我想在CustomScrollView
中使用动画切换状态,但它引发了错误。
class SliverAnimatedSwitcher extends StatefulWidget {
final state;
const SliverAnimatedSwitcher({Key key, this.state}) : super(key: key);
@override
_SliverAnimatedSwitcherState createState() => _SliverAnimatedSwitcherState();
}
class _SliverAnimatedSwitcherState extends State<SliverAnimatedSwitcher> {
@override
Widget build(BuildContext context) {
return Scaffold(
body: CustomScrollView(
slivers: <Widget>[
SliverAppBar(
title: Text('SliverAnimatedSwitcher'),
),
_buildContent(),
],
),
);
}
get state => widget.state;
Widget _buildContent() {
var content;
if (state.isNotEmpty == true) {
content = SliverList(
delegate: SliverChildBuilderDelegate(
(context, index) {
var item = state.items[index];
return ListTile(
title: Text(item.title),
);
},
childCount: state.items.length,
),
);
} else if (state.isError) {
content = SliverFillRemaining(
key: Key('error'),
child: Container(alignment: Alignment.center, child: Text('Error')),
);
} else if (state.isLoading) {
content = SliverFillRemaining(
key: Key('loading'),
child: Container(alignment: Alignment.center, child: Text('Loading')),
);
} else {
content = SliverFillRemaining(
key: Key('empty'),
child: Container(alignment: Alignment.center, child: Text('Empty')),
);
}
return AnimatedSwitcher(
duration: Duration(milliseconds: 300),
child: content,
);
}
}