Android片段在FragmentTransaction之后还原TextView

Question

I have 2 fragments: FragmentA and FragmentB . Both fragments have basically the same code that looks like this:

public class FragmentB extends Fragment{

    private TextView textView;
    private EditText editText;
    private Button button;

    boolean visible = true;

    @Nullable
    @Override
    public View onCreateView(LayoutInflater inflater, @Nullable ViewGroup container, Bundle savedInstanceState){
        final View rootView = inflater.inflate(R.layout.test_fragment, container, false);

        if (textView != null)
            Log.e("FragmentB", "Text was: " + textView.getText().toString());

        textView = (TextView) rootView.findViewById(R.id.textView);
        editText = (EditText) rootView.findViewById(R.id.editText);
        button = (Button) rootView.findViewById(R.id.button);
        ((TextView)rootView.findViewById(R.id.fragment)).setText("Fragment B");

        button.setOnClickListener(new View.OnClickListener(){
            @Override
            public void onClick(View v){
                Log.e("FragmentB", "Set text: " + editText.getText());
                textView.setText(editText.getText());
                visible = !visible;
                textView.setVisibility(visible ? View.VISIBLE : View.INVISIBLE);
            }
        });

        Log.e("FragmentB", "Text now: " + textView.getText());

        return rootView;
    }
}

To switch between the 2 fragments, i am calling fragmentTransaction.replace(R.id.main_content_frame, currentFragment); where currentFragment is the same instance that was created when the application started. The problem is whenever i press the button in FragmentB to hide the TextView , switch to FragmentA , then back to FragmentB , the TextView is visible again, although i still want to be hidden. Additionally, if i go back and forth one more time, the text in the TextView also gets reset, but only after going back and forth TWICE.

How can i keep the state of the fragments when switching between them?

I have tried using onSaveInstanceState() and onViewStateRestored() , but onViewStateRestored() keeps getting called with the Bundle set to null . Why does that happen?

Here is the code:

@Override
public void onViewStateRestored(Bundle savedInstanceState){
    Log.e("FragmentB", "Bundle: " + savedInstanceState);

    super.onViewStateRestored(savedInstanceState);
    try{
        textView.setText(savedInstanceState.getString("text"));
    }catch (NullPointerException e){
        e.printStackTrace();
    }

    Log.e("FragmentB", "Bundle: " + savedInstanceState);
    Log.e("FragmentB", "onViewStateRestored");
}

@Override
public void onSaveInstanceState(Bundle outState){
    super.onSaveInstanceState(outState);
    outState.putString("text", textView.getText().toString());
    Log.e("FragmentB", "onSaveInstanceState");
}

Answer 1

Using replace will destroy the fragment which is replaced . So each time you switch fragment ,a new fragment will be created. use hide and show will be better for you .

fragmentTransaction.add(fragmentA).add(fragmentB).commit();
fragmentTransaction.show(fragmentA).hide(fragmentB).commit();

Answer 2

Try to use:

fragmentTransaction.add(R.id.main_content_frame, currentFragment);

instead of:

fragmentTransaction.replace(R.id.main_content_frame, currentFragment);