以读取图片为例，读取assets下image文件夹中的某个图片

 /**
     * 从Assets/image中读取图片
     * @param fileName 文件名
     */
    public static Bitmap getImageFromAssetsFile(Context context, String fileName ) {
        Bitmap image = null;
        AssetManager am = context.getResources().getAssets();
        try {
            InputStream is = am.open("image/"+fileName+".png");
            image = BitmapFactory.decodeStream(is);
            is.close();
        } catch (IOException e) {
            e.printStackTrace();
        }
        return image;
    }