java片段不工作并且有错误

Question

让应用程序从服务器获取图像和文本，然后在卡片视图中显示 还有另一个应用程序，它有不同的标签，哪个标签是从Fragment扩展而来的

所以我想把我的第一个应用放在第二个应用标签中。 这样地：

因此，在片段中粘贴第一个应用程序中的我的主要活动代码，但有错误：

public class news extends Fragment {

    private RecyclerView recyclerView;
    private ArrayList<Deatails> data;
    private DataAdapter adapter;


    private View myFragmentView;
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {

    myFragmentView= inflater.inflate(R.layout.news, container, false);
      initViews();
    return myFragmentView;
}

    private void initViews() {

        recyclerView = (RecyclerView)myFragmentView.findViewById(R.id.card_recycler_view);
        recyclerView.setHasFixedSize(true);
        RecyclerView.LayoutManager layoutManager = new LinearLayoutManager(getApplicationContext());
        recyclerView.setLayoutManager(layoutManager);
        loadJSON();
    }

    private void loadJSON() {

            Retrofit retrofit = new Retrofit.Builder()
                    .baseUrl("http://memaraneha.ir/")
                    .addConverterFactory(GsonConverterFactory.create())
                    .build();
            RequestInterface request = retrofit.create(RequestInterface.class);
            Call<JSONResponse> call = request.getJSON();

            final ProgressDialog progressDialog = new ProgressDialog(this);
            progressDialog.show();

            call.enqueue(new Callback<JSONResponse>() {
                @Override
                public void onResponse(Call<JSONResponse> call, Response<JSONResponse> response) {
                    progressDialog.dismiss();

                    JSONResponse jsonResponse = response.body();
                    data = new ArrayList<>(Arrays.asList(jsonResponse.getAndroid()));
                    adapter = new DataAdapter(MainActivity.this, data);
                    recyclerView.setAdapter(adapter);
                }

                @Override
                public void onFailure(Call<JSONResponse> call, Throwable t) {
                    progressDialog.dismiss();
                    Log.d("Error", t.getMessage());
                }
            });
    }
}

这是我的错误：

,

,

Answer 1

您应该在Fragment中使用指向View的链接

内部片段

private View myFragmentView;

    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
    myFragmentView = inflater.inflate(R.layout.news, container, false);
    return myFragmentView;
}

不能只是将粘贴代码从活动复制到片段中。 您需要从片段视图启动findViewById

myFragmentView.findViewById(R.id.addYourViewHere);

不能在片段的OnCreateView方法之前运行init方法

Answer 2

我解决了我的问题，因此它为人们提供了正确的代码：

public class news extends Fragment {

    private RecyclerView recyclerView;
    private ArrayList<Deatails> data;
    private DataAdapter adapter;
    private View myFragmentView;



    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {


        myFragmentView= inflater.inflate(R.layout.news, container, false);
        initViews();
        return myFragmentView;
    }

    private void initViews() {

        recyclerView = (RecyclerView)myFragmentView.findViewById(R.id.card_recycler_view);
        recyclerView.setHasFixedSize(true);
        RecyclerView.LayoutManager layoutManager = new LinearLayoutManager(getActivity().getApplicationContext());
        recyclerView.setLayoutManager(layoutManager);
        loadJSON();
    }

    private void loadJSON() {

            Retrofit retrofit = new Retrofit.Builder()
                    .baseUrl("http://memaraneha.ir/")
                    .addConverterFactory(GsonConverterFactory.create())
                    .build();
            RequestInterface request = retrofit.create(RequestInterface.class);
            Call<JSONResponse> call = request.getJSON();

            final ProgressDialog progressDialog = new ProgressDialog(getActivity());
            progressDialog.show();

            call.enqueue(new Callback<JSONResponse>() {
                @Override
                public void onResponse(Call<JSONResponse> call, Response<JSONResponse> response) {
                    progressDialog.dismiss();

                    JSONResponse jsonResponse = response.body();
                    data = new ArrayList<>(Arrays.asList(jsonResponse.getAndroid()));
                    adapter = new DataAdapter(getActivity(), data);
                    recyclerView.setAdapter(adapter);
                }

                @Override
                public void onFailure(Call<JSONResponse> call, Throwable t) {
                    progressDialog.dismiss();
                    Log.d("Error", t.getMessage());
                }
            });
    }
}

Answer 3

当您使用fragment时，必须重写它的onCreateView方法

例如：

public class FavFragment extends Fragment {

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

    mRecyclerView = (RecyclerView) v.findViewById(R.id.my_recycler_view);
    layoutEmpty = (RelativeLayout) v.findViewById(R.id.layoutEmpty);
    btnShowOnMap = (FloatingActionButton) v.findViewById(R.id.btnShowOnMap);
    fabRoulette = (FloatingActionButton) v.findViewById(R.id.fabRoulette);
    mainView = v.findViewById(R.id.mainView);


    return v;
}