:mStackSupervisor是ActivityStackSupervisor的成员变量,用于描述Activity组件堆栈
在startActivityLocked方法里,对传过来的参数做一些校验,然后创建ActivityRecord对象,再调用startActivityUncheckedLocked方法启动Activity。
startActivityUncheckedLocked方法负责调度ActivityRecord和Task,理解该方法是理解Actvity启动模式的关键。
- ActivityStack堆栈组件???
- Activity与Window对应关系?