Glide的ARGB_8888设置不适用于android

Question

我正在使用Glide在ViewPager上显示一些图片。如您所知，当Glide加载图像时，RGB_565是默认类型。但是，为了显示高质量的图像，我在自定义format()类的instantiateItem()方法中使用了ViewPager Glide方法。

    @Override
    public Object instantiateItem(ViewGroup container, int position) {
        View view = mLayoutInflater.inflate(R.layout.item_viewerlayout, null);
        ViewHolder viewHolder = new ViewHolder();
        viewHolder.mImageView = (ImageView)view.findViewById(R.id.image_viewerlayout);
        viewHolder.mImageViewPlay = (ImageView)view.findViewById(R.id.image_viewerlayoutplay);
        viewHolder.mImageView.setOnClickListener(new OnClickListener() {
            @Override
            public void onClick(View view) {
                if (mGalleryActivity.mMenuLayout.getVisibility() == GONE) mGalleryActivity.openGalleryMenu();
                else mGalleryActivity.closeGalleryMenu();
            }
        });

        if (mArrItemType.get(position) == ToolleryMediaDB.TYPE_VIDEO) {
            viewHolder.mImageViewPlay.setVisibility(VISIBLE);
            viewHolder.mImageViewPlay.setOnClickListener(new OnClickListener() {
                @Override
                public void onClick(View view) {
                    Log.i("CheckLog", "Play Video!");
                }
            });
        }

        Glide.with(mContext).load(mArrItemPath.get(position)).asBitmap().format(DecodeFormat.PREFER_ARGB_8888).into(viewHolder.mImageView);
        container.addView(view, 0);

        return view;
    }

而且......这是ViewHolder类。

public class ViewHolder {
    ImageView mImageView;
    ImageView mImageViewPlay;
}

尽管调用format(DecodeFormat.PREFER_ARGB_8888)，ViewPager上显示的图片仍为RGB_565类型。我不知道为什么。我还需要另外设置吗？