android - 如何在不恢复中间 fragment 的情况下清除 Android fragment 返回堆栈

Question

我需要清除返回堆栈中的所有 fragment 。

问题是我需要确保在某个时间点，堆栈已成功清除，之后不会恢复弹出的 fragment 。

一些 fragment 显示与当前登录用户相关的内容。现在，如果用户决定注销，我想清除堆栈，注销用户并将应用程序转换为初始 fragment 。问题是，堆栈弹出被推迟，在我注销后，一些与用户相关的 fragment 试图恢复并询问用户配置文件数据。如果没有登录用户，底层 API 会抛出异常。因此 fragment 崩溃，因为它不应该在这种状态下使用。

我试过很多方法:

@Override
public void onSignOutConfirmed() {
    Log.d(TAG, "onSignOutConfirmed");

    getSupportFragmentManager().popBackStackImmediate(null, FragmentManager.POP_BACK_STACK_INCLUSIVE);

    Log.d(TAG, "onSignOutConfirmed - signing out");

    UserProfileService.signOut();
    Analytics.trackEvent(EventType.SIGN_OUT);
    showStartupScreen();
}

或

@Override
public void onSignOutConfirmed() {
    Log.d(TAG, "onSignOutConfirmed");

    FragmentManager fm = getSupportFragmentManager();

    int backStackCount = fm.getBackStackEntryCount();

    while(backStackCount-- != 0) {
        fm.popBackStackImmediate();
    }

    Log.d(TAG, "onSignOutConfirmed - signing out");

    UserProfileService.signOut();
    Analytics.trackEvent(EventType.SIGN_OUT);
    showStartupScreen();
}

日志显示当我调用 UserProfileService.signOut() 时 fragment 仍在处理其生命周期方法。当 fragment 暂停时，为其中一个 fragment 检索配置文件数据的 AsyncTask 被取消(带有中断)。但是 fragment 暂停得太晚了。

而且错误并不总是命中。但大多数时候它会在 Samsung S2 (Android 4.1.2) 上出现。

06-09 19:46:54.760 D/com.myapp.application.MainActivity( 4562): **onSignOutConfirmed**
06-09 19:46:54.765 D/com.myapp.application.screens.main.MainFragment( 4562): onCreateView
06-09 19:46:54.826 D/com.myapp.application.screens.main.MainFragment( 4562): onCreateAnimation (transit 0, enter true, nextAnim 0)
06-09 19:46:54.831 D/com.myapp.application.screens.main.TranscriptionsFragment( 4562): onCreateView
06-09 19:46:54.856 D/com.myapp.application.screens.main.MainFragment( 4562): onResume
06-09 19:46:54.856 D/com.myapp.application.screens.main.TranscriptionsFragment( 4562): **onResume**
06-09 19:46:54.866 D/com.myapp.application.MainActivity( 4562): **onSignOutConfirmed - signing out**
06-09 19:46:54.876 D/myappDB( 4562): Application settings: id 1.
06-09 19:46:54.876 D/myappDB( 4562): Application settings (id 1): updated, [_activeProfileId] = [null].
06-09 19:46:54.916 D/myappDB( 4562): Application settings: active user profile null.
06-09 19:46:54.941 D/myappDB( 4562): Application settings: active user profile null.
06-09 19:46:54.951 D/com.myapp.application.screens.main.TranscriptionsFragment( 4562): **onPause**
06-09 19:46:54.951 D/com.myapp.application.screens.main.MainFragment( 4562): onPause
06-09 19:46:54.961 D/com.myapp.application.screens.main.TranscriptionsFragment( 4562): onDestroyView
06-09 19:46:54.961 D/com.myapp.application.screens.main.MainFragment( 4562): onDestroyView
06-09 19:46:54.961 D/com.myapp.application.screens.main.MainFragment( 4562): onCreateAnimation (transit 0, enter false, nextAnim 0)
06-09 19:46:55.381 E/AndroidRuntime( 4562):     at com.myapp.application.impls.sqlite.SQLiteApplicationSettingsPersistance.getAndCheckActiveUserProfileId(SQLiteApplicationSettingsPersistance.java:421)
06-09 19:46:55.381 E/AndroidRuntime( 4562):     at com.myapp.application.impls.sqlite.SQLiteTranscriptionPersistance.getTranscriptionStats(SQLiteTranscriptionPersistance.java:54)
06-09 19:46:55.381 E/AndroidRuntime( 4562):     at com.myapp.application.impls.finders.TranscriptionListFinder.getTranscriptions(TranscriptionListFinder.java:45)
06-09 19:46:55.381 E/AndroidRuntime( 4562):     at com.myapp.application.screens.main.TranscriptionsFragment$RetrieveTranscriptionsAsyncTask.doInBackground(TranscriptionsFragment.java:244)
06-09 19:46:55.381 E/AndroidRuntime( 4562):     at com.myapp.application.screens.main.TranscriptionsFragment$RetrieveTranscriptionsAsyncTask.doInBackground(TranscriptionsFragment.java:241)
06-09 19:46:55.421 D/com.myapp.application.screens.main.TranscriptionsFragment( 4562): onDetach

Answer 1

试试这个:

private void clearFragmentBackStack() {
    FragmentManager fm = getSupportFragmentManager();
    for(int i = 0; i < fm.getBackStackEntryCount(); ++i) {
        fm.popBackStack();
    }
}