ContentProvider启动流程示例解析

ContentProvider是内容提供者，可以跨进程提供数据。

大家都知道，ContentProvider的启动，是在Application的onCreate方法之前的，所以ContentProvider的初始化时间会影响整个App的启动速度。

那ContentProvider启动流程具体是什么样的呢？让我们进入源码的世界来一探究竟。

App启动

App启动时，AMS会通过跨进程Binder调用，访问到ApplicationThread种的bindApplication方法。

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public final void bindApplication(String processName, ApplicationInfo appInfo,           List<ProviderInfo> providers, ComponentName instrumentationName,           ProfilerInfo profilerInfo, Bundle instrumentationArgs,           IInstrumentationWatcher instrumentationWatcher,           IUiAutomationConnection instrumentationUiConnection, int debugMode,           boolean enableBinderTracking, boolean trackAllocation,           boolean isRestrictedBackupMode, boolean persistent, Configuration config,           CompatibilityInfo compatInfo, Map services, Bundle coreSettings,           String buildSerial, boolean autofillCompatibilityEnabled) {       // 拼接AppBindData，发送给ActivityThread的H       sendMessage(H.BIND_APPLICATION, data);   }

这个方法主要作用是，拼接AppBindData，发送给ActivityThread中的Handler mH。在这个Handler中，会处理Message，然后调用handleBindApplication(data)方法。

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private void handleBindApplication(AppBindData data) {     final InstrumentationInfo ii;     // 创建 mInstrumentation 实例     if (ii != null) {         //创建ContextImpl         final ContextImpl appContext = ContextImpl.createAppContext(this, pi);         try {             //创建mInstrumentation实例             final ClassLoader cl = appContext.getClassLoader();             mInstrumentation = (Instrumentation) cl.loadClass(data.instrumentationName.getClassName()).newInstance();         } catch (Exception e) {}     } else {         mInstrumentation = new Instrumentation();     }     Application app;     try {         // 创建 Application 实例         app = data.info.makeApplication(data.restrictedBackupMode, null);         mInitialApplication = app;         // 如果不是backup模式，则调用installContentProvider，启动ContentProvider          if (!data.restrictedBackupMode) {                 if (!ArrayUtils.isEmpty(data.providers)) {                     //启动ContentProvider                     installContentProviders(app, data.providers);                     mH.sendEmptyMessageDelayed(H.ENABLE_JIT, 10*1000);                 }             }         try {             //调用Application的onCreate             mInstrumentation.callApplicationOnCreate(app);         } catch (Exception e) { }     } }

这个方法非常长，主要做的事情有以下四点：

• 创建一个ContentImpl对象
• 创建一个Instrument对象
• 创建Application实例
• 如果不是backup模式，调用installContentProviders，启动ContentProvider
• 调用Application的onCreate方法

installContentProviders

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private void installContentProviders(Context context, List providers) {         final ArrayList results = new ArrayList<>();         // 遍历所有的providers         for (ProviderInfo cpi : providers) {             // 开始启动ContentProvider             ContentProviderHolder cph = installProvider(context, null, cpi,                     false /*noisy*/, true /*noReleaseNeeded*/, true /*stable*/);              results.add(cph);         }         // 将成功启动的provider存储到AMS的mProviderMap中         ActivityManager.getService().publishContentProviders(getApplicationThread(), results);     }

这个方法，循环遍历所有待启动的ContentProvider，调用installProvider启动。

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private ContentProviderHolder installProvider(Context context,            ContentProviderHolder holder, ProviderInfo info,            boolean noisy, boolean noReleaseNeeded, boolean stable) {                // 反射创建ContentProvider                final java.lang.ClassLoader cl = c.getClassLoader();                LoadedApk packageInfo = peekPackageInfo(ai.packageName, true);                localProvider = cl.loadClass(className).newInstance();                provider = localProvider.getIContentProvider();                // 调用ContentProvider的attachInfo方法                localProvider.attachInfo(c, info);    }

这个方法，通过反射创建ContentProvider，然后调用attachInfo方法。

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private void attachInfo(Context context, ProviderInfo info, boolean testing) {         // 调用onCreate方法        ContentProvider.this.onCreate();  }