1、ContentProvider介绍
ContentProvider主要用于向外部提供数据
1、自己应用进程提供数据
2、其它app进程的提供数据
这里分析本进程的ContentProvider的启动过程
2、ContentProvider启动分析
1、我们知道Android程序入口在ActivityThread.java文件的main函数里面，如下代码
public static void main(String[] args) { Trace.traceBegin(Trace.TRACE_TAG_ACTIVITY_MANAGER, "ActivityThreadMain"); SamplingProfilerIntegration.start(); // CloseGuard defaults to true and can be quite spammy. We // disable it here, but selectively enable it later (via // StrictMode) on debug builds, but using DropBox, not logs. CloseGuard.setEnabled(false); Environment.initForCurrentUser(); // Set the reporter for event logging in libcore EventLogger.setReporter(new EventLoggingReporter()); AndroidKeyStoreProvider.install(); // Make sure TrustedCertificateStore looks in the right place for CA certificates final File configDir = Environment.getUserConfigDirectory(UserHandle.myUserId()); TrustedCertificateStore.setDefaultUserDirectory(configDir); Process.setArgV0("<pre-initialized>"); Looper.prepareMainLooper(); ActivityThread thread = new ActivityThread(); thread.attach(false); if (sMainThreadHandler == null) { sMainThreadHandler = thread.getHandler(); } if (false) { Looper.myLooper().setMessageLogging(new LogPrinter(Log.DEBUG, "ActivityThread")); } // End of event ActivityThreadMain. Trace.traceEnd(Trace.TRACE_TAG_ACTIVITY_MANAGER); Looper.loop(); throw new RuntimeException("Main thread loop unexpectedly exited"); }
2、我们这里可以看到有关键函数thread.attach(false)方法，我们跟踪进去，attach部分方法如下
private void attach(boolean system) { sCurrentActivityThread = this; mSystemThread = system; if (!system) { ViewRootImpl.addFirstDrawHandler(new Runnable() { @Override public void run() { ensureJitEnabled(); } }); android.ddm.DdmHandleAppName.setAppName("<pre-initialized>", UserHandle.myUserId()); RuntimeInit.setApplicationObject(mAppThread.asBinder()); final IActivityManager mgr = ActivityManagerNative.getDefault(); try { mgr.attachApplication(mAppThread); } catch (RemoteException ex) { // Ignore } // Watch for getting close to heap limit. BinderInternal.addGcWatcher(new Runnable() { @Override public void run() { if (!mSomeActivitiesChanged) { return; } Runtime runtime = Runtime.getRuntime(); long dalvikMax = runtime.maxMemory(); long dalvikUsed = runtime.totalMemory() - runtime.freeMemory(); if (dalvikUsed > ((3*dalvikMax)/4)) { if (DEBUG_MEMORY_TRIM) Slog.d(TAG, "Dalvik max=" + (dalvikMax/1024) + " total=" + (runtime.totalMemory()/1024) + " used=" + (dalvikUsed/1024)); mSomeActivitiesChanged = false; try { mgr.releaseSomeActivities(mAppThread); } catch (RemoteException e) { } } } }); *******
3、这里有个关键方法，mgr.attachApplication(mAppThread)，我们看下这个方法ActivityManagerService.java文件里面的实现
@Override public final void attachApplication(IApplicationThread thread) { synchronized (this) { int callingPid = Binder.getCallingPid(); final long origId = Binder.clearCallingIdentity(); attachApplicationLocked(thread, callingPid); Binder.restoreCallingIdentity(origId); } }
4、我们再看关键函数attachApplicationLocked函数部分实现
private final boolean attachApplicationLocked(IApplicationThread thread, int pid) { ******* boolean normalMode = mProcessesReady || isAllowedWhileBooting(app.info); List<ProviderInfo> providers = normalMode ? generateApplicationProvidersLocked(app) : null; ******* thread.bindApplication(processName, appInfo, providers, app.instrumentationClass, profilerInfo, app.instrumentationArguments, app.instrumentationWatcher, app.instrumentationUiAutomationConnection, testMode, enableOpenGlTrace, isRestrictedBackupMode || !normalMode, app.persistent, new Configuration(mConfiguration), app.compat, getCommonServicesLocked(app.isolated), mCoreSettingsObserver.getCoreSettingsLocked()); updateLruProcessLocked(app, false, null); app.lastRequestedGc = app.lastLowMemory = SystemClock.uptimeMillis();
5、这里又调用了generateApplicationProvidersLocked(app)函数，这个函数返回了一个ProviderInfo对象的集合，我们跟踪这个函数看是如何得到这个集合的。
private final List<ProviderInfo> generateApplicationProvidersLocked(ProcessRecord app) { List<ProviderInfo> providers = null; try { ParceledListSlice<ProviderInfo> slice = AppGlobals.getPackageManager(). queryContentProviders(app.processName, app.uid, STOCK_PM_FLAGS | PackageManager.GET_URI_PERMISSION_PATTERNS); providers = slice != null ? slice.getList() : null; } catch (RemoteException ex) { } if (DEBUG_MU) Slog.v(TAG_MU, "generateApplicationProvidersLocked, app.info.uid = " + app.uid); int userId = app.userId; if (providers != null) { int N = providers.size(); app.pubProviders.ensureCapacity(N + app.pubProviders.size()); for (int i=0; i<N; i++) { ProviderInfo cpi = (ProviderInfo)providers.get(i); boolean singleton = isSingleton(cpi.processName, cpi.applicationInfo, cpi.name, cpi.flags); if (singleton && UserHandle.getUserId(app.uid) != UserHandle.USER_OWNER) { providers.remove(i); N--; i--; continue; } ComponentName comp = new ComponentName(cpi.packageName, cpi.name); ContentProviderRecord cpr = mProviderMap.getProviderByClass(comp, userId); if (cpr == null) { cpr = new ContentProviderRecord(this, cpi, app.info, comp, singleton); mProviderMap.putProviderByClass(comp, cpr); } if (DEBUG_MU) Slog.v(TAG_MU, "generateApplicationProvidersLocked, cpi.uid = " + cpr.uid); app.pubProviders.put(cpi.name, cpr); if (!cpi.multiprocess || !"android".equals(cpi.packageName)) { app.addPackage(cpi.applicationInfo.packageName, cpi.applicationInfo.versionCode, mProcessStats); } ensurePackageDexOpt(cpi.applicationInfo.packageName); } } return providers; }
这里很明显是查询ContentProvider通过app进程名字和app的uid,然后得到一个ProviderInfo的集合，就是这里的providers,然后我们遍历这个集合，通过每个ProviderInfo的packageName和name属性构建ComponentName这个对象，然后再去构建ContentProviderRecord对象，key为ComponentName,value为ContentProviderRecord添加到这个ProviderMap对象里面，也就是这行代码
mProviderMap.putProviderByClass(comp, cpr);
然后把返回的providers作为参数，传递给了bindApplication函数。
