Flutter – How to apply BorderRadius for a Container with Stack widget?

i’m trying to figure out what exactly your problem is. your possible needs will found in the following code

here are some of done work:

• making the image rounded because it’s the background for the whole
  content.
• making the container which uses ClipRRect rounded and it’s proved
  by shpe of its borders

, try to remove border property of the BoxDeconration of that container.

here’s the code:

SizedBox(
        height: 250,
        child: Stack(
          children: [
            Positioned.fill(
              child: ClipRRect(
                borderRadius: BorderRadius.circular(12),
                  child: Image.asset('images/1.jpg', fit: BoxFit.cover)
              ),
            ),
            Positioned.fill(
              child: Container(
                decoration: BoxDecoration(
                  borderRadius: BorderRadius.circular(12),
                  color: Colors.black.withOpacity(0.35),
                ),
              ),
            ),
            Center(
              child: Container(
                padding: const EdgeInsets.all(20),
                decoration: BoxDecoration(
                  // you can remove borders.
                  border: Border.all(color: Colors.white, width: 1),
                  // i'm setting border to show you it's rounded
                  color: Colors.transparent,
                  borderRadius: BorderRadius.circular(12),
                ),
              
                child: const Text(
                  'Scrollable Component at the Top',
                  style: TextStyle(
                    fontSize: 20,
                    color: Colors.white,
                  ),
                ),
              ),
            ),
          ],
        ),
      ),

here’s the result:

you can remove the white borders of the container just by removing border property from BoxDecoration.

hope it helps you.