RecyclerView onCreateViewHolder沒有被調用

Question

我想在RecyclerView裏面添加數據。完成編譯後，RecyclerView沒有顯示在虛擬mobile裏面。當我再次檢查時，onCreateViewHolder沒有被調用。希望你們可以幫我解決這個問題。

activity_main.xml中

<?xml version="1.0" encoding="utf-8"?> 
<RelativeLayout 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="com.example.user.mycustomvolley.MainActivity"> 

    <android.support.v7.widget.RecyclerView 
     android:layout_width="match_parent" 
     android:layout_height="100dp" 
     android:id="@+id/recyclerview" 
     > 

    </android.support.v7.widget.RecyclerView> 
</RelativeLayout> 

row_list.xml

<?xml version="1.0" encoding="utf-8"?> 
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android" 
    android:layout_width="fill_parent" 
    android:layout_height="wrap_content" 
    android:padding="8dp" 
    android:background="#BBDEFB" 
    > 

    <com.android.volley.toolbox.NetworkImageView 
     android:layout_width="150dp" 
     android:layout_height="150dp" 
     android:layout_alignParentLeft="true" 
     android:layout_margin="8dp" 
     android:id="@+id/networkImage"/> 

    <TextView 
     android:layout_width="wrap_content" 
     android:layout_height="wrap_content" 
     android:id="@+id/textName" 
     android:text="@string/title" 
     android:layout_toRightOf="@+id/networkImage" 
     android:padding="8dp" 
     android:textColor="@color/colorText" 
     android:textSize="18dp" 
     android:textStyle="bold"/> 

</RelativeLayout> 

MainActivity.java

package com.example.user.mycustomvolley; 

import android.support.v7.app.AppCompatActivity; 
import android.os.Bundle; 
import android.support.v7.widget.LinearLayoutManager; 
import android.support.v7.widget.RecyclerView; 

import java.util.ArrayList; 

public class MainActivity extends AppCompatActivity { 
    RecyclerView recyclerView; 
    RecyclerView.Adapter adapter; 
    RecyclerView.LayoutManager layoutManager; 
    ArrayList<ArtInformation> arrayList = new ArrayList<>(); 
    @Override 
    protected void onCreate(Bundle savedInstanceState) { 
     super.onCreate(savedInstanceState); 
     setContentView(R.layout.activity_main); 

     recyclerView = (RecyclerView) findViewById(R.id.recyclerview); 
     recyclerView.setHasFixedSize(true); 

     layoutManager = new LinearLayoutManager(this); 
     recyclerView.setLayoutManager(layoutManager); 


     BackgroundTask backgroundTask = new BackgroundTask(MainActivity.this); 
     arrayList = backgroundTask.getArrayList(); 
     adapter = new RecyclerAdapter(arrayList,this); 
     recyclerView.setAdapter(adapter); 

    } 
} 

BackgroundTask.java

package com.example.user.mycustomvolley; 

import android.app.ProgressDialog; 
import android.content.Context; 
import android.util.Log; 
import android.widget.Toast; 

import com.android.volley.Request; 
import com.android.volley.Response; 
import com.android.volley.VolleyError; 
import com.android.volley.toolbox.JsonArrayRequest; 

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

import java.util.ArrayList; 

/** 
* Created by User on 9/17/2016. 
*/ 
public class BackgroundTask { 
    Context context; 
    ArrayList<ArtInformation> arrayList = new ArrayList<>(); 
    private static final String json_url = "http://192.168.1.7/volley/imagetext/getData.php"; 

    public BackgroundTask(Context context){ 
     this.context = context; 
    } 

    public ArrayList<ArtInformation> getArrayList(){ 

     //make json request. 
     JsonArrayRequest jsonArrayRequest = new JsonArrayRequest(Request.Method.POST,json_url,(String) null, new Response.Listener<JSONArray>() { 
      @Override 
      public void onResponse(JSONArray response) { 

       int count = 0; 
       while (count < response.length()) { 
        try{ 
         JSONObject jsonObject = response.getJSONObject(count); 
         String artTemp = jsonObject.getString("art"); 
         String imageTemp = jsonObject.getString("image"); 

         ArtInformation artInformation = new ArtInformation(artTemp,imageTemp); 
         arrayList.add(artInformation); 
         count++; 

        }catch (JSONException ex){ 
         ex.printStackTrace(); 
        } 
       } 
      } 
     }, new Response.ErrorListener() { 
      @Override 
      public void onErrorResponse(VolleyError error) { 
       Toast.makeText(context,"Error:[JSON Process",Toast.LENGTH_LONG).show(); 
       //progressDialog.hide(); 
       error.printStackTrace(); 
      } 
     }); 
     MySingleton.getmInstances(context).addToRequestQueue(jsonArrayRequest); 
     return arrayList; 
    } 


} 

RecyclerAdapter.java

package com.example.user.mycustomvolley; 

import android.content.Context; 
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.TextView; 
import android.widget.Toast; 

import com.android.volley.toolbox.ImageLoader; 
import com.android.volley.toolbox.NetworkImageView; 

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

/** 
* Created by User on 9/17/2016. 
*/ 
public class RecyclerAdapter extends RecyclerView.Adapter<RecyclerAdapter.MyViewHolder> { 

    ArrayList<ArtInformation> arrayList = new ArrayList<>(); 
    Context context; 
    private ImageLoader imageLoader; 

    public RecyclerAdapter(ArrayList<ArtInformation> list, Context context){ 
     super(); 
     this.arrayList = list; 
     this.context = context; 

    } 
    @Override 
    public MyViewHolder onCreateViewHolder(ViewGroup parent, int viewType) { 
     Log.d("","call onCreateViewHolder"); 
     View view = LayoutInflater.from(parent.getContext()).inflate(R.layout.row_list,parent,false); 
     MyViewHolder myViewHolder = new MyViewHolder(view); 

     return myViewHolder; 
    } 

    @Override 
    public void onBindViewHolder(MyViewHolder holder, int position) { 

     ArtInformation artInformation = arrayList.get(position); 
     // Log.d("Check:","art:"+artInformation.getArt_name()+"/path:"+artInformation.getImage_path()); 
     imageLoader = MySingleton.getmInstances(context).getImageLoader(); 
     imageLoader.get(artInformation.getImage_path(), ImageLoader.getImageListener(holder.image, R.mipmap.ic_launcher, android.R.drawable.ic_dialog_alert)); 

     holder.image.setImageUrl(artInformation.getImage_path(),imageLoader); 
     holder.artName.setText(artInformation.getArt_name()); 

    } 

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

    public static class MyViewHolder extends RecyclerView.ViewHolder{ 
     TextView artName; 
     NetworkImageView image; 


     public MyViewHolder(View itemView){ 
      super(itemView); 

      artName = (TextView) itemView.findViewById(R.id.textName); 
      image = (NetworkImageView) itemView.findViewById(R.id.networkImage); 


     } 

    } 

} 

Answer 1

如果getItemCount方法返回0即arrayList.size() == 0然後RecyclerView從未嘗試實例的視圖。