使用帶進度條的asynctask的JSON解析器

Question

使用帶進度條的asynctask的JSON解析器。什麼是正確的方法來做到這一點？

我申請和適應我從TUTS讀，但是從downloadTask

這裏返回數據時，它返回null是我downloadTask任務：

private class DownloadTask extends AsyncTask<Void, Integer, Void> { 

    private ProgressDialog dialog; 

    @Override 
    protected void onProgressUpdate(Integer... values) { 
     dialog.setProgress(values[0]); 
    } 

    @Override 
    protected void onPreExecute() { 
     super.onPreExecute(); 
     this.dialog = new ProgressDialog(ma); 
     this.dialog.setIndeterminate(false); 
     this.dialog.setMax(100); 
     this.dialog.setProgressStyle(ProgressDialog.STYLE_HORIZONTAL); 
     this.dialog.setCancelable(false); 
     this.dialog.setTitle(R.string.updating); 
     this.dialog.setMessage(getString(R.string.downloading)); 
     this.dialog.show(); 

     // progress = 0; 
    } 

    @Override 
    protected String doInBackground(String... arg0) { 

     int count; 
     byte data[] = null; 
       url = "http://arsonicdemo.digify.com.ph/webapi/campaigns?pf=1"; 

      try { 
       URL url1 = new URL(url); 
       URLConnection conexion = url1.openConnection(); 
       conexion.connect(); 
       int lenghtOfFile = conexion.getContentLength(); 
       InputStream input = new BufferedInputStream(url1.openStream()); 
       campaignObj = new JSONObject(parser(url)); 
       populateCampaigns(campaignObj); 
       appClass.updateList(); 
       data = new byte[1024]; 
       long total = 0; 
       while ((count = input.read(data)) != -1) { 
        total += count; 
        publishProgress((int) (total * 100/lenghtOfFile)); 
       } 
       input.close(); 
      } catch (Exception e) { 
      } 
     return new String(data); 
    } 
    @Override 
    protected void onPostExecute(Void result) { 
     super.onPostExecute(result); 
     dialog.dismiss(); 
     Toast.makeText(ma, "Update Successful", Toast.LENGTH_SHORT).show(); 
     ma.initMarkers(); 
    } 
} 

這基本上是populateCampaigns方法：

public void populateCampaigns(String url) throws JSONException { 

    campaignObj = new JSONObject(parser(url)); 
    campaignData = campaignObj.getJSONObject("data"); 
} 

最後，這裏是解析器方法：

public static String parser(String url) { 
    StringBuilder builder = new StringBuilder(); 
    System.setProperty("http.keepAlive", "false"); 
    HttpClient client = new DefaultHttpClient(); 
    HttpGet httpGet = new HttpGet(url); 
    final HttpParams httpParams = new BasicHttpParams(); 
    HttpConnectionParams.setConnectionTimeout(httpParams, timeout * 1000); 
    client = new DefaultHttpClient(httpParams); 
    try { 
     HttpResponse response = client.execute(httpGet); 
     StatusLine statusLine = response.getStatusLine(); 
     int statusCode = statusLine.getStatusCode(); 
     if (statusCode == 200) { 
      HttpEntity entity = response.getEntity(); 
      InputStream content = entity.getContent(); 
      BufferedReader reader = new BufferedReader(new InputStreamReader(content)); 
      String line; 
      while ((line = reader.readLine()) != null) { 
       builder.append(line); 
      } 
     } else { 
      Log.e("CAMPAIGN DOWNLOADER ERROR", "Failed to download file"); 
     } 
    } catch (ClientProtocolException e) { 
     e.printStackTrace(); 
    } catch (IOException e) { 
     e.printStackTrace(); 
    } 

    return builder.toString(); 
} 

Answer 1

我終於想通了，這是我整個的AsyncTask代碼，有任何意見或建議，受到了高度評​​價：

private class DownloadTask extends AsyncTask<Void, Integer, Void> { 

    private ProgressDialog dialog; 

    @Override 
    protected void onProgressUpdate(Integer... progress) { 
     int current = progress[0]; 
     int total = progress[1]; 

     float percentage = 100 * (float) current/(float) total; 

     dialog.setProgress((int) percentage); 
    } 

    @Override 
    protected void onPreExecute() { 
     super.onPreExecute(); 
     this.dialog = new ProgressDialog(ma); 
     this.dialog.setIndeterminate(false); 
     this.dialog.setMax(100); 
     this.dialog.setProgressStyle(ProgressDialog.STYLE_HORIZONTAL); 
     this.dialog.setCancelable(false); 
     this.dialog.setTitle(R.string.updating); 
     this.dialog.setMessage(getString(R.string.downloading)); 
     this.dialog.show(); 

     // progress = 0; 
    } 

    @Override 
    protected Void doInBackground(Void... arg0) { 
     try { 
      timestampPref = appClass.getSharedStringPref("updateTimestamp", null); 

      if (null != timestampPref) { 
       url = getResources().getString(R.string.updateUrl1) + timestampPref + getResources().getString(R.string.updateUrl2); 
       Log.i("URL", url); 
      } else { 
       url = getResources().getString(R.string.firstUrl); 
       Log.i("URL", url); 
      } 
      downloadCampaigns: { 
       try { 

        System.setProperty("http.keepAlive", "false"); 
        campaignObj = new JSONObject(parser(url)); 

        try { 
         campaignData = campaignObj.getJSONObject("data"); 
         dataLength = campaignData.length(); 

         for (int x = 0; x < dataLength; x++) { 
          if (reachable()) { 
           campaignCtr = campaignData.getJSONObject(String.valueOf(x)); 
           tempType = campaignCtr.getString("template_type"); 
           populateCampaigns(campaignCtr, tempType); 

           publishProgress(x, dataLength); 

          } else { 
           // AlertDialog.Builder builder = new 
           // AlertDialog.Builder(ma); 
           // builder.setTitle("NO INTERNET"); 
           // builder.setMessage("Please turn on wifi or cellular data in your mobile Settings to continue."); 
           // builder.setPositiveButton("Okay", null); 
           // builder.show(); 
           break downloadCampaigns; 
          } 
         } 
        } catch (Exception e) { 
         e.printStackTrace(); 
        } 

        updateTimestamp = campaignObj.getString("date"); 
        updateTimestamp = updateTimestamp.substring(0, updateTimestamp.indexOf(" ")); 
        appClass.setSharedStringPref("updateTimestamp", updateTimestamp); 
        Log.i("UPDATETIMESTAMP", updateTimestamp); 

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

     } catch (Exception e) { 
      Log.e("UPDATE ERROR", e.toString()); 
      e.printStackTrace(); 
     } 
     return null; 
    } 

    @Override 
    protected void onPostExecute(Void result) { 
     super.onPostExecute(result); 
     appClass.updateList(); 
     dialog.dismiss(); 
     Toast.makeText(ma, "Update Successful", Toast.LENGTH_SHORT).show(); 
     ma.initMarkers(); 
    } 
} 

Answer 2

您正在嘗試從url下載兩次。首先你開始使用UrlConnection開始下載，然後你打電話給你的parser方法，該方法不解析，但也使用HttpClient從該URL下載。相當混雜了所有。