Android Content Provider的启动过程源码分析-白红宇

本文參考Android应用程序组件Content Provider的启动过程源码分析和《Android系统源码情景分析》，作者罗升阳。

0、总图流程图例如以下：

1、MainActivity进程向ActivityServiceManager主线程发送GET_CONTENT_PORVIDER_TRANSACTION

例如以下图：

如图：第一步

~/Android/frameworks/base/core/java/android/app

----ActivityManagerNative.java

class ActivityManagerProxy implements IActivityManager{	......    public ContentProviderHolder getContentProvider(IApplicationThread caller,                                                    String name) throws RemoteException    {            Parcel data = Parcel.obtain();        Parcel reply = Parcel.obtain();        data.writeInterfaceToken(IActivityManager.descriptor);        data.writeStrongBinder(caller != null ? caller.asBinder() : null);        data.writeString(name);        mRemote.transact(GET_CONTENT_PROVIDER_TRANSACTION, data, reply, 0);        reply.readException();        int res = reply.readInt();        ContentProviderHolder cph = null;        if (res != 0) {             cph = ContentProviderHolder.CREATOR.createFromParcel(reply);        }            data.recycle();        reply.recycle();        return cph;     }    	......}

当中name为shy.luo.providers.articles。

如图：第二步，省略binder_transaction传输过程，由于上面已经分析过了。

如图：第三步

~/Android/frameworks/base/core/java/android/app

----ActivityManagerNative.java

public abstract class ActivityManagerNative extends Binder implements IActivityManager{    ......    public boolean onTransact(int code, Parcel data, Parcel reply, int flags)            throws RemoteException {        switch (code) {        case GET_CONTENT_PROVIDER_TRANSACTION: {            data.enforceInterface(IActivityManager.descriptor);            IBinder b = data.readStrongBinder();            IApplicationThread app = ApplicationThreadNative.asInterface(b);            String name = data.readString();            ContentProviderHolder cph = getContentProvider(app, name);            reply.writeNoException();            if (cph != null) {                reply.writeInt(1);                cph.writeToParcel(reply, 0);            } else {                reply.writeInt(0);            }            return true;        }      .......}

当中name为

shy.luo.providers.articles。

如图：第四步

～/Android/frameworks/base/services/java/com/android/server/am

----ActivityManagerService.java

public final class ActivityManagerService extends ActivityManagerNative		implements Watchdog.Monitor, BatteryStatsImpl.BatteryCallback {	......	public final ContentProviderHolder getContentProvider(			IApplicationThread caller, String name) {		......		return getContentProviderImpl(caller, name);	}	......}

它调用getContentProviderImpl函数来进一步运行操作。

public final class ActivityManagerService extends ActivityManagerNative		implements Watchdog.Monitor, BatteryStatsImpl.BatteryCallback {	......	private final ContentProviderHolder getContentProviderImpl(			IApplicationThread caller, String name) {		ContentProviderRecord cpr;		ProviderInfo cpi = null;		synchronized(this) {			ProcessRecord r = null;			if (caller != null) {				r = getRecordForAppLocked(caller);				......			}			// First check if this content provider has been published...			cpr = mProvidersByName.get(name);			if (cpr != null) {				......			} else {				try {					cpi = AppGlobals.getPackageManager().						resolveContentProvider(name,						STOCK_PM_FLAGS | PackageManager.GET_URI_PERMISSION_PATTERNS);				} catch (RemoteException ex) {				}				......			}			cpr = mProvidersByClass.get(cpi.name);			final boolean firstClass = cpr == null;			if (firstClass) {				try {					ApplicationInfo ai =						AppGlobals.getPackageManager().						getApplicationInfo(						cpi.applicationInfo.packageName,						STOCK_PM_FLAGS);					......					cpr = new ContentProviderRecord(cpi, ai);				} catch (RemoteException ex) {					// pm is in same process, this will never happen.				}			}			if (r != null && cpr.canRunHere(r)) {				// If this is a multiprocess provider, then just return its				// info and allow the caller to instantiate it.  Only do				// this if the provider is the same user as the caller's				// process, or can run as root (so can be in any process).				return cpr;			}			......			// This is single process, and our app is now connecting to it.			// See if we are already in the process of launching this			// provider.			final int N = mLaunchingProviders.size();			int i;			for (i=0; i
    
     = N) {				final long origId = Binder.clearCallingIdentity();				ProcessRecord proc = startProcessLocked(cpi.processName,					cpr.appInfo, false, 0, "content provider",					new ComponentName(cpi.applicationInfo.packageName,					cpi.name), false);				......				mLaunchingProviders.add(cpr);				......			}			// Make sure the provider is published (the same provider class			// may be published under multiple names).			if (firstClass) {				mProvidersByClass.put(cpi.name, cpr);			}			cpr.launchingApp = proc;			mProvidersByName.put(name, cpr);			......		}		// Wait for the provider to be published...		synchronized (cpr) {			while (cpr.provider == null) {				......				try {					cpr.wait();				} catch (InterruptedException ex) {				}			}		}		return cpr;	}		......}

主要做了下面几件事：

（1）依据传递过来的name创建了ProviderInfo对象和ApplicationInfo对象，然后依据它们两个对象创建了ContentProviderRecord对象。

（2）创建了ProcessRecord对象，并创建ArticlesProvider子线程。

（3）循环等待cpr.provider的值不为null。

2、创建ArticlesProvider子线程，略。

3、ArticlesProvider子线程向ActivityManagerService子线程发送ATTACH_APPLICATION_TRANSACTION

第一、二、三步所有省略。仅仅看第四步。

～/Android/frameworks/base/services/java/com/android/server/am

----ActivityManagerService.java

public final class ActivityManagerService extends ActivityManagerNative		implements Watchdog.Monitor, BatteryStatsImpl.BatteryCallback {	......	private final boolean attachApplicationLocked(IApplicationThread thread,			int pid) {		// Find the application record that is being attached...  either via		// the pid if we are running in multiple processes, or just pull the		// next app record if we are emulating process with anonymous threads.		ProcessRecord app;		if (pid != MY_PID && pid >= 0) {			synchronized (mPidsSelfLocked) {				app = mPidsSelfLocked.get(pid);			}		} else if (mStartingProcesses.size() > 0) {			......		} else {			......		}		......		app.thread = thread;		app.curAdj = app.setAdj = -100;		app.curSchedGroup = Process.THREAD_GROUP_DEFAULT;		app.setSchedGroup = Process.THREAD_GROUP_BG_NONINTERACTIVE;		app.forcingToForeground = null;		app.foregroundServices = false;		app.debugging = false;		......		boolean normalMode = mProcessesReady || isAllowedWhileBooting(app.info);		List providers = normalMode ? generateApplicationProvidersLocked(app) : null;		try {			......			thread.bindApplication(processName, app.instrumentationInfo != null				?

app.instrumentationInfo : app.info, providers, app.instrumentationClass, app.instrumentationProfileFile, app.instrumentationArguments, app.instrumentationWatcher, testMode, isRestrictedBackupMode || !normalMode, mConfiguration, getCommonServicesLocked()); ...... } catch (Exception e) { ...... } ...... return true; } ...... private final List generateApplicationProvidersLocked(ProcessRecord app) { List providers = null; try { providers = AppGlobals.getPackageManager(). queryContentProviders(app.processName, app.info.uid, STOCK_PM_FLAGS | PackageManager.GET_URI_PERMISSION_PATTERNS); } catch (RemoteException ex) { } if (providers != null) { final int N = providers.size(); for (int i=0; i<N; i++) { ProviderInfo cpi = (ProviderInfo)providers.get(i); ContentProviderRecord cpr = mProvidersByClass.get(cpi.name); if (cpr == null) { cpr = new ContentProviderRecord(cpi, app.info); mProvidersByClass.put(cpi.name, cpr); } app.pubProviders.put(cpi.name, cpr); app.addPackage(cpi.applicationInfo.packageName); ensurePackageDexOpt(cpi.applicationInfo.packageName); } } return providers; } ...... }

主要做了下面几件事：

（1）获取了刚在ActivityServiceManager主线程创建的ProcessRecord对象。

（2）依据这个ProcessRecord对象获得刚在ActivityServiceManager主线程中的ProviderInfo对象。

（3）ActivityServiceManager子线程向ArticlesProvider子线程发送BIND_APPLICATION_TRANSACTION。

4、ActivityServiceManager子线程向ArticlesProvider子线程发送BIND_APPLICATION_TRANSACTION

如图：第一步

~/Android/frameworks/base/core/java/android/app

----ApplicationThreadNative.java。ApplicationThreadProxy类

public final void bindApplication(String packageName, ApplicationInfo info,            List
    
      providers, ComponentName testName,            String profileName, Bundle testArgs, IInstrumentationWatcher testWatcher, int debugMode,            boolean restrictedBackupMode, Configuration config,            Map
     
       services) throws RemoteException {        Parcel data = Parcel.obtain();        data.writeInterfaceToken(IApplicationThread.descriptor);        data.writeString(packageName);        info.writeToParcel(data, 0);        data.writeTypedList(providers);        if (testName == null) {            data.writeInt(0);        } else {            data.writeInt(1);            testName.writeToParcel(data, 0);        }        data.writeString(profileName);        data.writeBundle(testArgs);        data.writeStrongInterface(testWatcher);        data.writeInt(debugMode);        data.writeInt(restrictedBackupMode ? 1 : 0);        config.writeToParcel(data, 0);        data.writeMap(services);        mRemote.transact(BIND_APPLICATION_TRANSACTION, data, null,                IBinder.FLAG_ONEWAY);        data.recycle();    }

当中providers是在ActivityServiceManager主线程依据传递过来的name创建了ProviderInfo对象。

如图：第二步，省略binder_transaction传输过程，由于上面已经分析过了。

如图：第三步

~/Android/frameworks/base/core/java/android/app

----ApplicationThreadNative.java

public abstract class ApplicationThreadNative extends Binder        implements IApplicationThread {    ........    public boolean onTransact(int code, Parcel data, Parcel reply, int flags)            throws RemoteException {        switch (code) {        case BIND_APPLICATION_TRANSACTION:        {            data.enforceInterface(IApplicationThread.descriptor);            String packageName = data.readString();            ApplicationInfo info =                ApplicationInfo.CREATOR.createFromParcel(data);            List
    
      providers =                data.createTypedArrayList(ProviderInfo.CREATOR);            ComponentName testName = (data.readInt() != 0)                ? new ComponentName(data) : null;            String profileName = data.readString();            Bundle testArgs = data.readBundle();            IBinder binder = data.readStrongBinder();            IInstrumentationWatcher testWatcher = IInstrumentationWatcher.Stub.asInterface(binder);            int testMode = data.readInt();            boolean restrictedBackupMode = (data.readInt() != 0);            Configuration config = Configuration.CREATOR.createFromParcel(data);            HashMap
     
       services = data.readHashMap(null);            bindApplication(packageName, info,                            providers, testName, profileName,                            testArgs, testWatcher, testMode, restrictedBackupMode,                            config, services);            return true;        }        .....}

当中providers是在ActivityServiceManager主线程

依据传递过来的name创建了

ProviderInfo对象。

如图：第四步

～/Android/frameworks/base/core/java/android/app

----ActivityThread.java

public final class ActivityThread {	......	private final class ApplicationThread extends ApplicationThreadNative {		......		public final void bindApplication(String processName,				ApplicationInfo appInfo, List
    
      providers,				ComponentName instrumentationName, String profileFile,				Bundle instrumentationArgs, IInstrumentationWatcher instrumentationWatcher,				int debugMode, boolean isRestrictedBackupMode, Configuration config,				Map
     
       services) {			if (services != null) {				// Setup the service cache in the ServiceManager				ServiceManager.initServiceCache(services);			}			AppBindData data = new AppBindData();			data.processName = processName;			data.appInfo = appInfo;			data.providers = providers;			data.instrumentationName = instrumentationName;			data.profileFile = profileFile;			data.instrumentationArgs = instrumentationArgs;			data.instrumentationWatcher = instrumentationWatcher;			data.debugMode = debugMode;			data.restrictedBackupMode = isRestrictedBackupMode;			data.config = config;			queueOrSendMessage(H.BIND_APPLICATION, data);		}		......	}	......}

这个函数把相关的信息都封装成一个AppBindData对象，然后以一个消息的形式发送到主线程的消息队列中去等等待处理。这个消息终于在ArticlesProvider主线程中处理。

5、ArticlesProvider主线程installContentProvider

主要做了下面几件事：

（1）依据传递过来的providers把ArticlesProvider这个Content Provider类载入到内存中来了，并调用了它的onCreat方法。

（2）创建了Transport对象，它的关系图例如以下：

（3）ArticlesProvider主线程ActivityServiceManager子线程发送PUBLISH_CONTENT_PROVIDER_TRANSACTION

6、ArticlesProvider主线程ActivityServiceManager子线程发送PUBLISH_CONTENT_PROVIDER_TRANSACTION

第一、二、三步所有省略。仅仅看第四步。

～/Android/frameworks/base/services/java/com/android/server/am

----ActivityManagerService.java

public final class ActivityManagerService extends ActivityManagerNative		implements Watchdog.Monitor, BatteryStatsImpl.BatteryCallback {	......	public final void publishContentProviders(IApplicationThread caller,			List
    
      providers) {		......		synchronized(this) {			final ProcessRecord r = getRecordForAppLocked(caller);			......			final int N = providers.size();			for (int i=0; i

还记得ActivityServiceManager在循环等待么？这里dst.provider = src.provider，为ContentProviderProxy对象（实现了IContentProvider）。

之后调用notifyAll通知ActivityManagerService主线程，让它从等待中返回。

7、notifyAll通知ActivityManagerService主线程

8、ActivityManagerService主线程向MainActivity进程发送返回结果

~/Android/frameworks/base/core/java/android/app

----ActivityThread.java

private final IContentProvider getProvider(Context context, String name) {		IContentProvider existing = getExistingProvider(context, name);		if (existing != null) {			return existing;		}		IActivityManager.ContentProviderHolder holder = null;		try {			holder = ActivityManagerNative.getDefault().getContentProvider(				getApplicationThread(), name);		} catch (RemoteException ex) {		}		IContentProvider prov = installProvider(context, holder.provider,			holder.info, true);		......		return prov;	}

public class ArticlesAdapter {	......	private ContentResolver resolver = null;	public ArticlesAdapter(Context context) {		resolver = context.getContentResolver();	}	......	public int getArticleCount() {		int count = 0;		try {			IContentProvider provider = resolver.acquireProvider(Articles.CONTENT_URI);			Bundle bundle = provider.call(Articles.METHOD_GET_ITEM_COUNT, null, null);			count = bundle.getInt(Articles.KEY_ITEM_COUNT, 0);		} catch(RemoteException e) {			e.printStackTrace();		}		return count;	}	......}

最后返回的是ContentProviderProxy对象，指向了ArticlesProvider主线程中Transport对象。例如以下图：

Bundle bundle = provider.call(Articles.METHOD_GET_ITEM_COUNT, null, null);

使用进程间通信的方式取得博客栏目数量。

由于要传输的数据比較小。

本文转自mfrbuaa博客园博客，原文链接：http://www.cnblogs.com/mfrbuaa/p/5155039.html，如需转载请自行联系原作者