java - RecyclerView 列表不可见

Question

我试图通过 recyclerview 从 fragment 上的服务器获取的 json 数据创建一个列表，但它不起作用。一切都很好，但列表没有填充，应用程序没有崩溃，我看不到错误在哪里，请帮我解决这个问题。

示例 json

{
    "status": 1,
    "message": "success",
    "notice": [
        {
            "id": 21,
            "name": "RSP TEST1",
            "up_date": "08/03/2020",
            "file_address": "noticeFiles/Event_lists1583650658.pdf"
        },
        {
            "id": 20,
            "name": "RSP TEST1",
            "up_date": "08/03/2020",
            "file_address": "noticeFiles/Event_lists1583650567.pdf"
        },
        {
            "id": 19,
            "name": "RSP TEST1",
            "up_date": "08/03/2020",
            "file_address": "noticeFiles/Event_lists1583650554.pdf"
        },
        {
            "id": 18,
            "name": "RSP TEST1",
            "up_date": "08/03/2020",
            "file_address": "noticeFiles/Event_lists1583650534.pdf"
        },
        {
            "id": 17,
            "name": "RSP TEST1",
            "up_date": "08/03/2020",
            "file_address": "noticeFiles/Event_lists1583650491.pdf"
        },
        {
            "id": 16,
            "name": "RSP TEST1",
            "up_date": "08/03/2020",
            "file_address": "noticeFiles/Event_lists1583649707.pdf"
        },
        {
            "id": 15,
            "name": "TEST1",
            "up_date": "08/03/2020",
            "file_address": "noticeFiles/Event_lists1583649660.pdf"
        },
        {
            "id": 14,
            "name": "TEST1",
            "up_date": "08/03/2020",
            "file_address": "noticeFiles/Event_lists1583649332.pdf"
        },
        {
            "id": 13,
            "name": "TEST1",
            "up_date": "08/03/2020",
            "file_address": "noticeFiles/Event_lists1583649185.pdf"
        },
        {
            "id": 12,
            "name": "TEST1",
            "up_date": "08/03/2020",
            "file_address": "noticeFiles/Event_lists1583649031.pdf"
        }
    ]
}

Notifications.java( fragment )

package org.gsac.techfiesta;

import android.app.AlertDialog;
import android.os.Bundle;

import androidx.fragment.app.Fragment;
import androidx.recyclerview.widget.LinearLayoutManager;
import androidx.recyclerview.widget.RecyclerView;
import dmax.dialog.SpotsDialog;

import android.util.Log;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.Toast;

import com.android.volley.Request;
import com.android.volley.RequestQueue;
import com.android.volley.Response;
import com.android.volley.VolleyError;
import com.android.volley.toolbox.StringRequest;
import com.android.volley.toolbox.Volley;

import org.gsac.techfiesta.Adapters.NoticeAdapter;
import org.gsac.techfiesta.Pojos.NoticePojo;
import org.json.JSONArray;
import org.json.JSONException;
import org.json.JSONObject;

import java.util.ArrayList;
import java.util.List;

public class Notifications extends Fragment {
    AlertDialog dialog;
    RecyclerView mList;
    LinearLayoutManager manager;
    List<NoticePojo> noticePojoList;
    RecyclerView.Adapter adapter;

    public Notifications() {

    }

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

        mList = v.findViewById(R.id.rv_notice);
        noticePojoList = new ArrayList<>();
        adapter = new NoticeAdapter(getContext(), noticePojoList);
        manager = new LinearLayoutManager(getContext());
        manager.setOrientation(LinearLayoutManager.VERTICAL);


        mList.setHasFixedSize(true);
        mList.setLayoutManager(manager);
        mList.setAdapter(adapter);

        //getNotices();

        return v;
    }

    private void getNotices() {
        String url = "https://example/api/v1/getNotices.php";
        dialog = new SpotsDialog.Builder().setContext(getContext()).build();
        dialog.setMessage("Loading...");
        dialog.show();
        RequestQueue requestQueue = Volley.newRequestQueue(getContext());
        StringRequest stringRequest = new StringRequest(Request.Method.GET, url, new Response.Listener<String>() {
            @Override
            public void onResponse(String response) {
                try {
                    JSONObject jsonObject = new JSONObject(response);
                    int status = jsonObject.getInt("status");
                    if (status == 1) {
                        JSONArray jsonArray = jsonObject.getJSONArray("notice");
                        for (int i = 0; i < jsonArray.length(); i++) {
                            JSONObject noticeObject = jsonArray.getJSONObject(i);
                            NoticePojo noticePojo = new NoticePojo();
                            noticePojo.setId(noticeObject.getInt("id"));
                            Log.i("NOTICE", "" + noticeObject.getInt("id"));
                            noticePojo.setName(noticeObject.getString("name"));
                            noticePojo.setDate(noticeObject.getString("up_date"));
                            noticePojo.setAddress(noticeObject.getString("file_address"));
                            //Line of code added from here ---------------
                            noticePojoList.add(noticePojo);
                            // to here -----------------------------------
                        }
                        Log.i("NOTICE", "State Changed!");
                        adapter.notifyDataSetChanged();
                        dialog.dismiss();
                    } else {
                        dialog.dismiss();
                        Toast.makeText(getContext(), "Failed to get Notices", Toast.LENGTH_LONG).show();
                    }
                } catch (JSONException e) {
                    e.printStackTrace();
                    dialog.dismiss();
                    Toast.makeText(getContext(), "Something went wrong", Toast.LENGTH_LONG).show();
                }
            }
        }, new Response.ErrorListener() {
            @Override
            public void onErrorResponse(VolleyError error) {
                dialog.dismiss();
                Toast.makeText(getContext(), "Network issue", Toast.LENGTH_LONG).show();
            }
        });

        requestQueue.add(stringRequest);

    }

    @Override
    public void setUserVisibleHint(boolean isVisibleToUser) {
        super.setUserVisibleHint(isVisibleToUser);
        if (isVisibleToUser) {
            getNotices();
        } else {
            // Do your Work
        }
    }

}

fragment_notification.xml

<?xml version="1.0" encoding="utf-8"?>
<FrameLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context=".Notifications">

    <androidx.recyclerview.widget.RecyclerView
        android:id="@+id/rv_notice"
        android:layout_width="match_parent"
        android:layout_height="match_parent" />

</FrameLayout>

lv_single_notice.xml

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout
    android:background="@color/colorPrimary"
    xmlns:android="http://schemas.android.com/apk/res/android" android:layout_width="match_parent"
    android:layout_height="wrap_content">
    <RelativeLayout
        android:layout_width="match_parent"
        android:layout_height="50dp">
        <ImageView
            android:id="@+id/iv_single_notice"
            android:src="@drawable/ic_notifications_black_24dp"
            android:layout_width="40dp"
            android:layout_height="40dp"
            android:layout_margin="5dp"/>
        <TextView
            android:layout_toRightOf="@id/iv_single_notice"
            android:text="TESTING"
            android:id="@+id/tv_notice_name"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:textSize="20sp"
            android:textColor="#fff"/>
        <TextView
            android:layout_below="@id/tv_notice_name"
            android:layout_marginLeft="52dp"
            android:text="2020"
            android:id="@+id/tv_notice_date"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:textSize="15sp"
            android:textColor="#fff"/>
        <ImageView
            android:layout_marginTop="15dp"
            android:layout_alignParentEnd="true"
            android:layout_width="30dp"
            android:layout_height="30dp"
            android:src="@drawable/ic_keyboard_arrow_right_black_24dp"/>
        <View
            android:layout_alignParentBottom="true"
            android:layout_width="match_parent"
            android:layout_height="2dp"
            android:background="#C8C3C3"/>
    </RelativeLayout>
</LinearLayout>

NoticePojo.java

package org.gsac.techfiesta.Pojos;

public class NoticePojo {
    public String name,address,date;
    public int id;

    public NoticePojo(int id, String name, String address, String date){
        this.id=id;
        this.name=name;
        this.address=address;
        this.date=date;
    }

    public NoticePojo(){

    }

    public int getId(){
        return this.id;
    }
    public String getName(){
        return this.name;
    }
    public String getAddress(){
        return this.address;
    }
    public String getDate(){
        return this.date;
    }

    public void setId(int id){
        this.id=id;
    }
    public void setName(String name){
        this.name=name;
    }
    public void setAddress(String address){
        this.address=address;
    }
    public void setDate(String date){
        this.date=date;
    }

}

NoticeAdapter.java

package org.gsac.techfiesta.Adapters;
import android.content.Context;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.TextView;

import org.gsac.techfiesta.Pojos.NoticePojo;
import org.gsac.techfiesta.R;

import java.util.List;

import androidx.annotation.NonNull;
import androidx.recyclerview.widget.RecyclerView;

public class NoticeAdapter extends RecyclerView.Adapter<NoticeAdapter.ViewHolder> {

    private Context context;
    private List<NoticePojo> list;

    public NoticeAdapter(Context context, List<NoticePojo> list){
        this.context=context;
        this.list=list;
    }

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

    @Override
    public void onBindViewHolder(@NonNull ViewHolder holder, int position){
        NoticePojo noticePojo = list.get(position);
        holder.noticeName.setText(noticePojo.getName());
        holder.noticeDate.setText(noticePojo.getAddress());
    }

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

    public class ViewHolder extends RecyclerView.ViewHolder {
        public TextView noticeName,noticeDate;
        public ViewHolder(@NonNull View itemView) {
            super(itemView);
            noticeName=itemView.findViewById(R.id.tv_notice_name);
            noticeDate=itemView.findViewById(R.id.tv_notice_date);
        }
    }
}

Answer 1

您错过了将 noticePojo 添加到 noticePojoList

在 for 循环中添加以下行。

noticePojoList.add(noticePojo);