Android：在列表視圖Json解析

Question

我試圖解析列表視圖中的一些項目，當我向下滾動我想獲得更多產品並將它們添加到列表中。 但我的代碼沒有做到它要麼刷新它或崩潰。 有什麼幫助嗎？ 還加入了頁腳不工作或者我得到一個ClassCastException異常

JSONParser：

package com.lars.json; 

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

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

import com.lars.R.drawable; 

import android.R; 
import android.util.Log; 

/** A class to parse json data */ 
public class JSONParser { 

    // Receives a JSONObject and returns a list 
    public List<HashMap<String,Object>> parse(JSONObject jObject){  

     JSONArray jProducts = null; 
     try {  
      // Retrieves all the elements in the 'countries' array 
      jProducts = jObject.getJSONArray("products"); 
     } catch (JSONException e) { 
      e.printStackTrace(); 
     } 

     // Invoking getCountries with the array of json object 
     // where each json object represent a country 
     return getProducts(jProducts); 
    } 


    private List<HashMap<String, Object>> getProducts(JSONArray jProducts){ 
     int productsCount = jProducts.length(); 
     List<HashMap<String, Object>> productList = new ArrayList<HashMap<String,Object>>(); 
     HashMap<String, Object> product = null; 

     // Taking each country, parses and adds to list object 
     for(int i=0; i<productsCount;i++){ 
      try { 
       // Call getCountry with country JSON object to parse the country 
       product = getJSON((JSONObject)jProducts.get(i)); 
       productList.add(product); 

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

     return productList; 
    } 

    // Parsing the Country JSON object 
    private HashMap<String, Object> getJSON(JSONObject f){ 

     HashMap<String, Object> country = new HashMap<String, Object>(); 

     String id = ""; 
     String naam = ""; 
     String status = ""; 
     String prijs = ""; 
     String productnum = ""; 


     try { 
      String priceone = f.getString("prijsex"); 

      id = f.getString("id"); 
      naam = f.getString("naam"); 
      status = f.getString("status"); 
      prijs = "€" + priceone; 
      productnum = f.getString("productnum"); 


      country.put("id", id); 
      country.put("naam", naam); 
      country.put("img", com.lars.R.drawable.tlogotrans); 
      country.put("prijs", prijs); 
      country.put("img_path", "http://www.lars.com/images/" + productnum + ".jpg"); 

      if(Integer.parseInt(status) > 0){ 
      country.put("status", com.lars.R.drawable.stock); 
      }else{ 
      country.put("status", com.lars.R.drawable.nostock); 
      } 


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

下載任務和ListView裝載機：

/** A method to download json data from url */ 
    private String downloadUrl(String strUrl) throws IOException{ 
     String data = ""; 
     InputStream iStream = null; 
     try{ 
       URL url = new URL(strUrl); 

       // Creating an http connection to communicate with url 
       HttpURLConnection urlConnection = (HttpURLConnection) url.openConnection(); 

       // Connecting to url 
       urlConnection.connect(); 

       // Reading data from url 
       iStream = urlConnection.getInputStream(); 

       BufferedReader br = new BufferedReader(new InputStreamReader(iStream)); 

       StringBuffer sb = new StringBuffer(); 

       String line = ""; 
       while((line = br.readLine()) != null){ 
        sb.append(line); 
       } 

       data = sb.toString(); 

       br.close(); 

     }catch(Exception e){ 
       Log.d("Exception while downloading url", e.toString()); 
     }finally{ 
       iStream.close(); 
     } 

     return data; 
    } 



    /** AsyncTask to download json data */ 
    private class DownloadTask extends AsyncTask<String, Integer, String>{ 
     String data = null; 




       @Override 
       protected String doInBackground(String... url) { 

         try{ 

          data = downloadUrl(url[0]); 

         }catch(Exception e){ 
          Log.d("Background Task",e.toString()); 
         } 
         return data; 
       } 

       @Override 
       protected void onPostExecute(String result) { 

         // The parsing of the xml data is done in a non-ui thread 
         ListViewLoaderTask listViewLoaderTask = new ListViewLoaderTask(); 
         Log.i("Result", result); 

         if(result.equals(" ")){ 
          Log.i("No img", "No Img"); 
         }else{ 

           listViewLoaderTask.execute(result); 


         } 
         // Start parsing xml data 


       } 
    } 

    /** AsyncTask to parse json data and load ListView */ 
    private class ListViewLoaderTask extends AsyncTask<String, Void, SimpleAdapter>{ 



     JSONObject jObject; 
     private List<HashMap<String, Object>> products; 
     // Doing the parsing of xml data in a non-ui thread 
     @Override 
     protected SimpleAdapter doInBackground(String... strJson) { 
      try{ 

       jObject = new JSONObject(strJson[0]); 
       JSONParser jsonpars = new JSONParser(); 
       jsonpars.parse(jObject); 
      }catch(Exception e){ 
       Log.d("JSON Exception1",e.toString()); 
      } 

      // Instantiating json parser class 
      JSONParser jsonpars = new JSONParser(); 

      // A list object to store the parsed countries list 


      try{ 
       // Getting the parsed data as a List construct 
       if(set == 0){ 
       products = jsonpars.parse(jObject); 
       }else{ 
        products.addAll(jsonpars.parse(jObject)); 

       } 

      }catch(Exception e){ 
       Log.d("Exception",e.toString()); 
      }   

      // Keys used in Hashmap 
      String[] from = { "img","naam","status","prijs"}; 
      // Ids of views in listview_layout 
      int[] to = { R.id.imPThumb,R.id.tvPRName,R.id.imstock,R.id.tvPRPrijs}; 

      // Instantiating an adapter to store each items 
      // R.layout.listview_layout defines the layout of each item   
      SimpleAdapter adapter = new SimpleAdapter(getBaseContext(), products, R.layout.productlijstrow, from, to); 

      return adapter; 
     } 

     @Override 
     protected void onProgressUpdate(Void... values) { 
      // TODO Auto-generated method stub 
      publishProgress(); 
      Log.i("ListView Loader Task", "Update"); 
      super.onProgressUpdate(values); 
     } 

     /** Invoked by the Android on "doInBackground" is executed */ 
     @SuppressWarnings("unchecked") 
     @Override 
     protected void onPostExecute(SimpleAdapter adapter) { 

      // View v = getLayoutInflater().inflate(R.layout.footerview, null); 
      //list.addFooterView(v); 
      // Setting adapter for the listview 


      list.setAdapter(adapter); 



      if(set == 0){ 
      list.setOnScrollListener(onAnswersScrolled); 
      set++; 
      } 
      list.setOnItemClickListener(onAnswerClicked); 

       list.setTextFilterEnabled(true); 
      /* list.setOnItemClickListener(new OnItemClickListener() { 
       public void onItemClick(AdapterView<?> parent, View view, int position, long id) { 
        @SuppressWarnings("unchecked") 
        HashMap<String, String> o = (HashMap<String, String>) lv.getItemAtPosition(position); 

        Bundle extra = new Bundle(); 
        Intent i = new Intent("com.lars.productdescription"); 
        extra.putString("id", o.get("id")); 
        i.putExtras(extra); 
        startActivity(i); 

        } 
       });*/ 

      for(int i=0;i<adapter.getCount();i++){ 
       HashMap<String, Object> hm = (HashMap<String, Object>) adapter.getItem(i); 
       String imgUrl = (String) hm.get("img_path"); 
       Log.i("imgurlonPost", imgUrl); 
       ImageLoaderTask imageLoaderTask = new ImageLoaderTask(); 

       HashMap<String, Object> hmDownload = new HashMap<String, Object>(); 
       hmDownload.put("img_path",imgUrl); 

       hmDownload.put("position", i); 

       // Starting ImageLoaderTask to download and populate image in the listview 
       imageLoaderTask.execute(hmDownload); 
       adapter.notifyDataSetChanged(); 
      } 

     /* list.setOnScrollListener(new OnScrollListener(){ 



      });*/ 

     }  
    } 

    /** AsyncTask to download and load an image in ListView */ 
    private class ImageLoaderTask extends AsyncTask<HashMap<String, Object>, Void, HashMap<String, Object>>{ 

     @Override 
     protected HashMap<String, Object> doInBackground(HashMap<String, Object>... hm) { 


      InputStream iStream=null; 
      String imgUrl = (String) hm[0].get("img_path"); 
      int position = (Integer) hm[0].get("position"); 
      HashMap<String, Object> hmBitmap = new HashMap<String, Object>(); 
      URL url; 
      try { 
       url = new URL(imgUrl); 



       // Creating an http connection to communicate with url 
       HttpURLConnection urlConnection = (HttpURLConnection) url.openConnection(); 
       Log.i("imgUrl", imgUrl); 
       // Connecting to url     
       urlConnection.connect(); 
      //  Log.i("Response", urlConnection.getResponseMessage()); 
       // Reading data from url 

       if(urlConnection.getResponseMessage().contains("OK")){ 
       iStream = urlConnection.getInputStream(); 




       // Getting Caching directory 
       File cacheDirectory = getBaseContext().getCacheDir(); 
       cacheDirectory.delete(); 
       // Temporary file to store the downloaded image 
       File tmpFile = new File(cacheDirectory.getPath() + "/wpta_"+position+".png");    

       // The FileOutputStream to the temporary file 
       FileOutputStream fOutStream = new FileOutputStream(tmpFile); 

       // Creating a bitmap from the downloaded inputstream 
       Bitmap b = BitmapFactory.decodeStream(iStream);    

       // Writing the bitmap to the temporary file as png file 
       b.compress(Bitmap.CompressFormat.PNG,100, fOutStream);    

       // Flush the FileOutputStream 
       fOutStream.flush(); 

       //Close the FileOutputStream 
       fOutStream.close();    

       // Create a hashmap object to store image path and its position in the listview 


       // Storing the path to the temporary image file 
       hmBitmap.put("img",tmpFile.getPath()); 

       // Storing the position of the image in the listview 
       hmBitmap.put("position",position);    

       // Returning the HashMap object containing the image path and position 
       return hmBitmap; 


       }else{ 
        Log.i("nope", "nb"); 
        String uriStr = "android.resource://" + "com.lars" + "/" + R.drawable.ic_launcher; 
        hmBitmap.put("img", uriStr); 


        hmBitmap.put("position",position); 
        return hmBitmap; 
       } 

      }catch (Exception e) {    
       e.printStackTrace(); 
      } 
      return null; 
     } 

     @SuppressWarnings("unchecked") 
     @Override 
     protected void onPostExecute(HashMap<String, Object> result) { 
      // Getting the path to the downloaded image 

      String path = (String) result.get("img");   

      // Getting the position of the downloaded image 
      int position = (Integer) result.get("position"); 

      // Getting adapter of the listview 

      adapter = (SimpleAdapter) list.getAdapter(); 

      // Getting the hashmap object at the specified position of the listview 
      HashMap<String, Object> hm = (HashMap<String, Object>) adapter.getItem(position); 

      // Overwriting the existing path in the adapter 
      hm.put("img",path); 


      // Noticing listview about the dataset changes 
      adapter.notifyDataSetChanged(); 

     } 

     @Override 
     protected void onProgressUpdate(Void... values) { 
      // TODO Auto-generated method stub 
      publishProgress(); 

      adapter.notifyDataSetChanged(); 
      Log.i("Image Task", "Update"); 

      super.onProgressUpdate(values); 
     } 
    } 

    private OnItemClickListener onAnswerClicked = new OnItemClickListener() { 

     public void onItemClick(AdapterView<?> parent, View view, int position, 
       long id) { 
      @SuppressWarnings("unchecked") 
      HashMap<String, String> o = (HashMap<String, String>) parent.getItemAtPosition(position); 

      Bundle extra = new Bundle(); 
      Intent i = new Intent("com.lars.productdescription"); 
      extra.putString("id", o.get("id")); 
      i.putExtras(extra); 
      startActivity(i); 
     } 

    }; 

    private OnScrollListener onAnswersScrolled = new OnScrollListener() { 


     public void onScroll(AbsListView view, int first, int visibleitems, int totalitemcount) { 
      // TODO Auto-generated method stub 
      int lastInScreen = first + visibleitems; 
      if(lastInScreen == totalitemcount){ 
      if(kf == 0){ 
       Log.i("onScroll", "" + c); 
       Log.i("kf", "0"); 
       String filfinal = keuze.replace(" ", "thisisaspace"); 
       String strUrl = "http://www.lars.nl/getName.php?name=" + filfinal + "&page=" + c ; 
       DownloadTask downloadTask = new DownloadTask(); 
        downloadTask.execute(strUrl); 
        c = c + o; 
        Log.i("After Scroll", "" + c); 
      }else{ 
       Log.i("onScroll", "" + c); 
       Log.i("kf", "1"); 
       String strUrl = "http://www.lars.nl/get.php?id=" + filter + "&page=" + c ; 
        DownloadTask downloadTask = new DownloadTask(); 
         downloadTask.execute(strUrl); 
         c = c + o; 
         Log.i("After Scroll", "" + c); 
      } 
      } 
     } 

     public void onScrollStateChanged(AbsListView view, int scrollstate) { 
      // TODO Auto-generated method stub 

     } 
    }; 

    } 

Answer 1

我想用非等向您介紹CWAC-ENDLESS比輝煌的標誌墨菲（普通軟件）。它不僅是將適配器放置在另一個適配器中的強大示例，還可以處理所有後臺任務以及滾動，以便您可以通過以下方式輕鬆添加數據列表：demo

真誠地希望這可以幫助你，就像幫助我一樣。