Question

在我的应用中，当您点击按钮时，我正在从网址下载图片。它正确显示图像一段时间但有时显示为空。 *问题有时候位图对象（即代码中的“结果”）返回null。 *请任何人帮助我。

以下是我的代码

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

尝试将getDrawableFromUrl设为：

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;
}

也不要在同一功能内压缩图像。尝试成功接收图像后执行此操作。将getDrawableFromUrl函数写入线程但在同一个类中更多一件事。希望这对你有用。

android - 从url下载图像无法正确显示

1 个答案: