Android8.1 Launcher3启动源码解析之第一个Activity启动_starthomeactivity

前一篇文章说了与Launcher有关的AMS启动过程，这篇文章来说一说与Launcher启动有关的Activity的启动过程

一、AMS启动Launcher

接上篇文章看AMS中启动HomeActivity的方法

boolean startHomeActivityLocked(int userId, String reason) {
  ......
    Intent intent = getHomeIntent();//获取启动Launcher的意图
    ActivityInfo aInfo = resolveActivityInfo(intent, STOCK_PM_FLAGS, userId);
    if (aInfo != null) {
        intent.setComponent(new ComponentName(aInfo.applicationInfo.packageName, aInfo.name));
        // Don't do this if the home app is currently being
        // instrumented.
        aInfo = new ActivityInfo(aInfo);
        aInfo.applicationInfo = getAppInfoForUser(aInfo.applicationInfo, userId);
        ProcessRecord app = getProcessRecordLocked(aInfo.processName,
                aInfo.applicationInfo.uid, true);
        if (app == null || app.instr == null) {
 //这里app肯定是null的
            intent.setFlags(intent.getFlags() | Intent.FLAG_ACTIVITY_NEW_TASK);
            final int resolvedUserId = UserHandle.getUserId(aInfo.applicationInfo.uid);
            // For ANR debugging to verify if the user activity is the one that actually
            // launched.
            final String myReason = reason + ":" + userId + ":" + resolvedUserId;
            mActivityStarter.startHomeActivityLocked(intent, aInfo, myReason); //开始启动laucher
        }
    } else {
        Slog.wtf(TAG, "No home screen found for " + intent, new Throwable());
    }

    return true;
}

由此我们可以看ActivityStarter中的startHomeActivityLock方法

二、ActivityStarter

1、startHomeActivityLocked

void startHomeActivityLocked(Intent intent, ActivityInfo aInfo, String reason) {
    mSupervisor.moveHomeStackTaskToTop(reason);
    mLastHomeActivityStartResult = startActivityLocked(null /*caller*/, intent,
            null /*ephemeralIntent*/, null /*resolvedType*/, aInfo, null /*rInfo*/,
            null /*voiceSession*/, null /*voiceInteractor*/, null /*resultTo*/,
            null /*resultWho*/, 0 /*requestCode*/, 0 /*callingPid*/, 0 /*callingUid*/,
            null /*callingPackage*/, 0 /*realCallingPid*/, 0 /*realCallingUid*/,
            0 /*startFlags*/, null /*options*/, false /*ignoreTargetSecurity*/,
            false /*componentSpecified*/, mLastHomeActivityStartRecord /*outActivity*/,
            null /*inTask*/, "startHomeActivity: " + reason);
    if (mSupervisor.inResumeTopActivity) { //初始化为false
        // 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();
    }
}

没啥实质性进展，就是传递默认值。看startActivityLocked方法

2、startActivityLocked

int startActivityLocked(IApplicationThread caller, Intent intent, Intent ephemeralIntent,
                        String resolvedType, ActivityInfo aInfo, ResolveInfo rInfo,
                        IVoiceInteractionSession voiceSession, IVoiceInteractor voiceInteractor,
                        IBinder resultTo, String resultWho, int requestCode, int callingPid, int callingUid,
                        String callingPackage, int realCallingPid, int realCallingUid, int startFlags,
                        ActivityOptions options, boolean ignoreTargetSecurity, boolean componentSpecified,
                        ActivityRecord[] outActivity, TaskRecord inTask, String reason) {

    if (TextUtils.isEmpty(reason)) {
        throw new IllegalArgumentException("Need to specify a reason.");
    }
    mLastStartReason = reason;
    mLastStartActivityTimeMs = System.currentTimeMillis();
    mLastStartActivityRecord[0] = null;

    mLastStartActivityResult = startActivity(caller, intent, ephemeralIntent, resolvedType,
            aInfo, rInfo, voiceSession, voiceInteractor, resultTo, resultWho, requestCode,
            callingPid, callingUid, callingPackage, realCallingPid, realCallingUid, startFlags,
            options, ignoreTargetSecurity, componentSpecified, mLastStartActivityRecord,
            inTask);

    if (outActivity != null) {
        // mLastStartActivityRecord[0] is set in the call to startActivity above.
        outActivity[0] = mLastStartActivityRecord[0];
    }

    // Aborted results are treated as successes externally, but we must track them internally.
    return mLastStartActivityResult != START_ABORTED ? mLastStartActivityResult : START_SUCCESS;
}

从这里看出，只是赋值了一些变量，然后直接掉startActivity方法。

3、startActivity

/** DO NOT call this method directly. Use {
   @link #startActivityLocked} instead. */
private int startActivity(IApplicationThread caller, Intent intent, Intent ephemeralIntent,
                          String resolvedType, ActivityInfo aInfo, ResolveInfo rInfo,
                          IVoiceInteractionSession voiceSession, IVoiceInteractor voiceInteractor,
                          IBinder resultTo, String resultWho, int requestCode, int callingPid, int callingUid,
                          String callingPackage, int realCallingPid, int realCallingUid, int startFlags,
                          ActivityOptions options, boolean ignoreTargetSecurity, boolean componentSpecified,
                          ActivityRecord[] outActivity, TaskRecord inTask) {
    int err = ActivityManager.START_SUCCESS;
    // Pull the optional Ephemeral Installer-only bundle out of the options early.
    final Bundle verificationBundle
            = options != null ? options.popAppVerificationBundle() : null;

    ProcessRecord callerApp = null;
    if (caller != null) { //此时caller为
        callerApp = mService.getRecordForAppLocked(caller);
        if (callerApp != null) {
            callingPid = callerApp.pid;
            callingUid = callerApp.info.uid;
        } else {
            Slog.w(TAG, "Unable to find app for caller " + caller
                    + " (pid=" + callingPid + ") when starting: "
                    + intent.toString());
            err = ActivityManager.START_PERMISSION_DENIED;
        }
    }

    final int userId = aInfo != null ? UserHandle.getUserId(aInfo.applicationInfo.uid) : 0;