答案 0 :(得分:1)
/// Flutter code sample for SliverAppBar
// This sample shows a [SliverAppBar] and it's behavior when using the
// [pinned], [snap] and [floating] parameters.
import 'package:flutter/material.dart';
void main() => runApp(MyApp());
/// This is the main application widget.
class MyApp extends StatelessWidget {
static const String _title = 'Flutter Code Sample';
@override
Widget build(BuildContext context) {
return const MaterialApp(
title: _title,
home: MyStatefulWidget(),
);
}
}
/// This is the stateful widget that the main application instantiates.
class MyStatefulWidget extends StatefulWidget {
const MyStatefulWidget();
@override
_MyStatefulWidgetState createState() => _MyStatefulWidgetState();
}
/// This is the private State class that goes with MyStatefulWidget.
class _MyStatefulWidgetState extends State<MyStatefulWidget> {
bool _pinned = true;
bool _snap = false;
bool _floating = false;
// [SliverAppBar]s are typically used in [CustomScrollView.slivers], which in
// turn can be placed in a [Scaffold.body].
@override
Widget build(BuildContext context) {
return Scaffold(
body: CustomScrollView(
slivers: <Widget>[
SliverAppBar(
pinned: _pinned,
snap: _snap,
floating: _floating,
expandedHeight: 160.0,
flexibleSpace: const FlexibleSpaceBar(
title: Text('SliverAppBar'),
background: FlutterLogo(),
),
),
const SliverToBoxAdapter(
child: SizedBox(
height: 20,
child: Center(
child: Text('Scroll to see the SliverAppBar in effect.'),
),
),
),
SliverList(
delegate: SliverChildBuilderDelegate(
(BuildContext context, int index) {
return Container(
color: index.isOdd ? Colors.white : Colors.black12,
height: 100.0,
child: Center(
child: Text('$index', textScaleFactor: 5),
),
);
},
childCount: 20,
),
),
],
),
bottomNavigationBar: BottomAppBar(
child: ButtonBar(
alignment: MainAxisAlignment.spaceEvenly,
children: <Widget>[
Row(
children: <Widget>[
const Text('pinned'),
Switch(
onChanged: (bool val) {
setState(() {
_pinned = val;
});
},
value: _pinned,
),
],
),
Row(
children: <Widget>[
const Text('snap'),
Switch(
onChanged: (bool val) {
setState(() {
_snap = val;
// Snapping only applies when the app bar is floating.
_floating = _floating || _snap;
});
},
value: _snap,
),
],
),
Row(
children: <Widget>[
const Text('floating'),
Switch(
onChanged: (bool val) {
setState(() {
_floating = val;
_snap = _snap && _floating;
});
},
value: _floating,
),
],
),
],
),
),
);
}
}
来源 - https://api.flutter.dev/flutter/material/SliverAppBar-class.html