我的customAdapter用于回收器视图不起作用

Question

导致回收者视图不显示的问题是什么?

MainActivity.java

import androidx.appcompat.app.AppCompatActivity;
import androidx.recyclerview.widget.LinearLayoutManager;
import androidx.recyclerview.widget.RecyclerView;
import android.app.ProgressDialog;
import android.os.Bundle;
import android.util.Log;
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.JsonObjectRequest;
import com.android.volley.toolbox.Volley;
import org.json.JSONArray;
import org.json.JSONException;
import org.json.JSONObject;
import java.util.ArrayList;
import java.util.List;
public class MainActivity extends AppCompatActivity {
    RecyclerView recyclerView;
    private ProgressDialog dialog;
    List<ModelRecycler> newslist;
    RequestQueue requestQueue;
    private static final String API_URL = "https://newsapi.in/newsapi/news.php?key=qEhn6RWpLRebtTmkOpQcr7CxDKRGHi&category=tamil_state";
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        recyclerView=findViewById(R.id.recyclerView);
        newslist = new ArrayList<>();
        requestQueue = Volley.newRequestQueue(this);
        JsonObjectRequest jsonObjectRequest = new JsonObjectRequest(Request.Method.GET, API_URL, null, new Response.Listener<JSONObject>() {
            @Override
            public void onResponse(JSONObject response) {
                try{
                    JSONArray array = response.getJSONArray("News");
                    for(int i=0;i<array.length();i++){
                        JSONObject c = array.getJSONObject(i);
                        String image = c.getString("image");
                        Log.d("App", "Log : " + c.getString("image"));
                        String title = c.getString("title");
                        Log.d("App", "Log : " + c.getString("title"));
                        String description = c.getString("description");
                        Log.d("App", "Log : " + c.getString("description"));
                        String published_date = c.getString("published_date");
                        Log.d("App", "Log : " + c.getString("published_date"));
                        String url = c.getString("url");
                        Log.d("App", "Log : " + c.getString("url"));
//                        Toast.makeText(MainActivity.this, "Log : " + c.getString("published_date"), Toast.LENGTH_SHORT).show();
                        ModelRecycler modelRecycler = new ModelRecycler(image,title,description,published_date,url);
                        newslist.add(modelRecycler);
                    }
                }catch (JSONException e){
                    Log.d("Error", "Json parsing error: " + e.getMessage());
                }
            }
        }, new Response.ErrorListener() {
            @Override
            public void onErrorResponse(VolleyError error) {
                Toast.makeText(MainActivity.this, "Error Occured: " + error, Toast.LENGTH_SHORT).show();
            }
        });
        requestQueue.add(jsonObjectRequest);
        LinearLayoutManager l1 = new LinearLayoutManager(getApplicationContext());
        l1.setOrientation(LinearLayoutManager.VERTICAL);
        recyclerView.setLayoutManager(l1);
        MyAdapter myAdapter = new MyAdapter(this, newslist);
        recyclerView.setAdapter(myAdapter);
    }
}

MyAdapter.java

import android.content.Context;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.Adapter;
import android.widget.ImageView;
import android.widget.TextView;
import androidx.annotation.NonNull;
import androidx.recyclerview.widget.RecyclerView;
import com.bumptech.glide.Glide;
import java.util.List;
public class MyAdapter extends RecyclerView.Adapter<MyAdapter.MyViewHolder> {
    private Context mContext;
    private List<ModelRecycler> mData;
    public MyAdapter (Context mContext, List<ModelRecycler> mData) {
        this.mContext = mContext;
        this.mData = mData;
    }
    @NonNull
    @Override
    public MyViewHolder onCreateViewHolder(@NonNull ViewGroup parent, int viewType) {
        View v;
        LayoutInflater inflater = LayoutInflater.from(mContext);
        v = inflater.inflate(R.layout.list_item, parent, false);
        return new MyViewHolder(v);
    }
    @Override
    public void onBindViewHolder(@NonNull MyViewHolder holder, int position) {
        holder.news_title.setText(mData.get(position).getTitle());
        holder.news_description.setText(mData.get(position).getDescription());
        holder.news_time.setText(mData.get(position).getTime());
        Glide.with(mContext)
                .load(mData.get(position).getImage())
                .into(holder.news_image);
    }
    @Override
    public int getItemCount() {
        return mData.size();
    }
    public static class MyViewHolder extends RecyclerView.ViewHolder {
        TextView news_title, news_description, news_time;
        ImageView news_image;
        public MyViewHolder(@NonNull View itemView) {
            super(itemView);
            news_title = itemView.findViewById(R.id.news_title);
            news_description = itemView.findViewById(R.id.news_description);
            news_time = itemView.findViewById(R.id.news_time);
            news_image = itemView.findViewById(R.id.news_image);
        }
    }
}

ModelRecycler.java

public class ModelRecycler {
    String image, title, description, time, url;
    public ModelRecycler(String image, String title, String description, String time, String url) {
        this.image = image;
        this.title = title;
        this.description = description;
        this.time = time;
        this.url = url;
    }
    public ModelRecycler() {
    }
    public String getImage() {
        return image;
    }
    public String getTitle() {
        return title;
    }
    public String getDescription() {
        return description;
    }
    public String getTime() {
        return time;
    }
    public String getUrl() {
        return url;
    }
}

清单

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    package="com.technoapps.tamilnews">
    <uses-permission android:name="android.permission.INTERNET"/>
    <uses-permission android:name="android.permission.READ_EXTERNAL_STORAGE"/>
    <uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE"/>
    <uses-permission android:name="android.permission.MANAGE_EXTERNAL_STORAGE"/>
    <uses-permission android:name="android.permission.WAKE_LOCK" />
    <application
        android:allowBackup="true"
        android:icon="@mipmap/ic_launcher"
        android:label="@string/app_name"
        android:roundIcon="@mipmap/ic_launcher_round"
        android:supportsRtl="true"
        android:theme="@style/Theme.TamilNews">
        <activity
            android:name=".MainActivity"
            android:exported="true">
            <intent-filter>
                <action android:name="android.intent.action.MAIN" />
                <category android:name="android.intent.category.LAUNCHER" />
            </intent-filter>
        </activity>
    </application>
</manifest>

list_layout

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="wrap_content"
    android:layout_height="match_parent"
    android:background="#F8FFFFFF">
    <ScrollView
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:padding="4dp">
        <LinearLayout
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:orientation="vertical">
            <RelativeLayout
                android:layout_width="match_parent"
                android:layout_height="190dp"
                android:background="#fff"
                android:elevation="8dp"
                android:padding="10dp">
                <TextView
                    android:id="@+id/news_title"
                    android:layout_width="240dp"
                    android:layout_height="wrap_content"
                    android:text="Lorem Ipsum Dolor Amet, Consectetur Adipiscing Elit Ipsum Dolor Amet"
                    android:textSize="18sp"
                    android:textStyle="bold" />
                <TextView
                    android:id="@+id/news_description"
                    android:layout_width="240dp"
                    android:layout_height="wrap_content"
                    android:layout_below="@+id/news_title"
                    android:layout_marginTop="10dp"
                    android:text="There are many variations of passages of Lorem Ipsum available, but the majority have suffered alteration in some form..."
                    android:textSize="14dp" />
                <TextView
                    android:id="@+id/news_time"
                    android:layout_width="wrap_content"
                    android:layout_height="wrap_content"
                    android:layout_below="@+id/news_description"
                    android:layout_marginTop="10dp"
                    android:text="30 min ago"
                    android:textSize="12dp"
                    android:textStyle="bold" />
                <ImageView
                    android:id="@+id/news_image"
                    android:layout_width="wrap_content"
                    android:layout_height="150dp"
                    android:layout_marginLeft="5dp"
                    android:layout_toRightOf="@+id/news_title"
                    android:scaleType="centerCrop"
                    android:src="@drawable/search" />
            </RelativeLayout>
        </LinearLayout>
    </ScrollView>
</LinearLayout>

我正在从json中获取数据，并试图在回收器视图中显示。日志显示我正在获取数据，但回收者视图未显示。

如何解决这个问题?

Answer 1

请使用下面的代码，

public class MainActivity extends AppCompatActivity {
    RecyclerView recyclerView;
    private ProgressDialog dialog;
    List<ModelRecycler> newslist;
    RequestQueue requestQueue;
    private static final String API_URL = "https://newsapi.in/newsapi/news.php?key=qEhn6RWpLRebtTmkOpQcr7CxDKRGHi&category=tamil_state";
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        recyclerView=findViewById(R.id.recyclerView);
        newslist = new ArrayList<>();
        requestQueue = Volley.newRequestQueue(this);
        JsonObjectRequest jsonObjectRequest = new JsonObjectRequest(Request.Method.GET, API_URL, null, new Response.Listener<JSONObject>() {
            @Override
            public void onResponse(JSONObject response) {
                try{
                    JSONArray array = response.getJSONArray("News");
                    for(int i=0;i<array.length();i++){
                        JSONObject c = array.getJSONObject(i);
                        String image = c.getString("image");
                        Log.d("App", "Log : " + c.getString("image"));
                        String title = c.getString("title");
                        Log.d("App", "Log : " + c.getString("title"));
                        String description = c.getString("description");
                        Log.d("App", "Log : " + c.getString("description"));
                        String published_date = c.getString("published_date");
                        Log.d("App", "Log : " + c.getString("published_date"));
                        String url = c.getString("url");
                        Log.d("App", "Log : " + c.getString("url"));
//                        Toast.makeText(MainActivity.this, "Log : " + c.getString("published_date"), Toast.LENGTH_SHORT).show();
                        ModelRecycler modelRecycler = new ModelRecycler(image,title,description,published_date,url);
                        newslist.add(modelRecycler);
 LinearLayoutManager l1 = new LinearLayoutManager(getApplicationContext());
        l1.setOrientation(LinearLayoutManager.VERTICAL);
        recyclerView.setLayoutManager(l1);
        MyAdapter myAdapter = new MyAdapter(this, newslist);
        recyclerView.setAdapter(myAdapter);
                    }
                }catch (JSONException e){
                    Log.d("Error", "Json parsing error: " + e.getMessage());
                }
            }
        }, new Response.ErrorListener() {
            @Override
            public void onErrorResponse(VolleyError error) {
                Toast.makeText(MainActivity.this, "Error Occured: " + error, Toast.LENGTH_SHORT).show();
            }
        });
        requestQueue.add(jsonObjectRequest);
       
    }
}