android - 從url下載圖片顯示不正確

Question

在我的應用程序中，當你點擊按鈕，然後我從網址下載圖片。它正確地顯示一些圖像，但有一段時間它顯示爲空。 *問題是某些時候位圖對象（即代碼中的「結果」）返回null。 *請任何人都可以幫助我。

以下是我的代碼

try 
      { 

      String ImageUrl = ((eachReview)RB_Constant.revht.get(title_value)).UserImageUrl; 
      System.out.println("Image Url:"+ImageUrl); 
      if(ImageUrl != null) 
      { 
       DownLoadImageInAThreadHandler(ImageUrl,holder);                  
      } 
      else 
      { 
       System.out.println("Image url is null then display the default image"); 
       holder.userImage.setImageResource(R.drawable.defaultuserimage); 
      } 
     } 
     catch(Exception e){ 
      System.out.println("Error from Userimage fetching.."+e.toString()); 
     } 



private void DownLoadImageInAThreadHandler(final String imgurl,final ViewHolder holder) 
{ 



    //Thread for getting the attributes values 
    Thread t = new Thread() 
    { 
     public void run() 
     {      
      try 
      { 

       Bitmap drawable = getDrawableFromUrl(imgurl);      
       System.out.println("Drawable(after downloading):"+drawable);       
       if(drawable != null) 
       {            
        holder.userImage.setImageBitmap(drawable);      
       } 
       else 
       { 
        System.out.println("after downloading drawable is null then set the default image"); 
        holder.userImage.setImageResource(R.drawable.defaultuserimage); 
       }            
      } 
      catch(Exception exp) 
      { 
       System.out.println("Exception in DownLoadImageInAThread : " + exp.getMessage()); 
      } 
     } 

     private Bitmap getDrawableFromUrl(String imageUrl) 
     {        
       try 
       { 
        URL myFileUrl = new URL(imageUrl); 
        HttpURLConnection conn = (HttpURLConnection) myFileUrl.openConnection();      
        conn.setDoInput(true); 
        conn.connect(); 
        InputStream is = conn.getInputStream(); 
        final Bitmap result = BitmapFactory.decodeStream(is); 
        is.close(); 
        new Thread() { 
         public void run() { 
          ByteArrayOutputStream bytes = new ByteArrayOutputStream(); 
          if(result != null) 
          { 
           result.compress(Bitmap.CompressFormat.JPEG, 40, bytes); 
          }                         
         } 
        }.start();       
        return result; 
       } 
       catch (FileNotFoundException e) 
       { 
        e.printStackTrace(); 
       } 
       catch (MalformedURLException e) 
       { 
        e.printStackTrace(); 
       } 
       catch (IOException e) 
       { 
        e.printStackTrace(); 
       } 
       return null;        
     }             
    }; 
    t.start();        
} 

Answer 1

嘗試使你getDrawableFromUrl爲：

public static Drawable getDrawableFromUrl(String url) { 

    Drawable image = null; 

    try { 
     InputStream in = (java.io.InputStream) new java.net.URL(url).getContent(); 
     if (in != null) { 
      image = Drawable.createFromStream(in, "image"); 
      in.close(); 
     } 
    } catch (Exception ex) { 
     ex.printStackTrace(); 

    } 
    return image; 
} 

而且不相同的函數內壓縮圖像。嘗試在成功接收圖像後執行此操作。還有一件事是在線程中寫入getDrawableFromUrl函數，但在同一個類中。希望這對你有用。