实现从网络上下载图片转化成Bitmap

public  Bitmap getBitmap(String url) {
    InputStream inputStream=null;
    ByteArrayOutputStream outputStream=null;
    try {
                URL url=new URL(url);
                HttpURLConnection httpURLConnection=(HttpURLConnection) url.openConnection();
                httpURLConnection.setRequestMethod("GET");
                httpURLConnection.setReadTimeout(2000);
                httpURLConnection.connect();

                if(httpURLConnection.getResponseCode()==200){
                    inputStream = httpURLConnection.getInputStream();
                    outputStream = new ByteArrayOutputStream();

                    byte buffer[]=new byte[1024*8];
                    int len=-1;
                    while ((len = inputStream.read(buffer)) != -1) {
                        outputStream.write(buffer, 0, len);
                    }

                    byte[] bu=outputStream.toByteArray();

                    Bitmap bitmap=BitmapFactory.decodeByteArray(bu, 0, bu.length);
                    return bitmap;
                }
            } catch (Exception e) {
                // TODO: handle exception
            }finally{
                if(inputStream!=null){
                    try {
                        inputStream.close();
                    } catch (IOException e) {
                        // TODO Auto-generated catch block
                        e.printStackTrace();
                    }
                }
                if(outputStream!=null){
                    try {
                        outputStream.close();
                    } catch (IOException e) {
                        // TODO Auto-generated catch block
                        e.printStackTrace();
                    }
                }
            }
            return null;
        }
    }