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Android Content Provider的启动过程源代码分析

       本文参考Android应用程序组件Content Provider的启动过程源代码分析http://blog.csdn.net/luoshengyang/article/details/6963418和《Android系统源代码情景分析》,作者罗升阳。

       0、总图流程图如下:



       1、MainActivity进程向ActivityServiceManager主线程发送GET_CONTENT_PORVIDER_TRANSACTION

       如下图:


         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 = http://www.mamicode.com/Parcel.obtain();>
        其中name为shy.luo.providers.articles。


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


        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;
        }
  
    .......
}
       其中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函数来进一步执行操作。

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; i++) {
				if (mLaunchingProviders.get(i) == cpr) {
					break;
				}
			}

			// If the provider is not already being launched, then get it
			// started.
			if (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;
	}
	
	......
}
      主要做了以下几件事:

     (1)根据传递过来的name创建了ProviderInfo对象和ApplicationInfo对象,然后根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、三步全部省略,只看第四步。

       ~/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;
	}

	......
}
      主要做了以下几件事:

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

     (2)根据这个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<ProviderInfo> providers, ComponentName testName,
            String profileName, Bundle testArgs, IInstrumentationWatcher testWatcher, int debugMode,
            boolean restrictedBackupMode, Configuration config,
            Map<String, IBinder> services) throws RemoteException {
        Parcel data = http://www.mamicode.com/Parcel.obtain();>       

       其中providers是在ActivityServiceManager主线程根据传递过来的name创建了ProviderInfo对象。

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


       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<ProviderInfo> 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<String, IBinder> services = data.readHashMap(null);
            bindApplication(packageName, info,
                            providers, testName, profileName,
                            testArgs, testWatcher, testMode, restrictedBackupMode,
                            config, services);
            return true;
        }
        .....
}
     其中providers是在ActivityServiceManager主线程根据传递过来的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<ProviderInfo> providers,
				ComponentName instrumentationName, String profileFile,
				Bundle instrumentationArgs, IInstrumentationWatcher instrumentationWatcher,
				int debugMode, boolean isRestrictedBackupMode, Configuration config,
				Map<String, IBinder> services) {
			if (services != null) {
				// Setup the service cache in the ServiceManager
				ServiceManager.initServiceCache(services);
			}

			AppBindData data = http://www.mamicode.com/new AppBindData();>

      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。这个消息最终在ArticlesProvider主线程中处理。


      5、ArticlesProvider主线程installContentProvider
      主要做了以下几件事:

    (1)根据传递过来的providers把ArticlesProvider这个Content Provider类加载到内存中来了,并调用了它的onCreat方法。

    (2)创建了Transport对象,它的关系图如下:


  (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、三步全部省略,只看第四步。

       ~/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<ContentProviderHolder> providers) {
		......

		synchronized(this) {
			final ProcessRecord r = getRecordForAppLocked(caller);
			......

			final int N = providers.size();
			for (int i=0; i<N; i++) {
				ContentProviderHolder src = http://www.mamicode.com/providers.get(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。如下图:



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。因为要传输的数据比较小。