將數據和圖像從網站提取到ListView

Question

我正在運行以下代碼以通過JSON將數據和圖像從網站提取到ListView。

現在它顯示相同的錯誤。

你能幫助發現問題嗎？

 public class FoodView extends ListActivity 
     { 
      private ProgressDialog pDialog; 


      JSONParser jParser = new JSONParser(); 

      ArrayList<HashMap<String, String>> productsList; 

      private static String url_all_products = "http://ambrogroup.com/app/index/file/food"; 
     private static final String TAG_SUCCESS = "success"; 
     private static final String TAG_PRODUCTS = "products"; 
     private static final String TAG_PID = "pid"; 
     private static final String TAG_NAME = "name"; 
     private static final String TAG_IMAGE = "img"; 
     private static final String TAG_DESTINATION = "destination"; 
     private static final String TAG_PRICE = "price"; 

      JSONArray products = null; 

     @Override 
      public void onCreate(Bundle savedInstanceState) 
      { 
       super.onCreate(savedInstanceState); 
       setContentView(R.layout.food_view); 

     //  productsList = new ArrayList<HashMap<String, String>>();  // Hashmap for ListView 
     new LoadAllProducts().execute();        // Loading products in Background Thread by explicit function 

     ListView listview = getListView();         // Get listview 



     listview.setOnItemClickListener(new OnItemClickListener() {   // on seleting single product // launching Edit Product Screen 
     @Override 
        public void onItemClick(AdapterView<?> parent, View view, int position, long id) 
        { 
         //getting values from selected ListItem 
         String pid = ((TextView) view.findViewById(R.id.pid)).getText().toString(); 
         String pname = ((TextView) view.findViewById(R.id.name)).getText().toString(); 
         String pimg = ((TextView) view.findViewById(R.id.img)).getText().toString(); 
         String pdestination = ((TextView) view.findViewById(R.id.destination)).getText().toString(); 
         String pprice = ((TextView) view.findViewById(R.id.price)).getText().toString(); 
        } 
       }); 

      } 

     class LoadAllProducts extends AsyncTask<String, String, String> 
     {  
      ListView listView; 
      ArrayList<ItemList> listArray = new ArrayList<ItemList>(); 
      CustomListViewAdapter customGridAdapter; 

       @Override 
       protected void onPreExecute() 
       { 
        super.onPreExecute(); 
        pDialog = new ProgressDialog(FoodView.this); 
        pDialog.setMessage("Loading list. Please wait..."); 
        pDialog.setIndeterminate(false); 
        pDialog.setCancelable(false); 
        pDialog.show(); 
       } 

     /** 
     * getting All products from url 
     * */ 
     protected String doInBackground(String... args) { 
      // Building Parameters 
     List<NameValuePair> params = new ArrayList<NameValuePair>(); 
     // getting JSON string from URL 
     JSONObject json = jParser.makeHttpRequest(url_all_products, "GET", params); 

     // Check your log cat for JSON reponse 
     Log.d("Getting all the list : ", json.toString()); 

     try { 
      // Checking for SUCCESS TAG 
      int success = json.getInt(TAG_SUCCESS); 

      if (success == 1) 
      { 
       products = json.getJSONArray(TAG_PRODUCTS); 
       String[] mStrings= new String[products.length()]; 
       for (int i = 0; i < products.length(); i++) 
       { 
        JSONObject c = products.getJSONObject(i); 
        String id = c.getString(TAG_PID); 
        String name = c.getString(TAG_NAME); 
        String img = c.getString(TAG_IMAGE); 
        String destination = c.getString(TAG_DESTINATION); 
        String price = c.getString(TAG_PRICE); 

        mStrings[i] = img; 
        String urldisplay = mStrings[i]; 
        Bitmap mIcon11 = null; 
         try { 
         InputStream in = new java.net.URL(urldisplay).openStream(); 
         mIcon11 = BitmapFactory.decodeStream(in); 
         } catch (Exception e) { 
          Log.e("Error", e.getMessage()); 
             e.printStackTrace(); 
            } 
           listArray.add(new ItemList(mIcon11,id,name,destination,price)); 

           listView = (ListView) findViewById(R.id.list_item); 
           customGridAdapter = new CustomListViewAdapter(FoodView.this, R.layout.row_grid, listArray); 
           listView.setAdapter(customGridAdapter); 

          } 
         } 
         else 
         { 

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

        return null; 
       } 



      } 
     } 

logcat的

04-24 05:17:35.508: W/System.err(1072):  at android.os.AsyncTask$2.call(AsyncTask.java:288) 
04-24 05:17:35.508: W/System.err(1072):  at java.util.concurrent.FutureTask.run(FutureTask.java:237) 
04-24 05:17:35.558: I/Choreographer(1072): Skipped 36 frames! The application may be doing too much work on its main thread. 
04-24 05:17:36.038: W/System.err(1072):  at android.os.AsyncTask$SerialExecutor$1.run(AsyncTask.java:231) 
04-24 05:17:36.038: W/System.err(1072):  at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1112) 
04-24 05:17:36.038: W/System.err(1072):  at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:587) 
04-24 05:17:36.068: W/System.err(1072):  at java.lang.Thread.run(Thread.java:841) 
04-24 05:17:36.068: W/dalvikvm(1072): threadid=11: thread exiting with uncaught exception (group=0xb4afcba8) 
04-24 05:17:36.138: I/Choreographer(1072): Skipped 50 frames! The application may be doing too much work on its main thread. 
04-24 05:17:36.688: E/AndroidRuntime(1072): FATAL EXCEPTION: AsyncTask #1 
04-24 05:17:36.688: E/AndroidRuntime(1072): Process: com.ambrogroup, PID: 1072 
04-24 05:17:36.688: E/AndroidRuntime(1072): java.lang.RuntimeException: An error occured while executing doInBackground() 
04-24 05:17:36.688: E/AndroidRuntime(1072):  at android.os.AsyncTask$3.done(AsyncTask.java:300) 
04-24 05:17:36.688: E/AndroidRuntime(1072):  at java.util.concurrent.FutureTask.finishCompletion(FutureTask.java:355) 
04-24 05:17:36.688: E/AndroidRuntime(1072):  at java.util.concurrent.FutureTask.setException(FutureTask.java:222) 
04-24 05:17:36.688: E/AndroidRuntime(1072):  at java.util.concurrent.FutureTask.run(FutureTask.java:242) 
04-24 05:17:36.688: E/AndroidRuntime(1072):  at android.os.AsyncTask$SerialExecutor$1.run(AsyncTask.java:231) 
04-24 05:17:36.688: E/AndroidRuntime(1072):  at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1112) 
04-24 05:17:36.688: E/AndroidRuntime(1072):  at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:587) 
04-24 05:17:36.688: E/AndroidRuntime(1072):  at java.lang.Thread.run(Thread.java:841) 
04-24 05:17:36.688: E/AndroidRuntime(1072): Caused by: java.lang.NullPointerException 
04-24 05:17:36.688: E/AndroidRuntime(1072):  at com.ambrogroup.FoodView$LoadAllProducts.doInBackground(FoodView.java:136) 
04-24 05:17:36.688: E/AndroidRuntime(1072):  at com.ambrogroup.FoodView$LoadAllProducts.doInBackground(FoodView.java:1) 
04-24 05:17:36.688: E/AndroidRuntime(1072):  at android.os.AsyncTask$2.call(AsyncTask.java:288) 
04-24 05:17:36.688: E/AndroidRuntime(1072):  at java.util.concurrent.FutureTask.run(FutureTask.java:237) 
04-24 05:17:36.688: E/AndroidRuntime(1072):  ... 4 more 

Answer 1

你不應該在setAdapter doInBackGround（）方法的ListView。您可以在的AsyncTask

protected String postExecute() 
{ 
    listView = (ListView) findViewById(R.id.list_item); 
    customGridAdapter = new CustomListViewAdapter(FoodView.this, R.layout.row_grid, listArray); 
    listView.setAdapter(customGridAdapter); 
} 

Answer 2

稱之爲postExecute（）刪除ListView控件中的類LoadAllProducts.Declare的FoodView類的new LoadAllProducts().execute();