详解Android.activity销毁流程的工作原理
继续我们的源码解析,上一篇文章我们介绍了Activity的启动流程,一个典型的场景就是Activitya启动了一个Activityb,他们的生命周期回调方法是:
onPause(a)–>onCreate(b)–>onStart(b)–>onResume(b)–>onStop(a)
而我们根据源码也验证了这样的生命周期调用序列,那么Activity的销毁流程呢?它的生命周期的调用顺序又是这样的呢?
这里我们我做一个简单的demo,让一个Activitya启动Activityb,然后在b中调用finish()方法,它们的生命周期执行顺序是:
onPause(b)
onRestart(a)
onStart(a)
onResume(a)
onStop(b)
onDestory(b)
好吧,根据我们测试的生命周期方法的回调过程开始对Activity销毁流程的分析,一般而言当我们需要销毁Activity的时候都会调用其自身的finish方法,所以我们的流程开始是以finish方法开始的。
一:请求销毁当前Activity
MyActivity.finish()
Activity.finish()
ActivityManagerNative.getDefault().finishActivity()
ActivityManagerService.finishActivity()
ActivityStack.requestFinishActivityLocked()
ActivityStack.finishActivityLocked()
ActivityStack.startPausingLocked()
首先我们在自己的Activity调用了finish方法,它实际上调用的是Activity的finish方法:
publicvoidfinish(){ finish(false); }
然后我们可以发现其调用了finish方法的重载方法,并且传递了一个参数值:
privatevoidfinish(booleanfinishTask){ if(mParent==null){ intresultCode; IntentresultData; synchronized(this){ resultCode=mResultCode; resultData=mResultData; } if(false)Log.v(TAG,"Finishingself:token="+mToken); try{ if(resultData!=null){ resultData.prepareToLeaveProcess(); } if(ActivityManagerNative.getDefault() .finishActivity(mToken,resultCode,resultData,finishTask)){ mFinished=true; } }catch(RemoteExceptione){ //Empty } }else{ mParent.finishFromChild(this); } }
好吧,这个参数值似乎并没什么用。。。这里就不在讨论了,然后调用了ActivityManagerNative.getDefault().finishActivity方法,好吧,根据上一篇文章的介绍,我们知道了ActivityManagerNative是一个Binder对象,这里调用的方法最终会被ActivityManagerService执行,所以这了的finishActivity最终被执行的是ActivityManagerService.finishActivity方法,好吧,我们来看一下ActivityManagerService的finishActivity方法的执行逻辑。。。
@Override publicfinalbooleanfinishActivity(IBindertoken,intresultCode,IntentresultData,booleanfinishTask){ ... res=tr.stack.requestFinishActivityLocked(token,resultCode,resultData,"app-request",true); ... }
这里我们可以发现,经过一系列逻辑判断之后,最终调用了ActivityStack的requestFinishActivityLocked方法,这里应该就是执行finishActivity的逻辑了。
finalbooleanrequestFinishActivityLocked(IBindertoken,intresultCode, IntentresultData,Stringreason,booleanoomAdj){ ActivityRecordr=isInStackLocked(token); if(DEBUG_RESULTS||DEBUG_STATES)Slog.v(TAG_STATES, "Finishingactivitytoken="+token+"r=" +",result="+resultCode+",data="+resultData +",reason="+reason); if(r==null){ returnfalse; } finishActivityLocked(r,resultCode,resultData,reason,oomAdj); returntrue; }
这个方法体里面又调用了finishActivityLocked方法,那我们继续看一下finishActivityLocked方法的实现:
finalbooleanfinishActivityLocked(ActivityRecordr,intresultCode,IntentresultData, Stringreason,booleanoomAdj){ ... startPausingLocked(false,false,false,false); ... returnfalse; }
好吧,在这里调用了startPausingLocked方法,看名字应该是开始要执行Activity的onPause方法请求了,然后我们看一下startPausingLocked方法的实现:
finalbooleanstartPausingLocked(booleanuserLeaving,booleanuiSleeping,booleanresuming,booleandontWait){ ... try{ EventLog.writeEvent(EventLogTags.AM_PAUSE_ACTIVITY, prev.userId,System.identityHashCode(prev), prev.shortComponentName); mService.updateUsageStats(prev,false); prev.app.thread.schedulePauseActivity(prev.appToken,prev.finishing, userLeaving,prev.configChangeFlags,dontWait); }catch(Exceptione){ //Ignoreexception,ifprocessdiedothercodewillcleanup. Slog.w(TAG,"Exceptionthrownduringpause",e); mPausingActivity=null; mLastPausedActivity=null; mLastNoHistoryActivity=null; } ... }
这样从应用程序调用finish方法,ActivityManagerService接收请求并执行startPausingLocked方法。
二:执行当前Activity的onPause方法
IApplicationThread.schedulePauseActivity()
ActivityThread.schedulePauseActivity()
ActivityThread.sendMessage()
ActivityThread.H.sendMessage()
ActivityThread.H.handleMessage()
ActivityThread.handlePauseActivity()
ActivityThread.performPauseActivity()
Instrumentation.callActivityOnPause()
Activity.performPause()
Activity.onPause()
ActivityManagerNative.getDefault().activityPaused()
ActivityManagerService.activityPaused()
ActivityStack.activityPausedLocked()
ActivityStack.completePauseLocked()
在方法startPausingLocked中我们调用了:prev.app.thread.schedulePauseActivity这里实际上调用的是IApplicationThread的schedulePauseActivity方法,IApplicationThread也是一个Binder对象,它是ActivityThread中ApplicationThread的Binderclient端,所以最终会调用的是ApplicationThread的schedulePauseActivity方法,好吧我们看一下ActivityThread的schedulePauseActivity方法的具体实现:
publicfinalvoidschedulePauseActivity(IBindertoken,booleanfinished,booleanuserLeaving,intconfigChanges,booleandontReport){ sendMessage( finished?H.PAUSE_ACTIVITY_FINISHING:H.PAUSE_ACTIVITY, token,(userLeaving?1:0)|(dontReport?2:0), configChanges); }
然后调用了ActivityThread的sendMessage方法:
privatevoidsendMessage(intwhat,Objectobj,intarg1,intarg2){ sendMessage(what,obj,arg1,arg2,false); }
然后又回调了sendMessage的重载方法。。
privatevoidsendMessage(intwhat,Objectobj,intarg1,intarg2,booleanasync){ if(DEBUG_MESSAGES)Slog.v( TAG,"SCHEDULE"+what+""+mH.codeToString(what) +":"+arg1+"/"+obj); Messagemsg=Message.obtain(); msg.what=what; msg.obj=obj; msg.arg1=arg1; msg.arg2=arg2; if(async){ msg.setAsynchronous(true); } mH.sendMessage(msg); }
最终调用mH发送异步消息,然后在mH的handleMessge方法中处理异步消息并调用handlePauseActivity方法:
privatevoidhandlePauseActivity(IBindertoken,booleanfinished, booleanuserLeaving,intconfigChanges,booleandontReport){ ActivityClientRecordr=mActivities.get(token); if(r!=null){ //Slog.v(TAG,"userLeaving="+userLeaving+"handlingpauseof"+r); if(userLeaving){ performUserLeavingActivity(r); } r.activity.mConfigChangeFlags|=configChanges; performPauseActivity(token,finished,r.isPreHoneycomb()); //Makesureanypendingwritesarenowcommitted. if(r.isPreHoneycomb()){ QueuedWork.waitToFinish(); } //Telltheactivitymanagerwehavepaused. if(!dontReport){ try{ ActivityManagerNative.getDefault().activityPaused(token); }catch(RemoteExceptionex){ } } mSomeActivitiesChanged=true; } }
好吧,这里回调了performPauseActivity方法,上篇文章中我们已经分析过了这段代码:
performPauseActivity()
Instrumentation.callActivityOnPause()
Activity.performPause()
Activity.onPause()
这样我们就回调了第一个生命周期方法:onPause。。。
在handlePauseActivity方法中我们调用了ActivityManagerNative.getDefault().activityPaused(token)方法,好吧又是回调ActivityManagerService的方法,这样最终会调用ActivityManagerService的activityPaused方法:
@Override publicfinalvoidactivityPaused(IBindertoken){ finallongorigId=Binder.clearCallingIdentity(); synchronized(this){ ActivityStackstack=ActivityRecord.getStackLocked(token); if(stack!=null){ stack.activityPausedLocked(token,false); } } Binder.restoreCallingIdentity(origId); }
这样,我们继续看一下activityPausedLocked方法的实现:
finalvoidactivityPausedLocked(IBindertoken,booleantimeout){ ... completePauseLocked(true); ... }
里面又经过一系列的逻辑判断之后,开始执行completePauseLocked方法:
privatevoidcompletePauseLocked(booleanresumeNext){ ...mStackSupervisor.resumeTopActivitiesLocked(topStack,null,null); ... }
这样栈顶Activity的onPause操作就执行完成了,接下来就就是开始执行上一个Activity的onResume操作了。。。
三:执行上一个Activity的onResume操作
这样调用了ActivityStackSupervisor.resumeTopActivitiesLocked方法。。,又开始调用这个方法,通过上一篇文章的介绍,我们知道这个方法实际上是执行Activity的初始化,我们看一下其具体的调用过程:
ActivityStack.resumeTopActivityLocked()
ActivityStack.resumeTopInnerLocked()
IApplicationThread.scheduleResumeActivity()
ActivityThread.scheduleResumeActivity()
ActivityThread.sendMessage()
ActivityTherad.H.sendMessage()
ActivityThread.H.handleMessage()
ActivityThread.H.handleResumeMessage()
Activity.performResume()
Activity.performRestart()
Instrumentation.callActivityOnRestart()
Activity.onRestart()
Activity.performStart()
Instrumentation.callActivityOnStart()
Activity.onStart()
Instrumentation.callActivityOnResume()
Activity.onResume()
好吧,这个过程其实上一篇文章中已经做了介绍,这里不做过多的分析了,通过这样调用过程我们最终执行了当前栈顶Activity上一个Activity的onRestart方法,onStart方法,onResume方法等,下面我们将调用栈顶Activity的onStop方法,onDestory方法。
四:执行栈顶Activity的销毁操作
Looper.myQueue().addIdleHandler(newIdler())
ActivityManagerNative.getDefault().activityIdle()
ActivityManagerService.activityIdle()
ActivityStackSupervisor.activityIdleInternalLocked()
ActivityStack.destroyActivityLocked()
IApplicationThread.scheduleDestoryActivity()
ActivityThread.scheduleDestoryActivity()
ActivityThread.sendMessage()
ActivityThread.H.sendMessage()
ActivityThread.H.handleMessage()
ActivityThread.handleDestoryActivity()
ActivityThread.performDestoryActivity()
Activity.performStop()
Instrumentation.callActivityOnStop()
Activity.onStop()
Instrumentation.callActivityOnDestory()
Activity.performDestory()
Acitivity.onDestory()
ActivityManagerNative.getDefault().activityDestoryed()
ActivityManagerService.activityDestoryed()
ActivityStack.activityDestoryedLocked()
我们在ActivityThread.handleResumeActivity方法中调用了Looper.myQueue().addIdleHandler(newIdler()),下面看一下这个方法的实现:
privateclassIdlerimplementsMessageQueue.IdleHandler{ @Override publicfinalbooleanqueueIdle(){ ActivityClientRecorda=mNewActivities; booleanstopProfiling=false; if(mBoundApplication!=null&&mProfiler.profileFd!=null &&mProfiler.autoStopProfiler){ stopProfiling=true; } if(a!=null){ mNewActivities=null; IActivityManageram=ActivityManagerNative.getDefault(); ActivityClientRecordprev; do{ if(localLOGV)Slog.v( TAG,"Reportingidleof"+a+ "finished="+ (a.activity!=null&&a.activity.mFinished)); if(a.activity!=null&&!a.activity.mFinished){ try{ am.activityIdle(a.token,a.createdConfig,stopProfiling); a.createdConfig=null; }catch(RemoteExceptionex){ //Ignore } } prev=a; a=a.nextIdle; prev.nextIdle=null; }while(a!=null); } if(stopProfiling){ mProfiler.stopProfiling(); } ensureJitEnabled(); returnfalse; } }
内部有一个queueIdle的回调方法,当它被添加到MessageQueue之后就会回调该方法,我们可以发现在这个方法体中调用了ActivityManagerNative.getDefault.activityIdle方法,通过上一篇文章以及上面的讲解,我们应该知道这了最终调用的是ActivityManagerService.activityIdle方法,好吧,这里看一下activityIdle方法的具体实现:
publicfinalvoidactivityIdle(IBindertoken,Configurationconfig,booleanstopProfiling){ finallongorigId=Binder.clearCallingIdentity(); synchronized(this){ ActivityStackstack=ActivityRecord.getStackLocked(token); if(stack!=null){ ActivityRecordr= mStackSupervisor.activityIdleInternalLocked(token,false,config); if(stopProfiling){ if((mProfileProc==r.app)&&(mProfileFd!=null)){ try{ mProfileFd.close(); }catch(IOExceptione){ } clearProfilerLocked(); } } } } Binder.restoreCallingIdentity(origId); }
可以发现这里又调用了ActivityStackSupervisor.activityIdleInternalLocked方法,然后我们看一下activityIdleInternalLocked方法的具体实现:
finalActivityRecordactivityIdleInternalLocked(finalIBindertoken,booleanfromTimeout,Configurationconfig){ .... stack.destroyActivityLocked(r,true,"finish-idle"); .... }
可以看到这里调用ActivityStack.destroyActivityLocked方法,可以看一下其具体实现:
finalbooleandestroyActivityLocked(ActivityRecordr,booleanremoveFromApp,Stringreason){ ... r.app.thread.scheduleDestroyActivity(r.appToken,r.finishing,r.configChangeFlags); ... }
好吧,这里又开始执行IApplicationThread.scheduleDestoryActivity方法,上文已经做了说明这里最终调用的是ActivityThread.scheduleDestroyActivity方法,好吧,看一下ActivityThread.scheduleDestryActivity方法的实现:
publicfinalvoidscheduleDestroyActivity(IBindertoken,booleanfinishing,intconfigChanges){ sendMessage(H.DESTROY_ACTIVITY,token,finishing?1:0, configChanges); }
这里有开始执行sendMessage方法,通过一系列的调用sendMessage方法最终调用了handleDestroyActivity方法:
privatevoidhandleDestroyActivity(IBindertoken,booleanfinishing, intconfigChanges,booleangetNonConfigInstance){ ActivityClientRecordr=performDestroyActivity(token,finishing, configChanges,getNonConfigInstance); if(r!=null){ cleanUpPendingRemoveWindows(r); WindowManagerwm=r.activity.getWindowManager(); Viewv=r.activity.mDecor; if(v!=null){ if(r.activity.mVisibleFromServer){ mNumVisibleActivities--; } IBinderwtoken=v.getWindowToken(); if(r.activity.mWindowAdded){ if(r.onlyLocalRequest){ //Holdoffonremovingthisuntilthenewactivity's //windowisbeingadded. r.mPendingRemoveWindow=v; r.mPendingRemoveWindowManager=wm; }else{ wm.removeViewImmediate(v); } } if(wtoken!=null&&r.mPendingRemoveWindow==null){ WindowManagerGlobal.getInstance().closeAll(wtoken, r.activity.getClass().getName(),"Activity"); } r.activity.mDecor=null; } if(r.mPendingRemoveWindow==null){ //Ifwearedelayingtheremovaloftheactivitywindow,then //wecan'tcleanupallwindowshere.Notethatwecan'tdo //solatereither,whichmeansanywindowsthataren'tclosed //bytheappwillleak.Wellwetrytowarningthemalot //aboutleakingwindows,becausethatisabug,soiftheyare //usingthisrecreatefacilitythentheygettolivewithleaks. WindowManagerGlobal.getInstance().closeAll(token, r.activity.getClass().getName(),"Activity"); } //Mockedoutcontextswon'tbeparticipatinginthenormal //processlifecycle,butifwe'rerunningwithaproper //ApplicationContextweneedtohaveitteardownthings //cleanly. Contextc=r.activity.getBaseContext(); if(cinstanceofContextImpl){ ((ContextImpl)c).scheduleFinalCleanup( r.activity.getClass().getName(),"Activity"); } } if(finishing){ try{ ActivityManagerNative.getDefault().activityDestroyed(token); }catch(RemoteExceptionex){ //Ifthesystemprocesshasdied,it'sgameoverforeveryone. } } mSomeActivitiesChanged=true; }
可以看到这里调用了performDestroyActivity方法,用来执行Avtivity的onDestroy方法:
privateActivityClientRecordperformDestroyActivity(IBindertoken,booleanfinishing, intconfigChanges,booleangetNonConfigInstance){ ... r.activity.performStop(); ... mInstrumentation.callActivityOnDestroy(r.activity); ... }
然后调用了Activity.performStop()方法,查看performStop方法:
finalvoidperformStop(){ ... mInstrumentation.callActivityOnStop(this); ... }
然后调用了Instrumentation.callActivityOnStop()方法:
publicvoidcallActivityOnStop(Activityactivity){ activity.onStop(); }
好吧,终于调用了Activity的onStop方法。。。
我们继续看一下Instrumentation.callActivityOnDestroy()。。。。又是通过Instrumentation来调用Activity的onDestroy方法:
publicvoidcallActivityOnDestroy(Activityactivity){ ... activity.performDestroy(); ... }
然后看一下Activity的performDestroy()方法的实现:
finalvoidperformDestroy(){ mDestroyed=true; mWindow.destroy(); mFragments.dispatchDestroy(); onDestroy(); mFragments.doLoaderDestroy(); if(mVoiceInteractor!=null){ mVoiceInteractor.detachActivity(); } }
O(∩_∩)O哈哈~,终于回调了Activity的onDestroy方法。。。。
总结:
Activity的销毁流程是从finish方法开始的
Activity销毁过程是:onPause–>onRestart–>onStart–>onResume–>onStop–>onDestroy
Activity的销毁流程是ActivityThread与ActivityManagerService相互配合销毁的
以上就是本文的全部内容,希望对大家的学习有所帮助,也希望大家多多支持毛票票。
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