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AMS和ActivityThread 通信 appToken ApplicationThread等

2016-09-07

在之前的博客中对应用启动流程都做了分析,这篇博客主要是一个补充的作用,说下ActivityThread和AMS的通信,以及ActivityClientRecord ApplicationThread AppToken等说明。

在之前的博客中对应用启动流程都做了分析,这篇博客主要是一个补充的作用,说下ActivityThread和AMS的通信,以及ActivityClientRecord ApplicationThread AppToken等说明。

AMS启动Activity 、新建ActivityRecord

我们还是从一个Activity启动另一个Activity为切入点说起,startActivity最终会调用ActivityStackSupervisor的startActivityLocked函数,会新建一个ActivityRecord对象。

        ActivityRecord r = new ActivityRecord(mService, callerApp, callingUid, callingPackage,
                intent, resolvedType, aInfo, mService.mConfiguration, resultRecord, resultWho,
                requestCode, componentSpecified, voiceSession != null, this, container, options);

我们先来看看ActivityRecord对象,在构造函数中会新建一个Token对象,作为自己的appToken成员变量。

    ActivityRecord(ActivityManagerService _service, ProcessRecord _caller,
            int _launchedFromUid, String _launchedFromPackage, Intent _intent, String _resolvedType,
            ActivityInfo aInfo, Configuration _configuration,
            ActivityRecord _resultTo, String _resultWho, int _reqCode,
            boolean _componentSpecified, boolean _rootVoiceInteraction,
            ActivityStackSupervisor supervisor,
            ActivityContainer container, Bundle options) {
        service = _service;
        appToken = new Token(this, service);

我们再来看看Token对象是一个Binder服务,但是这个appToken一般只作为一个唯一标识使用。

    static class Token extends IApplicationToken.Stub {
        private final WeakReference weakActivity;
        private final ActivityManagerService mService;

        Token(ActivityRecord activity, ActivityManagerService service) {
            weakActivity = new WeakReference<>(activity);
            mService = service;
        }

继续到ActivityStack的startActivityLocked函数,这个函数主要把ActivityRecord保存在mTaskHistory中的TaskRecord中。后面还会调用mWindowManager.addAppToken在WMS创建AppWindowToken。

    final void startActivityLocked(ActivityRecord r, boolean newTask,
            boolean doResume, boolean keepCurTransition, Bundle options) {
        TaskRecord rTask = r.task;
        final int taskId = rTask.taskId;
        if (!r.mLaunchTaskBehind && (taskForIdLocked(taskId) == null || newTask)) {
            // Last activity in task had been removed or ActivityManagerService is reusing task.
            // Insert or replace.
            // Might not even be in.
            insertTaskAtTop(rTask, r);
            mWindowManager.moveTaskToTop(taskId);
        }
        TaskRecord task = null;
        if (!newTask) {
            // If starting in an existing task, find where that is...
            boolean startIt = true;
            for (int taskNdx = mTaskHistory.size() - 1; taskNdx >= 0; --taskNdx) {
                task = mTaskHistory.get(taskNdx);
                if (task.getTopActivity() == null) {
                    // All activities in task are finishing.
                    continue;
                }
                if (task == r.task) {
                    // Here it is!  Now, if this is not yet visible to the
                    // user, then just add it without starting; it will
                    // get started when the user navigates back to it.
                    if (!startIt) {
                        if (DEBUG_ADD_REMOVE) Slog.i(TAG, "Adding activity " + r + " to task "
                                + task, new RuntimeException("here").fillInStackTrace());
                        task.addActivityToTop(r);
        ......
         mWindowManager.addAppToken(task.mActivities.indexOf(r),
                    r.appToken, r.task.taskId, mStackId, r.info.screenOrientation, r.fullscreen,
                    (r.info.flags & ActivityInfo.FLAG_SHOW_FOR_ALL_USERS) != 0, r.userId,
                    r.info.configChanges, task.voiceSession != null, r.mLaunchTaskBehind);

继续我们到ActivityStack的resumeTopActivityInnerLocked函数,看下面代码,只要相关ActivityThread的app和appThread不为null,说明已经开启过进程然后ActivityThread到AMS了,所以才会保存这个对象。后面我们会分析到。然后调用next.app.thread.scheduleResumeActivity到ActivityThread的scheduleResumeActivity函数。而当进程没有开启,就会调用mStackSupervisor.startSpecificActivityLocked函数开启进程。

        if (next.app != null && next.app.thread != null) {
            if (DEBUG_SWITCH) Slog.v(TAG_SWITCH, "Resume running: " + next);

            // This activity is now becoming visible.
            mWindowManager.setAppVisibility(next.appToken, true);

            // schedule launch ticks to collect information about slow apps.
            next.startLaunchTickingLocked();

            ActivityRecord lastResumedActivity =
                    lastStack == null ? null :lastStack.mResumedActivity;
            ActivityState lastState = next.state;

            mService.updateCpuStats();

            if (DEBUG_STATES) Slog.v(TAG_STATES, "Moving to RESUMED: " + next + " (in existing)");
            next.state = ActivityState.RESUMED;
            mResumedActivity = next;
            next.task.touchActiveTime();
            mRecentTasks.addLocked(next.task);
            mService.updateLruProcessLocked(next.app, true, null);
            updateLRUListLocked(next);
            mService.updateOomAdjLocked();

            // Have the window manager re-evaluate the orientation of
            // the screen based on the new activity order.
            boolean notUpdated = true;
            if (mStackSupervisor.isFrontStack(this)) {
                Configuration config = mWindowManager.updateOrientationFromAppTokens(
                        mService.mConfiguration,
                        next.mayFreezeScreenLocked(next.app) ? next.appToken : null);
                if (config != null) {
                    next.frozenBeforeDestroy = true;
                }
                notUpdated = !mService.updateConfigurationLocked(config, next, false, false);
            }

            if (notUpdated) {
                // The configuration update wasn&#39;t able to keep the existing
                // instance of the activity, and instead started a new one.
                // We should be all done, but let&#39;s just make sure our activity
                // is still at the top and schedule another run if something
                // weird happened.
                ActivityRecord nextNext = topRunningActivityLocked(null);
                if (DEBUG_SWITCH || DEBUG_STATES) Slog.i(TAG_STATES,
                        "Activity config changed during resume: " + next
                        + ", new next: " + nextNext);
                if (nextNext != next) {
                    // Do over!
                    mStackSupervisor.scheduleResumeTopActivities();
                }
                if (mStackSupervisor.reportResumedActivityLocked(next)) {
                    mNoAnimActivities.clear();
                    if (DEBUG_STACK) mStackSupervisor.validateTopActivitiesLocked();
                    return true;
                }
                if (DEBUG_STACK) mStackSupervisor.validateTopActivitiesLocked();
                return false;
            }

            try {
                // Deliver all pending results.
                ArrayList a = next.results;
                if (a != null) {
                    final int N = a.size();
                    if (!next.finishing && N > 0) {
                        if (DEBUG_RESULTS) Slog.v(TAG_RESULTS,
                                "Delivering results to " + next + ": " + a);
                        next.app.thread.scheduleSendResult(next.appToken, a);
                    }
                }

                if (next.newIntents != null) {
                    next.app.thread.scheduleNewIntent(next.newIntents, next.appToken);
                }

                EventLog.writeEvent(EventLogTags.AM_RESUME_ACTIVITY, next.userId,
                        System.identityHashCode(next), next.task.taskId, next.shortComponentName);

                next.sleeping = false;
                mService.showAskCompatModeDialogLocked(next);
                next.app.pendingUiClean = true;
                next.app.forceProcessStateUpTo(mService.mTopProcessState);
                next.clearOptionsLocked();
                next.app.thread.scheduleResumeActivity(next.appToken, next.app.repProcState,
                        mService.isNextTransitionForward(), resumeAnimOptions);

                mStackSupervisor.checkReadyForSleepLocked();

                if (DEBUG_STATES) Slog.d(TAG_STATES, "resumeTopActivityLocked: Resumed " + next);
            } catch (Exception e) {
                // Whoops, need to restart this activity!
                if (DEBUG_STATES) Slog.v(TAG_STATES, "Resume failed; resetting state to "
                        + lastState + ": " + next);
                next.state = lastState;
                if (lastStack != null) {
                    lastStack.mResumedActivity = lastResumedActivity;
                }
                Slog.i(TAG, "Restarting because process died: " + next);
                if (!next.hasBeenLaunched) {
                    next.hasBeenLaunched = true;
                } else  if (SHOW_APP_STARTING_PREVIEW && lastStack != null &&
                        mStackSupervisor.isFrontStack(lastStack)) {
                    mWindowManager.setAppStartingWindow(
                            next.appToken, next.packageName, next.theme,
                            mService.compatibilityInfoForPackageLocked(next.info.applicationInfo),
                            next.nonLocalizedLabel, next.labelRes, next.icon, next.logo,
                            next.windowFlags, null, true);
                }
                mStackSupervisor.startSpecificActivityLocked(next, true, false);
                if (DEBUG_STACK) mStackSupervisor.validateTopActivitiesLocked();
                return true;
            }

            // From this point on, if something goes wrong there is no way
            // to recover the activity.
            try {
                next.visible = true;
                completeResumeLocked(next);
            } catch (Exception e) {
                // If any exception gets thrown, toss away this
                // activity and try the next one.
                Slog.w(TAG, "Exception thrown during resume of " + next, e);
                requestFinishActivityLocked(next.appToken, Activity.RESULT_CANCELED, null,
                        "resume-exception", true);
                if (DEBUG_STACK) mStackSupervisor.validateTopActivitiesLocked();
                return true;
            }
            next.stopped = false;

        } else {
            EventLog.writeEvent(EventLogTags.AM_RESUME_ACTIVITY, "ActivityStack resumeTopActivityInnerLock startSpecificActivityLocked fork process");
            // Whoops, need to restart this activity!
            if (!next.hasBeenLaunched) {
                next.hasBeenLaunched = true;
            } else {
                if (SHOW_APP_STARTING_PREVIEW) {
                    mWindowManager.setAppStartingWindow(
                            next.appToken, next.packageName, next.theme,
                            mService.compatibilityInfoForPackageLocked(
                                    next.info.applicationInfo),
                            next.nonLocalizedLabel,
                            next.labelRes, next.icon, next.logo, next.windowFlags,
                            null, true);
                }
                if (DEBUG_SWITCH) Slog.v(TAG_SWITCH, "Restarting: " + next);
            }
            if (DEBUG_STATES) Slog.d(TAG_STATES, "resumeTopActivityLocked: Restarting " + next);
            mStackSupervisor.startSpecificActivityLocked(next, true, true);
        }

我们来看下ActivityStackSupervisor.startSpecificActivityLocked函数,如果进程没有会调用AMS的startProcessLocked函数,在这个函数会新建一个ProcessRecord对象保存进程信息,然后调用Process类的start来启动进程。

    void startSpecificActivityLocked(ActivityRecord r,
            boolean andResume, boolean checkConfig) {
        // Is this activity&#39;s application already running?
        ProcessRecord app = mService.getProcessRecordLocked(r.processName,
                r.info.applicationInfo.uid, true);

        r.task.stack.setLaunchTime(r);

        if (app != null && app.thread != null) {
            try {
                if ((r.info.flags&ActivityInfo.FLAG_MULTIPROCESS) == 0
                        || !"android".equals(r.info.packageName)) {
                    // Don&#39;t add this if it is a platform component that is marked
                    // to run in multiple processes, because this is actually
                    // part of the framework so doesn&#39;t make sense to track as a
                    // separate apk in the process.
                    app.addPackage(r.info.packageName, r.info.applicationInfo.versionCode,
                            mService.mProcessStats);
                }
                realStartActivityLocked(r, app, andResume, checkConfig);
                return;
            } catch (RemoteException e) {
                Slog.w(TAG, "Exception when starting activity "
                        + r.intent.getComponent().flattenToShortString(), e);
            }

            // If a dead object exception was thrown -- fall through to
            // restart the application.
        }

        mService.startProcessLocked(r.processName, r.info.applicationInfo, true, 0,
                "activity", r.intent.getComponent(), false, false, true);
    }

应用进程启动、 ActivityThread新建

进程开启后就直接到ActivityThread的main方法,主要是下面代码我们来看下,新建了一个ActivityThread,然后调用其attach方法,参数为false,代表是应用进程。

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

在attach函数中主要是调用了AMS的attachApplication,把名mAppthread传过去了。

    private void attach(boolean system) {
        sCurrentActivityThread = this;
        mSystemThread = system;
        if (!system) {
            ViewRootImpl.addFirstDrawHandler(new Runnable() {
                @Override
                public void run() {
                    ensureJitEnabled();
                }
            });
            android.ddm.DdmHandleAppName.setAppName("",
                                                    UserHandle.myUserId());
            RuntimeInit.setApplicationObject(mAppThread.asBinder());
            final IActivityManager mgr = ActivityManagerNative.getDefault();
            try {
                mgr.attachApplication(mAppThread);
            } catch (RemoteException ex) {
                // Ignore
            }

ApplicationThread类

mAppThread在ActivityThread构造的时候就创建了,我们来看下这个类:

final ApplicationThread mAppThread = new ApplicationThread();

其继承与ApplicationThreadNative类,我们来看下这个父类:

private class ApplicationThread extends ApplicationThreadNative

ApplicationThreadNative类就是典型的Binder服务类,只是这里直接写的而没用aidl那种机制。

public abstract class ApplicationThreadNative extends Binder
        implements IApplicationThread {
    /**
     * Cast a Binder object into an application thread interface, generating
     * a proxy if needed.
     */
    static public IApplicationThread asInterface(IBinder obj) {
        if (obj == null) {
            return null;
        }
        IApplicationThread in =
            (IApplicationThread)obj.queryLocalInterface(descriptor);
        if (in != null) {
            return in;
        }
        
        return new ApplicationThreadProxy(obj);
    }
    
    public ApplicationThreadNative() {
        attachInterface(this, descriptor);
    }
    
    @Override
    public boolean onTransact(int code, Parcel data, Parcel reply, int flags)
            throws RemoteException {
        switch (code) {
        case SCHEDULE_PAUSE_ACTIVITY_TRANSACTION:
        {
            data.enforceInterface(IApplicationThread.descriptor);
            IBinder b = data.readStrongBinder();
            boolean finished = data.readInt() != 0;
            boolean userLeaving = data.readInt() != 0;
            int configChanges = data.readInt();
            boolean dontReport = data.readInt() != 0;
            schedulePauseActivity(b, finished, userLeaving, configChanges, dontReport);
            return true;
        }

        ......
        }

        return super.onTransact(code, data, reply, flags);
    }

    public IBinder asBinder()
    {
        return this;
    }
}

class ApplicationThreadProxy implements IApplicationThread {
    private final IBinder mRemote;
    
    public ApplicationThreadProxy(IBinder remote) {
        mRemote = remote;
    }
    
    public final IBinder asBinder() {
        return mRemote;
    }
    
    public final void schedulePauseActivity(IBinder token, boolean finished,
            boolean userLeaving, int configChanges, boolean dontReport) throws RemoteException {
        Parcel data = Parcel.obtain();
        data.writeInterfaceToken(IApplicationThread.descriptor);
        data.writeStrongBinder(token);
        data.writeInt(finished ? 1 : 0);
        data.writeInt(userLeaving ? 1 :0);
        data.writeInt(configChanges);
        data.writeInt(dontReport ? 1 : 0);
        mRemote.transact(SCHEDULE_PAUSE_ACTIVITY_TRANSACTION, data, null,
                IBinder.FLAG_ONEWAY);
        data.recycle();
    }
而在ApplicationThread 类中只是对各个接口的实现。

    private class ApplicationThread extends ApplicationThreadNative {
        private static final String DB_INFO_FORMAT = "  %8s %8s %14s %14s  %s";

        private int mLastProcessState = -1;

        private void updatePendingConfiguration(Configuration config) {
            synchronized (mResourcesManager) {
                if (mPendingConfiguration == null ||
                        mPendingConfiguration.isOtherSeqNewer(config)) {
                    mPendingConfiguration = config;
                }
            }
        }

        public final void schedulePauseActivity(IBinder token, boolean finished,
                boolean userLeaving, int configChanges, boolean dontReport) {
            sendMessage(
                    finished ? H.PAUSE_ACTIVITY_FINISHING : H.PAUSE_ACTIVITY,
                    token,
                    (userLeaving ? 1 : 0) | (dontReport ? 2 : 0),
                    configChanges);
        }

AMS的attachApplication方法

我们先来看AMS的attachApplication中有下面这么一句,这句话就把IAPPlicationThread保存在ProcessRecord的thread中。这里app对象是ProcessRecord对象。

        app.makeActive(thread, mProcessStats);

我们继续看AMS的attachApplication函数中先会利用刚才从ActivityThread传过来的IApplicationThread的Binder服务反调bindApplication接口,来完成应用进程的一些初始化。

            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());

随后会继续调用mStackSupervisor.attachApplicationLocked函数,继续开启Activity

        if (normalMode) {
            try {
                if (mStackSupervisor.attachApplicationLocked(app)) {
                    didSomething = true;
                }
            } catch (Exception e) {
                Slog.wtf(TAG, "Exception thrown launching activities in " + app, e);
                badApp = true;
            }
        }

在ActivityStackSupervisor中会得到当前启动的ActivityRecord,然后调用realStartActivityLocked函数继续启动Activity。

    boolean attachApplicationLocked(ProcessRecord app) throws RemoteException {
        final String processName = app.processName;
        boolean didSomething = false;
        for (int displayNdx = mActivityDisplays.size() - 1; displayNdx >= 0; --displayNdx) {
            ArrayList stacks = mActivityDisplays.valueAt(displayNdx).mStacks;
            for (int stackNdx = stacks.size() - 1; stackNdx >= 0; --stackNdx) {
                final ActivityStack stack = stacks.get(stackNdx);
                if (!isFrontStack(stack)) {
                    continue;
                }
                ActivityRecord hr = stack.topRunningActivityLocked(null);
                if (hr != null) {
                    if (hr.app == null && app.uid == hr.info.applicationInfo.uid
                            && processName.equals(hr.processName)) {
                        try {
                            if (realStartActivityLocked(hr, app, true, true)) {
                                didSomething = true;
                            }
                        } catch (RemoteException e) {
                            Slog.w(TAG, "Exception in new application when starting activity "
                                  + hr.intent.getComponent().flattenToShortString(), e);
                            throw e;
                        }
                    }
                }
            }
        }

而在realStartActivityLocked,会把ProcessRecord对象保存在ActivityRecord中的app中。所以在AMS启动Activity时候,看这个Activity的进程有没有启动就是看ActivityRecord的app和app.thread是否为null。而这个函数最后会通过app.thread也就是IAPplicationThread调用ThreadActivity的scheduleLaunchActivity函数。

    final boolean realStartActivityLocked(ActivityRecord r,
            ProcessRecord app, boolean andResume, boolean checkConfig)
            throws RemoteException {

        if (andResume) {
            r.startFreezingScreenLocked(app, 0);
            mWindowManager.setAppVisibility(r.appToken, true);

            // schedule launch ticks to collect information about slow apps.
            r.startLaunchTickingLocked();
        }

        // Have the window manager re-evaluate the orientation of
        // the screen based on the new activity order.  Note that
        // as a result of this, it can call back into the activity
        // manager with a new orientation.  We don&#39;t care about that,
        // because the activity is not currently running so we are
        // just restarting it anyway.
        if (checkConfig) {
            Configuration config = mWindowManager.updateOrientationFromAppTokens(
                    mService.mConfiguration,
                    r.mayFreezeScreenLocked(app) ? r.appToken : null);
            mService.updateConfigurationLocked(config, r, false, false);
        }

        r.app = app;

ActivityThread 启动Activity

而我们再来看ActivityThread的scheduleLaunchActivity函数,会创建一个ActivityClientRecord 对象,注意这里的token就是AMS的ActivityRecord中的appToken对象,来保证每个Activity的唯一性。继续发送消息。

        @Override
        public final void scheduleLaunchActivity(Intent intent, IBinder token, int ident,
                ActivityInfo info, Configuration curConfig, Configuration overrideConfig,
                CompatibilityInfo compatInfo, String referrer, IVoiceInteractor voiceInteractor,
                int procState, Bundle state, PersistableBundle persistentState,
                List pendingResults, List pendingNewIntents,
                boolean notResumed, boolean isForward, ProfilerInfo profilerInfo) {

            updateProcessState(procState, false);

            ActivityClientRecord r = new ActivityClientRecord();

            r.token = token;
            r.ident = ident;
            r.intent = intent;
            r.referrer = referrer;
            r.voiceInteractor = voiceInteractor;
            r.activityInfo = info;
            r.compatInfo = compatInfo;
            r.state = state;
            r.persistentState = persistentState;

            r.pendingResults = pendingResults;
            r.pendingIntents = pendingNewIntents;

            r.startsNotResumed = notResumed;
            r.isForward = isForward;

            r.profilerInfo = profilerInfo;

            r.overrideConfig = overrideConfig;
            updatePendingConfiguration(curConfig);

            sendMessage(H.LAUNCH_ACTIVITY, r);
        }

然后在handleLaunchActivity函数中调用performLaunchActivity函数,在performLaunchActivity函数中完成新建Activity,调用Activity的attach方法,以及将ActivityClientRecord放入mActivities中。

    private Activity performLaunchActivity(ActivityClientRecord r, Intent customIntent) {
        ......

        Activity activity = null;
        try {
            java.lang.ClassLoader cl = r.packageInfo.getClassLoader();
            activity = mInstrumentation.newActivity(//新建Activity
                    cl, component.getClassName(), r.intent);
            StrictMode.incrementExpectedActivityCount(activity.getClass());
            r.intent.setExtrasClassLoader(cl);
            r.intent.prepareToEnterProcess();
            if (r.state != null) {
                r.state.setClassLoader(cl);
            }
        } catch (Exception e) {
            if (!mInstrumentation.onException(activity, e)) {
                throw new RuntimeException(
                    "Unable to instantiate activity " + component
                    + ": " + e.toString(), e);
            }
        }

        try {
            Application app = r.packageInfo.makeApplication(false, mInstrumentation);

            if (localLOGV) Slog.v(TAG, "Performing launch of " + r);
            if (localLOGV) Slog.v(
                    TAG, r + ": app=" + app
                    + ", appName=" + app.getPackageName()
                    + ", pkg=" + r.packageInfo.getPackageName()
                    + ", comp=" + r.intent.getComponent().toShortString()
                    + ", dir=" + r.packageInfo.getAppDir());

            if (activity != null) {
                Context appContext = createBaseContextForActivity(r, activity);
                CharSequence title = r.activityInfo.loadLabel(appContext.getPackageManager());
                Configuration config = new Configuration(mCompatConfiguration);
                if (DEBUG_CONFIGURATION) Slog.v(TAG, "Launching activity "
                        + r.activityInfo.name + " with config " + config);
                activity.attach(appContext, this, getInstrumentation(), r.token,//调用Activity的attach方法
                        r.ident, app, r.intent, r.activityInfo, title, r.parent,
                        r.embeddedID, r.lastNonConfigurationInstances, config,
                        r.referrer, r.voiceInteractor);

                if (customIntent != null) {
                    activity.mIntent = customIntent;
                }
                r.lastNonConfigurationInstances = null;
                activity.mStartedActivity = false;
                int theme = r.activityInfo.getThemeResource();
                if (theme != 0) {
                    activity.setTheme(theme);
                }

                activity.mCalled = false;
                if (r.isPersistable()) {
                    mInstrumentation.callActivityOnCreate(activity, r.state, r.persistentState);
                } else {
                    mInstrumentation.callActivityOnCreate(activity, r.state);//调用Activity的onCreate方法
                }
            ......

            mActivities.put(r.token, r);//放入mActivities中

        }
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