可以在再次调用片段时恢复片段UI中的数据状态吗？

Question

如果我有片段A和片段B。我使用下面的代码从A调用片段B

FragmentManager fragmentManager =getFragmentManager();
    FragmentTransaction fragmentTransaction =
            fragmentManager.beginTransaction();


    fragmentTransaction.add(R.id.frame_step, fragment,TAG).hide(SourceFragment.this).addToBackStack((SourceFragment.class.getName()));
    fragmentTransaction.commit();

现在在片段B中，我有EditText，并且我在其中输入了“ Hello”，如果我按片段B的“后退”按钮，然后根据getSupportFragmentManager().popBackStack();，它将恢复片段A的

现在，如果我再次从片段A调用片段B，我希望不再创建FragmentB，但仍然可以在EditText中看到“ Hello”。

注意-我不想为此使用变量或共享首选项，因为我有多个具有多个视图的片段，例如大表格。有没有什么可以从恢复状态中调用片段而不是再次调用它，或者我是否可以检查此片段是否已经创建。在此先感谢

Answer 1

您想要的是可能的。您需要先保存片段状态，然后再进行正向导航，并需要在从Backstack中还原片段后再进行还原。

片段中

private Bundle savedState = null;

 @Override
    public void onDestroyView() {
        super.onDestroyView();
        savedState = saveState();
    }

    private Bundle saveState() { /* called either from onDestroyView() or onSaveInstanceState() */
        Bundle state = new Bundle();
        state.putCharSequence("TEXT_HELLO_WORD", helloWordTextView.getText());
        return state;
    }

 @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
        /* (...) */

        if(savedInstanceState != null && savedState == null) {
            savedState = savedInstanceState.getBundle("FRAGMENT_HELLO_WORD");
        }
        if(savedState != null) {
         helloWordTextView.setText(savedState.getCharSequence("TEXT_HELLO_WORD"));
        }
        savedState = null;

        /* (...) */
        return view;
    }
...
@Override
public void onSaveInstanceState(Bundle outState) {
    super.onSaveInstanceState(outState);

    //Save the fragment's state here somehow like this
    outState.putBundle("FRAGMENT_HELLO_WORD", (savedState != null) ? savedState : saveState());
}

活动中

public void onCreate(Bundle savedInstanceState) {
    ...
    if (savedInstanceState != null) {
        //Restore the fragment's instance
        mContent = getSupportFragmentManager().getFragment(savedInstanceState, "myFragmentName");
        ...
    }
    ...
}

@Override
protected void onSaveInstanceState(Bundle outState) {
    super.onSaveInstanceState(outState);

    //Save the fragment's instance
    getSupportFragmentManager().putFragment(outState, "myFragmentName", mContent);
}

从here和here编译的答案

希望有帮助。