Android中级——四大组件工作过程

Activity

startActivity()最终都会调用到startActivityForResult()

public void startActivityForResult(@RequiresPermission Intent intent, int requestCode, @Nullable Bundle options) {if (mParent == null) {options = transferSpringboardActivityOptions(options);Instrumentation.ActivityResult ar =mInstrumentation.execStartActivity(this, mMainThread.getApplicationThread(), mToken, this,intent, requestCode, options);if (ar != null) {mMainThread.sendActivityResult(mToken, mEmbeddedID, requestCode, ar.getResultCode(),ar.getResultData());}if (requestCode >= 0) {mStartedActivity = true;}cancelInputsAndStartExitTransition(options);}......
}

上面调用Instrumentation的execStartActivity()

public ActivityResult execStartActivity(......) {......try {......int result = ActivityTaskManager.getService().startActivity(whoThread,who.getBasePackageName(), who.getAttributionTag(), intent,intent.resolveTypeIfNeeded(who.getContentResolver()), token,target != null ? target.mEmbeddedID : null, requestCode, 0, null, options);checkStartActivityResult(result, intent);} catch (RemoteException e) {throw new RuntimeException("Failure from system", e);}return null;
}

上面获取ActivityTaskManagerService，是IPC过程，调用其startActivity()启动，然后调到startActivityAsUser()

private int startActivityAsUser(......) {......return getActivityStartController().obtainStarter(intent, "startActivityAsUser").setCaller(caller).setCallingPackage(callingPackage).setCallingFeatureId(callingFeatureId).setResolvedType(resolvedType).setResultTo(resultTo).setResultWho(resultWho).setRequestCode(requestCode).setStartFlags(startFlags).setProfilerInfo(profilerInfo).setActivityOptions(bOptions).setUserId(userId).execute();
}

上面通过ActivityStartController获取ActivityStarter

• 调用 ActivityStarter 的 execute()、executeRequest()、startActivityUnchecked()、startActivityInner()
• 调用 ActivityStack 的 startActivityLocked() 、positionChildAtTop()、positionChildAt()
• 调用 RootWindowContainer 的 resumeFocusedStacksTopActivities()
• 调用 ActivityStack 的 resumeTopActivityUncheckedLocked()、resumeTopActivityInnerLocked()
• 调用 ActivityStackSupervisor 的 startSpecificActivity()、realStartActivityLocked()
• 调用 ClientLifecycleManager 的 scheduleTransaction()
• 调用 ClientTransaction 的 schedule()
• 调用 ActivityThread 中 ApplicationThread 的 scheduleTransaction()
• 调用 ClientTransactionHandler 的 scheduleTransaction()
• 调用 ClientTransaction() 的 preExecute()
• 向 ActivityThread 发送 H.EXECUTE_TRANSACTION
• 调用 TransactionExecutor 的 execute()、executeCallbacks()、cycleToPath()、performLifecycleSequence()
• 调用 ClientTransactionHandler 子类 ActivityThread 的handleLaunchActivity()、performLaunchActivity()

下面主要分析performLaunchActivity()，首先从ActivityClientRecord获取Activity的信息，创建ContextImpl，其是Context的具体实现

ActivityInfo aInfo = r.activityInfo;
if (r.packageInfo == null) {r.packageInfo = getPackageInfo(aInfo.applicationInfo, r.compatInfo,Context.CONTEXT_INCLUDE_CODE);
}
ComponentName component = r.intent.getComponent();
if (component == null) {component = r.intent.resolveActivity(mInitialApplication.getPackageManager());r.intent.setComponent(component);
}
if (r.activityInfo.targetActivity != null) {component = new ComponentName(r.activityInfo.packageName,r.activityInfo.targetActivity);
}
ContextImpl appContext = createBaseContextForActivity(r);

通过Instrumentation的newActivity()使用ClassLoader创建Activity，返回 (Activity) cl.loadClass(className).newInstance();

try {java.lang.ClassLoader cl = appContext.getClassLoader();activity = mInstrumentation.newActivity(cl, component.getClassName(), r.intent);StrictMode.incrementExpectedActivityCount(activity.getClass());r.intent.setExtrasClassLoader(cl);r.intent.prepareToEnterProcess();if (r.state != null) {r.state.setClassLoader(cl);}
}......

通过LoadedApk的makeApplication()创建Application

• 若已创建则不再创建
• Instrumentation的newApplication() 返回 (Application) cl.loadClass(className).newInstance();
• Instrumentation的callApplicationOnCreate() 调用onCreate()方法

@UnsupportedAppUsage
public Application makeApplication(boolean forceDefaultAppClass,Instrumentation instrumentation) {if (mApplication != null) {return mApplication;}Application app = null;String appClass = mApplicationInfo.className;if (forceDefaultAppClass || (appClass == null)) {appClass = "android.app.Application";}try {final java.lang.ClassLoader cl = getClassLoader();if (!mPackageName.equals("android")) {initializeJavaContextClassLoader();}SparseArray<String> packageIdentifiers = getAssets().getAssignedPackageIdentifiefalse, false);for (int i = 0, n = packageIdentifiers.size(); i < n; i++) {final int id = packageIdentifiers.keyAt(i);if (id == 0x01 || id == 0x7f) {continue;}rewriteRValues(cl, packageIdentifiers.valueAt(i), id);}ContextImpl appContext = ContextImpl.createAppContext(mActivityThread, this);NetworkSecurityConfigProvider.handleNewApplication(appContext);app = mActivityThread.mInstrumentation.newApplication(cl, appClass, appContext);appContext.setOuterContext(app);}......mActivityThread.mAllApplications.add(app);mApplication = app;if (instrumentation != null) {try {instrumentation.callApplicationOnCreate(app);}......}......return app;
}

通过Activity的attach初始化数据，包括和ContextImpl建立关联、创建Window及关联

CharSequence title = r.activityInfo.loadLabel(appContext.getPackageManager());
Configuration config = new Configuration(mCompatConfiguration);
if (r.overrideConfig != null) {config.updateFrom(r.overrideConfig);
}Window window = null;
if (r.mPendingRemoveWindow != null && r.mPreserveWindow) {window = r.mPendingRemoveWindow;r.mPendingRemoveWindow = null;r.mPendingRemoveWindowManager = null;
}appContext.getResources().addLoaders(app.getResources().getLoaders().toArray(new ResourcesLoader[0]));
appContext.setOuterContext(activity);
activity.attach(appContext, this, getInstrumentation(), r.token,r.ident, app, r.intent, r.activityInfo, title, r.parent,r.embeddedID, r.lastNonConfigurationInstances, config,r.referrer, r.voiceInteractor, window, r.configCallback,r.assistToken);

通过Instrumentation的callActivityOnCreate调用onCreate()，至此Activity启动完成

Service

startService()过程

会调用到ContextWrapper的startService()，mBase为ContextImpl

@Override
public ComponentName startService(Intent service) {return mBase.startService(service);
}

会调用到ContextImpl的startServiceCommon()

private ComponentName startServiceCommon(Intent service, boolean requireForeground,UserHandle user) {try {validateServiceIntent(service);service.prepareToLeaveProcess(this);ComponentName cn = ActivityManager.getService().startService(mMainThread.getApplicationThread(), service,service.resolveTypeIfNeeded(getContentResolver()), requireForeground,getOpPackageName(), getAttributionTag(), user.getIdentifier());......return cn;} catch (RemoteException e) {throw e.rethrowFromSystemServer();}
}

会调用到ActivityManagerService的startService()

@Override
public ComponentName startService(......)  throws TransactionTooLargeException {......synchronized (this) {final int callingPid = Binder.getCallingPid();final int callingUid = Binder.getCallingUid();final long origId = Binder.clearCallingIdentity();ComponentName res;try {res = mServices.startServiceLocked(caller, service,resolvedType, callingPid, callingUid,requireForeground, callingPackage, callingFeatureId, userId);} finally {Binder.restoreCallingIdentity(origId);}return res;}
}

会调用

• ActiveServices 的 startServiceLocked()、startServiceInnerLocked()、bringUpServiceLocked()、realStartServiceLocked()、sendServiceArgsLocked()这里会调用onStartCommand()
• ActivityThread 中 ApplicationThread 的 scheduleCreateService()、发送H.CREATE_SERVICE、handleCreateService()

主要分析handleCreateService()

• 创建ContextImpl、Application、Service
• 调用attach，建立ContextImpl和Service的联系
• 调用onCreate()，将service放到mServices列表

private void handleCreateService(CreateServiceData data) {unscheduleGcIdler();LoadedApk packageInfo = getPackageInfoNoCheck(data.info.applicationInfo, data.compatInfo);Service service = null;try {ContextImpl context = ContextImpl.createAppContext(this, packageInfo);Application app = packageInfo.makeApplication(false, mInstrumentation);java.lang.ClassLoader cl = packageInfo.getClassLoader();service = packageInfo.getAppFactory().instantiateService(cl, data.info.name, data.intent);context.getResources().addLoaders(app.getResources().getLoaders().toArray(new ResourcesLoader[0]));context.setOuterContext(service);service.attach(context, this, data.info.name, data.token, app,ActivityManager.getService());service.onCreate();mServices.put(data.token, service);try {ActivityManager.getService().serviceDoneExecuting(data.token, SERVICE_DONE_EXECUTING_ANON, 0, 0);} catch (RemoteException e) {throw e.rethrowFromSystemServer();}}......
}

bindService()过程

会调用到ContextWrapper的bindService()，mBase为ContextImpl

@Override
public boolean bindService(Intent service, ServiceConnection conn,int flags) {return mBase.bindService(service, conn, flags);
}

上面调用到ContextImpl的bindServiceCommon()

@Override
public boolean bindService(Intent service, ServiceConnection conn, int flags) {warnIfCallingFromSystemProcess();return bindServiceCommon(service, conn, flags, null, mMainThread.getHandler(), null,getUser());
}private boolean bindServiceCommon(Intent service, ServiceConnection conn, int flags,String instanceName, Handler handler, Executor executor, UserHandle user) {IServiceConnection sd;......if (mPackageInfo != null) {if (executor != null) {sd = mPackageInfo.getServiceDispatcher(conn, getOuterContext(), executor, flags);} else {sd = mPackageInfo.getServiceDispatcher(conn, getOuterContext(), handler, flags);}}......validateServiceIntent(service);try {IBinder token = getActivityToken();if (token == null && (flags&BIND_AUTO_CREATE) == 0 && mPackageInfo != null&& mPackageInfo.getApplicationInfo().targetSdkVersion< android.os.Build.VERSION_CODES.ICE_CREAM_SANDWICH) {flags |= BIND_WAIVE_PRIORITY;}service.prepareToLeaveProcess(this);int res = ActivityManager.getService().bindIsolatedService(mMainThread.getApplicationThread(), getActivityToken(), service,service.resolveTypeIfNeeded(getContentResolver()),sd, flags, instanceName, getOpPackageName(), user.getIdentifier());......return res != 0;}......
}

上面调用到LoadedApk的getServiceDispatcher()、getServiceDispatcherCommon()

• 先查找是否存在当前ServiceConnection所对应的ServiceDispatcher，不存在则创建并存在mServices中
• 将ServiceConnection转为ServiceDispatcher.InnerConnection对象（充当Binder），因为绑定服务可能是跨进程的

private IServiceConnection getServiceDispatcherCommon(ServiceConnection c,Context context, Handler handler, Executor executor, int flags) {synchronized (mServices) {LoadedApk.ServiceDispatcher sd = null;ArrayMap<ServiceConnection, LoadedApk.ServiceDispatcher> map = mServices.get(context);if (map != null) {sd = map.get(c);}if (sd == null) {if (executor != null) {sd = new ServiceDispatcher(c, context, executor, flags);} else {sd = new ServiceDispatcher(c, context, handler, flags);}if (map == null) {map = new ArrayMap<>();mServices.put(context, map);}map.put(c, sd);} else {sd.validate(context, handler, executor);}return sd.getIServiceConnection();}
}

接下来调用

• ActivityManagerService 的 bindIsolatedService()
• ActiveServices 的 bindServiceLocked()、bringUpServiceLocked()、realStartServiceLocked()
• ActivityThread 中 ApplicationThread 的 scheduleCreateService()创建Service，同上
• ActiveServices 的 requestServiceBindingsLocked()、requestServiceBindingLocked()
• ActivityThread 中 ApplicationThread 的 scheduleBindService()、发送H.BIND_SERVICE、handleBindService()

主要分析handleBindService()，从mServices取出Service，调用onBind()获取服务端Binder，此时已经绑定成功

private void handleBindService(BindServiceData data) {Service s = mServices.get(data.token);......if (s != null) {try {data.intent.setExtrasClassLoader(s.getClassLoader());data.intent.prepareToEnterProcess();try {if (!data.rebind) {IBinder binder = s.onBind(data.intent);ActivityManager.getService().publishService(data.token, data.intent, binder);} else {s.onRebind(data.intent);ActivityManager.getService().serviceDoneExecuting(data.token, SERVICE_DONE_EXECUTING_ANON, 0, 0);}}......}......}
}

接下来调用

• ActivityManagerService() 的 publishService()
• ActiveServices 的 publishServiceLocked()
• ConnectionRecord 中 ServiceDispatcher.InnerConnection 的 connected()，传入onBind()获取的服务端Binder
• LoadedApk 中 ServiceDispatcher 的 connected()

mActivityThread等于调用ContextImpl的bindService()时传入的mMainThread.getHandler()，故RunConnection会运行在主线程中

public void connected(ComponentName name, IBinder service, boolean dead) {if (mActivityExecutor != null) {mActivityExecutor.execute(new RunConnection(name, service, 0, dead));} else if (mActivityThread != null) {mActivityThread.post(new RunConnection(name, service, 0, dead));} else {doConnected(name, service, dead);}
}

调用LoadedApk 中 ServiceDispatcher 的 doConnected()

private final class RunConnection implements Runnable {RunConnection(ComponentName name, IBinder service, int command, boolean dead) {mName = name;mService = service;mCommand = command;mDead = dead;}public void run() {if (mCommand == 0) {doConnected(mName, mService, mDead);} else if (mCommand == 1) {doDeath(mName, mService);}}final ComponentName mName;final IBinder mService;final int mCommand;final boolean mDead;
}

doConnected()会调用onServiceConnected()，并将服务端Binder传回客户端

public void doConnected(ComponentName name, IBinder service, boolean dead) {ServiceDispatcher.ConnectionInfo old;ServiceDispatcher.ConnectionInfo info;synchronized (this) {if (mForgotten) {return;}old = mActiveConnections.get(name);if (old != null && old.binder == service) {return;}if (service != null) {info = new ConnectionInfo();info.binder = service;info.deathMonitor = new DeathMonitor(name, service);try {service.linkToDeath(info.deathMonitor, 0);mActiveConnections.put(name, info);} catch (RemoteException e) {mActiveConnections.remove(name);return;}} else {mActiveConnections.remove(name);}if (old != null) {old.binder.unlinkToDeath(old.deathMonitor, 0);}}if (old != null) {mConnection.onServiceDisconnected(name);}if (dead) {mConnection.onBindingDied(name);}if (service != null) {mConnection.onServiceConnected(name, service);} else {mConnection.onNullBinding(name);}
}

BroadcastReceiver

注册过程

静态注册在应用安装时由PackageManagerService完成注册，动态注册从ContextWrapper的registerReceiver()开始，mBase为ContextImpl

@Override
public Intent registerReceiver(BroadcastReceiver receiver, IntentFilter filter) {return mBase.registerReceiver(receiver, filter);
}

上面调用到ContextImpl的registerReceiverInternal()

• 将BroadcastReceiver转为LoadedApk.ReceiverDispatcher中的InnerReceiver（充当Binder），因为注册可能是跨进程的

private Intent registerReceiverInternal(BroadcastReceiver receiver, int userId,IntentFilter filter, String broadcastPermission,Handler scheduler, Context context, int flags) {IIntentReceiver rd = null;if (receiver != null) {if (mPackageInfo != null && context != null) {if (scheduler == null) {scheduler = mMainThread.getHandler();}rd = mPackageInfo.getReceiverDispatcher(receiver, context, scheduler,mMainThread.getInstrumentation(), true);} else {if (scheduler == null) {scheduler = mMainThread.getHandler();}rd = new LoadedApk.ReceiverDispatcher(receiver, context, scheduler, null, true).getIIntentReceiver();}}try {final Intent intent = ActivityManager.getService().registerReceiverWithFeature(mMainThread.getApplicationThread(), mBasePackageName, getAttributionTag(), rfilter, broadcastPermission, userId, flags);if (intent != null) {intent.setExtrasClassLoader(getClassLoader());intent.prepareToEnterProcess();}return intent;} catch (RemoteException e) {throw e.rethrowFromSystemServer();}
}

上面调用到ActivityManagerService的registerReceiverWithFeature()，将InnerReceiver和IntentFilter存储起来

public Intent registerReceiverWithFeature(IApplicationThread caller, String callerPackage,String callerFeatureId, IIntentReceiver receiver, String permission, int userId, int flags) {......synchronized (this) {......ReceiverList rl = mRegisteredReceivers.get(receiver.asBinder());if (rl == null) {rl = new ReceiverList(this, callerApp, callingPid, callingUid,userId, receiver);if (rl.app != null) {final int totalReceiversForApp = rl.app.receivers.size();rl.app.receivers.add(rl);} else {try {receiver.asBinder().linkToDeath(rl, 0);} catch (RemoteException e) {return sticky;}rl.linkedToDeath = true;}mRegisteredReceivers.put(receiver.asBinder(), rl);}......BroadcastFilter bf = new BroadcastFilter(filter, rl, callerPackage, callerFeatureId,permission, callingUid, userId, instantApp, visibleToInstantApps);if (rl.containsFilter(filter)) {......} else {rl.add(bf);......mReceiverResolver.addFilter(bf);}......}
}

发送和接收过程

ContextWrapper的sendBroadcast()开始，mBase为ContextImpl

@Override
public void sendBroadcast(Intent intent) {mBase.sendBroadcast(intent);
}

上面调用ContextImpl的sendBroadcast()

@Override
public void sendBroadcast(Intent intent) {warnIfCallingFromSystemProcess();String resolvedType = intent.resolveTypeIfNeeded(getContentResolver());try {intent.prepareToLeaveProcess(this);ActivityManager.getService().broadcastIntentWithFeature(mMainThread.getApplicationThread(), getAttributionTag(), intent, resolvedType,null, Activity.RESULT_OK, null, null, null, AppOpsManager.OP_NONE, null, false,false, getUserId());} catch (RemoteException e) {throw e.rethrowFromSystemServer();}
}

上面调用ActivityManagerService的broadcastIntentWithFeature()、broadcastIntentLocked()

• FLAG_EXCLUDE_STOPPED_PACKAGES表示不会向已停止的app发送广播
• 根据intent-filter查找匹配的BroadcastReceiver，并添加到BroadcastQueue

final int broadcastIntentLocked(ProcessRecord callerApp, String callerPackage,@Nullable String callerFeatureId, Intent intent, String resolvedType,IIntentReceiver resultTo, int resultCode, String resultData,Bundle resultExtras, String[] requiredPermissions, int appOp, Bundle bOptions,boolean ordered, boolean sticky, int callingPid, int callingUid, int realCallingUid,int realCallingPid, int userId, boolean allowBackgroundActivityStarts,@Nullable int[] broadcastWhitelist) {intent = new Intent(intent);......intent.addFlags(Intent.FLAG_EXCLUDE_STOPPED_PACKAGES);......final BroadcastQueue queue = broadcastQueueForIntent(intent);BroadcastRecord r = new BroadcastRecord(queue, intent, callerApp, callerPackage,callerFeatureId, callingPid, callingUid, callerInstantApp, resolvedType,requiredPermissions, appOp, brOptions, registeredReceivers, resultTo,resultCode, resultData, resultExtras, ordered, sticky, false, userId,allowBackgroundActivityStarts, timeoutExempt);final boolean replaced = replacePending&& (queue.replaceParallelBroadcastLocked(r) != null);if (!replaced) {queue.enqueueParallelBroadcastLocked(r);queue.scheduleBroadcastsLocked();}
}

上面再调用

• BroadcastQueue的scheduleBroadcastsLocked()、发送BROADCAST_INTENT_MSG、processNextBroadcast()、processNextBroadcastLocked()、deliverToRegisteredReceiverLocked()、performReceiveLocked()
• ActivityThread 中 ApplicationThread 的 scheduleRegisteredReceiver()
• LoadedApk.ReceiverDispatcher中InnerReceiver的performReceive()
• LoadedApk.ReceiverDispatcher的performReceive()

public void performReceive(Intent intent, int resultCode, String data,Bundle extras, boolean ordered, boolean sticky, int sendingUser) {final Args args = new Args(intent, resultCode, data, extras, ordered,sticky, sendingUser);......if (intent == null || !mActivityThread.post(args.getRunnable())) {if (mRegistered && ordered) {IActivityManager mgr = ActivityManager.getService();args.sendFinished(mgr);}}
}

mActivityThread等于调用ContextImpl的sendBroadcast()时传入的mMainThread.getHandler()，故Args会运行在主线程中，回调onReceive()，此时应用已接收到广播

final class Args extends BroadcastReceiver.PendingResult {......public final Runnable getRunnable() {return () -> {.....try {ClassLoader cl = mReceiver.getClass().getClassLoader();intent.setExtrasClassLoader(cl);intent.prepareToEnterProcess();setExtrasClassLoader(cl);receiver.setPendingResult(this);receiver.onReceive(mContext, intent);}......};}
}

ContentProvider

以query()为例，调用ContentResolver的acquireUnstableProvider()或acquireProvider()获取IContentProvider，其是抽象方法

@Override
public final @Nullable Cursor query(final @RequiresPermission.Read @NonNull Uri uri,@Nullable String[] projection, @Nullable Bundle queryArgs,@Nullable CancellationSignal cancellationSignal) {......IContentProvider unstableProvider = acquireUnstableProvider(uri);if (unstableProvider == null) {return null;}IContentProvider stableProvider = null;Cursor qCursor = null;try {......            try {qCursor = unstableProvider.query(mPackageName, uri, projection,queryArgs, remoteCancellationSignal);} catch (DeadObjectException e) {unstableProviderDied(unstableProvider);stableProvider = acquireProvider(uri);if (stableProvider == null) {return null;}qCursor = stableProvider.query(mPackageName, uri, projection, queryArgs, remoteCancellationSignal);}if (qCursor == null) {return null;}qCursor.getCount();final IContentProvider provider = (stableProvider != null) ? stableProvider: acquireProvider(uri);final CursorWrapperInner wrapper = new CursorWrapperInner(qCursor, provider);stableProvider = null;qCursor = null;return wrapper;}.....
}

会调用ContextImpl.ApplicationContentResolver 的 acquireProvider()

private static final class ApplicationContentResolver extends ContentResolver {@UnsupportedAppUsageprivate final ActivityThread mMainThread;public ApplicationContentResolver(Context context, ActivityThread mainThread) {super(context);mMainThread = Objects.requireNonNull(mainThread);}@Override@UnsupportedAppUsageprotected IContentProvider acquireProvider(Context context, String auth) {return mMainThread.acquireProvider(context,ContentProvider.getAuthorityWithoutUserId(auth),resolveUserIdFromAuthority(auth), true);}......@Overrideprotected IContentProvider acquireUnstableProvider(Context c, String auth) {return mMainThread.acquireProvider(c,ContentProvider.getAuthorityWithoutUserId(auth),resolveUserIdFromAuthority(auth), false);}......
}

调用到ActivityThread 的 acquireProvider()、acquireExistingProvider()判断IContentProvider是否已经加载到mProviderMap

public final IContentProvider acquireProvider(Context c, String auth, int userId, boolean stable) {final IContentProvider provider = acquireExistingProvider(c, auth, userId, stable);if (provider != null) {return provider;}ContentProviderHolder holder = null;try {synchronized (getGetProviderLock(auth, userId)) {holder = ActivityManager.getService().getContentProvider(getApplicationThread(), c.getOpPackageName(), auth, userId, stable);}} catch (RemoteException ex) {throw ex.rethrowFromSystemServer();}if (holder == null) {......return null;}......holder = installProvider(c, holder, holder.info,true /*noisy*/, holder.noReleaseNeeded, stable);return holder.provider;
}

若没加载，则调用ActivityManagerService的getContentProvider()，startProcessLocked()启动ContentProvider所在的进程，进程入口方法为ActivityThread的main()，在此创建ActivityThread和主线程消息队列

public static void main(String[] args) {......Looper.prepareMainLooper();long startSeq = 0;if (args != null) {for (int i = args.length - 1; i >= 0; --i) {if (args[i] != null && args[i].startsWith(PROC_START_SEQ_IDENT)) {startSeq = Long.parseLong(args[i].substring(PROC_START_SEQ_IDENT.length()));}}}ActivityThread thread = new ActivityThread();thread.attach(false, startSeq);if (sMainThreadHandler == null) {sMainThreadHandler = thread.getHandler();}......Looper.loop();throw new RuntimeException("Main thread loop unexpectedly exited");
}

上面调用

• ActivityThread 的 attach()
• ActivityManagerService 的 attachApplication()、attachApplicationLocked()，传入ApplicationThread，其是Binder，用于ActivityThread和ActivityManagerService之间的通信
• ApplicationThread 的 bindApplication()、发送H.BIND_APPLICATION、handleBindApplication()

在handleBindApplication()，创建Application、加载ContentProviders、然后再调用Application的OnCreate()

private void handleBindApplication(AppBindData data) {......Application app;try {app = data.info.makeApplication(data.restrictedBackupMode, null);.....if (!data.restrictedBackupMode) {if (!ArrayUtils.isEmpty(data.providers)) {installContentProviders(app, data.providers);}}try {mInstrumentation.onCreate(data.instrumentationArgs);}......try {mInstrumentation.callApplicationOnCreate(app);}......}......
}

在installContentProviders()中又调用installProvider()、instantiateProvider()通过反射创建ContentProvider，调用attachInfo()、回调onCreate()

private ContentProviderHolder installProvider(Context context,ContentProviderHolder holder, ProviderInfo info,boolean noisy, boolean noReleaseNeeded, boolean stable) {......try {final java.lang.ClassLoader cl = c.getClassLoader();LoadedApk packageInfo = peekPackageInfo(ai.packageName, true);if (packageInfo == null) {packageInfo = getSystemContext().mPackageInfo;}localProvider = packageInfo.getAppFactory().instantiateProvider(cl, info.name);provider = localProvider.getIContentProvider();if (provider == null) {Slog.e(TAG, "Failed to instantiate class " +info.name + " from sourceDir " +info.applicationInfo.sourceDir);return null;}if (DEBUG_PROVIDER) Slog.v(TAG, "Instantiating local provider " + info.name);localProvider.attachInfo(c, info);}.......synchronized (mProviderMap) {IBinder jBinder = provider.asBinder();if (localProvider != null) {ComponentName cname = new ComponentName(info.packageName, info.name);ProviderClientRecord pr = mLocalProvidersByName.get(cname);if (pr != null) {provider = pr.mProvider;} else {holder = new ContentProviderHolder(info);holder.provider = provider;holder.noReleaseNeeded = true;pr = installProviderAuthoritiesLocked(provider, localProvider, holder);mLocalProviders.put(jBinder, pr);mLocalProvidersByName.put(cname, pr);}retHolder = pr.mHolder;}
}

调用installProviderAuthoritiesLocked()，将ContentProvider封装到ProviderClientRecord存放在mProviderMap

private ProviderClientRecord installProviderAuthoritiesLocked(IContentProvider provider,ContentProvider localProvider, ContentProviderHolder holder) {......final ProviderClientRecord pcr = new ProviderClientRecord(auths, provider, localProvider, holder);for (String auth : auths) {final ProviderKey key = new ProviderKey(auth, userId);final ProviderClientRecord existing = mProviderMap.get(key);if (existing != null) {Slog.w(TAG, "Content provider " + pcr.mHolder.info.name+ " already published as " + auth);} else {mProviderMap.put(key, pcr);}}return pcr;
}