Launcher进程启动流程_launched external handler for-优快云博客

本文链接：https://blog.youkuaiyun.com/iamfuturetoo/article/details/120734305

本文详细解析了Android系统中Launcher进程的启动过程，从ActivityTaskManagerService开始，经过启动HomeActivity，到处理Activity启动流程，深入探讨了如何通过Zygote进程fork子进程，并在新进程中运行ActivityThread，直至Activity的真正启动。涉及到的关键步骤包括ActivityStackSupervisor的调度，跨进程通信以及ActivityThread的main方法等。

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Launcher进程启动流程

在分析ActivityManagerService启动流程的时候说过，ActivityManagerService启动完成后，会调用ActivityTaskManagerService启动HomeActivity并启动Launcher进程

    mAtmInternal.startHomeOnAllDisplays(currentUserId, "systemReady");

    mAtmInternal.showSystemReadyErrorDialogsIfNeeded();

ActivityTaskManagerService.LocalService -> startHomeOnAllDisplays(currentUserId, “systemReady”)

    @Override
    public boolean startHomeOnAllDisplays(int userId, String reason) {
        synchronized (mGlobalLock) {
            return mRootActivityContainer.startHomeOnAllDisplays(userId, reason);
        }
    }

RootActivityContainer -> startHomeOnAllDisplays

    boolean startHomeOnAllDisplays(int userId, String reason) {
   
        boolean homeStarted = false;
        for (int i = mActivityDisplays.size() - 1; i >= 0; i--) {
   
            final int displayId = mActivityDisplays.get(i).mDisplayId;
            homeStarted |= startHomeOnDisplay(userId, reason, displayId);
        }
        return homeStarted;
    }

根据注释mActivityDisplays是一个List，包含多个Activity，按照Z轴排序，最后一个entry表示显示在最上面的Activity。

RootActivityContainer ->startHomeOnDisplay()

    boolean startHomeOnDisplay(int userId, String reason, int displayId, boolean allowInstrumenting,
            boolean fromHomeKey) {
   
        // Fallback to top focused display if the displayId is invalid.
        if (displayId == INVALID_DISPLAY) {
   
            displayId = getTopDisplayFocusedStack().mDisplayId;
        }

        Intent homeIntent = null;
        ActivityInfo aInfo = null;
        if (displayId == DEFAULT_DISPLAY) {
   
            homeIntent = mService.getHomeIntent();
            aInfo = resolveHomeActivity(userId, homeIntent);
        } else if (shouldPlaceSecondaryHomeOnDisplay(displayId)) {
   
            Pair<ActivityInfo, Intent> info = resolveSecondaryHomeActivity(userId, displayId);
            aInfo = info.first;
            homeIntent = info.second;
        }
        if (aInfo == null || homeIntent == null) {
   
            return false;
        }

        if (!canStartHomeOnDisplay(aInfo, displayId, allowInstrumenting)) {
   
            return false;
        }

        // Updates the home component of the intent.
        homeIntent.setComponent(new ComponentName(aInfo.applicationInfo.packageName, aInfo.name));
        homeIntent.setFlags(homeIntent.getFlags() | FLAG_ACTIVITY_NEW_TASK);
        // Updates the extra information of the intent.
        if (fromHomeKey) {
   
            homeIntent.putExtra(WindowManagerPolicy.EXTRA_FROM_HOME_KEY, true);
        }
        // Update the reason for ANR debugging to verify if the user activity is the one that
        // actually launched.
        final String myReason = reason + ":" + userId + ":" + UserHandle.getUserId(
                aInfo.applicationInfo.uid) + ":" + displayId;
        mService.getActivityStartController().startHomeActivity(homeIntent, aInfo, myReason,
                displayId);
        return true;
    }

在上面的方法中，通过ActivityTaskManagerService获取HomeIntent，即intent中category为android.intent.category.HOME的Activity。代码中可以看到是以FLAG_ACTIVITY_NEW_TASK方式启动。

ActivityStartController -> startHomeActivity

    void startHomeActivity(Intent intent, ActivityInfo aInfo, String reason, int displayId) {
   
        final ActivityOptions options = ActivityOptions.makeBasic();
        options.setLaunchWindowingMode(WINDOWING_MODE_FULLSCREEN);
        if (!ActivityRecord.isResolverActivity(aInfo.name)) {
   
            // The resolver activity shouldn't be put in home stack because when the foreground is
            // standard type activity, the resolver activity should be put on the top of current
            // foreground instead of bring home stack to front.
            options.setLaunchActivityType(ACTIVITY_TYPE_HOME);
        }
        options.setLaunchDisplayId(displayId);
        mLastHomeActivityStartResult = obtainStarter(intent, "startHomeActivity: " + reason)
                .setOutActivity(tmpOutRecord)
                .setCallingUid(0)
                .setActivityInfo(aInfo)
                .setActivityOptions(options.toBundle())
                .execute();
        mLastHomeActivityStartRecord = tmpOutRecord[0];
        final ActivityDisplay display =
                mService.mRootActivityContainer.getActivityDisplay(displayId);
        final ActivityStack homeStack = display != null ? display.getHomeStack() : null;
        if (homeStack != null && homeStack.mInResumeTopActivity) {
   
            // If we are in resume section already, home activity will be initialized, but not
            // resumed (to avoid recursive resume) and will stay that way until something pokes it
            // again. We need to schedule another resume.
            mSupervisor.scheduleResumeTopActivities();
        }