java - 无法从不同扩展检索 SharedPreferences 值

Question

我试图将matrix_id的值从MainActivity(扩展Activity)传递到HomeActivity(扩展Activity)和ScheduleFragment(扩展Fragment)。 当我运行应用程序时，它会崩溃。

我对 Java 编程非常业余。

我应该做什么？

请帮帮我，谢谢。

这是 MainActivity.java 的一部分

    public class MainActivity extends Activity {

    public static final String PREFS_NAME="PreferencesValue";

    @Override
    public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.login_screen);

    b = (Button)findViewById(R.id.btnLogin);  
    matrix_id = (EditText)findViewById(R.id.txtMatric);


    b.setOnClickListener(new OnClickListener() {
        @Override
        public void onClick(View v) {

            SharedPreferences settings = getSharedPreferences(PREFS_NAME, 0);
            SharedPreferences.Editor editor = settings.edit();
            editor.putString("matrix", matrix_id.getText().toString());

            editor.commit(); 

            Intent i = new Intent(getApplicationContext(), HomeActivity.class);
    startActivity(i);
    finish();
        }
       });
      }

这是 HomeActivity.java 的一部分

     /**
 * Displaying fragment view for selected nav drawer list item
 * */
private void displayView(int position) {
    // update the main content by replacing fragments
    Fragment fragment = null;
    switch (position) {
    case 0: fragment = new ScheduleFragment();
        break;

    case 1: fragment = new ReminderFragment();
        break;

    case 2: fragment = new AboutFragment();
        break;

    case 3: fragment = new LogoutFragment();
        break;
            }

这是 ScheduleFragment.java

    public class ScheduleFragment extends Fragment {
private final Context context;


public static final String PREFS_NAME="PreferencesValue";

public ScheduleFragment(Context context){
    this.context = context;

}

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

    TextView tvmatrix = (TextView)rootView.findViewById(R.id.textViewMatrix);

    SharedPreferences settings = context.getSharedPreferences(PREFS_NAME, 0);

    tvmatrix.setText(settings.getString("matrix", "A324142"));



    return rootView;

 }
  }

Answer 1

你有

public ScheduleFragment(Context context){
this.context = context;
}

fragment 构造函数不得有任何参数。您可以使用 getActivity() 获取托管 fragment 的 Activity 的 Activity 上下文

SharedPreferences settings = getActivity().getSharedPreferences(PREFS_NAME, 0);