尝试将嵌套片段附加到正在销毁的活动中

Question

我有一个包含片段的活动：ConversationsFragment

以这种方式添加到活动中：

private void showFragment(BaseFragment fragment, String tag) {
    FragmentTransaction transaction = fragmentManager
            .beginTransaction()
            .replace(R.id.content_frame, fragment, tag);

    transaction.commit();

    try {
        fragmentManager.executePendingTransactions();
    } catch (Exception e) {
        Log.e(TAG, "Fail executing pending transactions", e);
    }       
}

在ConversationsFragment中，我想添加一个＆＃34;空案例＆＃34;片段：

@Override
public void onActivityCreated(Bundle savedInstanceState) {
    super.onActivityCreated(savedInstanceState);

    searchEmptyCaseFragment = new SearchEmptyCaseFragment();
    FragmentTransaction fragmentTransaction = getChildFragmentManager().beginTransaction();
    fragmentTransaction.add(R.id.empty_case_container, searchEmptyCaseFragment);
    fragmentTransaction.commit();

    getFragmentManager().executePendingTransactions();  //Added just for testing
    getChildFragmentManager().executePendingTransactions(); //Added just for testing
}

但有时候，当我进入活动并快速离开时，我会得到这个例外：

 E/AndroidRuntime( 8232): java.lang.RuntimeException: Unable to destroy activity {com.mycompany.messenger/com.mycompany.messenger.ui.activity.MainActivity}: java.lang.NullPointerException
    E/AndroidRuntime( 8232):    at android.app.ActivityThread.performDestroyActivity(ActivityThread.java:3273)
    E/AndroidRuntime( 8232):    at android.app.ActivityThread.handleDestroyActivity(ActivityThread.java:3291)
    E/AndroidRuntime( 8232):    at android.app.ActivityThread.access$1200(ActivityThread.java:130)
    E/AndroidRuntime( 8232):    at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1248)
    E/AndroidRuntime( 8232):    at android.os.Handler.dispatchMessage(Handler.java:99)
    E/AndroidRuntime( 8232):    at android.os.Looper.loop(Looper.java:137)
    E/AndroidRuntime( 8232):    at android.app.ActivityThread.main(ActivityThread.java:4745)
    E/AndroidRuntime( 8232):    at java.lang.reflect.Method.invokeNative(Native Method)
    E/AndroidRuntime( 8232):    at java.lang.reflect.Method.invoke(Method.java:511)
    E/AndroidRuntime( 8232):    at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:786)
    --
    E/AndroidRuntime( 8232): Caused by: java.lang.NullPointerException
    E/AndroidRuntime( 8232):    at com.mycompany.ioc.IoCActivity.eK(SourceFile:57)
    E/AndroidRuntime( 8232):    at com.mycompany.ioc.IoCFragment.ahu(SourceFile:55)
    E/AndroidRuntime( 8232):    at com.mycompany.ioc.IoCFragment.onAttach(SourceFile:42)
    E/AndroidRuntime( 8232):    at com.mycompany.messenger.search.ui.SearchEmptyCaseFragment.onAttach(SourceFile:43)
    E/AndroidRuntime( 8232):    at android.support.v4.app.Fragment.onAttach(SourceFile:1152)
    E/AndroidRuntime( 8232):    at dh.a(SourceFile:968)
    E/AndroidRuntime( 8232):    at dh.a(SourceFile:1197)
    E/AndroidRuntime( 8232):    at cy.run(SourceFile:738)
    E/AndroidRuntime( 8232):    at dh.execPendingActions(SourceFile:1562)
    E/AndroidRuntime( 8232):    at dh.executePendingTransactions(SourceFile:535)

这基本上告诉我片段在活动被破坏时试图执行onAttach。

有没有办法确保在销毁活动之前已经执行了所有交易？

提前感谢您的时间。