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上文再次调用了

一：再次回到本地

  mClient.scheduleTransaction(this);

这里和之前的逻辑一样，只是这次这里

public void execute(ClientTransaction transaction) {        final IBinder token = transaction.getActivityToken();        log("Start resolving transaction for client: " + mTransactionHandler + ", token: " + token);        executeCallbacks(transaction);        executeLifecycleState(transaction);        mPendingActions.clear();        log("End resolving transaction");    }

这次callBack里有东西了

看下executeCallbacks方法

/** Cycle through all states requested by callbacks and execute them at proper times. */    @VisibleForTesting    public void executeCallbacks(ClientTransaction transaction) {        final List
   
     callbacks = transaction.getCallbacks();        if (callbacks == null) {            // No callbacks to execute, return early.            return;        }        log("Resolving callbacks");        final IBinder token = transaction.getActivityToken();        ActivityClientRecord r = mTransactionHandler.getActivityClient(token);        // In case when post-execution state of the last callback matches the final state requested        // for the activity in this transaction, we won't do the last transition here and do it when        // moving to final state instead (because it may contain additional parameters from server).        final ActivityLifecycleItem finalStateRequest = transaction.getLifecycleStateRequest();        final int finalState = finalStateRequest != null ? finalStateRequest.getTargetState()                : UNDEFINED;        // Index of the last callback that requests some post-execution state.        final int lastCallbackRequestingState = lastCallbackRequestingState(transaction);        final int size = callbacks.size();        for (int i = 0; i < size; ++i) {            final ClientTransactionItem item = callbacks.get(i);            log("Resolving callback: " + item);            final int postExecutionState = item.getPostExecutionState();            final int closestPreExecutionState = mHelper.getClosestPreExecutionState(r,                    item.getPostExecutionState());            if (closestPreExecutionState != UNDEFINED) {                cycleToPath(r, closestPreExecutionState);            }            item.execute(mTransactionHandler, token, mPendingActions);            item.postExecute(mTransactionHandler, token, mPendingActions);            if (r == null) {                // Launch activity request will create an activity record.                r = mTransactionHandler.getActivityClient(token);            }            if (postExecutionState != UNDEFINED && r != null) {                // Skip the very last transition and perform it by explicit state request instead.                final boolean shouldExcludeLastTransition =                        i == lastCallbackRequestingState && finalState == postExecutionState;                cycleToPath(r, postExecutionState, shouldExcludeLastTransition);            }        }    }
   

我们在前面知道这里放了一个 LaunchActivityItem 所以

二 LaunchActivityItem类

看下LauncherActivityItem类的execute方法

@Override    public void execute(ClientTransactionHandler client, IBinder token,            PendingTransactionActions pendingActions) {        Trace.traceBegin(TRACE_TAG_ACTIVITY_MANAGER, "activityStart");        ActivityClientRecord r = new ActivityClientRecord(token, mIntent, mIdent, mInfo,                mOverrideConfig, mCompatInfo, mReferrer, mVoiceInteractor, mState, mPersistentState,                mPendingResults, mPendingNewIntents, mIsForward,                mProfilerInfo, client);        client.handleLaunchActivity(r, pendingActions, null /* customIntent */);        Trace.traceEnd(TRACE_TAG_ACTIVITY_MANAGER);    }

在这里终于handleLaunchActivity 了，注意，这里的ClientTransactionHandler其实是ActivityThread

三 handleLauncherActivity

看下handleLauncherActivity方法

/**     * Extended implementation of activity launch. Used when server requests a launch or relaunch.     */    @Override    public Activity handleLaunchActivity(ActivityClientRecord r,            PendingTransactionActions pendingActions, Intent customIntent) {        // If we are getting ready to gc after going to the background, well        // we are back active so skip it.        unscheduleGcIdler();        mSomeActivitiesChanged = true;        if (r.profilerInfo != null) {            mProfiler.setProfiler(r.profilerInfo);            mProfiler.startProfiling();        }        // Make sure we are running with the most recent config.        handleConfigurationChanged(null, null);        if (localLOGV) Slog.v(            TAG, "Handling launch of " + r);        // Initialize before creating the activity        if (!ThreadedRenderer.sRendererDisabled) {            GraphicsEnvironment.earlyInitEGL();        }        WindowManagerGlobal.initialize();        final Activity a = performLaunchActivity(r, customIntent);        if (a != null) {            r.createdConfig = new Configuration(mConfiguration);            reportSizeConfigurations(r);            if (!r.activity.mFinished && pendingActions != null) {                pendingActions.setOldState(r.state);                pendingActions.setRestoreInstanceState(true);                pendingActions.setCallOnPostCreate(true);            }        } else {            // If there was an error, for any reason, tell the activity manager to stop us.            try {                ActivityManager.getService()                        .finishActivity(r.token, Activity.RESULT_CANCELED, null,                                Activity.DONT_FINISH_TASK_WITH_ACTIVITY);            } catch (RemoteException ex) {                throw ex.rethrowFromSystemServer();            }        }        return a;    }

这里有个注意点：在api27及之前，调用的是scheduleLaunchActivity  到28之后，这个方法找不到了，

换成了handleLaunchActivity

handleLaunchActivity可以说是activity启动的本地操作真正的入口了，下文将会以这个方法为起点继续探索activity启动过程

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