关于BitmapFactory.decodeByteArray为空，的问题

String stra = d.getResult().getImage();

            try {
                byte[] data=null;
                data = stra.getBytes("UTF-8");
                // 为UTF8编码
                // 把二进制图片转成位图
                Bitmap bitmap = BitmapFactory.decodeByteArray(data, 0,
                        data.length,null);
                image.setImageBitmap(bitmap); 
            } catch (UnsupportedEncodingException e) {
                // TODO Auto-generated catch block
                e.printStackTrace();
            }

data中有数据，bitmap为空