android - 片段 savedInstanceState 不起作用

Question

我这里有几个片段，有一个片段，当我回到它时，我想保存它的状态。我尝试在 testfragment 中执行此操作，当我单击按钮时，textview 文本将更改为“test1”（textview 的默认文本是“New Text”）。因此，textview 更改了文本，但是当我移动到另一个片段并返回到它时（HomeFragment），textview 将进入其默认状态文本（“新文本”）。所以我认为savedInstanceState它不起作用，因为如果它起作用，当我回到片段时它应该有“test1”。这是我的代码：

public class HomeFragment extends Fragment {
    public Button button;
    public TextView txt_test;
    public String data_test;
    public HomeFragment() {
        // Required empty public constructor
    }

    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container,
                         Bundle savedInstanceState) {
        View view = inflater.inflate(R.layout.fragment_home, container, false);

        return view;
    }

    public void onActivityCreated(Bundle savedInstanceState){
        super.onActivityCreated(savedInstanceState);
        if(savedInstanceState == null){

        }
        else{
            data_test = savedInstanceState.getString("txt_test");
            txt_test = (TextView) getActivity().findViewById(R.id.textView2);
            txt_test.setText(data_test);
        }
        button = (Button) getActivity().findViewById(R.id.button3);
        txt_test = (TextView) getActivity().findViewById(R.id.textView2);
        button.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                txt_test.setText("test1");

            }
        });
    }

    public void onSaveInstanceState(Bundle savedInstanceState){
        super.onSaveInstanceState(savedInstanceState);
        savedInstanceState.putString("txt_test",data_test);
    }

}

Answer 1

public class HomeFragment extends Fragment {
    Button button;
    TextView txt_test;
    String data_test;

    public HomeFragment() {
        // Required empty public constructor
    }

    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container,
                         Bundle savedInstanceState) {
        View view = inflater.inflate(R.layout.fragment_home, container, false);
        txt_test = (TextView) view.findViewById(R.id.textView2);
        button = (Button) view.findViewById(R.id.button3);

        button.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                txt_test.setText("test1");
            }
        });

        if(savedInstanceState == null) {
            // do nothing
        } else {
            data_test = savedInstanceState.getString("txt_test");
            txt_test.setText(data_test);
        }
        return view;
    }

    @Override
    public void onSaveInstanceState(Bundle savedInstanceState){
        super.onSaveInstanceState(savedInstanceState);
        savedInstanceState.putString("txt_test",data_test);
    }
}