RecyclerView 最初不加载数据
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【中文标题】RecyclerView 最初不加载数据【英文标题】：RecyclerView Does Not Load Data Initially 【发布时间】：2019-06-19 13:14:16 【问题描述】：我在我的 android 项目的 Fragment 中使用 Spinner 和 RecyclerView。 在我在 Spinner 中选择一个项目之前，我的 RecyclerView 不会显示任何数据。 如果不从 Spinner 中选择项目，我应该怎么做才能显示 RecyclerView 的结果？ 在第一个回收站应该显示 10 吸引力。
我的代码：
Attraction.java
package com.rayantec.reservation.reservationdemo.Model;
import android.app.ProgressDialog;
import android.os.Bundle;
import android.support.annotation.NonNull;
import android.support.annotation.Nullable;
import android.support.v4.app.Fragment;
import android.support.v7.widget.LinearLayoutManager;
import android.support.v7.widget.RecyclerView;
import android.util.Log;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.AdapterView;
import android.widget.ArrayAdapter;
import android.widget.BaseAdapter;
import android.widget.Spinner;
import android.widget.TextView;
import android.widget.Toast;
import com.android.volley.DefaultRetryPolicy;
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.JsonArrayRequest;
import com.android.volley.toolbox.JsonObjectRequest;
import com.android.volley.toolbox.Volley;
import com.rayantec.reservation.reservationdemo.Adapter.AttractionAdapter;
import com.rayantec.reservation.reservationdemo.G;
import com.rayantec.reservation.reservationdemo.Lists.AttractionList;
import com.rayantec.reservation.reservationdemo.Lists.CityList;
import com.rayantec.reservation.reservationdemo.R;
import com.toptoche.searchablespinnerlibrary.SearchableSpinner;
import org.json.JSONArray;
import org.json.JSONException;
import org.json.JSONObject;
import java.util.ArrayList;
public class Attractions extends Fragment
RecyclerView recyclerView;
ArrayList<AttractionList> AttractionData = new ArrayList<>();
public SearchableSpinner spinnerCitiest;
ArrayList<CityList> cityLists = new ArrayList<>();
ProgressDialog progressDialog;
public void showCity(View view)
spinnerCitiest = (SearchableSpinner) view.findViewById(R.id.SpinnerCitiestId);
spinnerCitiest.setTitle("Please Select City");
spinnerCitiest.setPositiveButton("Ok");
//spinnerCitiest.setSelection(2);
JsonArrayRequest JsonObjectRequest = new JsonArrayRequest(Request.Method.GET, G.serverURL + "/android/jsyncs/getdata/city", null, new Response.Listener<JSONArray>()
@Override
public void onResponse(JSONArray response)
//progressDialog.dismiss();
try
for (int i = 0; i < response.length(); i++)
JSONObject jsonOBJ = response.getJSONObject(i);
String id = jsonOBJ.getString("id");
String title = jsonOBJ.getString("title");
cityLists.add(new CityList(id, title));
catch (JSONException e1)
e1.printStackTrace();
, new Response.ErrorListener()
@Override
public void onErrorResponse(VolleyError error)
//progressDialog.dismiss();
Toast.makeText(G.context, "Server Connection error", Toast.LENGTH_SHORT).show();
);
JsonObjectRequest.setRetryPolicy(new DefaultRetryPolicy(7000, DefaultRetryPolicy.DEFAULT_MAX_RETRIES, DefaultRetryPolicy.DEFAULT_BACKOFF_MULT));
RequestQueue requestQueue = Volley.newRequestQueue(G.context);
requestQueue.add(JsonObjectRequest);
ArrayAdapter<CityList> adapterCities = new ArrayAdapter<CityList>(G.context, android.R.layout.simple_spinner_item, cityLists);
adapterCities.setDropDownViewResource(android.R.layout.simple_spinner_dropdown_item);
spinnerCitiest.setAdapter(adapterCities);
spinnerCitiest.setOnItemSelectedListener(new AdapterView.OnItemSelectedListener()
@Override
public void onItemSelected(AdapterView<?> adapterView, View view, int position, long l)
CityList cityList = (CityList) adapterView.getSelectedItem();
Toast.makeText(G.context, "City ID: " + cityList.getId() + ", City Name : " + cityList.getTitle(), Toast.LENGTH_SHORT).show();
@Override
public void onNothingSelected(AdapterView<?> adapterView)
);
public void showRandomAttractions(View view)
recyclerView = (RecyclerView) view.findViewById(R.id.RecyclerAttracionId);
JsonArrayRequest JsonObjectRequests = new JsonArrayRequest(Request.Method.GET, G.serverURL + "/android/jsyncs/getdata/randattraction", null, new Response.Listener<JSONArray>()
@Override
public void onResponse(JSONArray response)
progressDialog.dismiss();
//AttractionList sampledata = new AttractionList();
try
for (int i = 0; i < response.length(); i++)
JSONObject jsonOBJs = response.getJSONObject(i);
String id = jsonOBJs.getString("id");
String title = jsonOBJs.getString("title");
String imageUrl = jsonOBJs.getString("imageUrl");
String location = jsonOBJs.getString("location");
String type = jsonOBJs.getString("type");
String body = jsonOBJs.getString("body");
AttractionData.add(new AttractionList(id, title, body, location, imageUrl, type));
catch (JSONException e1)
e1.printStackTrace();
, new Response.ErrorListener()
@Override
public void onErrorResponse(VolleyError error)
progressDialog.dismiss();
Toast.makeText(G.context, "Server Connection error", Toast.LENGTH_SHORT).show();
);
JsonObjectRequests.setRetryPolicy(new DefaultRetryPolicy(7000, DefaultRetryPolicy.DEFAULT_MAX_RETRIES, DefaultRetryPolicy.DEFAULT_BACKOFF_MULT));
RequestQueue requestQueue = Volley.newRequestQueue(G.context);
requestQueue.add(JsonObjectRequests);
recyclerView.setLayoutManager(new LinearLayoutManager(G.context, LinearLayoutManager.VERTICAL, false));
AttractionAdapter attractionAdapter = new AttractionAdapter(AttractionData);
recyclerView.setAdapter(attractionAdapter);
public View onCreateView(@NonNull LayoutInflater inflater, @Nullable ViewGroup container, @Nullable Bundle savedInstanceState)
View view = inflater.inflate(R.layout.attraction, container, false);
progressDialog = new ProgressDialog(getActivity());
progressDialog.setMessage("Please wait ...");
progressDialog.setCancelable(false);
progressDialog.show();
showCity(view);
showRandomAttractions(view);
return view;
Attraction.xml
<?xml version="1.0" encoding="utf-8"?>
<android.support.constraint.ConstraintLayout 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_
android:layout_>
<android.support.v7.widget.CardView
android:id="@+id/cardviewattraction"
android:layout_
android:layout_
android:layout_marginStart="8dp"
android:layout_marginTop="16dp"
android:layout_marginEnd="8dp"
android:layout_marginBottom="8dp"
android:padding="3dp"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toTopOf="parent">
<com.toptoche.searchablespinnerlibrary.SearchableSpinner
android:id="@+id/SpinnerCitiestId"
android:layout_
android:layout_
android:layout_marginLeft="8dp"
android:layout_marginTop="8dp"
android:layout_marginRight="8dp"
android:layout_marginBottom="8dp"
android:padding="3dp"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toTopOf="parent"
/>
</android.support.v7.widget.CardView>
<android.support.v7.widget.RecyclerView
android:id="@+id/RecyclerAttracionId"
android:layout_
android:layout_
android:layout_marginTop="8dp"
android:layout_marginBottom="8dp"
app:layout_constraintBottom_toBottomOf="parent"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toBottomOf="@+id/cardviewattraction"
tools:ignore="MissingConstraints" />
</android.support.constraint.ConstraintLayout>景点适配器
package com.rayantec.reservation.reservationdemo.Adapter;
import android.support.annotation.NonNull;
import android.support.v7.widget.RecyclerView;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.ImageView;
import android.widget.TextView;
import com.rayantec.reservation.reservationdemo.Lists.AttractionList;
import com.rayantec.reservation.reservationdemo.R;
import com.squareup.picasso.Picasso;
import java.util.ArrayList;
public class AttractionAdapter extends RecyclerView.Adapter<AttractionAdapter.AttractionViewHolder>
ArrayList<AttractionList> attractionArrayList;
public AttractionAdapter(ArrayList<AttractionList> attractions)
attractionArrayList = new ArrayList<>();
attractionArrayList = attractions;
@NonNull
@Override
public AttractionViewHolder onCreateViewHolder(@NonNull ViewGroup parent, int viewType)
View view = LayoutInflater.from(parent.getContext()).inflate(R.layout.recycler_attraction, parent, false);
return new AttractionViewHolder(view);
@Override
public void onBindViewHolder(@NonNull AttractionViewHolder holder, int position)
AttractionList dataModel = attractionArrayList.get(position);
holder.txtTitle.setText(dataModel.getTitle());
holder.txtBody.setText(dataModel.getBody());
holder.txtType.setText(dataModel.getType());
holder.txtLocation.setText(dataModel.getLocation());
Picasso.get().load(dataModel.getImgUrl()).resize(130, 100).centerCrop().into(holder.imgAttraction);
@Override
public int getItemCount()
return attractionArrayList.size();
public class AttractionViewHolder extends RecyclerView.ViewHolder
public ImageView imgAttraction;
public TextView txtTitle;
public TextView txtBody;
public TextView txtLocation;
public TextView txtType;
public AttractionViewHolder(View itemView)
super(itemView);
imgAttraction = (ImageView)itemView.findViewById(R.id.img_recycler_attraction);
txtTitle = (TextView)itemView.findViewById(R.id.txt_recycler_attractionTitle);
txtBody = (TextView)itemView.findViewById(R.id.txt_recycler_attractionBody);
txtLocation = (TextView)itemView.findViewById(R.id.txt_recycler_attractionPositions);
txtType = (TextView)itemView.findViewById(R.id.txt_recycler_attractionType);
//
AttractionList.java
package com.rayantec.reservation.reservationdemo.Lists;
public class AttractionList
private String id;
private String title;
private String body;
private String location;
private String imgUrl;
public AttractionList(String id, String title, String body, String location, String imgUrl, String type)
this.id = id;
this.title = title;
this.body = body;
this.location = location;
this.imgUrl = imgUrl;
this.type = type;
public String getType()
return type;
public void setType(String type)
this.type = type;
private String type;
public String getId()
return id;
public void setId(String id)
this.id = id;
public String getTitle()
return title;
public void setTitle(String title)
this.title = title;
public String getBody()
return body;
public void setBody(String body)
this.body = body;
public String getLocation()
return location;
public void setLocation(String location)
this.location = location;
public String getImgUrl()
return imgUrl;
public void setImgUrl(String imgUrl)
this.imgUrl = imgUrl;
【问题讨论】：
代码无法通过替换此方法正常工作。 【参考方案1】：您应该测试一些东西，您是否检查过您的showRandomAttractions(View view) 方法中是否收到了onResponse 回调？这将验证 Get 调用是否按预期工作。
如果您收到onResponse 调用，请在您完成将数据添加到AttractionData ArrayList 后尝试在for 循环之后调用attractionAdapter.notifyDataSetChanged()。它看起来像这样：
try
for (int i = 0; i < response.length(); i++)
JSONObject jsonOBJs = response.getJSONObject(i);
String id = jsonOBJs.getString("id");
String title = jsonOBJs.getString("title");
String imageUrl = jsonOBJs.getString("imageUrl");
String location = jsonOBJs.getString("location");
String type = jsonOBJs.getString("type");
String body = jsonOBJs.getString("body");
AttractionData.add(new AttractionList(id, title, body, location, imageUrl, type));
// Notify your adapter that its data has changed.
attractionAdapter.notifyDataSetChanged();
catch (JSONException e1)
e1.printStackTrace();
您可以查看此documentation，了解有关notifyDataSetChanged 工作原理的更多信息。
【讨论】：
感谢回答，在循环后创建吸引适配器（在代码末尾），我不能使用吸引适配器.notifyDataSetChanged();在 for 循环之后，我在创建吸引适配器后使用此代码，但代码也不起作用。所有代码都运行良好，意味着从服务器接收数据并进行解析。但是当打开的片段数据不显示并且在我选择任何城市后，将显示回收站视图。【参考方案2】：我相信您对服务器收集数据的请求是 Asynchronous 并且发生在 Worker Thread 上。如果是这种情况，那么您的视图会在实际获取数据之前呈现。
我建议在您的适配器中添加一个setData 函数：
public void setData(ArrayList<Attractions> attractions)
this.attractionArrayList = attractions
notifyDataSetChanged()
然后在您的活动上，当您收到响应并构建吸引力数组时，只需致电adapter.setData(attractions)
更新： 确保在视图实际初始化时设置您的适配器，因此您需要在 onViewCreated 上调用它：
public void onViewCreated(View view,Bundle savedInstanceState)
super.onViewCreated(view, savedInstanceState);
showCity(view);
showRandomAttractions(view);
【讨论】：
感谢您的回答，我对其进行了测试，但尚未运行，代码稍后运行，例如，如果我选择第一个城市回收站，则稍后显示 10 吸引力，然后我选择第二个城市和回收商展示与第一个城市相关的景点，这是上一步的【参考方案3】：在 try/catch 这个问题解决后替换这一行
recyclerView.setLayoutManager(new LinearLayoutManager(G.context, LinearLayoutManager.VERTICAL, false));
AttractionAdapter attractionAdapter = new AttractionAdapter(AttractionData);
recyclerView.setAdapter(attractionAdapter);
【讨论】：
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