Question

我正在尝试解析JSON数据，并使用RecyclerView将其显示在片段中。但是，当我运行该应用程序时，出现黑屏。我第一次使用Activity完成了这段代码，效果很好。然后，我将其转换为Fragment。在Fragment中显示空白屏幕。

这是我的Fragment

的代码

public class Tab1 extends Fragment {
    private RecyclerView mRecyclerView;
    private ExampleAdapter mExampleAdapter;
    private ArrayList<ExampleItem> mExampleList;
    private RequestQueue mRequestQueue;
    @Nullable
    @Override
    public View onCreateView(@NonNull LayoutInflater inflater, @Nullable ViewGroup container, @Nullable Bundle savedInstanceState) {

        View rootView = inflater.inflate(R.layout.tab1, container, false);
        mRecyclerView = rootView.findViewById(R.id.recycler_view);
        mRecyclerView.setHasFixedSize(true);
        mRecyclerView.setLayoutManager(new LinearLayoutManager(getActivity(), LinearLayoutManager.HORIZONTAL, false));
        mExampleList = new ArrayList<>();
        mRequestQueue = Volley.newRequestQueue(requireActivity());
        parseJson();
        return rootView;
    }

    private void parseJson(){
        String url ="http://maranamassapp.cf/json_getdata.php";
        JsonObjectRequest request = new JsonObjectRequest(Request.Method.GET, url, null,
                new Response.Listener<JSONObject>() {
                    @Override
                    public void onResponse(JSONObject response) {
                        try {
                            JSONArray jsonArray = response.getJSONArray("server_response");
                            for(int i = 0; i < jsonArray.length(); i++){
                                JSONObject ser =jsonArray.getJSONObject(i);
                                String creatorname =  ser.getString("filmname");
                                String imageUrl = ser.getString("filmimage");
                                String cat = ser.getString("filmcat");

                                mExampleList.add(new ExampleItem(imageUrl,creatorname,cat));
                            }

                            mExampleAdapter = new ExampleAdapter(getContext(),mExampleList);
                            mRecyclerView.setAdapter(mExampleAdapter);
                        } catch (JSONException e) {
                            e.printStackTrace();
                        }
                    }
                }, new Response.ErrorListener() {
            @Override
            public void onErrorResponse(VolleyError error) {
                error.printStackTrace();
            }
        });

        mRequestQueue.add(request);
    }
}

以及适配器代码

public class ExampleAdapter extends RecyclerView.Adapter <ExampleAdapter.ExampleViewHolder>{
    private Context mContext;
    private ArrayList<ExampleItem> mExampleList;
    public ExampleAdapter(Context context, ArrayList<ExampleItem> examplelist){
        mContext =context;
        mExampleList = examplelist;
    }

    @NonNull
    @Override
    public ExampleViewHolder onCreateViewHolder(@NonNull ViewGroup parent, int viewType) {
        View v = LayoutInflater.from(mContext).inflate(R.layout.example_item,parent,false);
        return new ExampleViewHolder(v);
    }

    @Override
    public void onBindViewHolder(@NonNull ExampleViewHolder holder, int position) {
        ExampleItem currentItem = mExampleList.get(position);
        String imageUrl = currentItem.getmImageUrl();
        String creatorName = currentItem.getmCreator();
        String cat =currentItem.getmCat();

        holder.mTextViewCreator.setText(creatorName);
        holder.mTextViewCat.setText(cat);
        Glide.with(mContext)
                .load(imageUrl)
                .into(holder.mImageView);
    }

    @Override
    public int getItemCount() {
        return mExampleList.size();
    }

    public class ExampleViewHolder extends RecyclerView.ViewHolder{
        public ImageView mImageView;
        public TextView mTextViewCreator;
        public TextView mTextViewCat;
        public ExampleViewHolder(View itemView) {
            super(itemView);
            mImageView = itemView.findViewById(R.id.image_view);
            mTextViewCreator = itemView.findViewById(R.id.text_view_creator);
            mTextViewCat = itemView.findViewById(R.id.text_view_cat);
        }
    }
}

有人可以帮忙吗？

Answer 1

我建议您像下面这样实现declare namespace some { type Api = { foo(n: number): string; bar(s: string, n: number): string } function api(): Api; } function wrapBuilder<T extends Record<keyof T, (...a: any[]) => any>>(fn: () => T) { return function <K extends keyof T>(functionName: K): T[K] { return ((...args: any[]) => { try { return fn()[functionName](...args); } catch (error) { throw error; } }); } } const wrapCallByName = wrapBuilder(() => some.api()); const foo = wrapCallByName('foo'); foo(1); //returns string const bar = wrapCallByName('bar'); bar('', 1); //returns string。

RecyclerView

请注意，我在@Nullable @Override public View onCreateView(@NonNull LayoutInflater inflater, @Nullable ViewGroup container, @Nullable Bundle savedInstanceState) { View rootView = inflater.inflate(R.layout.tab1, container, false); mRecyclerView = rootView.findViewById(R.id.recycler_view); mRecyclerView.setHasFixedSize(true); mRecyclerView.setLayoutManager(new LinearLayoutManager(getActivity(), LinearLayoutManager.HORIZONTAL, false)); mExampleList = new ArrayList<>(); mRequestQueue = Volley.newRequestQueue(requireActivity()); // Set the adapter here. // Use getActivity() instead of getContext() mExampleAdapter = new ExampleAdapter(getContext(),mExampleList); parseJson(); return rootView; } private void parseJson(){ String url ="http://maranamassapp.cf/json_getdata.php"; JsonObjectRequest request = new JsonObjectRequest(Request.Method.GET, url, null, new Response.Listener<JSONObject>() { @Override public void onResponse(JSONObject response) { try { JSONArray jsonArray = response.getJSONArray("server_response"); for(int i = 0; i < jsonArray.length(); i++){ JSONObject ser =jsonArray.getJSONObject(i); String creatorname = ser.getString("filmname"); String imageUrl = ser.getString("filmimage"); String cat = ser.getString("filmcat"); mExampleList.add(new ExampleItem(imageUrl,creatorname,cat)); } // Just call notifyDataSetChanged here mExampleAdapter.notifyDataSetChanged(); } catch (JSONException e) { e.printStackTrace(); } } }, new Response.ErrorListener() { @Override public void onErrorResponse(VolleyError error) { error.printStackTrace(); } }); mRequestQueue.add(request); }（而不是onCreateView）中将getActivity()作为上下文来设置适配器。在getContext函数中，当parseJson用新添加的数据更新时，我只是在调用notifyDataSetChanged。

此外，请检查从服务器正确获取响应，并且在解析响应时是否没有任何异常。

希望这行得通！

回收者视图中的片段为空

1 个答案: