"未能提供结果" - onActivityForResult

Question

我有一个LoginActivity(用户登录).它基本上是它自己Activity的主题就像一个对话框(看起来像一个对话框).它出现在一个SherlockFragmentActivity.我想要的是:如果登录成功,应该有两个FragmentTransaction更新视图.这是代码:

在LoginActivity,如果成功登录,

setResult(1, new Intent());

在SherlockFragmentActivity:

@Override
protected void onActivityResult(int requestCode, int resultCode, Intent data) {
    super.onActivityResult(requestCode, resultCode, data);

    if (resultCode == 1) {
        LoggedStatus = PrefActivity.getUserLoggedInStatus(this);
        FragmentTransaction t = MainFragmentActivity.this.getSupportFragmentManager().beginTransaction();
        SherlockListFragment mFrag = new MasterFragment();
        t.replace(R.id.menu_frame, mFrag);
        t.commit();

        // Set up Main Screen
        FragmentTransaction t2 = MainFragmentActivity.this.getSupportFragmentManager().beginTransaction();
        SherlockListFragment mainFrag = new FeaturedFragment();
        t2.replace(R.id.main_frag, mainFrag);
        t2.commit();
    }
}

它在第一次提交时崩溃,使用此LogCat:

E/AndroidRuntime(32072): Caused by: java.lang.IllegalStateException: Can not perform this action after onSaveInstanceState
E/AndroidRuntime(32072):    at android.support.v4.app.FragmentManagerImpl.checkStateLoss(FragmentManager.java:1299)
E/AndroidRuntime(32072):    at android.support.v4.app.FragmentManagerImpl.enqueueAction(FragmentManager.java:1310)
E/AndroidRuntime(32072):    at android.support.v4.app.BackStackRecord.commitInternal(BackStackRecord.java:541)
E/AndroidRuntime(32072):    at android.support.v4.app.BackStackRecord.commit(BackStackRecord.java:525)
E/AndroidRuntime(32072):    at com.kickinglettuce.rate_this.MainFragmentActivity.onActivityResult(MainFragmentActivity.java:243)
E/AndroidRuntime(32072):    at android.app.Activity.dispatchActivityResult(Activity.java:5293)
E/AndroidRuntime(32072):    at android.app.ActivityThread.deliverResults(ActivityThread.java:3315)

Answer 1

首先,您应该阅读我的博客文章以获取更多信息(它讨论了为什么会发生此异常以及您可以采取哪些措施来防止它).

呼叫commitAllowingStateLoss()更像是一种破解而非修复.国家损失很严重,应该不惜一切代价避免.在onActivityResult()调用时,活动/片段的状态可能尚未恢复,因此在此期间发生的任何事务都将丢失.这是一个非常重要的错误,必须解决!(请注意,只有当你Activity的系统被系统杀死后才会出现这个错误...这取决于设备有多少内存,有时候很少见......所以这种错误不是在测试时非常容易捕获).

尝试移动您的交易onPostResume()(注意onPostResume()总是在之后调用,onResume()并且onResume()总是在之后调用onActivityResult()):

private boolean mReturningWithResult = false;

@Override
protected void onActivityResult(int requestCode, int resultCode, Intent data) {
    super.onActivityResult(requestCode, resultCode, data);
    mReturningWithResult = true;
}

@Override
protected void onPostResume() {
    super.onPostResume();
    if (mReturningWithResult) {
        // Commit your transactions here.
    }
    // Reset the boolean flag back to false for next time.
    mReturningWithResult = false;
}

这似乎有点不可思议,但在做这样的事情是必要的,以确保您FragmentTransactions的始终致力于后的Activity的状态已经恢复到原来的状态(onPostResume()是保证之后调用Activity的状态有所恢复) .