片段savedInstanceState不起作用

Question

我在這裏有幾個片段，這裏有一個片段，當我回到它時，我想保存它的狀態。我試着在testfragment中做這件事，當我點擊按鈕時，textview文本將變爲「test1」（textview的默認文本是「New Text」）。所以textview改變了文本，但是當我移動到另一個片段並回到它（HomeFragment）時，textview將轉到它的默認狀態文本（「New Text」）。所以我認爲savedInstanceState不能正常工作，因爲如果有的話，當我回到片段時它應該有「test1」。這裏是我的代碼：

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); 
    } 
}