Java 如何在两个片段之间通信

我正在尝试创建一个Android应用程序，它将包含两个片段。一个包含各种城市的列表，另一个包含这些城市的详细信息。我是移动开发的新手，很难弄清楚如何在他们之间进行通信。到目前为止，我已经将城市列表存储在一个片段中，但仍然需要弄清楚当单击其中一个列表项时如何显示描述。此外，我甚至不确定这些描述将存储在哪里，或者如何访问它。任何帮助都很好，谢谢你

cityDetails文件：

public class cityDetails extends Fragment {
    // TODO: Rename parameter arguments, choose names that match
    // the fragment initialization parameters, e.g. ARG_ITEM_NUMBER
    private static final String ARG_PARAM1 = "param1";
    private static final String ARG_PARAM2 = "param2";

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

    private OnFragmentInteractionListener mListener;

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

    /**
     * Use this factory method to create a new instance of
     * this fragment using the provided parameters.
     *
     * @param param1 Parameter 1.
     * @param param2 Parameter 2.
     * @return A new instance of fragment cityDetails.
     */
    // TODO: Rename and change types and number of parameters
    public static cityDetails newInstance(String param1, String param2) {
        cityDetails fragment = new cityDetails();
        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);
        }
    }

    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container,
                             Bundle savedInstanceState) {
        // Inflate the layout for this fragment
        return inflater.inflate(R.layout.fragment_city_details, container, false);
    }

    // TODO: Rename method, update argument and hook method into UI event
    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;
    }

    /**
     * This interface must be implemented by activities that contain this
     * fragment to allow an interaction in this fragment to be communicated
     * to the activity and potentially other fragments contained in that
     * activity.
     * <p>
     * See the Android Training lesson <a href=
     * "http://developer.android.com/training/basics/fragments/communicating.html"
     * >Communicating with Other Fragments</a> for more information.
     */
    public interface OnFragmentInteractionListener {
        // TODO: Update argument type and name
        void onFragmentInteraction(Uri uri);
    }

}

---

问题的两个部分：

如何在片段之间通信

如何存储详细信息的数据

对于第一个问题，最干净的解决方案是创建一个接口。基本上，在一个片段中有一个侦听器，它通知另一个片段更新。 或者更简单地说，不涉及所有这些，对于短期解决方案，在细节片段中创建一个更新函数或类似的东西。因此，当用户在列表片段中选择一个城市时，只需调用update函数，将城市名称作为键传入

---

关于第二个问题。简短的解决方案是创建一个散列图，其中键是城市名称，值是细节。因此，当细节片段获得城市名称时，它可以轻松地查找细节。随着需求的变化，您可以继续将其复杂化，例如将数据保存在单独的文件中并加载，拥有本地键值数据库，甚至在Firebase或AWS等云上拥有一个数据库来动态更新数据。

这些是CodingFlow的billiant视频，他用一个示例解释了如何更新数据

---

1.借助ViewModel

ViewModel过程非常简单，通过阅读MindWorks的共享ViewModel博客，您可以了解如何使用ViewModel在片段之间进行通信

2.借助接口

在你的碎片中创建一个接口a

在您的活动中实现FragmentA的接口

从活动中调用接口方法

---

在您的活动中，调用FragmentB进行所需的更改

我将如何创建该方法？我已经试了一段时间了，似乎做不好。我试图在片段中创建一个等于textview id的textview，然后使用if-else语句来设置文本，但这不起作用，我不知道如何知道列表中的哪个项目正在被单击。

public class citiesFragment extends Fragment {

    // TODO: Customize parameter argument names
    private static final String ARG_COLUMN_COUNT = "column-count";
    // TODO: Customize parameters
    private int mColumnCount = 1;
    private OnListFragmentInteractionListener mListener;

    /**
     * Mandatory empty constructor for the fragment manager to instantiate the
     * fragment (e.g. upon screen orientation changes).
     */
    public citiesFragment() {
    }

    // TODO: Customize parameter initialization
    @SuppressWarnings("unused")
    public static citiesFragment newInstance(int columnCount) {
        citiesFragment fragment = new citiesFragment();
        Bundle args = new Bundle();
        args.putInt(ARG_COLUMN_COUNT, columnCount);
        fragment.setArguments(args);
        return fragment;
    }

    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);

        if (getArguments() != null) {
            mColumnCount = getArguments().getInt(ARG_COLUMN_COUNT);
        }
    }

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

        if (view instanceof RecyclerView) {
            Context context = view.getContext();

            String[] cities = context.getResources().getStringArray(R.array.Cities);
            List<DummyItem> mValues = new ArrayList<>();
            for(int i = 0; i < cities.length; i++) {
                mValues.add(new DummyItem(String.valueOf(i + 1), cities[i], ""));
            }

            RecyclerView recyclerView = (RecyclerView) view;
            if (mColumnCount <= 1) {
                recyclerView.setLayoutManager(new LinearLayoutManager(context));
            } else {
                recyclerView.setLayoutManager(new GridLayoutManager(context, mColumnCount));
            }

            recyclerView.setAdapter(new MycitiesRecyclerViewAdapter(mValues, mListener));
        }

        return view;
    }


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

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

    /**
     * This interface must be implemented by activities that contain this
     * fragment to allow an interaction in this fragment to be communicated
     * to the activity and potentially other fragments contained in that
     * activity.
     * <p/>
     * See the Android Training lesson <a href=
     * "http://developer.android.com/training/basics/fragments/communicating.html"
     * >Communicating with Other Fragments</a> for more information.
     */
    public interface OnListFragmentInteractionListener {
        // TODO: Update argument type and name
        void onListFragmentInteraction(DummyItem item);
    }
}

public class MainActivity extends AppCompatActivity implements citiesFragment.OnListFragmentInteractionListener, cityDetails.OnFragmentInteractionListener{

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
    }

    @Override
    public void onListFragmentInteraction(DummyContent.DummyItem item) {

    }

    @Override
    public void onFragmentInteraction(Uri uri) {

    }
}