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Question

非常感谢您的光临，我正在为学校开发一个应用程序，我遇到了另一个问题。该应用程序的主要思想是跟踪您的卡路里，我希望它能节省卡路里，所以当应用程序关闭时，它仍然会记住他们。我已经忙了一段时间了，现在尝试使用SavedPreferences，但我总是出现错误。我希望有人能帮我。

public class CaloriesEaten extends Fragment {

private Context mContext;
private static final String ARG_PARAM1 = "param1";
private static final String ARG_PARAM2 = "param2";
private static EditText caleaten;
private static EditText calalready;
private static TextView caltotal;
private static Button btnClick;
private EditText editText;
//private String calalreadystring = calalready.getText().toString();
//int CalCount = Integer.parseInt(calalreadystring);
Context context = getActivity();
SharedPreferences pref = context.getSharedPreferences("MyCalories", Context.MODE_PRIVATE);

// TODO: Rename and change types of parameters
private String mParam1;
private String mParam2;

private OnFragmentInteractionListener mListener;

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

public static CaloriesEaten newInstance(String param1, String param2) {
    CaloriesEaten fragment = new CaloriesEaten();
    Bundle args = new Bundle();
    args.putString(ARG_PARAM1, param1);
    args.putString(ARG_PARAM2, param2);
    fragment.setArguments(args);
    return fragment;
}

@Override
public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    if (getArguments() != null) {
        mParam1 = getArguments().getString(ARG_PARAM1);
        mParam2 = getArguments().getString(ARG_PARAM2);
    }
    String keki = pref.getString("CalorieCounter", "");
    editText.setText(keki);
}

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


    caleaten = (EditText) view.findViewById(R.id.CalorieInput);
    calalready = (EditText) view.findViewById(R.id.Cals);
    caltotal = (TextView) view.findViewById(R.id.CalNumber);
    btnClick = (Button)view.findViewById(R.id.addcalories);
    btnClick.setOnClickListener(new View.OnClickListener() {
        public void onClick(View v) {
            buttonClicked(v);
        }
    });

    return view;
}
public void buttonClicked (View view) {

    int x = Integer.parseInt(caleaten.getText().toString());

    int y = Integer.parseInt(calalready.getText().toString());

    int total = x + y;

    caltotal.setText(Integer.toString(total));
    calalready.setText(Integer.toString(total));
    caleaten.setText("");
    SharedPreferences.Editor edit = pref.edit();
    String calalreadystring = calalready.getText().toString();
    int CalCount = Integer.parseInt(calalreadystring);
    edit.putInt("CalorieCounter", CalCount);
    edit.commit();


}
public void onButtonPressed(Uri uri) {
    if (mListener != null) {
        mListener.onFragmentInteraction(uri);
    }
}

@Override
public void onAttach(Context context) {
    super.onAttach(context);
    if (context instanceof OnFragmentInteractionListener) {
        mListener = (OnFragmentInteractionListener) context;
    } else {
        throw new RuntimeException(context.toString()
                + " must implement OnFragmentInteractionListener");
    }
}

@Override
public void onDetach() {
    super.onDetach();
    mListener = null;
}

public interface OnFragmentInteractionListener {
    // TODO: Update argument type and name
    void onFragmentInteraction(Uri uri);
}

}

我可能做了很多明显的愚蠢的事情，但我真的弄不明白。

多谢！

Answer 1

全局声明SharedPreferences并在onCreateView方法内部初始化,

例如：

Context context; 
SharedPreferences pref;
.......
...
@Override 
public View onCreateView(LayoutInflater inflater, ViewGroup container,
                         Bundle savedInstanceState) {        View view =  inflater.inflate(R.layout.fragment_calories_eaten,
        container, false);

context = getActivity();
pref = context.getSharedPreferences("MyCalories", Context.MODE_PRIVATE);

.............
....
}