ActivityManagerService第四讲之ContentProvider启动流程

一.ContentProvider的启动流程

应用进程的启动最终会调用ActivityThread的main()方法上，我们从这个方法开始看。（注意：ContentProvider的onCreate方法会早于Application的onCreate方法执行的）

1.ActivityThread#main

    public static void main(String[] args) {
        Trace.traceBegin(Trace.TRACE_TAG_ACTIVITY_MANAGER, "ActivityThreadMain");

        ......
        ActivityThread thread = new ActivityThread();
        thread.attach(false, startSeq);

        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.ActivityThread#attach

会调用IActivityManager的attachApplication()方法，IActivityManager是一个AIDL文件，我们从之前的学习中知道对应的实现就是ActivityManagerService。

    @UnsupportedAppUsage
    private void attach(boolean system, long startSeq) {
        sCurrentActivityThread = this;
        mSystemThread = system;
        if (!system) {
            android.ddm.DdmHandleAppName.setAppName("<pre-initialized>",
                                                    UserHandle.myUserId());
            RuntimeInit.setApplicationObject(mAppThread.asBinder());
            final IActivityManager mgr = ActivityManager.getService();
            try {
                // 关键方法
                mgr.attachApplication(mAppThread, startSeq);
            } catch (RemoteException ex) {
                throw ex.rethrowFromSystemServer();
            }
            ......
        };
        ViewRootImpl.addConfigCallback(configChangedCallback);
    }

3.ActivityManagerService#attachApplication

    @Override
    public final void attachApplication(IApplicationThread thread, long startSeq) {
        synchronized (this) {
            int callingPid = Binder.getCallingPid();
            final int callingUid = Binder.getCallingUid();
            final long origId = Binder.clearCallingIdentity();
            // 关键方法
            attachApplicationLocked(thread, callingPid, callingUid, startSeq);
            Binder.restoreCallingIdentity(origId);
        }
    }

4.ActivityManagerService#attachApplicationLocked

代码有点长，我们截取我们需要的，会调用IApplicationThread的bindApplication()方法，IApplicationThread也是一个AIDL，在之前Activity启动流程中我们已经知道ApplicationThread现在是ActivityThread的内部类。

    @GuardedBy("this")
    private final boolean attachApplicationLocked(IApplicationThread thread,
            int pid, int callingUid, long startSeq) {

        ......
        if (DEBUG_ALL) Slog.v(
            TAG, "New app record " + app
            + " thread=" + thread.asBinder() + " pid=" + pid);
        final BackupRecord backupTarget = mBackupTargets.get(app.userId);
        try {
            ......

            checkTime(startTime, "attachApplicationLocked: immediately before bindApplication");
            bindApplicationTimeMillis = SystemClock.elapsedRealtime();
            mAtmInternal.preBindApplication(app.getWindowProcessController());
            final ActiveInstrumentation instr2 = app.getActiveInstrumentation();
            long[] disabledCompatChanges = CompatConfig.get().getDisabledChanges(app.info);
            if (mPlatformCompat != null) {
                mPlatformCompat.resetReporting(app.info);
            }
            if (app.isolatedEntryPoint != null) {
                // This is an isolated process which should just call an entry point instead of
                // being bound to an application.
                thread.runIsolatedEntryPoint(app.isolatedEntryPoint, app.isolatedEntryPointArgs);
            } else if (instr2 != null) {
                thread.bindApplication(processName, appInfo, providers,
                        instr2.mClass,
                        profilerInfo, instr2.mArguments,
                        instr2.mWatcher,
                        instr2.mUiAutomationConnection, testMode,
                        mBinderTransactionTrackingEnabled, enableTrackAllocation,
                        isRestrictedBackupMode || !normalMode, app.isPersistent(),
                        new Configuration(app.getWindowProcessController().getConfiguration()),
                        app.compat, getCommonServicesLocked(app.isolated),
                        mCoreSettingsObserver.getCoreSettingsLocked(),
                        buildSerial, autofillOptions, contentCaptureOptions,
                        disabledCompatChanges);
            } else {
                thread.bindApplication(processName, appInfo, providers, null, profilerInfo,
                        null, null, null, testMode,
                        mBinderTransactionTrackingEnabled, enableTrackAllocation,
                        isRestrictedBackupMode || !normalMode, app.isPersistent(),
                        new Configuration(app.getWindowProcessController().getConfiguration()),
                        app.compat, getCommonServicesLocked(app.isolated),
                        mCoreSettingsObserver.getCoreSettingsLocked(),
                        buildSerial, autofillOptions, contentCaptureOptions,
                        disabledCompatChanges);
            }
            if (profilerInfo != null) {
                profilerInfo.closeFd();
                profilerInfo = null;
            }
		   .......
        return true;
    }

5.ActivityThread.ApplicationThread#bindApplication

该方法最后会发送一个BIND_APPLICATION的消息。

        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, AutofillOptions autofillOptions,
                ContentCaptureOptions contentCaptureOptions,
                long[] disabledCompatChanges) {
            ......

            setCoreSettings(coreSettings);

            AppBindData data = new AppBindData();
            data.processName = processName;
            data.appInfo = appInfo;
            data.providers = providers;
            data.instrumentationName = instrumentationName;
            data.instrumentationArgs = instrumentationArgs;
            data.instrumentationWatcher = instrumentationWatcher;
            data.instrumentationUiAutomationConnection = instrumentationUiConnection;
            data.debugMode = debugMode;
            data.enableBinderTracking = enableBinderTracking;
            data.trackAllocation = trackAllocation;
            data.restrictedBackupMode = isRestrictedBackupMode;
            data.persistent = persistent;
            data.config = config;
            data.compatInfo = compatInfo;
            data.initProfilerInfo = profilerInfo;
            data.buildSerial = buildSerial;
            data.disabledCompatChanges = disabledCompatChanges;
            sendMessage(H.BIND_APPLICATION, data);
        }

6.ActivityThread#handleMessage

        public void handleMessage(Message msg) {
            if (DEBUG_MESSAGES) Slog.v(TAG, ">>> handling: " + codeToString(msg.what));
            switch (msg.what) {
                case BIND_APPLICATION:
                    Trace.traceBegin(Trace.TRACE_TAG_ACTIVITY_MANAGER, "bindApplication");
                    AppBindData data = (AppBindData)msg.obj;
                    // 关键方法
                    handleBindApplication(data);
                    Trace.traceEnd(Trace.TRACE_TAG_ACTIVITY_MANAGER);
                    break;
                 ......
            }
         }

7.ActivityThread#handleBindApplication

注释1的地方是通过makeApplication()方法创建Application对象；

注释2的地方是调用installContentProviders()方法，启动当前进程的ContentProvider，并通过installProvider()->attachInfo()最终会调用到ContentProvider的onCreate()方法；

注释3的地方是调用callApplicationOnCreate()方法，最终调用Application的onCreate()方法；

    @UnsupportedAppUsage
    private void handleBindApplication(AppBindData data) {
        ......
        try {
            // If the app is being launched for full backup or restore, bring it up in
            // a restricted environment with the base application class.
            // 1
            app = data.info.makeApplication(data.restrictedBackupMode, null);

            // Propagate autofill compat state
            app.setAutofillOptions(data.autofillOptions);

            // Propagate Content Capture options
            app.setContentCaptureOptions(data.contentCaptureOptions);

            mInitialApplication = app;
            // don't bring up providers in restricted mode; they may depend on the
            // app's custom Application class
            if (!data.restrictedBackupMode) {
                if (!ArrayUtils.isEmpty(data.providers)) {
                    // 2
                    installContentProviders(app, data.providers);
                }
            }

            // Do this after providers, since instrumentation tests generally start their
            // test thread at this point, and we don't want that racing.
            try {
                mInstrumentation.onCreate(data.instrumentationArgs);
            }
            catch (Exception e) {
                throw new RuntimeException(
                    "Exception thrown in onCreate() of "
                    + data.instrumentationName + ": " + e.toString(), e);
            }
            try {
                // 3
                mInstrumentation.callApplicationOnCreate(app);
            } catch (Exception e) {
                if (!mInstrumentation.onException(app, e)) {
                    throw new RuntimeException(
                      "Unable to create application " + app.getClass().getName()
                      + ": " + e.toString(), e);
                }
            }
        } finally {
            // If the app targets < O-MR1, or doesn't change the thread policy
            // during startup, clobber the policy to maintain behavior of b/36951662
            if (data.appInfo.targetSdkVersion < Build.VERSION_CODES.O_MR1
                    || StrictMode.getThreadPolicy().equals(writesAllowedPolicy)) {
                StrictMode.setThreadPolicy(savedPolicy);
            }
        }

        // Preload fonts resources
        FontsContract.setApplicationContextForResources(appContext);
        if (!Process.isIsolated()) {
            try {
                final ApplicationInfo info =
                        getPackageManager().getApplicationInfo(
                                data.appInfo.packageName,
                                PackageManager.GET_META_DATA /*flags*/,
                                UserHandle.myUserId());
                if (info.metaData != null) {
                    final int preloadedFontsResource = info.metaData.getInt(
                            ApplicationInfo.METADATA_PRELOADED_FONTS, 0);
                    if (preloadedFontsResource != 0) {
                        data.info.getResources().preloadFonts(preloadedFontsResource);
                    }
                }
            } catch (RemoteException e) {
                throw e.rethrowFromSystemServer();
            }
        }
    }

二.小结

这个流程比较简单，这里我们就直接附上上述代码的流程图：

来源：CSDN

作者：adroid_newbie

链接：https://blog.csdn.net/zplxl99/article/details/104416049