我有以下小部件：

class _PhotoViewState extends State<PhotoView> {
  @override
  Widget build(BuildContext context) {
    return Scaffold(
      body: Stack(
        fit: StackFit.passthrough,
        children: [
          PhotoViewGallery.builder(
            itemCount: widget.imageUrls.length,
            builder: (context, index) {
              return PhotoViewGalleryPageOptions(
                imageProvider:
                    CachedNetworkImageProvider(widget.imageUrls[index]),
                initialScale: PhotoViewComputedScale.contained,
                minScale: PhotoViewComputedScale.contained,
                maxScale: PhotoViewComputedScale.covered * 2,
              );
            },
            scrollPhysics: const BouncingScrollPhysics(),
            backgroundDecoration: const BoxDecoration(color: Colors.black),
            loadingBuilder: (context, event) => Center(
              child: Container(
                width: 20.0,
                height: 20.0,
                child: CircularProgressIndicator(
                  value: event == null
                      ? 0
                      : event.cumulativeBytesLoaded / event.expectedTotalBytes!,
                ),
              ),
            ),
          ),
          Positioned(
            top: 0,
            left: 0,
            right: 0,
            bottom: 0,
            child: Container(
              color: Colors.green.withOpacity(0.5),
              child: Text("This is an overlay"),
            ),
          ),
        ],
      ),
    );
  }
}

Photoview会返回一个图片大小的Widget，这通常意味着有很多多余的空间。我尝试实现的是一个容器，它可以覆盖整个屏幕，除了照片，当触摸它时，屏幕会弹出。然而，正如你在下面的图片中看到的，我的容器占据了整个屏幕，并位于图片的顶部。

有人知道我怎么做才能让容器避开图像吗？
谢谢!