如何解决使用 recyclerview 和 volley 错误解析 JSON 数据
我正在尝试按照 this 从 MysqL 获取 JSON 数据到 Android 应用程序。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);
}
}
}
另外,我像这样设置类:
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;
}
}
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>
还有 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>
预先感谢您的建议!
解决方法
在您的代码中,当获得新数据时,适配器将始终重新设置。最好设置一次适配器,并在获得新数据时通知数据更改。 这是我的建议。 onCreate 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();
}
在数据更新后的getMovieData()
中,调用adapter.notifyDataSetChanged()
而不是设置新的适配器
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);
}
,
您可以使用以下代码
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,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);
}
}
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