java - RecyclerView不显示数据

Question

我是 android 新手，正在开发 android 应用程序，但我停留在这里。 RecyclerView 显示为空。日志中没有错误或崩溃。我删除并创建了新的但相同的问题。我找不到问题所在。

主要 Activity 的java代码

public class HomeActivity extends AppCompatActivity {
        private RecyclerView rcview1;
        private RecyclerView.Adapter cmpadapter1;
        private List<commdtylist> listitems2;
        protected void onCreate(Bundle savedInstanceState) {
            super.onCreate(savedInstanceState);
            setContentView(R.layout.activity_home);
     rcview1 = (RecyclerView) findViewById(R.id.commoditylist);
            rcview1.setItemAnimator(new DefaultItemAnimator());
            listitems2 = new ArrayList<>();
            rcview1.setHasFixedSize(true);
            viewcmp();
    }
     public void viewcmp() {
            StringRequest stringRequest=new StringRequest(Request.Method.POST, otpur, new Response.Listener<String>() {
                @Override
                public void onResponse(String response) {
                    try {
                        JSONObject jobj = new JSONObject(response);



                        JSONArray jsonArray = jobj.getJSONArray("Details");
                        for (int i = 0; i < jsonArray.length(); i++) {
                            jobj = jsonArray.getJSONObject(i);
                            commdtylist item = new commdtylist(
                                    jobj.getString("quantity_entitle"),
                                    jobj.getString("comm_code"),
                                    jobj.getString("item_description")


                            );
                            listitems2.add(item);
                        }
                        cmpadapter1 = new CommdityviewAdapter(listitems2, getApplicationContext());
                        rcview1.setAdapter(cmpadapter1);
                    } catch (JSONException e) {
                        e.printStackTrace();
                    }
                }
            }, new Response.ErrorListener() {
                @Override
                public void onErrorResponse(VolleyError error) {

                }
            }){
                @Override
                protected Map<String, String> getParams() throws AuthFailureError {
                    Map<String, String> param = new HashMap<>();
                    param.put("rc_no", crd);

                    return param;
                }
            };
            RequestQueue requestQueue= Volley.newRequestQueue(this);
            requestQueue.add(stringRequest);
        }
commdtylist

    public class commdtylist {

        private String quantity_entitle;
        private String comm_code;
        private String item_description;


        public commdtylist(String quantity_entitle, String comm_code, String item_description) {
            this.quantity_entitle = quantity_entitle;
            this.comm_code = comm_code;
            this.item_description = item_description;

        }

        public String getquantity_entitle() {
            return quantity_entitle;
        }

        public String getcomm_code() {
            return comm_code;
        }


        public String getitem_description() {
            return item_description;
        }        

    }

适配器

public class CommdityviewAdapter extends RecyclerView.Adapter<CommdityviewAdapter.RViewHolder> {

    private List<commdtylist> listitems2;
    private Context context;
    int lastPosition = -1;

    public CommdityviewAdapter(List<commdtylist> listitems2, Context context) {
        this.listitems2 = listitems2;
        this.context = context;
    }
    public static Toast t = null;

    @Override
    public RViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
        View v= LayoutInflater.from(parent.getContext()).inflate(R.layout.view_cmdstyle,parent,false);

        return new RViewHolder(v);
    }


    @Override
    public void onBindViewHolder(final RViewHolder holder,final int position) {
        final commdtylist listitem=listitems2.get(position);

        holder.quantity_entitle.setText(listitem.getquantity_entitle());
        holder.comm_code.setText(listitem.getcomm_code());
        holder.item_description.setText(listitem.getitem_description());

        setAnimation(holder.itemView, position);
    }

    private void setAnimation(View itemView, int position) {
        // If the bound view wasn't previously displayed on screen, it's animated
        if (position > lastPosition)
        {
            Animation animation = AnimationUtils.loadAnimation(itemView.getContext(), R.anim.up_from_bottom);
            itemView.startAnimation(animation);
            lastPosition = position;
        }

        else{
            Animation animation = AnimationUtils.loadAnimation(itemView.getContext(), R.anim.down_from_top);
            //android.R.anim.slide_in_left
            itemView.startAnimation(animation);
            lastPosition = position;
        }
    }

    @Override
    public int getItemCount() {
        return listitems2.size();
    }
    @Override
    public long getItemId(int position) {
        return position;
    }

    @Override
    public int getItemViewType(int position) {
        return position;
    }
    public class RViewHolder extends RecyclerView.ViewHolder{

        public TextView quantity_entitle,comm_code,item_description;

        public RViewHolder(View itemView) {
            super(itemView);

            quantity_entitle=(TextView)itemView.findViewById(R.id.quantity_entitle);
            comm_code=(TextView)itemView.findViewById(R.id.comm_code);
            item_description=(TextView)itemView.findViewById(R.id.item_description);


        }
    }
}

Answer 1

您必须添加 LayoutManager到 RecyclerView 。使用setLayoutManager (RecyclerView.LayoutManager layout)方法将 LayoutManager 设置为 RecyclerView。如果您没有设置任何LayoutManager，您将看不到任何数据。

LinearLayoutManager manager = new LinearLayoutManager(this);
recyclerView.setLayoutManager(manager);