Android - 确认ImageView的图片是否加载成功

      if (mPhotoView.getDrawable() == null) {
//            Toast.makeText(getActivity(), "图片加载失败", Toast.LENGTH_SHORT).show();
            mPhotoView.setImageDrawable(getResources().getDrawable(R.drawable.icon_default_user_photo));
        }

ByteArrayOutputStream out = new ByteArrayOutputStream();
bitmap.compress(Bitmap.CompressFormat.PNG, 100, out);
byte[] array= out.toByteArray();

Bitmap bitmap = BitmapFactory.decodeByteArray(data, 0, data.length);

Drawable drawable = new FastBitmapDrawable(bitmap);

      Canvas canvas = new Canvas(bitmap)
      drawable.draw(canvas)

Drawable drawable = activity.getResources().getDrawable(R.drawable.icon);

Bitmap bitmap = BitmapFactory. decodeResource (Resources   res, int id)