Activity中onStart里面的NullPointerException

Question

我在扩展AppCompatActivity的Activity中得到偶尔的空指针异常。请注意，它偶尔会发生，因此剩下的时间代码工作正常。活动中的onStart函数非常空，只调用super函数，如下所示。

@Override
protected void onStart() {
    super.onStart();  //**<---- line 242**
}

这是crashlog

java.lang.RuntimeException: Unable to start activity ComponentInfo{com.korneto.android/com.korneto.android.activities.GenericActivity}: java.lang.NullPointerException
    at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1654)
    at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:1670)
    at android.app.ActivityThread.access$1500(ActivityThread.java:118)
    at android.app.ActivityThread$H.handleMessage(ActivityThread.java:938)
    at android.os.Handler.dispatchMessage(Handler.java:99)
    at android.os.Looper.loop(Looper.java:130)
    at android.app.ActivityThread.main(ActivityThread.java:3704)
    at java.lang.reflect.Method.invokeNative(Native Method)
    at java.lang.reflect.Method.invoke(Method.java:507)
    at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:842)
    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:600)
    at dalvik.system.NativeStart.main(Native Method)
Caused by: java.lang.NullPointerException
    at android.support.v4.app.BackStackRecord.run(SourceFile:714)
    at android.support.v4.app.FragmentManagerImpl.execPendingActions(SourceFile:1501)
    at android.support.v4.app.FragmentActivity.onStart(SourceFile:551)
    at com.korneto.android.activities.GenericActivity.onStart(SourceFile:242)
    at android.app.Instrumentation.callActivityOnStart(Instrumentation.java:1129)
    at android.app.Activity.performStart(Activity.java:3791)
    at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1627)

的OnCreate

// Checks if fragment has already been added, otherwise add a new
    mFragment = getSupportFragmentManager().findFragmentByTag(tag);

    if (mFragment != null) {
        Utils.bringFragmentToTop(getSupportFragmentManager(), mFragment);
        return;
    }

    if(isDialog) {
        try {
            Fragment fragment = (Fragment) fragmentClass.newInstance();
            if (null != b) {
                fragment.setArguments(b);
            }
            ((DialogFragment) fragment).show(getSupportFragmentManager(), tag);
            getSupportFragmentManager().executePendingTransactions();
            return;
        } catch (Exception e) {}

    }

    Utils.startFragment(getSupportFragmentManager(), fragmentClass, R.id.generic_frame, tag, b, addToStack);

下面是Utils.startFragment代码

public static Fragment startFragment(FragmentManager fm, Class c, int containerid, String tag, Bundle args, boolean addToStack) {
    if(TextUtils.isEmpty(tag)) {
        tag = getClassTag(c);
    }

    Fragment fragment = null;
    if(!TextUtils.isEmpty(tag)) {
        //if fragment is in backstack, we use it and return
        if(fm.popBackStackImmediate (tag, 0)) {
            return null;
        }

        //We see if Fragment manager has it
        fragment = fm.findFragmentByTag(tag);

        // if the fragment is currently visible, don't add it to stack or commit any trasaction
        if(null != fragment && fragment.isVisible()) {
            return fragment;
        }

    }

    if (fragment == null) {
        try {
            fragment = (Fragment) c.newInstance();
            if(null != args) {
                fragment.setArguments(args);
            }

        } catch (Exception e) {
            e.printStackTrace();
            return fragment;
        }
    }

    if(fragment instanceof DialogFragment) {
        DialogFragment df = (DialogFragment) fragment;

        // we do getDialog to check if setShowsDialog(false) was called on it (if dialog is used as both generic and dialog
        //if(null != df.getDialog()) {
            ((DialogFragment) fragment).show(fm, tag);
            fm.executePendingTransactions();
        return fragment;
        //}
    }

    FragmentTransaction transaction = fm.beginTransaction();
    if(fragment.isAdded()) {
        transaction.show(fragment);
    }
    else
        transaction.replace(containerid, fragment, tag);

    if(addToStack)
        transaction.addToBackStack(tag);

    if(null != args && args.getBoolean("commitAllowingStateLoss", false)) {
        Log.d(TAG, "commitAllowingStateLoss");
        transaction.commitAllowingStateLoss();
    }
    else
        transaction.commit();

    return fragment;

}

有什么想法吗？