ActivityThread简单分析,基于Android6.0

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("");

    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");
}

ActivityThread的main方法

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

这个方法里new 了一个自己的对象,回调了自己的attach方法,接下来我们看看attach方法

private void attach(boolean system) {
    sCurrentActivityThread = this;
    mSystemThread = system;
    if (!system) {
    //如果不是系统进程,也就是第一次运行
        ViewRootImpl.addFirstDrawHandler(new Runnable() {
            @Override
            public void run() {
            //第一次确认开启jit
                ensureJitEnabled();
            }
        });
        android.ddm.DdmHandleAppName.setAppName("",
                                                UserHandle.myUserId());
        RuntimeInit.setApplicationObject(mAppThread.asBinder());
        //这里获取的是Ams对象
        //  static public IActivityManager getDefault() {
        //return gDefault.get();
        //  }
        //getDefault()方法返回的是IActivityManager。
        //IActivityManager是一个接口,具体实现类是
        //public final class ActivityManagerService extends 
        //ActivityManagerNative
        //implements Watchdog.Monitor, 
        //BatteryStatsImpl.BatteryCallback
        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) {
                    }
                }
            }
        });
    } else {
        // Don't set application object here -- if the system crashes,
        // we can't display an alert, we just want to die die die.
        android.ddm.DdmHandleAppName.setAppName("system_process",
                UserHandle.myUserId());
        try {
            mInstrumentation = new Instrumentation();
            ContextImpl context = ContextImpl.createAppContext(
                    this, getSystemContext().mPackageInfo);
            mInitialApplication = context.mPackageInfo.makeApplication(true, null);
            mInitialApplication.onCreate();
        } catch (Exception e) {
            throw new RuntimeException(
                    "Unable to instantiate Application():" + e.toString(), e);
        }
    }

    // add dropbox logging to libcore
    DropBox.setReporter(new DropBoxReporter());

    ViewRootImpl.addConfigCallback(new ComponentCallbacks2() {
        @Override
        public void onConfigurationChanged(Configuration newConfig) {
            synchronized (mResourcesManager) {
                // We need to apply this change to the resources
                // immediately, because upon returning the view
                // hierarchy will be informed about it.
                if (mResourcesManager.applyConfigurationToResourcesLocked(newConfig, null)) {
                    // This actually changed the resources!  Tell
                    // everyone about it.
                    if (mPendingConfiguration == null ||
                            mPendingConfiguration.isOtherSeqNewer(newConfig)) {
                        mPendingConfiguration = newConfig;

                        sendMessage(H.CONFIGURATION_CHANGED, newConfig);
                    }
                }
            }
        }
        @Override
        public void onLowMemory() {
        }
        @Override
        public void onTrimMemory(int level) {
        }
    });
}

​ //首先

​ //这里获取的是Ams对象
​ // static public IActivityManager getDefault() {
​ //return gDefault.get();
​ // }
​ //getDefault()方法返回的是IActivityManager。
​ //IActivityManager是一个接口,具体实现类是
​ //public final class ActivityManagerService extends
​ //ActivityManagerNative
​ //implements Watchdog.Monitor,
​ //BatteryStatsImpl.BatteryCallback
​ final IActivityManager mgr = ActivityManagerNative.getDefault();

接下来调用了attachApplication,具体实现方法在Ams里

@Override
public final void attachApplication(IApplicationThread thread) {
    synchronized (this) {
        int callingPid = Binder.getCallingPid();
        final long origId = Binder.clearCallingIdentity();
        attachApplicationLocked(thread, callingPid);
        Binder.restoreCallingIdentity(origId);
    }
}

这里转给了attachApplicationLocked() 方法

private final boolean attachApplicationLocked(IApplicationThread thread,
        int pid) {

    // Find the application record that is being attached...  either via
    // the pid if we are running in multiple processes, or just pull the
    // next app record if we are emulating process with anonymous threads.
    ProcessRecord app;
    if (pid != MY_PID && pid >= 0) {
        synchronized (mPidsSelfLocked) {
            app = mPidsSelfLocked.get(pid);
        }
    } else {
        app = null;
    }

    if (app == null) {
        Slog.w(TAG, "No pending application record for pid " + pid
                + " (IApplicationThread " + thread + "); dropping process");
        EventLog.writeEvent(EventLogTags.AM_DROP_PROCESS, pid);
        if (pid > 0 && pid != MY_PID) {
            Process.killProcessQuiet(pid);
            //TODO: killProcessGroup(app.info.uid, pid);
        } else {
            try {
                thread.scheduleExit();
            } catch (Exception e) {
                // Ignore exceptions.
            }
        }
        return false;
    }

    // If this application record is still attached to a previous
    // process, clean it up now.
    if (app.thread != null) {
        handleAppDiedLocked(app, true, true);
    }

    // Tell the process all about itself.

    if (DEBUG_ALL) Slog.v(
            TAG, "Binding process pid " + pid + " to record " + app);

    final String processName = app.processName;
    try {
        AppDeathRecipient adr = new AppDeathRecipient(
                app, pid, thread);
        thread.asBinder().linkToDeath(adr, 0);
        app.deathRecipient = adr;
    } catch (RemoteException e) {
        app.resetPackageList(mProcessStats);
        startProcessLocked(app, "link fail", processName);
        return false;
    }

    EventLog.writeEvent(EventLogTags.AM_PROC_BOUND, app.userId, app.pid, app.processName);

    app.makeActive(thread, mProcessStats);
    app.curAdj = app.setAdj = -100;
    app.curSchedGroup = app.setSchedGroup = Process.THREAD_GROUP_DEFAULT;
    app.forcingToForeground = null;
    updateProcessForegroundLocked(app, false, false);
    app.hasShownUi = false;
    app.debugging = false;
    app.cached = false;
    app.killedByAm = false;

    mHandler.removeMessages(PROC_START_TIMEOUT_MSG, app);

    boolean normalMode = mProcessesReady || isAllowedWhileBooting(app.info);
    List providers = normalMode ? generateApplicationProvidersLocked(app) : null;

    if (!normalMode) {
        Slog.i(TAG, "Launching preboot mode app: " + app);
    }

    if (DEBUG_ALL) Slog.v(
        TAG, "New app record " + app
        + " thread=" + thread.asBinder() + " pid=" + pid);
    try {
        int testMode = IApplicationThread.DEBUG_OFF;
        if (mDebugApp != null && mDebugApp.equals(processName)) {
            testMode = mWaitForDebugger
                ? IApplicationThread.DEBUG_WAIT
                : IApplicationThread.DEBUG_ON;
            app.debugging = true;
            if (mDebugTransient) {
                mDebugApp = mOrigDebugApp;
                mWaitForDebugger = mOrigWaitForDebugger;
            }
        }
        String profileFile = app.instrumentationProfileFile;
        ParcelFileDescriptor profileFd = null;
        int samplingInterval = 0;
        boolean profileAutoStop = false;
        if (mProfileApp != null && mProfileApp.equals(processName)) {
            mProfileProc = app;
            profileFile = mProfileFile;
            profileFd = mProfileFd;
            samplingInterval = mSamplingInterval;
            profileAutoStop = mAutoStopProfiler;
        }
        boolean enableOpenGlTrace = false;
        if (mOpenGlTraceApp != null && mOpenGlTraceApp.equals(processName)) {
            enableOpenGlTrace = true;
            mOpenGlTraceApp = null;
        }

        // If the app is being launched for restore or full backup, set it up specially
        boolean isRestrictedBackupMode = false;
        if (mBackupTarget != null && mBackupAppName.equals(processName)) {
            isRestrictedBackupMode = (mBackupTarget.backupMode == BackupRecord.RESTORE)
                    || (mBackupTarget.backupMode == BackupRecord.RESTORE_FULL)
                    || (mBackupTarget.backupMode == BackupRecord.BACKUP_FULL);
        }

        ensurePackageDexOpt(app.instrumentationInfo != null
                ? app.instrumentationInfo.packageName
                : app.info.packageName);
        if (app.instrumentationClass != null) {
            ensurePackageDexOpt(app.instrumentationClass.getPackageName());
        }
        if (DEBUG_CONFIGURATION) Slog.v(TAG_CONFIGURATION, "Binding proc "
                + processName + " with config " + mConfiguration);
        ApplicationInfo appInfo = app.instrumentationInfo != null
                ? app.instrumentationInfo : app.info;
        app.compat = compatibilityInfoForPackageLocked(appInfo);
        if (profileFd != null) {
            profileFd = profileFd.dup();
        }
        ProfilerInfo profilerInfo = profileFile == null ? null
                : new ProfilerInfo(profileFile, profileFd, samplingInterval, profileAutoStop);
        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();
    } catch (Exception e) {
        // todo: Yikes!  What should we do?  For now we will try to
        // start another process, but that could easily get us in
        // an infinite loop of restarting processes...
        Slog.wtf(TAG, "Exception thrown during bind of " + app, e);

        app.resetPackageList(mProcessStats);
        app.unlinkDeathRecipient();
        startProcessLocked(app, "bind fail", processName);
        return false;
    }

    // Remove this record from the list of starting applications.
    mPersistentStartingProcesses.remove(app);
    if (DEBUG_PROCESSES && mProcessesOnHold.contains(app)) Slog.v(TAG_PROCESSES,
            "Attach application locked removing on hold: " + app);
    mProcessesOnHold.remove(app);

    boolean badApp = false;
    boolean didSomething = false;

    // See if the top visible activity is waiting to run in this process...
    if (normalMode) {
        try {
            if (mStackSupervisor.attachApplicationLocked(app)) {
                didSomething = true;
            }
        } catch (Exception e) {
            Slog.wtf(TAG, "Exception thrown launching activities in " + app, e);
            badApp = true;
        }
    }

    // Find any services that should be running in this process...
    if (!badApp) {
        try {
            didSomething |= mServices.attachApplicationLocked(app, processName);
        } catch (Exception e) {
            Slog.wtf(TAG, "Exception thrown starting services in " + app, e);
            badApp = true;
        }
    }

    // Check if a next-broadcast receiver is in this process...
    if (!badApp && isPendingBroadcastProcessLocked(pid)) {
        try {
            didSomething |= sendPendingBroadcastsLocked(app);
        } catch (Exception e) {
            // If the app died trying to launch the receiver we declare it 'bad'
            Slog.wtf(TAG, "Exception thrown dispatching broadcasts in " + app, e);
            badApp = true;
        }
    }

    // Check whether the next backup agent is in this process...
    if (!badApp && mBackupTarget != null && mBackupTarget.appInfo.uid == app.uid) {
        if (DEBUG_BACKUP) Slog.v(TAG_BACKUP,
                "New app is backup target, launching agent for " + app);
        ensurePackageDexOpt(mBackupTarget.appInfo.packageName);
        try {
            thread.scheduleCreateBackupAgent(mBackupTarget.appInfo,
                    compatibilityInfoForPackageLocked(mBackupTarget.appInfo),
                    mBackupTarget.backupMode);
        } catch (Exception e) {
            Slog.wtf(TAG, "Exception thrown creating backup agent in " + app, e);
            badApp = true;
        }
    }

    if (badApp) {
        app.kill("error during init", true);
        handleAppDiedLocked(app, false, true);
        return false;
    }

    if (!didSomething) {
        updateOomAdjLocked();
    }

    return true;
}

在这个方法中

boolean badApp = false;
boolean didSomething = false;

// See if the top visible activity is waiting to run in this process...
if (normalMode) {
    try {
        if (mStackSupervisor.attachApplicationLocked(app)) {
            didSomething = true;
        }
    } catch (Exception e) {
        Slog.wtf(TAG, "Exception thrown launching activities in " + app, e);
        badApp = true;
    }
}

// Find any services that should be running in this process...
if (!badApp) {
    try {
        didSomething |= mServices.attachApplicationLocked(app, processName);
    } catch (Exception e) {
        Slog.wtf(TAG, "Exception thrown starting services in " + app, e);
        badApp = true;
    }
}

正常模式下调用一个mStackSupervisor.attachApplicationLocked(app)

非正常模式下继续调用该方法mServices.attachApplicationLocked(app, processName);

接下来我们看看attachApplicationLocked(app)

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;
                    }
                }
            }
        }
    }
    if (!didSomething) {
        ensureActivitiesVisibleLocked(null, 0);
    }
    return didSomething;
}

这个方法里调用了realStartActivityLocked(),代码如下:

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'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;
    app.waitingToKill = null;
    r.launchCount++;
    r.lastLaunchTime = SystemClock.uptimeMillis();

    if (DEBUG_ALL) Slog.v(TAG, "Launching: " + r);

    int idx = app.activities.indexOf(r);
    if (idx < 0) {
        app.activities.add(r);
    }
    mService.updateLruProcessLocked(app, true, null);
    mService.updateOomAdjLocked();

    final TaskRecord task = r.task;
    if (task.mLockTaskAuth == LOCK_TASK_AUTH_LAUNCHABLE ||
            task.mLockTaskAuth == LOCK_TASK_AUTH_LAUNCHABLE_PRIV) {
        setLockTaskModeLocked(task, LOCK_TASK_MODE_LOCKED, "mLockTaskAuth==LAUNCHABLE", false);
    }

    final ActivityStack stack = task.stack;
    try {
        if (app.thread == null) {
            throw new RemoteException();
        }
        List results = null;
        List newIntents = null;
        if (andResume) {
            results = r.results;
            newIntents = r.newIntents;
        }
        if (DEBUG_SWITCH) Slog.v(TAG_SWITCH,
                "Launching: " + r + " icicle=" + r.icicle + " with results=" + results
                + " newIntents=" + newIntents + " andResume=" + andResume);
        if (andResume) {
            EventLog.writeEvent(EventLogTags.AM_RESTART_ACTIVITY,
                    r.userId, System.identityHashCode(r),
                    task.taskId, r.shortComponentName);
        }
        if (r.isHomeActivity() && r.isNotResolverActivity()) {
            // Home process is the root process of the task.
            mService.mHomeProcess = task.mActivities.get(0).app;
        }
        mService.ensurePackageDexOpt(r.intent.getComponent().getPackageName());
        r.sleeping = false;
        r.forceNewConfig = false;
        mService.showAskCompatModeDialogLocked(r);
        r.compat = mService.compatibilityInfoForPackageLocked(r.info.applicationInfo);
        ProfilerInfo profilerInfo = null;
        if (mService.mProfileApp != null && mService.mProfileApp.equals(app.processName)) {
            if (mService.mProfileProc == null || mService.mProfileProc == app) {
                mService.mProfileProc = app;
                final String profileFile = mService.mProfileFile;
                if (profileFile != null) {
                    ParcelFileDescriptor profileFd = mService.mProfileFd;
                    if (profileFd != null) {
                        try {
                            profileFd = profileFd.dup();
                        } catch (IOException e) {
                            if (profileFd != null) {
                                try {
                                    profileFd.close();
                                } catch (IOException o) {
                                }
                                profileFd = null;
                            }
                        }
                    }

                    profilerInfo = new ProfilerInfo(profileFile, profileFd,
                            mService.mSamplingInterval, mService.mAutoStopProfiler);
                }
            }
        }

        if (andResume) {
            app.hasShownUi = true;
            app.pendingUiClean = true;
        }
        app.forceProcessStateUpTo(mService.mTopProcessState);
        app.thread.scheduleLaunchActivity(new Intent(r.intent), r.appToken,
                System.identityHashCode(r), r.info, new Configuration(mService.mConfiguration),
                new Configuration(stack.mOverrideConfig), r.compat, r.launchedFromPackage,
                task.voiceInteractor, app.repProcState, r.icicle, r.persistentState, results,
                newIntents, !andResume, mService.isNextTransitionForward(), profilerInfo);

        if ((app.info.privateFlags&ApplicationInfo.PRIVATE_FLAG_CANT_SAVE_STATE) != 0) {
            // This may be a heavy-weight process!  Note that the package
            // manager will ensure that only activity can run in the main
            // process of the .apk, which is the only thing that will be
            // considered heavy-weight.
            if (app.processName.equals(app.info.packageName)) {
                if (mService.mHeavyWeightProcess != null
                        && mService.mHeavyWeightProcess != app) {
                    Slog.w(TAG, "Starting new heavy weight process " + app
                            + " when already running "
                            + mService.mHeavyWeightProcess);
                }
                mService.mHeavyWeightProcess = app;
                Message msg = mService.mHandler.obtainMessage(
                        ActivityManagerService.POST_HEAVY_NOTIFICATION_MSG);
                msg.obj = r;
                mService.mHandler.sendMessage(msg);
            }
        }

    } catch (RemoteException e) {
        if (r.launchFailed) {
            // This is the second time we failed -- finish activity
            // and give up.
            Slog.e(TAG, "Second failure launching "
                  + r.intent.getComponent().flattenToShortString()
                  + ", giving up", e);
            mService.appDiedLocked(app);
            stack.requestFinishActivityLocked(r.appToken, Activity.RESULT_CANCELED, null,
                    "2nd-crash", false);
            return false;
        }

        // This is the first time we failed -- restart process and
        // retry.
        app.activities.remove(r);
        throw e;
    }

    r.launchFailed = false;
    if (stack.updateLRUListLocked(r)) {
        Slog.w(TAG, "Activity " + r
              + " being launched, but already in LRU list");
    }

    if (andResume) {
        // As part of the process of launching, ActivityThread also performs
        // a resume.
        stack.minimalResumeActivityLocked(r);
    } else {
        // This activity is not starting in the resumed state... which
        // should look like we asked it to pause+stop (but remain visible),
        // and it has done so and reported back the current icicle and
        // other state.
        if (DEBUG_STATES) Slog.v(TAG_STATES,
                "Moving to STOPPED: " + r + " (starting in stopped state)");
        r.state = STOPPED;
        r.stopped = true;
    }

    // Launch the new version setup screen if needed.  We do this -after-
    // launching the initial activity (that is, home), so that it can have
    // a chance to initialize itself while in the background, making the
    // switch back to it faster and look better.
    if (isFrontStack(stack)) {
        mService.startSetupActivityLocked();
    }

    // Update any services we are bound to that might care about whether
    // their client may have activities.
    mService.mServices.updateServiceConnectionActivitiesLocked(r.app);

    return true;
}

这段代码里有如下一段代码

app.thread.scheduleLaunchActivity(new Intent(r.intent), r.appToken,
        System.identityHashCode(r), r.info, new Configuration(mService.mConfiguration),
        new Configuration(stack.mOverrideConfig), r.compat, r.launchedFromPackage,
        task.voiceInteractor, app.repProcState, r.icicle, r.persistentState, results,
        newIntents, !andResume, mService.isNextTransitionForward(), profilerInfo);

这里的app.thread是IApplicationThread,具体代码在ApplicationThread中如下

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);
}

这段代码中的最后一行sendMessage(H.LAUNCH_ACTIVITY, r);,发送了一个消息回调到了H类中

private class H extends Handler {
    public static final int LAUNCH_ACTIVITY         = 100;
    public static final int PAUSE_ACTIVITY          = 101;
    public static final int PAUSE_ACTIVITY_FINISHING= 102;
    public static final int STOP_ACTIVITY_SHOW      = 103;
    public static final int STOP_ACTIVITY_HIDE      = 104;
    public static final int SHOW_WINDOW             = 105;
    public static final int HIDE_WINDOW             = 106;
    public static final int RESUME_ACTIVITY         = 107;
    public static final int SEND_RESULT             = 108;
    public static final int DESTROY_ACTIVITY        = 109;
    public static final int BIND_APPLICATION        = 110;
    public static final int EXIT_APPLICATION        = 111;
    public static final int NEW_INTENT              = 112;
    public static final int RECEIVER                = 113;
    public static final int CREATE_SERVICE          = 114;
    public static final int SERVICE_ARGS            = 115;
    public static final int STOP_SERVICE            = 116;

    public static final int CONFIGURATION_CHANGED   = 118;
    public static final int CLEAN_UP_CONTEXT        = 119;
    public static final int GC_WHEN_IDLE            = 120;
    public static final int BIND_SERVICE            = 121;
    public static final int UNBIND_SERVICE          = 122;
    public static final int DUMP_SERVICE            = 123;
    public static final int LOW_MEMORY              = 124;
    public static final int ACTIVITY_CONFIGURATION_CHANGED = 125;
    public static final int RELAUNCH_ACTIVITY       = 126;
    public static final int PROFILER_CONTROL        = 127;
    public static final int CREATE_BACKUP_AGENT     = 128;
    public static final int DESTROY_BACKUP_AGENT    = 129;
    public static final int SUICIDE                 = 130;
    public static final int REMOVE_PROVIDER         = 131;
    public static final int ENABLE_JIT              = 132;
    public static final int DISPATCH_PACKAGE_BROADCAST = 133;
    public static final int SCHEDULE_CRASH          = 134;
    public static final int DUMP_HEAP               = 135;
    public static final int DUMP_ACTIVITY           = 136;
    public static final int SLEEPING                = 137;
    public static final int SET_CORE_SETTINGS       = 138;
    public static final int UPDATE_PACKAGE_COMPATIBILITY_INFO = 139;
    public static final int TRIM_MEMORY             = 140;
    public static final int DUMP_PROVIDER           = 141;
    public static final int UNSTABLE_PROVIDER_DIED  = 142;
    public static final int REQUEST_ASSIST_CONTEXT_EXTRAS = 143;
    public static final int TRANSLUCENT_CONVERSION_COMPLETE = 144;
    public static final int INSTALL_PROVIDER        = 145;
    public static final int ON_NEW_ACTIVITY_OPTIONS = 146;
    public static final int CANCEL_VISIBLE_BEHIND = 147;
    public static final int BACKGROUND_VISIBLE_BEHIND_CHANGED = 148;
    public static final int ENTER_ANIMATION_COMPLETE = 149;

    String codeToString(int code) {
        if (DEBUG_MESSAGES) {
            switch (code) {
                case LAUNCH_ACTIVITY: return "LAUNCH_ACTIVITY";
                case PAUSE_ACTIVITY: return "PAUSE_ACTIVITY";
                case PAUSE_ACTIVITY_FINISHING: return "PAUSE_ACTIVITY_FINISHING";
                case STOP_ACTIVITY_SHOW: return "STOP_ACTIVITY_SHOW";
                case STOP_ACTIVITY_HIDE: return "STOP_ACTIVITY_HIDE";
                case SHOW_WINDOW: return "SHOW_WINDOW";
                case HIDE_WINDOW: return "HIDE_WINDOW";
                case RESUME_ACTIVITY: return "RESUME_ACTIVITY";
                case SEND_RESULT: return "SEND_RESULT";
                case DESTROY_ACTIVITY: return "DESTROY_ACTIVITY";
                case BIND_APPLICATION: return "BIND_APPLICATION";
                case EXIT_APPLICATION: return "EXIT_APPLICATION";
                case NEW_INTENT: return "NEW_INTENT";
                case RECEIVER: return "RECEIVER";
                case CREATE_SERVICE: return "CREATE_SERVICE";
                case SERVICE_ARGS: return "SERVICE_ARGS";
                case STOP_SERVICE: return "STOP_SERVICE";
                case CONFIGURATION_CHANGED: return "CONFIGURATION_CHANGED";
                case CLEAN_UP_CONTEXT: return "CLEAN_UP_CONTEXT";
                case GC_WHEN_IDLE: return "GC_WHEN_IDLE";
                case BIND_SERVICE: return "BIND_SERVICE";
                case UNBIND_SERVICE: return "UNBIND_SERVICE";
                case DUMP_SERVICE: return "DUMP_SERVICE";
                case LOW_MEMORY: return "LOW_MEMORY";
                case ACTIVITY_CONFIGURATION_CHANGED: return "ACTIVITY_CONFIGURATION_CHANGED";
                case RELAUNCH_ACTIVITY: return "RELAUNCH_ACTIVITY";
                case PROFILER_CONTROL: return "PROFILER_CONTROL";
                case CREATE_BACKUP_AGENT: return "CREATE_BACKUP_AGENT";
                case DESTROY_BACKUP_AGENT: return "DESTROY_BACKUP_AGENT";
                case SUICIDE: return "SUICIDE";
                case REMOVE_PROVIDER: return "REMOVE_PROVIDER";
                case ENABLE_JIT: return "ENABLE_JIT";
                case DISPATCH_PACKAGE_BROADCAST: return "DISPATCH_PACKAGE_BROADCAST";
                case SCHEDULE_CRASH: return "SCHEDULE_CRASH";
                case DUMP_HEAP: return "DUMP_HEAP";
                case DUMP_ACTIVITY: return "DUMP_ACTIVITY";
                case SLEEPING: return "SLEEPING";
                case SET_CORE_SETTINGS: return "SET_CORE_SETTINGS";
                case UPDATE_PACKAGE_COMPATIBILITY_INFO: return "UPDATE_PACKAGE_COMPATIBILITY_INFO";
                case TRIM_MEMORY: return "TRIM_MEMORY";
                case DUMP_PROVIDER: return "DUMP_PROVIDER";
                case UNSTABLE_PROVIDER_DIED: return "UNSTABLE_PROVIDER_DIED";
                case REQUEST_ASSIST_CONTEXT_EXTRAS: return "REQUEST_ASSIST_CONTEXT_EXTRAS";
                case TRANSLUCENT_CONVERSION_COMPLETE: return "TRANSLUCENT_CONVERSION_COMPLETE";
                case INSTALL_PROVIDER: return "INSTALL_PROVIDER";
                case ON_NEW_ACTIVITY_OPTIONS: return "ON_NEW_ACTIVITY_OPTIONS";
                case CANCEL_VISIBLE_BEHIND: return "CANCEL_VISIBLE_BEHIND";
                case BACKGROUND_VISIBLE_BEHIND_CHANGED: return "BACKGROUND_VISIBLE_BEHIND_CHANGED";
                case ENTER_ANIMATION_COMPLETE: return "ENTER_ANIMATION_COMPLETE";
            }
        }
        return Integer.toString(code);
    }
    public void handleMessage(Message msg) {
        if (DEBUG_MESSAGES) Slog.v(TAG, ">>> handling: " + codeToString(msg.what));
        switch (msg.what) {
            case LAUNCH_ACTIVITY: {
                Trace.traceBegin(Trace.TRACE_TAG_ACTIVITY_MANAGER, "activityStart");
                final ActivityClientRecord r = (ActivityClientRecord) msg.obj;

                r.packageInfo = getPackageInfoNoCheck(
                        r.activityInfo.applicationInfo, r.compatInfo);
                handleLaunchActivity(r, null);
                Trace.traceEnd(Trace.TRACE_TAG_ACTIVITY_MANAGER);
            } break;
            case RELAUNCH_ACTIVITY: {
                Trace.traceBegin(Trace.TRACE_TAG_ACTIVITY_MANAGER, "activityRestart");
                ActivityClientRecord r = (ActivityClientRecord)msg.obj;
                handleRelaunchActivity(r);
                Trace.traceEnd(Trace.TRACE_TAG_ACTIVITY_MANAGER);
            } break;
            case PAUSE_ACTIVITY:
                Trace.traceBegin(Trace.TRACE_TAG_ACTIVITY_MANAGER, "activityPause");
                handlePauseActivity((IBinder)msg.obj, false, (msg.arg1&1) != 0, msg.arg2,
                        (msg.arg1&2) != 0);
                maybeSnapshot();
                Trace.traceEnd(Trace.TRACE_TAG_ACTIVITY_MANAGER);
                break;
            case PAUSE_ACTIVITY_FINISHING:
                Trace.traceBegin(Trace.TRACE_TAG_ACTIVITY_MANAGER, "activityPause");
                handlePauseActivity((IBinder)msg.obj, true, (msg.arg1&1) != 0, msg.arg2,
                        (msg.arg1&1) != 0);
                Trace.traceEnd(Trace.TRACE_TAG_ACTIVITY_MANAGER);
                break;
            case STOP_ACTIVITY_SHOW:
                Trace.traceBegin(Trace.TRACE_TAG_ACTIVITY_MANAGER, "activityStop");
                handleStopActivity((IBinder)msg.obj, true, msg.arg2);
                Trace.traceEnd(Trace.TRACE_TAG_ACTIVITY_MANAGER);
                break;
            case STOP_ACTIVITY_HIDE:
                Trace.traceBegin(Trace.TRACE_TAG_ACTIVITY_MANAGER, "activityStop");
                handleStopActivity((IBinder)msg.obj, false, msg.arg2);
                Trace.traceEnd(Trace.TRACE_TAG_ACTIVITY_MANAGER);
                break;
            case SHOW_WINDOW:
                Trace.traceBegin(Trace.TRACE_TAG_ACTIVITY_MANAGER, "activityShowWindow");
                handleWindowVisibility((IBinder)msg.obj, true);
                Trace.traceEnd(Trace.TRACE_TAG_ACTIVITY_MANAGER);
                break;
            case HIDE_WINDOW:
                Trace.traceBegin(Trace.TRACE_TAG_ACTIVITY_MANAGER, "activityHideWindow");
                handleWindowVisibility((IBinder)msg.obj, false);
                Trace.traceEnd(Trace.TRACE_TAG_ACTIVITY_MANAGER);
                break;
            case RESUME_ACTIVITY:
                Trace.traceBegin(Trace.TRACE_TAG_ACTIVITY_MANAGER, "activityResume");
                handleResumeActivity((IBinder) msg.obj, true, msg.arg1 != 0, true);
                Trace.traceEnd(Trace.TRACE_TAG_ACTIVITY_MANAGER);
                break;
            case SEND_RESULT:
                Trace.traceBegin(Trace.TRACE_TAG_ACTIVITY_MANAGER, "activityDeliverResult");
                handleSendResult((ResultData)msg.obj);
                Trace.traceEnd(Trace.TRACE_TAG_ACTIVITY_MANAGER);
                break;
            case DESTROY_ACTIVITY:
                Trace.traceBegin(Trace.TRACE_TAG_ACTIVITY_MANAGER, "activityDestroy");
                handleDestroyActivity((IBinder)msg.obj, msg.arg1 != 0,
                        msg.arg2, false);
                Trace.traceEnd(Trace.TRACE_TAG_ACTIVITY_MANAGER);
                break;
            case BIND_APPLICATION:
                Trace.traceBegin(Trace.TRACE_TAG_ACTIVITY_MANAGER, "bindApplication");
                AppBindData data = (AppBindData)msg.obj;
                handleBindApplication(data);
                Trace.traceEnd(Trace.TRACE_TAG_ACTIVITY_MANAGER);
                break;
            case EXIT_APPLICATION:
                if (mInitialApplication != null) {
                    mInitialApplication.onTerminate();
                }
                Looper.myLooper().quit();
                break;
            case NEW_INTENT:
                Trace.traceBegin(Trace.TRACE_TAG_ACTIVITY_MANAGER, "activityNewIntent");
                handleNewIntent((NewIntentData)msg.obj);
                Trace.traceEnd(Trace.TRACE_TAG_ACTIVITY_MANAGER);
                break;
            case RECEIVER:
                Trace.traceBegin(Trace.TRACE_TAG_ACTIVITY_MANAGER, "broadcastReceiveComp");
                handleReceiver((ReceiverData)msg.obj);
                maybeSnapshot();
                Trace.traceEnd(Trace.TRACE_TAG_ACTIVITY_MANAGER);
                break;
            case CREATE_SERVICE:
                Trace.traceBegin(Trace.TRACE_TAG_ACTIVITY_MANAGER, "serviceCreate");
                handleCreateService((CreateServiceData)msg.obj);
                Trace.traceEnd(Trace.TRACE_TAG_ACTIVITY_MANAGER);
                break;
            case BIND_SERVICE:
                Trace.traceBegin(Trace.TRACE_TAG_ACTIVITY_MANAGER, "serviceBind");
                handleBindService((BindServiceData)msg.obj);
                Trace.traceEnd(Trace.TRACE_TAG_ACTIVITY_MANAGER);
                break;
            case UNBIND_SERVICE:
                Trace.traceBegin(Trace.TRACE_TAG_ACTIVITY_MANAGER, "serviceUnbind");
                handleUnbindService((BindServiceData)msg.obj);
                Trace.traceEnd(Trace.TRACE_TAG_ACTIVITY_MANAGER);
                break;
            case SERVICE_ARGS:
                Trace.traceBegin(Trace.TRACE_TAG_ACTIVITY_MANAGER, "serviceStart");
                handleServiceArgs((ServiceArgsData)msg.obj);
                Trace.traceEnd(Trace.TRACE_TAG_ACTIVITY_MANAGER);
                break;
            case STOP_SERVICE:
                Trace.traceBegin(Trace.TRACE_TAG_ACTIVITY_MANAGER, "serviceStop");
                handleStopService((IBinder)msg.obj);
                maybeSnapshot();
                Trace.traceEnd(Trace.TRACE_TAG_ACTIVITY_MANAGER);
                break;
            case CONFIGURATION_CHANGED:
                Trace.traceBegin(Trace.TRACE_TAG_ACTIVITY_MANAGER, "configChanged");
                mCurDefaultDisplayDpi = ((Configuration)msg.obj).densityDpi;
                handleConfigurationChanged((Configuration)msg.obj, null);
                Trace.traceEnd(Trace.TRACE_TAG_ACTIVITY_MANAGER);
                break;
            case CLEAN_UP_CONTEXT:
                ContextCleanupInfo cci = (ContextCleanupInfo)msg.obj;
                cci.context.performFinalCleanup(cci.who, cci.what);
                break;
            case GC_WHEN_IDLE:
                scheduleGcIdler();
                break;
            case DUMP_SERVICE:
                handleDumpService((DumpComponentInfo)msg.obj);
                break;
            case LOW_MEMORY:
                Trace.traceBegin(Trace.TRACE_TAG_ACTIVITY_MANAGER, "lowMemory");
                handleLowMemory();
                Trace.traceEnd(Trace.TRACE_TAG_ACTIVITY_MANAGER);
                break;
            case ACTIVITY_CONFIGURATION_CHANGED:
                Trace.traceBegin(Trace.TRACE_TAG_ACTIVITY_MANAGER, "activityConfigChanged");
                handleActivityConfigurationChanged((ActivityConfigChangeData)msg.obj);
                Trace.traceEnd(Trace.TRACE_TAG_ACTIVITY_MANAGER);
                break;
            case PROFILER_CONTROL:
                handleProfilerControl(msg.arg1 != 0, (ProfilerInfo)msg.obj, msg.arg2);
                break;
            case CREATE_BACKUP_AGENT:
                Trace.traceBegin(Trace.TRACE_TAG_ACTIVITY_MANAGER, "backupCreateAgent");
                handleCreateBackupAgent((CreateBackupAgentData)msg.obj);
                Trace.traceEnd(Trace.TRACE_TAG_ACTIVITY_MANAGER);
                break;
            case DESTROY_BACKUP_AGENT:
                Trace.traceBegin(Trace.TRACE_TAG_ACTIVITY_MANAGER, "backupDestroyAgent");
                handleDestroyBackupAgent((CreateBackupAgentData)msg.obj);
                Trace.traceEnd(Trace.TRACE_TAG_ACTIVITY_MANAGER);
                break;
            case SUICIDE:
                Process.killProcess(Process.myPid());
                break;
            case REMOVE_PROVIDER:
                Trace.traceBegin(Trace.TRACE_TAG_ACTIVITY_MANAGER, "providerRemove");
                completeRemoveProvider((ProviderRefCount)msg.obj);
                Trace.traceEnd(Trace.TRACE_TAG_ACTIVITY_MANAGER);
                break;
            case ENABLE_JIT:
                ensureJitEnabled();
                break;
            case DISPATCH_PACKAGE_BROADCAST:
                Trace.traceBegin(Trace.TRACE_TAG_ACTIVITY_MANAGER, "broadcastPackage");
                handleDispatchPackageBroadcast(msg.arg1, (String[])msg.obj);
                Trace.traceEnd(Trace.TRACE_TAG_ACTIVITY_MANAGER);
                break;
            case SCHEDULE_CRASH:
                throw new RemoteServiceException((String)msg.obj);
            case DUMP_HEAP:
                handleDumpHeap(msg.arg1 != 0, (DumpHeapData)msg.obj);
                break;
            case DUMP_ACTIVITY:
                handleDumpActivity((DumpComponentInfo)msg.obj);
                break;
            case DUMP_PROVIDER:
                handleDumpProvider((DumpComponentInfo)msg.obj);
                break;
            case SLEEPING:
                Trace.traceBegin(Trace.TRACE_TAG_ACTIVITY_MANAGER, "sleeping");
                handleSleeping((IBinder)msg.obj, msg.arg1 != 0);
                Trace.traceEnd(Trace.TRACE_TAG_ACTIVITY_MANAGER);
                break;
            case SET_CORE_SETTINGS:
                Trace.traceBegin(Trace.TRACE_TAG_ACTIVITY_MANAGER, "setCoreSettings");
                handleSetCoreSettings((Bundle) msg.obj);
                Trace.traceEnd(Trace.TRACE_TAG_ACTIVITY_MANAGER);
                break;
            case UPDATE_PACKAGE_COMPATIBILITY_INFO:
                handleUpdatePackageCompatibilityInfo((UpdateCompatibilityData)msg.obj);
                break;
            case TRIM_MEMORY:
                Trace.traceBegin(Trace.TRACE_TAG_ACTIVITY_MANAGER, "trimMemory");
                handleTrimMemory(msg.arg1);
                Trace.traceEnd(Trace.TRACE_TAG_ACTIVITY_MANAGER);
                break;
            case UNSTABLE_PROVIDER_DIED:
                handleUnstableProviderDied((IBinder)msg.obj, false);
                break;
            case REQUEST_ASSIST_CONTEXT_EXTRAS:
                handleRequestAssistContextExtras((RequestAssistContextExtras)msg.obj);
                break;
            case TRANSLUCENT_CONVERSION_COMPLETE:
                handleTranslucentConversionComplete((IBinder)msg.obj, msg.arg1 == 1);
                break;
            case INSTALL_PROVIDER:
                handleInstallProvider((ProviderInfo) msg.obj);
                break;
            case ON_NEW_ACTIVITY_OPTIONS:
                Pair pair = (Pair) msg.obj;
                onNewActivityOptions(pair.first, pair.second);
                break;
            case CANCEL_VISIBLE_BEHIND:
                handleCancelVisibleBehind((IBinder) msg.obj);
                break;
            case BACKGROUND_VISIBLE_BEHIND_CHANGED:
                handleOnBackgroundVisibleBehindChanged((IBinder) msg.obj, msg.arg1 > 0);
                break;
            case ENTER_ANIMATION_COMPLETE:
                handleEnterAnimationComplete((IBinder) msg.obj);
                break;
        }
        if (DEBUG_MESSAGES) Slog.v(TAG, "<<< done: " + codeToString(msg.what));
    }

    private void maybeSnapshot() {
        if (mBoundApplication != null && SamplingProfilerIntegration.isEnabled()) {
            // convert the *private* ActivityThread.PackageInfo to *public* known
            // android.content.pm.PackageInfo
            String packageName = mBoundApplication.info.mPackageName;
            android.content.pm.PackageInfo packageInfo = null;
            try {
                Context context = getSystemContext();
                if(context == null) {
                    Log.e(TAG, "cannot get a valid context");
                    return;
                }
                PackageManager pm = context.getPackageManager();
                if(pm == null) {
                    Log.e(TAG, "cannot get a valid PackageManager");
                    return;
                }
                packageInfo = pm.getPackageInfo(
                        packageName, PackageManager.GET_ACTIVITIES);
            } catch (NameNotFoundException e) {
                Log.e(TAG, "cannot get package info for " + packageName, e);
            }
            SamplingProfilerIntegration.writeSnapshot(mBoundApplication.processName, packageInfo);
        }
    }
}

H 类中该消息回调了handleLaunchActivity

switch (msg.what) {
    case LAUNCH_ACTIVITY: {
        Trace.traceBegin(Trace.TRACE_TAG_ACTIVITY_MANAGER, "activityStart");
        final ActivityClientRecord r = (ActivityClientRecord) msg.obj;

        r.packageInfo = getPackageInfoNoCheck(
                r.activityInfo.applicationInfo, r.compatInfo);
        handleLaunchActivity(r, null);
        Trace.traceEnd(Trace.TRACE_TAG_ACTIVITY_MANAGER);
    } break;

handleLaunchActivity()如下

private void handleLaunchActivity(ActivityClientRecord r, 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
    WindowManagerGlobal.initialize();

    Activity a = performLaunchActivity(r, customIntent);

    if (a != null) {
        r.createdConfig = new Configuration(mConfiguration);
        Bundle oldState = r.state;
        handleResumeActivity(r.token, false, r.isForward,
                !r.activity.mFinished && !r.startsNotResumed);

        if (!r.activity.mFinished && r.startsNotResumed) {
            // The activity manager actually wants this one to start out
            // paused, because it needs to be visible but isn't in the
            // foreground.  We accomplish this by going through the
            // normal startup (because activities expect to go through
            // onResume() the first time they run, before their window
            // is displayed), and then pausing it.  However, in this case
            // we do -not- need to do the full pause cycle (of freezing
            // and such) because the activity manager assumes it can just
            // retain the current state it has.
            try {
                r.activity.mCalled = false;
                mInstrumentation.callActivityOnPause(r.activity);
                // We need to keep around the original state, in case
                // we need to be created again.  But we only do this
                // for pre-Honeycomb apps, which always save their state
                // when pausing, so we can not have them save their state
                // when restarting from a paused state.  For HC and later,
                // we want to (and can) let the state be saved as the normal
                // part of stopping the activity.
                if (r.isPreHoneycomb()) {
                    r.state = oldState;
                }
                if (!r.activity.mCalled) {
                    throw new SuperNotCalledException(
                        "Activity " + r.intent.getComponent().toShortString() +
                        " did not call through to super.onPause()");
                }

            } catch (SuperNotCalledException e) {
                throw e;

            } catch (Exception e) {
                if (!mInstrumentation.onException(r.activity, e)) {
                    throw new RuntimeException(
                            "Unable to pause activity "
                            + r.intent.getComponent().toShortString()
                            + ": " + e.toString(), e);
                }
            }
            r.paused = true;
        }
    } else {
        // If there was an error, for any reason, tell the activity
        // manager to stop us.
        try {
            ActivityManagerNative.getDefault()
                .finishActivity(r.token, Activity.RESULT_CANCELED, null, false);
        } catch (RemoteException ex) {
            // Ignore
        }
    }
}

该方法回调了performLaunchActivity

private Activity performLaunchActivity(ActivityClientRecord r, Intent customIntent) {
    // System.out.println("##### [" + System.currentTimeMillis() //+ "] ActivityThread.performLaunchActivity(" + r + ")");
    //1收集了activity的信息
    ActivityInfo aInfo = r.activityInfo;
    if (r.packageInfo == null) {
        r.packageInfo = getPackageInfo(aInfo.applicationInfo, r.compatInfo,
                Context.CONTEXT_INCLUDE_CODE);
    }

    ComponentName component = r.intent.getComponent();
    if (component == null) {
        component = r.intent.resolveActivity(
            mInitialApplication.getPackageManager());
        r.intent.setComponent(component);
    }

    if (r.activityInfo.targetActivity != null) {
        component = new ComponentName(r.activityInfo.packageName,
                r.activityInfo.targetActivity);
    }

    Activity activity = null;
    try {
        java.lang.ClassLoader cl = r.packageInfo.getClassLoader();
        //通过newactivity方法,加载进classloaser
        activity = mInstrumentation.newActivity(
                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 {
    //创建application对象
        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,
                    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()) {
            //回调activity的oncreate
                mInstrumentation.callActivityOnCreate(activity, r.state, r.persistentState);
            } else {
                mInstrumentation.callActivityOnCreate(activity, r.state);
            }
            if (!activity.mCalled) {
                throw new SuperNotCalledException(
                    "Activity " + r.intent.getComponent().toShortString() +
                    " did not call through to super.onCreate()");
            }
            r.activity = activity;
            r.stopped = true;
            if (!r.activity.mFinished) {
                activity.performStart();
                r.stopped = false;
            }
            if (!r.activity.mFinished) {
                if (r.isPersistable()) {
                    if (r.state != null || r.persistentState != null) {
                        mInstrumentation.callActivityOnRestoreInstanceState(activity, r.state,
                                r.persistentState);
                    }
                } else if (r.state != null) {
                    mInstrumentation.callActivityOnRestoreInstanceState(activity, r.state);
                }
            }
            if (!r.activity.mFinished) {
                activity.mCalled = false;
                if (r.isPersistable()) {
                    mInstrumentation.callActivityOnPostCreate(activity, r.state,
                            r.persistentState);
                } else {
                    mInstrumentation.callActivityOnPostCreate(activity, r.state);
                }
                if (!activity.mCalled) {
                    throw new SuperNotCalledException(
                        "Activity " + r.intent.getComponent().toShortString() +
                        " did not call through to super.onPostCreate()");
                }
            }
        }
        r.paused = true;

        mActivities.put(r.token, r);

    } catch (SuperNotCalledException e) {
        throw e;

    } catch (Exception e) {
        if (!mInstrumentation.onException(activity, e)) {
            throw new RuntimeException(
                "Unable to start activity " + component
                + ": " + e.toString(), e);
        }
    }

    return activity;
}

好了,这些就说到这儿,接下来

再继续attach。else里的就不看了,基本都是发消息机制了

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