Android的APP启动过程分析

Android应用程序，以ActivityThread.main()做为主入口

下图展示了Application以及Activity的创建过程

1、创建Application

每个应用程序在第一次启动时，都会先创建一个Application对象。Application对象，是通过ActivityThread的handleBindApplication()创建的

Java代码 

1. private void handleBindApplication(AppBindData data) {  
2.             Application app = data.info.makeApplication(data.restrictedBackupMode, null);//创建Application对象  
3.             mInstrumentation.callApplicationOnCreate(app);//调用Application.onCreate  
4.     }  

2、创建Activity
Activity对象，是通过ActivityThread的handleLaunchActivity()中的performLaunchActivity()创建的

Java代码 

1. private void handleLaunchActivity(ActivityClientRecord r, Intent customIntent) {  
2.           
3.         Activity a = performLaunchActivity(r, customIntent);  
4.   
5.         if (a != null) {  
6.             r.createdConfig = new Configuration(mConfiguration);  
7.             Bundle oldState = r.state;  
8.             handleResumeActivity(r.token, false, r.isForward);  
9. <pre style="font-size: 14px;" class="java" name="code"><span style="white-space: pre;">     </span>......</pre> } else { ...... } }  
10. <pre></pre>  
11. <pre></pre>  

Java代码 

1. private Activity performLaunchActivity(ActivityClientRecord r, Intent customIntent) {  
2.         // System.out.println("##### [" + System.currentTimeMillis() + "] ActivityThread.performLaunchActivity(" + r + ")");  
3.   
4.         ActivityInfo aInfo = r.activityInfo;  
5.         if (r.packageInfo == null) {  
6.             r.packageInfo = getPackageInfo(aInfo.applicationInfo, r.compatInfo,  
7.                     Context.CONTEXT_INCLUDE_CODE);  
8.         }  
9.   
10.         ComponentName component = r.intent.getComponent();  
11.         if (component == null) {  
12.             component = r.intent.resolveActivity(  
13.                 mInitialApplication.getPackageManager());  
14.             r.intent.setComponent(component);  
15.         }  
16.   
17.         if (r.activityInfo.targetActivity != null) {  
18.             component = new ComponentName(r.activityInfo.packageName,  
19.                     r.activityInfo.targetActivity);  
20.         }  
21.   
22.         Activity activity = null;  
23.         try {  
24.             java.lang.ClassLoader cl = r.packageInfo.getClassLoader();  
25.             activity = mInstrumentation.newActivity(  
26.                     cl, component.getClassName(), r.intent);  
27.             StrictMode.incrementExpectedActivityCount(activity.getClass());  
28.             r.intent.setExtrasClassLoader(cl);  
29.             if (r.state != null) {  
30.                 r.state.setClassLoader(cl);  
31.             }  
32.         } catch (Exception e) {  
33.             if (!mInstrumentation.onException(activity, e)) {  
34.                 throw new RuntimeException(  
35.                     "Unable to instantiate activity " + component  
36.                     + ": " + e.toString(), e);  
37.             }  
38.         }  
39.   
40.         try {  
41.             Application app = r.packageInfo.makeApplication(false, mInstrumentation);  
42.   
43.             if (localLOGV) Slog.v(TAG, "Performing launch of " + r);  
44.             if (localLOGV) Slog.v(  
45.                     TAG, r + ": app=" + app  
46.                     + ", appName=" + app.getPackageName()  
47.                     + ", pkg=" + r.packageInfo.getPackageName()  
48.                     + ", comp=" + r.intent.getComponent().toShortString()  
49.                     + ", dir=" + r.packageInfo.getAppDir());  
50.   
51.             if (activity != null) {  
52.                 ContextImpl appContext = new ContextImpl();  
53.                 appContext.init(r.packageInfo, r.token, this);  
54.                 appContext.setOuterContext(activity);  
55.                 CharSequence title = r.activityInfo.loadLabel(appContext.getPackageManager());  
56.                 Configuration config = new Configuration(mCompatConfiguration);  
57.                 if (DEBUG_CONFIGURATION) Slog.v(TAG, "Launching activity "  
58.                         + r.activityInfo.name + " with config " + config);  
59.                 activity.attach(appContext, this, getInstrumentation(), r.token,  
60.                         r.ident, app, r.intent, r.activityInfo, title, r.parent,  
61.                         r.embeddedID, r.lastNonConfigurationInstances, config);  
62.   
63.                 if (customIntent != null) {  
64.                     activity.mIntent = customIntent;  
65.                 }  
66.                 r.lastNonConfigurationInstances = null;  
67.                 activity.mStartedActivity = false;  
68.                 int theme = r.activityInfo.getThemeResource();  
69.                 if (theme != 0) {  
70.                     activity.setTheme(theme);  
71.                 }  
72.   
73.                 activity.mCalled = false;  
74.                 mInstrumentation.callActivityOnCreate(activity, r.state);  
75.                 if (!activity.mCalled) {  
76.                     throw new SuperNotCalledException(  
77.                         "Activity " + r.intent.getComponent().toShortString() +  
78.                         " did not call through to super.onCreate()");  
79.                 }  
80.                 r.activity = activity;  
81.                 r.stopped = true;  
82.                 if (!r.activity.mFinished) {  
83.                     activity.performStart();  
84.                     r.stopped = false;  
85.                 }  
86.                 if (!r.activity.mFinished) {  
87.                     if (r.state != null) {  
88.                         mInstrumentation.callActivityOnRestoreInstanceState(activity, r.state);  
89.                     }  
90.                 }  
91.                 if (!r.activity.mFinished) {  
92.                     activity.mCalled = false;  
93.                     mInstrumentation.callActivityOnPostCreate(activity, r.state);  
94.                     if (!activity.mCalled) {  
95.                         throw new SuperNotCalledException(  
96.                             "Activity " + r.intent.getComponent().toShortString() +  
97.                             " did not call through to super.onPostCreate()");  
98.                     }  
99.                 }  
100.             }  
101.             r.paused = true;  
102.   
103.             mActivities.put(r.token, r);  
104.   
105.         } catch (SuperNotCalledException e) {  
106.             throw e;  
107.   
108.         } catch (Exception e) {  
109.             if (!mInstrumentation.onException(activity, e)) {  
110.                 throw new RuntimeException(  
111.                     "Unable to start activity " + component  
112.                     + ": " + e.toString(), e);  
113.             }  
114.         }  
115.   
116.         return activity;  
117.     }  

根据文章刚开始描述应用启动过程的时序图，列出部分关键代码：

ActivityThread

主入口main

Java代码 

1. public static void main(String[] args) {  
2.     Looper. prepareMainLooper();  
3.     if ( sMainThreadHandler == null ) {  
4.         sMainThreadHandler = new Handler();  
5.     }  
6.   
7.     ActivityThread thread = new ActivityThread();  
8.     thread.attach( false);  
9.     
10.     Looper.loop();  
11. }  

Java代码 

1. private void attach( boolean system) {  
2.     sThreadLocal.set( this );  
3.     mSystemThread = system;  
4.     if (!system) {  
5.         IActivityManager mgr = ActivityManagerNative.getDefault();  
6.         try {  
7.             mgr.attachApplication( mAppThread );//mAppThread是一个ApplicationThread实例  
8.         } catch (RemoteException ex) {  
9.             // Ignore  
10.         }  
11.     } else {  
12.         // Don't set application object here -- if the system crashes,  
13.         // we can't display an alert, we just want to die die die.  
14.     }  
15. }  

Java代码 

1. public void handleMessage(Message msg) {  
2.             if (DEBUG_MESSAGES) Slog.v(TAG, ">>> handling: " + codeToString(msg.what));  
3.             switch (msg.what) {  
4.                 case LAUNCH_ACTIVITY: {  
5.                     Trace.traceBegin(Trace.TRACE_TAG_ACTIVITY_MANAGER, "activityStart");  
6.                     ActivityClientRecord r = (ActivityClientRecord)msg.obj;  
7.   
8.                     r.packageInfo = getPackageInfoNoCheck(  
9.                             r.activityInfo.applicationInfo, r.compatInfo);  
10.                     handleLaunchActivity(r, null);  
11.                     Trace.traceEnd(Trace.TRACE_TAG_ACTIVITY_MANAGER);  
12.                 } break;  
13.                 case RELAUNCH_ACTIVITY: {  
14.                     Trace.traceBegin(Trace.TRACE_TAG_ACTIVITY_MANAGER, "activityRestart");  
15.                     ActivityClientRecord r = (ActivityClientRecord)msg.obj;  
16.                     handleRelaunchActivity(r);  
17.                     Trace.traceEnd(Trace.TRACE_TAG_ACTIVITY_MANAGER);  
18.                 } break;  
19.                 case PAUSE_ACTIVITY:  
20.                     Trace.traceBegin(Trace.TRACE_TAG_ACTIVITY_MANAGER, "activityPause");  
21.                     handlePauseActivity((IBinder)msg.obj, false, msg.arg1 != 0, msg.arg2);  
22.                     maybeSnapshot();  
23.                     Trace.traceEnd(Trace.TRACE_TAG_ACTIVITY_MANAGER);  
24.                     break;  
25.                 case PAUSE_ACTIVITY_FINISHING:  
26.                     Trace.traceBegin(Trace.TRACE_TAG_ACTIVITY_MANAGER, "activityPause");  
27.                     handlePauseActivity((IBinder)msg.obj, true, msg.arg1 != 0, msg.arg2);  
28.                     Trace.traceEnd(Trace.TRACE_TAG_ACTIVITY_MANAGER);  
29.                     break;  
30.                 case STOP_ACTIVITY_SHOW:  
31.                     Trace.traceBegin(Trace.TRACE_TAG_ACTIVITY_MANAGER, "activityStop");  
32.                     handleStopActivity((IBinder)msg.obj, true, msg.arg2);  
33.                     Trace.traceEnd(Trace.TRACE_TAG_ACTIVITY_MANAGER);  
34.                     break;  
35.                 case STOP_ACTIVITY_HIDE:  
36.                     Trace.traceBegin(Trace.TRACE_TAG_ACTIVITY_MANAGER, "activityStop");  
37.                     handleStopActivity((IBinder)msg.obj, false, msg.arg2);  
38.                     Trace.traceEnd(Trace.TRACE_TAG_ACTIVITY_MANAGER);  
39.                     break;  
40.                 case SHOW_WINDOW:  
41.                     Trace.traceBegin(Trace.TRACE_TAG_ACTIVITY_MANAGER, "activityShowWindow");  
42.                     handleWindowVisibility((IBinder)msg.obj, true);  
43.                     Trace.traceEnd(Trace.TRACE_TAG_ACTIVITY_MANAGER);  
44.                     break;  
45.                 case HIDE_WINDOW:  
46.                     Trace.traceBegin(Trace.TRACE_TAG_ACTIVITY_MANAGER, "activityHideWindow");  
47.                     handleWindowVisibility((IBinder)msg.obj, false);  
48.                     Trace.traceEnd(Trace.TRACE_TAG_ACTIVITY_MANAGER);  
49.                     break;  
50.                 case RESUME_ACTIVITY:  
51.                     Trace.traceBegin(Trace.TRACE_TAG_ACTIVITY_MANAGER, "activityResume");  
52.                     handleResumeActivity((IBinder)msg.obj, true,  
53.                             msg.arg1 != 0);  
54.                     Trace.traceEnd(Trace.TRACE_TAG_ACTIVITY_MANAGER);  
55.                     break;  
56.                 case SEND_RESULT:  
57.                     Trace.traceBegin(Trace.TRACE_TAG_ACTIVITY_MANAGER, "activityDeliverResult");  
58.                     handleSendResult((ResultData)msg.obj);  
59.                     Trace.traceEnd(Trace.TRACE_TAG_ACTIVITY_MANAGER);  
60.                     break;  
61.                 case DESTROY_ACTIVITY:  
62.                     Trace.traceBegin(Trace.TRACE_TAG_ACTIVITY_MANAGER, "activityDestroy");  
63.                     handleDestroyActivity((IBinder)msg.obj, msg.arg1 != 0,  
64.                             msg.arg2, false);  
65.                     Trace.traceEnd(Trace.TRACE_TAG_ACTIVITY_MANAGER);  
66.                     break;  
67.                 case BIND_APPLICATION:  
68.                     Trace.traceBegin(Trace.TRACE_TAG_ACTIVITY_MANAGER, "bindApplication");  
69.                     AppBindData data = (AppBindData)msg.obj;  
70.                     handleBindApplication(data);  
71.                     Trace.traceEnd(Trace.TRACE_TAG_ACTIVITY_MANAGER);  
72.                     break;  
73.                 case EXIT_APPLICATION:  
74.                     if (mInitialApplication != null) {  
75.                         mInitialApplication.onTerminate();  
76.                     }  
77.                     Looper.myLooper().quit();  
78.                     break;  
79.                 case NEW_INTENT:  
80.                     Trace.traceBegin(Trace.TRACE_TAG_ACTIVITY_MANAGER, "activityNewIntent");  
81.                     handleNewIntent((NewIntentData)msg.obj);  
82.                     Trace.traceEnd(Trace.TRACE_TAG_ACTIVITY_MANAGER);  
83.                     break;  
84.                 case RECEIVER:  
85.                     Trace.traceBegin(Trace.TRACE_TAG_ACTIVITY_MANAGER, "broadcastReceiveComp");  
86.                     handleReceiver((ReceiverData)msg.obj);  
87.                     maybeSnapshot();  
88.                     Trace.traceEnd(Trace.TRACE_TAG_ACTIVITY_MANAGER);  
89.                     break;  
90.                 case CREATE_SERVICE:  
91.                     Trace.traceBegin(Trace.TRACE_TAG_ACTIVITY_MANAGER, "serviceCreate");  
92.                     handleCreateService((CreateServiceData)msg.obj);  
93.                     Trace.traceEnd(Trace.TRACE_TAG_ACTIVITY_MANAGER);  
94.                     break;  
95.                 case BIND_SERVICE:  
96.                     Trace.traceBegin(Trace.TRACE_TAG_ACTIVITY_MANAGER, "serviceBind");  
97.                     handleBindService((BindServiceData)msg.obj);  
98.                     Trace.traceEnd(Trace.TRACE_TAG_ACTIVITY_MANAGER);  
99.                     break;  
100.                 case UNBIND_SERVICE:  
101.                     Trace.traceBegin(Trace.TRACE_TAG_ACTIVITY_MANAGER, "serviceUnbind");  
102.                     handleUnbindService((BindServiceData)msg.obj);  
103.                     Trace.traceEnd(Trace.TRACE_TAG_ACTIVITY_MANAGER);  
104.                     break;  
105.                 case SERVICE_ARGS:  
106.                     Trace.traceBegin(Trace.TRACE_TAG_ACTIVITY_MANAGER, "serviceStart");  
107.                     handleServiceArgs((ServiceArgsData)msg.obj);  
108.                     Trace.traceEnd(Trace.TRACE_TAG_ACTIVITY_MANAGER);  
109.                     break;  
110.                 case STOP_SERVICE:  
111.                     Trace.traceBegin(Trace.TRACE_TAG_ACTIVITY_MANAGER, "serviceStop");  
112.                     handleStopService((IBinder)msg.obj);  
113.                     maybeSnapshot();  
114.                     Trace.traceEnd(Trace.TRACE_TAG_ACTIVITY_MANAGER);  
115.                     break;  
116.                 case REQUEST_THUMBNAIL:  
117.                     Trace.traceBegin(Trace.TRACE_TAG_ACTIVITY_MANAGER, "requestThumbnail");  
118.                     handleRequestThumbnail((IBinder)msg.obj);  
119.                     Trace.traceEnd(Trace.TRACE_TAG_ACTIVITY_MANAGER);  
120.                     break;  
121.                 case CONFIGURATION_CHANGED:  
122.                     Trace.traceBegin(Trace.TRACE_TAG_ACTIVITY_MANAGER, "configChanged");  
123.                     handleConfigurationChanged((Configuration)msg.obj, null);  
124.                     Trace.traceEnd(Trace.TRACE_TAG_ACTIVITY_MANAGER);  
125.                     break;  
126.                 case CLEAN_UP_CONTEXT:  
127.                     ContextCleanupInfo cci = (ContextCleanupInfo)msg.obj;  
128.                     cci.context.performFinalCleanup(cci.who, cci.what);  
129.                     break;  
130.                 case GC_WHEN_IDLE:  
131.                     scheduleGcIdler();  
132.                     break;  
133.                 case DUMP_SERVICE:  
134.                     handleDumpService((DumpComponentInfo)msg.obj);  
135.                     break;  
136.                 case LOW_MEMORY:  
137.                     Trace.traceBegin(Trace.TRACE_TAG_ACTIVITY_MANAGER, "lowMemory");  
138.                     handleLowMemory();  
139.                     Trace.traceEnd(Trace.TRACE_TAG_ACTIVITY_MANAGER);  
140.                     break;  
141.                 case ACTIVITY_CONFIGURATION_CHANGED:  
142.                     Trace.traceBegin(Trace.TRACE_TAG_ACTIVITY_MANAGER, "activityConfigChanged");  
143.                     handleActivityConfigurationChanged((IBinder)msg.obj);  
144.                     Trace.traceEnd(Trace.TRACE_TAG_ACTIVITY_MANAGER);  
145.                     break;  
146.                 case PROFILER_CONTROL:  
147.                     handleProfilerControl(msg.arg1 != 0, (ProfilerControlData)msg.obj, msg.arg2);  
148.                     break;  
149.                 case CREATE_BACKUP_AGENT:  
150.                     Trace.traceBegin(Trace.TRACE_TAG_ACTIVITY_MANAGER, "backupCreateAgent");  
151.                     handleCreateBackupAgent((CreateBackupAgentData)msg.obj);  
152.                     Trace.traceEnd(Trace.TRACE_TAG_ACTIVITY_MANAGER);  
153.                     break;  
154.                 case DESTROY_BACKUP_AGENT:  
155.                     Trace.traceBegin(Trace.TRACE_TAG_ACTIVITY_MANAGER, "backupDestroyAgent");  
156.                     handleDestroyBackupAgent((CreateBackupAgentData)msg.obj);  
157.                     Trace.traceEnd(Trace.TRACE_TAG_ACTIVITY_MANAGER);  
158.                     break;  
159.                 case SUICIDE:  
160.                     Process.killProcess(Process.myPid());  
161.                     break;  
162.                 case REMOVE_PROVIDER:  
163.                     Trace.traceBegin(Trace.TRACE_TAG_ACTIVITY_MANAGER, "providerRemove");  
164.                     completeRemoveProvider((ProviderRefCount)msg.obj);  
165.                     Trace.traceEnd(Trace.TRACE_TAG_ACTIVITY_MANAGER);  
166.                     break;  
167.                 case ENABLE_JIT:  
168.                     ensureJitEnabled();  
169.                     break;  
170.                 case DISPATCH_PACKAGE_BROADCAST:  
171.                     Trace.traceBegin(Trace.TRACE_TAG_ACTIVITY_MANAGER, "broadcastPackage");  
172.                     handleDispatchPackageBroadcast(msg.arg1, (String[])msg.obj);  
173.                     Trace.traceEnd(Trace.TRACE_TAG_ACTIVITY_MANAGER);  
174.                     break;  
175.                 case SCHEDULE_CRASH:  
176.                     throw new RemoteServiceException((String)msg.obj);  
177.                 case DUMP_HEAP:  
178.                     handleDumpHeap(msg.arg1 != 0, (DumpHeapData)msg.obj);  
179.                     break;  
180.                 case DUMP_ACTIVITY:  
181.                     handleDumpActivity((DumpComponentInfo)msg.obj);  
182.                     break;  
183.                 case DUMP_PROVIDER:  
184.                     handleDumpProvider((DumpComponentInfo)msg.obj);  
185.                     break;  
186.                 case SLEEPING:  
187.                     Trace.traceBegin(Trace.TRACE_TAG_ACTIVITY_MANAGER, "sleeping");  
188.                     handleSleeping((IBinder)msg.obj, msg.arg1 != 0);  
189.                     Trace.traceEnd(Trace.TRACE_TAG_ACTIVITY_MANAGER);  
190.                     break;  
191.                 case SET_CORE_SETTINGS:  
192.                     Trace.traceBegin(Trace.TRACE_TAG_ACTIVITY_MANAGER, "setCoreSettings");  
193.                     handleSetCoreSettings((Bundle) msg.obj);  
194.                     Trace.traceEnd(Trace.TRACE_TAG_ACTIVITY_MANAGER);  
195.                     break;  
196.                 case UPDATE_PACKAGE_COMPATIBILITY_INFO:  
197.                     handleUpdatePackageCompatibilityInfo((UpdateCompatibilityData)msg.obj);  
198.                     break;  
199.                 case TRIM_MEMORY:  
200.                     Trace.traceBegin(Trace.TRACE_TAG_ACTIVITY_MANAGER, "trimMemory");  
201.                     handleTrimMemory(msg.arg1);  
202.                     Trace.traceEnd(Trace.TRACE_TAG_ACTIVITY_MANAGER);  
203.                     break;  
204.                 case UNSTABLE_PROVIDER_DIED:  
205.                     handleUnstableProviderDied((IBinder)msg.obj, false);  
206.                     break;  
207.             }  
208.             if (DEBUG_MESSAGES) Slog.v(TAG, "<<< done: " + codeToString(msg.what));  
209.         }  

Java代码 

1. public final void bindApplication(String processName,  
2.                 ApplicationInfo appInfo, List<ProviderInfo> providers,  
3.                 ComponentName instrumentationName, String profileFile,  
4.                 ParcelFileDescriptor profileFd, boolean autoStopProfiler,  
5.                 Bundle instrumentationArgs, IInstrumentationWatcher instrumentationWatcher,  
6.                 int debugMode, boolean enableOpenGlTrace, boolean isRestrictedBackupMode,  
7.                 boolean persistent, Configuration config, CompatibilityInfo compatInfo,  
8.                 Map<String, IBinder> services, Bundle coreSettings) {  
9.   
10.             queueOrSendMessage(H.BIND_APPLICATION, data);  
11.         }  

ActivityManagerService

Java代码 

1. private final boolean attachApplicationLocked(IApplicationThread thread,  
2.         int pid) {     
3.     ProcessRecord app;  
4.     if (pid != MY_PID && pid >= 0) {  
5.         synchronized (mPidsSelfLocked ) {  
6.             app = mPidsSelfLocked .get(pid);  
7.         }  
8.     } else {  
9.         app = null ;  
10.     }  
11.       
12.   
13.     try {         
14.         thread.bindApplication(processName, appInfo, providers,  
15.                 app. instrumentationClass , profileFile, profileFd, profileAutoStop,  
16.                 app. instrumentationArguments , app.instrumentationWatcher , testMode,  
17.                 enableOpenGlTrace, isRestrictedBackupMode || !normalMode, app.persistent ,  
18.                 new Configuration(mConfiguration ), app. compat, getCommonServicesLocked(),  
19.                 mCoreSettingsObserver .getCoreSettingsLocked());  
20.         updateLruProcessLocked(app, false , true );  
21.     } catch (Exception e) {  
22.    
23.     }  
24.   
25.     return true ;  
26. }  

ActivityThread.ApplicationThread

Java代码 

1. public final void bindApplication(String processName,  
2.                 ApplicationInfo appInfo, List<ProviderInfo> providers,  
3.                 ComponentName instrumentationName, String profileFile,  
4.                 ParcelFileDescriptor profileFd, boolean autoStopProfiler,  
5.                 Bundle instrumentationArgs, IInstrumentationWatcher instrumentationWatcher,  
6.                 int debugMode, boolean enableOpenGlTrace, boolean isRestrictedBackupMode,  
7.                 boolean persistent, Configuration config, CompatibilityInfo compatInfo,  
8.                 Map<String, IBinder> services, Bundle coreSettings) {  
9.   
10.             ......  
11.             queueOrSendMessage(H.BIND_APPLICATION, data);  
12.         }  

最后

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