class _SliverAppBarDelegate extends SliverPersistentHeaderDelegate {
_SliverAppBarDelegate({
@required this.minHeight,
@required this.maxHeight,
@required this.child,
});
final double minHeight;
final double maxHeight;
final Widget child;
@override
double get minExtent => minHeight;
@override
double get maxExtent => math.max(maxHeight, minHeight);
@override
Widget build(
BuildContext context, double shrinkOffset, bool overlapsContent) {
return new SizedBox.expand(child: child);
}
@override
bool shouldRebuild(_SliverAppBarDelegate oldDelegate) {
return maxHeight != oldDelegate.maxHeight ||
minHeight != oldDelegate.minHeight ||
child != oldDelegate.child;
}
}
...
SliverPersistentHeader makeHeader(String headerText) {
return SliverPersistentHeader(
pinned: true,
delegate: _SliverAppBarDelegate(
minHeight: 60.0,
maxHeight: 200.0,
child: Container(
color: Colors.lightBlue, child: Center(child: Text(headerText))),
),
);
}
...
makeHeader('Header Section 1'),