使用 recyclerview 和 volley 错误解析 JSON 数据

Question

我正在尝试从 mySQL 获取 JSON 数据到 android 应用程序，跟随 this。我收到此错误 E/RecyclerView: No adapter attached; skipping layout。我尝试查找其他帖子的建议，但仍然无法解决问题。以下是我正在处理的代码：

import androidx.recyclerview.widget.RecyclerView;

import android.os.Bundle;

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.json.JSONArray;
import org.json.JSONException;
import org.json.JSONObject;

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

public class MainActivity extends AppCompatActivity {
    private static final String HI ="http://xxx/phpMyAdmin-5.0.4/Appi.php" ;   //xxx is ip and the user name
    private List<List_Data> list_data;
    private RecyclerView rv;
    private MyAdapter adapter;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        rv=(RecyclerView)findViewById(R.id.recyclerView);
        rv.setHasFixedSize(true);
        rv.setLayoutManager(new LinearLayoutManager(this));
        list_data=new ArrayList<>();
        adapter=new MyAdapter(list_data);

        getMovieData();

    }

    private void getMovieData() {
        StringRequest stringRequest=new StringRequest(Request.Method.GET, HI, new Response.Listener<String>() {
            @Override
            public void onResponse(String response) {
                try {
                    JSONObject jsonObject=new JSONObject(response);
                    JSONArray array=jsonObject.getJSONArray("data");
                    for (int i=0; i<array.length(); i++ ){
                        JSONObject ob=array.getJSONObject(i);
                        List_Data listData=new List_Data(ob.getString("name")
                                ,ob.getString("moive"));
                        list_data.add(listData);
                    }
                    rv.setAdapter(adapter);
                } catch (JSONException e) {
                    e.printStackTrace();
                }

            }
        }, new Response.ErrorListener() {
            @Override
            public void onErrorResponse(VolleyError error) {

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

JSON格式为：

 [{"ID":"1","name":"ab","movie":"cd"},{"ID":"2","name":"ef","movie":"gh"}]

适配器是：

import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.LinearLayout;
import android.widget.ListView;
import android.widget.TextView;
import androidx.recyclerview.widget.RecyclerView;

import java.util.List;

public class MyAdapter extends RecyclerView.Adapter<MyAdapter.ViewHolder>{
    private List<List_Data>list_data;

    public MyAdapter(List<List_Data> list_data) {
        this.list_data = list_data;
    }

    @Override
    public ViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
        View view= LayoutInflater.from(parent.getContext()).inflate(R.layout.list_data,parent,false);
        return new ViewHolder(view);
    }

    @Override
    public void onBindViewHolder(ViewHolder holder, int position) {
        List_Data listData=list_data.get(position);
        holder.txtname.setText(listData.getName());
        holder.txtmovie.setText(listData.getMoviename());
    }

    @Override
    public int getItemCount() {

        return list_data.size();
    }

    public class ViewHolder extends RecyclerView.ViewHolder{
        private TextView txtname,txtmovie;
        public ViewHolder(View itemView) {
            super(itemView);
            txtname=(TextView)itemView.findViewById(R.id.txt_name);
            txtmovie=(TextView)itemView.findViewById(R.id.txt_moviename);
        }
    }
}

此外，我这样设置 class：

    public class List_Data {
    private String name;
    private String moviename;

    public List_Data(String name, String moviename) {
        this.name = name;
        this.moviename = moviename;
    }

    public String getName() {
        return name;
    }

    public String getMoviename() {
        return moviename;
    }
}

而 activity_main.xml 是：

<RelativeLayout
    xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context=".MainActivity">

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

</RelativeLayout>

和lis_data.xml：

<LinearLayout
xmlns:android="http://schemas.android.com/apk/res/android" android:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="horizontal">
<androidx.cardview.widget.CardView
    android:padding="10dp"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    >
    <LinearLayout
        android:padding="10dp"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:orientation="vertical">
        <LinearLayout
            android:layout_marginLeft="10dp"
            android:layout_width="match_parent"
            android:layout_height="match_parent"
            android:orientation="horizontal">
            <TextView
                android:textColor="#111"
                android:layout_width="wrap_content"
                android:layout_height="wrap_content"
                android:text="name:"/>

            <TextView
                android:id="@+id/txt_name"
                android:textColor="#111"
                android:layout_marginLeft="10dp"
                style="@style/Base.TextAppearance.AppCompat.Medium"
                android:layout_width="wrap_content"
                android:layout_height="wrap_content"
                />
        </LinearLayout>
        <LinearLayout
            android:layout_marginTop="10dp"
            android:layout_marginLeft="10dp"
            android:layout_width="match_parent"
            android:layout_height="match_parent"
            android:orientation="horizontal">
            <LinearLayout
                android:layout_marginLeft="10dp"
                android:layout_width="match_parent"
                android:layout_height="match_parent"
                android:orientation="horizontal">
            <TextView
                android:textColor="#111"
                android:layout_width="wrap_content"
                android:layout_height="wrap_content"
                android:text="moivename:"/>

            <TextView
                android:id="@+id/txt_moviename"
                android:textColor="#111"
                android:layout_marginLeft="10dp"
                style="@style/Base.TextAppearance.AppCompat.Medium"
                android:layout_width="wrap_content"
                android:layout_height="wrap_content"
                />
        </LinearLayout>
    </LinearLayout>
    </LinearLayout>
</androidx.cardview.widget.CardView>

提前感谢您的建议！

Answer 1

在您的代码中，适配器总是在获取新数据时重新设置。最好设置一次适配器，并在每次获取新数据时通知数据更改。这是我的建议。在 onCreate 上设置回收器视图适配器

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
    rv=(RecyclerView)findViewById(R.id.recyclerView);
    rv.setHasFixedSize(true);
    rv.setLayoutManager(new LinearLayoutManager(this));
    list_data=new ArrayList<>();
    adapter=new MyAdapter(list_data);
    // set adapter
    rv.setAdapter(adapter);
    getMovieData();

}

在getMovieData()数据更新后，调用adapter.notifyDataSetChanged()而不是设置新适配器

private void getMovieData() {
    StringRequest stringRequest=new StringRequest(Request.Method.GET, HI, new Response.Listener<String>() {
        @Override
        public void onResponse(String response) {
            try {
                JSONObject jsonObject=new JSONObject(response);
                JSONArray array=jsonObject.getJSONArray("data");
                for (int i=0; i<array.length(); i++ ){
                    JSONObject ob=array.getJSONObject(i);
                    List_Data listData=new List_Data(ob.getString("name")
                            ,ob.getString("moive"));
                    list_data.add(listData);
                }
                adapter.notifyDataSetChanged()
            } catch (JSONException e) {
                e.printStackTrace();
            }

        }
    }, new Response.ErrorListener() {
        @Override
        public void onErrorResponse(VolleyError error) {

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

Answer 2

更新：我尝试了@hakim 的建议。该应用程序仍然运行但数据未显示。

我还发现 new Response.Listener<String>() 和 new Response.ErrorListener() 在下面的 getMoiveData() 中是灰色的：

private void getMovieData() {
    StringRequest stringRequest=new StringRequest(Request.Method.GET, HI, new Response.Listener<String>() {
        @Override
        public void onResponse(String response) {
            try {
                JSONArray array=new JSONArray(response);
                for (int i=0; i<array.length(); i++ ){
                    JSONObject ob=array.getJSONObject(i);
                    List_Data listData=new List_Data(ob.getString("name")
                            ,ob.getString("moive"));
                    list_data.add(listData);
                }
                adapter.notifyDataSetChanged();
            } catch (JSONException e) {
                e.printStackTrace();
            }

        }
    }, new Response.ErrorListener() {
        @Override
        public void onErrorResponse(VolleyError error) {

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

Answer 3

您可以使用下面的代码

  public class MainActivity extends AppCompatActivity {
    private static final String HI ="http://xxx/phpMyAdmin-5.0.4/Appi.php" ;   //xxx 
       is ip and the user name
    private List<List_Data> list_data;
    private RecyclerView rv;
    private MyAdapter adapter;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        rv=(RecyclerView)findViewById(R.id.recyclerView);
        rv.setHasFixedSize(true);
        rv.setLayoutManager(new LinearLayoutManager(this));
        list_data=new ArrayList<>();
     
        getMovieData();

    }

    private void getMovieData() {
        StringRequest stringRequest=new StringRequest(Request.Method.GET, HI, new Response.Listener<String>() {
            @Override
            public void onResponse(String response) {
                try {
                    JSONObject jsonObject=new JSONObject(response);
                    JSONArray array=jsonObject.getJSONArray("data");
                    for (int i=0; i<array.length(); i++ ){
                        JSONObject ob=array.getJSONObject(i);
                        List_Data listData=new List_Data(ob.getString("name")
                                ,ob.getString("moive"));
                        list_data.add(listData);
                    }
                       setAdapter(listData)
                } catch (JSONException e) {
                    e.printStackTrace();
                }

            }
        }, new Response.ErrorListener() {
            @Override
            public void onErrorResponse(VolleyError error) {

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

     public void setAdapter(List<List_Data> list_data){

  adapter=new MyAdapter(list_data);
    rv.setAdapter(adapter);
    

   }
   }

使用 recyclerview 和 volley 错误解析 JSON 数据

Parsing JSON data with recyclerview and volley error

java

android

android-volley

android-recyclerview