从堆栈中弹出片段时，应用程序在后台崩溃

Question

应用程序崩溃，当我命中服务器 RPC 时，当 RPC 正在进行时，我将应用程序置于后台。同时，当 RPC 从服务器获得响应时，它从堆栈中弹出一个片段。弹出片段时，应用程序崩溃。我读过有关创建 WeakReference 的内容，如果 activity 被销毁，它将为空。但不确定如何在这种情况下实施它。

以下是我的代码：

private void showFragment(SherlockFragment fragment) {
    FragmentManager fm = getSupportFragmentManager();
    fm.popBackStack(null, FragmentManager.POP_BACK_STACK_INCLUSIVE);
    FragmentTransaction ft = fm.beginTransaction();
    ft.replace(R.id.content, fragment);
    ft.commit();
}

我在执行以下行时崩溃：

fm.popBackStack(null, FragmentManager.POP_BACK_STACK_INCLUSIVE);

堆栈跟踪：

01-15 16:37:44.435: E/AndroidRuntime(28049): FATAL EXCEPTION: main
01-15 16:37:44.435: E/AndroidRuntime(28049): java.lang.IllegalStateException: Can not perform this action after onSaveInstanceState
01-15 16:37:44.435: E/AndroidRuntime(28049):    at android.support.v4.app.FragmentManagerImpl.checkStateLoss(FragmentManager.java:1299)
01-15 16:37:44.435: E/AndroidRuntime(28049):    at android.support.v4.app.FragmentManagerImpl.enqueueAction(FragmentManager.java:1310)
01-15 16:37:44.435: E/AndroidRuntime(28049):    at android.support.v4.app.FragmentManagerImpl.popBackStack(FragmentManager.java:452)
01-15 16:37:44.435: E/AndroidRuntime(28049):    at com.druva.inSync.ValidationActivity.run(ValidationActivity.java:93)

Answer 1

我遇到了完全相同的问题，我使用一个标志解决了这个问题。看起来有点"hacky"，但它确实有效

public abstract class PopActivity extends Activity {

    private boolean mVisible; 

   @Override
    public void onResume() {
        super.onResume();
        mVisible = true;
    }

    @Override
    protected void onPause() {
        super.onPause();
        mVisible = false;
    }

    private void popFragment() {
        if (!mVisible) {
            return;
        }

        FragmentManager fm = getSupportFragmentManager();
        fm.popBackStack(null, FragmentManager.POP_BACK_STACK_INCLUSIVE);
    }
}

所以当你单独实现上面的代码时，当你恢复应用程序时，你会发现自己处于一个你真正想要弹出的片段中。您可以使用以下片段来解决此问题：

public abstract class PopFragment extends Fragment {

    private static final String KEY_IS_POPPED = "KEY_IS_POPPED";
    private boolean mPopped;

    @Override
    public void onSaveInstanceState(Bundle outState) {
        outState.putBoolean(KEY_IS_POPPED, mPopped);
        super.onSaveInstanceState(outState);
    }

    @Override
    public void onCreate(@Nullable Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        if (savedInstanceState != null) {
            mPopped = savedInstanceState.getBoolean(KEY_IS_POPPED);
        }
    }

    @Override
    public void onResume() {
        super.onResume();
        if (mPopped) {
            popFragment();
        }
    }

    protected void popFragment() {
        mPopped = true;
        // null check and interface check advised
        ((PopActivity) getActivity()).popFragment();
    }
}

从堆栈中弹出片段时，应用程序在后台崩溃

Application crashes in background, when popping a fragment from stack

android

android-fragments

background-process

weak-references