Positioned Widget overlapping my CustomScrollView - flutter

Question

I have a CustomScrollView that I need a fixed text entry field at the bottom. A post here suggestion a Stack with a Positioned Widget which worked great:
Scaffold(
appBar: appBarBuilder == null ? null : appBarBuilder(context),
body: RefreshIndicator(
onRefresh: onRefresh,
child: Stack(
children: <Widget>[
CustomScrollView(
controller: controller,
slivers: <Widget>[
if (showImage)
SliverAppBar(
expandedHeight: showImage ? 100 : 50,
title: showImage ? image : null,
centerTitle: true,
floating: true,
pinned: false,
),
sliverList,
],
),
Positioned(
bottom: 0,
left: 0,
right: 0,
child: TextFormField(),
),
],
),
),
);
Except that the positioned widget overlaps my CustomScrollView. I could add a white background, but I'd rather the CustomScrollView stop short of my TextFormField. How do I do that? Below is the current rendering:

Answer 1

Screenshot:
I'm sharing with you a simple implementation of a Column with ListView (replace it with your CustomScrollView) and a TextField at the bottom. When you click on the TextField, the keyboard automatically slides up the ListView and all your contents remain visible.
Code:
#override
Widget build(BuildContext context) {
return Scaffold(
body: Column(
children: [
Expanded(
child: ListView.builder( // <-- Replace it with your CustomScrollView
itemCount: 20,
itemBuilder: (_, i) => ListTile(title: Text('Item $i')),
),
),
Padding(
padding: const EdgeInsets.all(20),
child: TextField(decoration: InputDecoration(hintText: 'Enter a message')),
)
],
),
);
}