無法從HttpUrlConnection（PNG到位圖）加載圖像，inputStream中的位圖爲空

Question

我已經在Stack Overflow和Internet上研究瞭如何從URL加載圖像並將其作爲Bitmap（原本一個.png文件）。我按照說明進行操作，代碼如下，代碼的類別爲AsyncTask。

try { 
    imageUrl = new URL(currentApp.getImageURL()); 
    HttpURLConnection urlConnection = (HttpURLConnection) 
    imageUrl.openConnection(); 
    urlConnection.setRequestMethod("GET"); 
    urlConnection.setDoInput(true); 

    ***urlConnection.connect(); 
    InputStream inputStream = urlConnection.getInputStream(); 
    imageBitmap = BitmapFactory.decodeStream(inputStream); 
    viewHolder.tvImage.setImageBitmap(imageBitmap); 
    inputStream.close();*** 

    } catch (MalformedURLException e) { 
     Log.d(TAG, "getView: " + e.toString()); 
    } catch (IOException e) { 
     Log.d(TAG, "getView: " + e.toString()); 
    } finally { 

} 

爲我所用的調試工具來幫助我，我發現，從連接響應代碼是200，但imageBitmap = BitmapFactory.decodeStream(inputStream);，我得到imageBitmap空值。

預先感謝您！

Answer 1

Decode Stream return null如果輸入流爲空或不能用於解碼位圖。嘗試從另一個URL下載圖像，我下載的YouTube播放列表的縮略圖和其工作110％爲我好，試試這個代碼

public class DownloadImagesTask extends AsyncTask<ImageView, Void, ImageView> { 
    ImageView iv=null; 
    Bitmap bitmap=null; 
    String url=null; 

    public DownloadImagesTask(ImageView iv,int position,String url) { 
     this.iv = iv; 
     this.position=position; 
     this.url = url; 
    } 

    @Override 
    protected void onPreExecute() { 
     super.onPreExecute(); 

    } 

    @Override 
    protected ImageView doInBackground(ImageView... url) { 
     try { 
       Log.e("url", this.url); 
       URL ulrn = new URL(this.url); 
       HttpURLConnection con = (HttpURLConnection) ulrn.openConnection(); 
       InputStream is = con.getInputStream(); 
       this.bitmap = BitmapFactory.decodeStream(is); 
       if (null != this.bitmap) 
       { 
        return iv; 
       } 
     }catch(Exception e){} 
     return null; 
    } 




    @Override 
    protected void onPostExecute(ImageView result) { 
     if(result!=null) { 
      this.iv.setImageBitmap(bitmap); 

     } 
     else 
      iv.setImageResource(R.drawable.loading); 
    } 


}