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// Copyright 2014 The Flutter Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
import 'package:flutter/material.dart';
import 'package:flutter/rendering.dart';
/// Flutter code sample for [ScrollDirection].
void main() => runApp(const ExampleApp());
class ExampleApp extends StatelessWidget {
const ExampleApp({super.key});
@override
Widget build(BuildContext context) {
return const MaterialApp(
home: MyWidget(),
);
}
}
class MyWidget extends StatefulWidget {
const MyWidget({super.key});
@override
State<MyWidget> createState() => _MyWidgetState();
}
class _MyWidgetState extends State<MyWidget> {
final List<String> alphabet = <String>[
'A', 'B', 'C', 'D', 'E', 'F', 'G', 'H', 'I', 'J', 'K', 'L', 'M', 'N', 'O',
'P', 'Q', 'R', 'S', 'T', 'U', 'V', 'W', 'X', 'Y', 'Z',
];
final Widget spacer = const SizedBox.square(dimension: 10);
ScrollDirection scrollDirection = ScrollDirection.idle;
AxisDirection _axisDirection = AxisDirection.down;
Widget _getArrows() {
final Widget arrow;
switch (_axisDirection) {
case AxisDirection.up:
arrow = const Icon(Icons.arrow_upward_rounded);
return Row(
mainAxisAlignment: MainAxisAlignment.center,
children: <Widget>[arrow, arrow],
);
case AxisDirection.down:
arrow = const Icon(Icons.arrow_downward_rounded);
return Row(
mainAxisAlignment: MainAxisAlignment.center,
children: <Widget>[arrow, arrow],
);
case AxisDirection.left:
arrow = const Icon(Icons.arrow_back_rounded);
return Column(
mainAxisAlignment: MainAxisAlignment.center,
children: <Widget>[arrow, arrow],
);
case AxisDirection.right:
arrow = const Icon(Icons.arrow_forward_rounded);
return Column(
mainAxisAlignment: MainAxisAlignment.center,
children: <Widget>[arrow, arrow],
);
}
}
void _onAxisDirectionChanged(AxisDirection? axisDirection) {
if (axisDirection != null && axisDirection != _axisDirection) {
setState(() {
// Respond to change in axis direction.
_axisDirection = axisDirection;
});
}
}
Widget _getLeading() {
return Container(
color: Colors.blue[100],
padding: const EdgeInsets.all(8.0),
child: Column(
mainAxisAlignment: MainAxisAlignment.spaceBetween,
children: <Widget>[
Text(axisDirectionToAxis(_axisDirection).toString()),
spacer,
Text(_axisDirection.toString()),
spacer,
const Text('GrowthDirection.forward'),
spacer,
Text(scrollDirection.toString()),
spacer,
_getArrows(),
],
),
);
}
Widget _getRadioRow() {
return DefaultTextStyle(
style: const TextStyle(fontWeight: FontWeight.bold, color: Colors.white),
child: RadioTheme(
data: RadioThemeData(
fillColor: MaterialStateProperty.all<Color>(Colors.white),
),
child: Padding(
padding: const EdgeInsets.all(8.0),
child: Row(
mainAxisAlignment: MainAxisAlignment.spaceAround,
children: <Widget>[
Radio<AxisDirection>(
value: AxisDirection.up,
groupValue: _axisDirection,
onChanged: _onAxisDirectionChanged,
),
const Text('up'),
spacer,
Radio<AxisDirection>(
value: AxisDirection.down,
groupValue: _axisDirection,
onChanged: _onAxisDirectionChanged,
),
const Text('down'),
spacer,
Radio<AxisDirection>(
value: AxisDirection.left,
groupValue: _axisDirection,
onChanged: _onAxisDirectionChanged,
),
const Text('left'),
spacer,
Radio<AxisDirection>(
value: AxisDirection.right,
groupValue: _axisDirection,
onChanged: _onAxisDirectionChanged,
),
const Text('right'),
spacer,
],
),
),
),
);
}
bool _handleNotification(UserScrollNotification notification) {
if (notification.direction != scrollDirection) {
setState(() {
scrollDirection = notification.direction;
});
}
return false;
}
@override
Widget build(BuildContext context) {
return Scaffold(
appBar: AppBar(
title: const Text('ScrollDirections'),
bottom: PreferredSize(
preferredSize: const Size.fromHeight(50),
child: Padding(
padding: const EdgeInsets.all(8.0),
child: _getRadioRow(),
),
),
),
body: NotificationListener<UserScrollNotification>(
onNotification: _handleNotification,
// Also works for ListView.builder, which creates a SliverList for itself.
// A CustomScrollView allows multiple slivers to be composed together.
child: CustomScrollView(
// This method is available to conveniently determine if an scroll
// view is reversed by its AxisDirection.
reverse: axisDirectionIsReversed(_axisDirection),
// This method is available to conveniently convert an AxisDirection
// into its Axis.
scrollDirection: axisDirectionToAxis(_axisDirection),
slivers: <Widget>[
SliverList.builder(
itemCount: 27,
itemBuilder: (BuildContext context, int index) {
final Widget child;
if (index == 0) {
child = _getLeading();
} else {
child = Container(
color: index.isEven ? Colors.amber[100] : Colors.amberAccent,
padding: const EdgeInsets.all(8.0),
child: Center(child: Text(alphabet[index - 1])),
);
}
return Padding(
padding: const EdgeInsets.all(8.0),
child: child,
);
},
),
],
),
),
);
}
}