解析來自JSON服務器的數據時Android ListView不顯示

Question

所以我測試了一個在listview上實現的android應用程序。該列表使用從JSON服務器獲取的數據。視圖中使用的三個字段是圖像，名稱，說明。我測試了所有的輸入，數據來自服務器，在適配器中設置（使用LOG標記檢查），但該應用程序沒有顯示任何視圖，有時會崩潰。總之，我無法看到任何listView。請幫助... :)

這些是我的項目使用的文件...

MainActivity.java

package com.example.aditya.jtest; 

import android.app.Activity; 
import android.app.ProgressDialog; 
import android.os.AsyncTask; 
import android.os.Bundle; 
import android.util.Log; 
import android.widget.ListView; 
import android.widget.Toast; 

import org.apache.http.HttpEntity; 
import org.apache.http.HttpResponse; 
import org.apache.http.client.HttpClient; 
import org.apache.http.client.methods.HttpPost; 
import org.apache.http.impl.client.DefaultHttpClient; 
import org.apache.http.util.EntityUtils; 
import org.json.JSONArray; 
import org.json.JSONException; 
import org.json.JSONObject; 

import java.io.IOException; 
import java.util.ArrayList; 


public class MainActivity extends Activity { 

    ListView list; 
    ActorsAdapter adapter; 
    ArrayList<Actors> actorsList; 


    @Override 
    protected void onCreate(Bundle savedInstanceState) { 
     super.onCreate(savedInstanceState); 
     setContentView(R.layout.activity_main); 

     list = (ListView) findViewById(R.id.list); 
     actorsList = new ArrayList<Actors>(); 

     new  ActorsAsynTask().execute("http://microblogging.wingnity.com/JSONParsingTutorial/ `jsonActors"); 
     list.setAdapter(adapter); 
    } 

    public class ActorsAsynTask extends AsyncTask<String, Void, Boolean> { 

     ProgressDialog dialog; 

     @Override 
     protected void onPreExecute() { 
     super.onPreExecute(); 
     dialog = new ProgressDialog(MainActivity.this); 
     dialog.setMessage("Loading, please wait"); 
     dialog.setTitle("Connecting server"); 
     dialog.show(); 
     dialog.setCancelable(false); 
    } 

     @Override 
     protected Boolean doInBackground(String... params) { 

      try { 
       HttpClient client = new DefaultHttpClient(); 
       HttpPost post = new HttpPost(params[0]); 
       HttpResponse response = client.execute(post); 

       int status = response.getStatusLine().getStatusCode(); 
       //Log.d("MyFilter2", "" + status + " Value Recieved: " + params[0]); 

       if (status == 200) { 
        HttpEntity entity = response.getEntity(); 
        String data = EntityUtils.toString(entity); 
        //Log.d("MyFilter", data); 

        JSONObject jObj = new JSONObject(data); 
        JSONArray jArray = jObj.getJSONArray("actors"); 
        //Log.d("MyFilterjObj: ", jObj.toString()); 
        //Log.d("MyFilterjArray: ", jArray.toString() + "\n" + jArray.length()); 

        for(int i = 0; i <= jArray.length(); i++) { 
         Actors actors = new Actors(); 
         JSONObject jRealObject = jArray.getJSONObject(i); 
         //Log.d("\nMyFilter JRealObject[" + i + "]: ", jRealObject.toString()); 

         actors.setName(jRealObject.getString("name")); 
         actors.setDescription(jRealObject.getString("description")); 
         actors.setImage(jRealObject.getString("image")); 

         Log.d("\nMyFilter ["+ i +"]", jRealObject.getString("name")); 
         Log.d("MyFilter ["+ i +"]", jRealObject.getString("description")); 
         Log.d("MyFilter ["+ i +"]", jRealObject.getString("image")); 

         actorsList.add(actors); 
        } 
        return true; 
       } 

      } catch (IOException e) { 
       e.printStackTrace(); 
      } catch (JSONException e) { 
       e.printStackTrace(); 
      } 

      return false; 
     } 

     @Override 
     protected void onPostExecute(Boolean aBoolean) { 
      super.onPostExecute(aBoolean); 
      dialog.cancel(); 
      adapter.notifyDataSetChanged(); 

      if(aBoolean == false){ 
       //Show a message that data was not parsed 
       Toast.makeText(getApplicationContext(), "Unable to fetch data from server", Toast.LENGTH_LONG).show(); 
      } 
     } 
    } 
} 

演員適配器

package com.example.aditya.jtest; 

import android.content.Context; 
import android.graphics.Bitmap; 
import android.graphics.BitmapFactory; 
import android.os.AsyncTask; 
import android.view.LayoutInflater; 
import android.view.View; 
import android.view.ViewGroup; 
import android.widget.ArrayAdapter; 
import android.widget.ImageView; 
import android.widget.TextView; 

import java.io.IOException; 
import java.io.InputStream; 
import java.net.MalformedURLException; 
import java.util.ArrayList; 
import java.util.Collection; 
import java.util.List; 

public class ActorsAdapter extends ArrayAdapter<Actors> { 

ArrayList<Actors> ArrayListActors; 
int Resource; 
Context context; 
LayoutInflater vi; 
ViewHolder holder; 


public ActorsAdapter(Context context, int resource, ArrayList<Actors> objects) { 
    super(context, R.layout.row, objects); 

    ArrayListActors = objects; 
    Resource = resource; 
    this.context = context; 
} 

@Override 
public View getView(int position, View convertView, ViewGroup parent) { 

    vi = (LayoutInflater) context.getSystemService(Context.LAYOUT_INFLATER_SERVICE); 
    View v = convertView; 
    if(v == null){ 
     v = vi.inflate(Resource, null); 
     holder = new ViewHolder(); 

     holder.image = (ImageView) convertView.findViewById(R.id.image); 
     holder.name = (TextView) convertView.findViewById(R.id.name); 
     holder.description = (TextView) convertView.findViewById(R.id.description); 

     convertView.setTag(holder); 
    } else{ 
     holder = (ViewHolder) convertView.getTag(); 
    } 

    new DownloadImageTask(holder.image).execute(ArrayListActors.get(position).getImage()); 
    holder.name.setText(ArrayListActors.get(position).getName()); 
    holder.description .setText(ArrayListActors.get(position).getDescription()); 

    return v; 
} 

static class ViewHolder{ 
    public ImageView image; 
    public TextView name; 
    public TextView description; 
} 

private class DownloadImageTask extends AsyncTask<String, Void, Bitmap>{ 

    ImageView bmImage; 

    public DownloadImageTask(ImageView bmImage) { 
     this.bmImage = bmImage; 
    } 

    @Override 
    protected Bitmap doInBackground(String... params) { 
     String urlDisplay = params[0]; 
     Bitmap mIcon1 = null; 
     try{ 
      InputStream in = new java.net.URL(urlDisplay).openStream(); 
      mIcon1 = BitmapFactory.decodeStream(in); 
     } catch (MalformedURLException e) { 
      e.printStackTrace(); 
     } catch (IOException e) { 
      e.printStackTrace(); 
     } 
     return mIcon1; 
    } 

    @Override 
    protected void onPostExecute(Bitmap bitmap) { 
     bmImage.setImageBitmap(bitmap); 
    } 
} 

}

Actors.java

package com.example.aditya.jtest; 

public class Actors { 

private String image; 
private String name; 
private String description; 

public Actors() { 
} 

public Actors(String name, String description, String image) { 
    super(); 
    this.name = name; 
    this.description = description; 
    this.image = image; 
} 

public String getImage() { 
    return image; 
} 

public void setImage(String image) { 
    this.image = image; 
} 

public String getName() { 
    return name; 
} 

public void setName(String name) { 
    this.name = name; 
} 

public String getDescription() { 
    return description; 
} 

public void setDescription(String description) { 
    this.description = description; 
} 

}

Answer 1

添加在ActorsAsynTask的onPostExecute()。

adapter = new ActorsAdapter(MainActivity.this, /*Your resource file id*/,actorsList); 
list.setAdapter(adapter) 

這樣做。

Answer 2

import java.io.BufferedReader; 
import java.io.InputStream; 
import java.io.InputStreamReader; 
import java.util.ArrayList; 
import java.util.List; 
import org.apache.http.HttpEntity; 
import org.apache.http.HttpResponse; 
import org.apache.http.client.HttpClient; 
import org.apache.http.client.methods.HttpPost; 
import org.apache.http.impl.client.DefaultHttpClient; 
import org.json.JSONArray; 
import org.json.JSONException; 
import org.json.JSONObject; 
import android.app.Fragment; 
import android.os.AsyncTask; 
import android.os.Bundle; 
import android.util.Log; 
import android.view.LayoutInflater; 
import android.view.View; 
import android.view.ViewGroup; 
import android.widget.ListView; 
import android.widget.Toast; 

public class PrivateJobList extends Fragment { 

    /**Declaring the data members **/ 
    List<PrivateData> list; 

    PrivateJobListAdapter adapter; 

    ListView listview; 

    PrivateJobList(){ 

    } 

    @Override 
    public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) 
    { 

     View v=inflater.inflate(R.layout.private_job_list,container,false); 

     listview=(ListView)v.findViewById(R.id.list); 
     /*converting or say initializing list as arraylist*/ 
     list=new ArrayList<PrivateData>(); 

     /*instantiating the class which deals with fetching*/ 
    ExecuteTaskprivate executetask= new ExecuteTaskprivate(); 


     /*calling execute method on class instance*/ 
     executetask.execute(); 

     /*initializing the adapter*/ 
     adapter = new PrivateJobListAdapter(getActivity(),list); 

     return v; 
    } 


/*class to handle background task*/ 
class ExecuteTaskprivate extends AsyncTask<String, Void,String>{ 


    @Override 
    protected String doInBackground(String... params) { 
     /**storing returned value from this method in res variable 
     * and pass it to the postData method**/ 
     String res=postData(params); 

     return res; 
    } 


    /**This method Deals with the posting the client request 
    * and storing the response in String variable which is 
    * nothing but a HttpResponse from the server**/ 
    private String postData(String[] params) { 

     String s=""; 

     try 
     { 
     HttpClient httpClient=new DefaultHttpClient(); 

     HttpPost httpPost=new HttpPost("http://10.0.2.2/loginpage/private_jobs_fetching.php"); 

     HttpResponse res= httpClient.execute(httpPost); 

     @SuppressWarnings("unused") 
     HttpEntity httpEntity=res.getEntity(); 
     s= readResponse(res); 

     } 
     catch(Exception exception) {} 
     return s; 
    } 
/**this method returns String representation of response from server**/ 
private String readResponse(HttpResponse res) { 
    String return_text=""; 

    InputStream is = null; 
    try{ 
    is=res.getEntity().getContent(); 
    BufferedReader bufferedReader=new BufferedReader(new InputStreamReader(is,"utf-8"),8); 
    String line=""; 
    StringBuffer sb=new StringBuffer(); 
    while ((line=bufferedReader.readLine())!=null) 
    { 
    sb.append(line); 
    } 


    return_text=sb.toString(); 
} catch (Exception e) 
{ 
     e.printStackTrace(); 
} 
return return_text; 
} 

/**In onPostExecute String variable returned from doInBackground is used as parameter**/ 
@Override 
protected void onPostExecute(String result) { 
    super.onPostExecute(result); 

    if(result.length()!=0){ 

    try { 

     /**parsing JSONArray first**/ 
     JSONArray jArray = new JSONArray(result); 
     /**looping through it's length**/ 
     for (int i = 0; i<jArray.length();i++) 
     { 
      /**And converting it to the JSONObject**/ 
      JSONObject json_data = jArray.getJSONObject(i); 
      /**Creating instance of Bean class**/ 
      PrivateData user= new PrivateData(); 
      /**fetching data directly from server by providing column names 
      * and setting to their respective setter method's of bean class**/ 
      user.setCompany_name(json_data.getString("company_name")); 
      user.setJob_title(json_data.getString("job_title")); 
      user.setLocation(json_data.getString("location")); 
      user.setEmail(json_data.getString("email")); 
      user.setUid(json_data.getInt("uid")); 
      /**Adding PrivateData object to the list**/ 
      list.add(user); 
     } 
     /**setting the adapter on listview**/ 
     listview.setAdapter(adapter); 
    } catch (JSONException e) { 
     Log.e("log_tag", "Error parsing data " + e.toString()); 
    } 

    } 
    else{ 

     Toast.makeText(getActivity(), result, Toast.LENGTH_SHORT).show(); 
    } 
} 

} 

} 

/************************************** *********************************/

/**Bean class with data members & their respective setter & getters**/ 
public class PrivateData { 

    String company_name; 

    String job_title; 

    String location; 

    String email; 

    int uid; 


    public String getCompany_name() { 
     return company_name; 
    } 

    public void setCompany_name(String company_name) { 
     this.company_name = company_name; 
    } 

    public String getJob_title() { 
     return job_title; 
    } 

    public void setJob_title(String job_title) { 
     this.job_title = job_title; 
    } 

    public String getLocation() { 
     return location; 
    } 

    public void setLocation(String location) { 
     this.location = location; 
    } 

    public String getEmail() { 
     return email; 
    } 

    public void setEmail(String email) { 
     this.email = email; 
    } 

    public int getUid() { 
     return uid; 
    } 

    public void setUid(int uid) { 
     this.uid = uid; 
    } 




} 

/******** ************************************************** ********************/

import java.util.List; 
import android.content.Context; 
import android.view.LayoutInflater; 
import android.view.View; 
import android.view.ViewGroup; 
import android.widget.ArrayAdapter; 
import android.widget.TextView; 
/**ListAdapter class**/ 
public class PrivateJobListAdapter extends ArrayAdapter<PrivateData> { 
    /**data members**/ 
    Context c; 

    //int layout; 

    List<PrivateData> list; 



    /**Constructor**/ 
    public PrivateJobListAdapter(Context context,List<PrivateData> objects) { 
     super(context,R.layout.row_view, objects); 

     this.c=context; 
     this.list=objects; 

    } 


/**this method is used to display your fetched data from server **/ 
    @Override 
    public View getView(int position, View convertView, ViewGroup parent) { 

     View row = convertView; 
     /**initializing class which has all textview required for showing column data 
      * of table on server**/ 
     UserHolder holder = null; 

     if(row==null){ 
      /**this is important step if your main class is an Activity 
       * then write it as 
       * LayoutInflater inflater = ((Activity) context).getLayoutInflater(); 
       * and import android.app.activity**/ 
      LayoutInflater inflater= LayoutInflater.from(c); 
      /****/ 
      row = inflater.inflate(R.layout.row_view, parent, false); 
       holder = new UserHolder(); 

       holder.textcompanyname=(TextView) row.findViewById(R.id.textview_company_name); 

       holder.textjobtitle=(TextView) row.findViewById(R.id.textview_job_title); 

       holder.textlocation=(TextView) row.findViewById(R.id.textview_location); 

       holder.textemail=(TextView) row.findViewById(R.id.textview_email); 


       /**setting tag**/ 
       row.setTag(holder); 

     } 
     else { 
      /**getting tag**/ 
       holder = (UserHolder) row.getTag(); 
       } 


     return row; 
    } 

    static class UserHolder { 
      TextView textcompanyname; 
      TextView textjobtitle; 
      TextView textlocation; 
      TextView textemail; 


     } 
} 

/********************* *******************************/

//private_job_list.xml 

<?xml version="1.0" encoding="utf-8"?> 
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android" 
    android:layout_width="match_parent" 
    android:layout_height="match_parent" 
    android:orientation="vertical" > 

<TextView android:id="@+id/textview_private_job_list" 
     android:layout_width="250dp" 
     android:layout_height="30dp" 
     android:background="@drawable/button_rounded" 
     android:layout_marginTop="20dp" 
     android:layout_marginStart="32dp" 
     android:text="@string/private_job_list_text" 
     android:textSize="20sp" 
     android:gravity="center"/> 


<ListView 

    android:id="@+id/list" 

    android:layout_height="match_parent" 
    android:layout_width="match_parent"></ListView> 



</LinearLayout> 

/*****************************************/

//row-view.xml 


<?xml version="1.0" encoding="utf-8"?> 
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android" 
    android:layout_width="match_parent" 
    android:layout_height="match_parent" > 


    <TextView 
     android:id="@+id/textview_company_name" 
     android:layout_width="wrap_content" 
     android:layout_height="wrap_content" 
     android:layout_alignParentStart="true" 
     android:layout_alignParentTop="true" 
     android:text="@string/company_name" 
     android:textSize="18sp"/> 

    <TextView 
     android:id="@+id/textview_job_title" 
     android:layout_width="wrap_content" 
     android:layout_height="wrap_content" 
     android:layout_alignParentStart="true" 
     android:layout_below="@+id/textview_company_name" 
     android:layout_marginTop="5dp" 
     android:text="@string/job_title" 
     android:textSize="18sp" /> 

    <Button 
     android:id="@+id/button_more" 
     android:layout_width="80dp" 
     android:layout_height="40dp" 
     android:layout_alignParentEnd="true" 
     android:layout_marginTop="40dp" 
     android:background="@drawable/button_rounded" 
     android:focusable="false" 
     android:focusableInTouchMode="false" 
     android:text="@string/btn_more" 
     android:textColor="#0099CC" /> 



    <TextView 
     android:id="@+id/textview_location" 
     android:layout_width="wrap_content" 
     android:layout_height="wrap_content" 
     android:layout_alignParentStart="true" 
     android:layout_below="@+id/textview_job_title" 
     android:layout_marginTop="5dp" 
     android:text="@string/location" 
     android:textSize="18sp"/> 


    <TextView 
     android:id="@+id/textview_email" 
     android:layout_width="wrap_content" 
     android:layout_height="wrap_content" 
     android:layout_alignParentStart="true" 
     android:layout_below="@+id/textview_location" 
     android:layout_marginTop="5dp" 
     android:text="@string/email" 
     android:textSize="18sp" /> 




</RelativeLayout> 

/*******************************************/

//button_rounded.xml 


<?xml version="1.0" encoding="utf-8"?> 
<shape xmlns:android="http://schemas.android.com/apk/res/android" 
    android:shape="rectangle"> 

    <solid android:color="#ec0b47"/> 
    <corners 
     android:radius="30dp"/>  

</shape> 

/*********/

//php code 


<?php 

$host='localhost:3306'; 
$uname='root'; 
$pwd=''; 
$db="mydb"; 

$connection=mysqli_connect($host,$uname,$pwd,$db); 
$database=mysqli_select_db($connection,$db); 

$query1=mysqli_query($connection,"SELECT * FROM private_jobs"); 


while($row=mysqli_fetch_assoc($query1)) 
{ 

    $result[]=$row; 
} 

print(json_encode($result)); 

mysqli_close($connection); 

?> 



happy coding!!!!