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Expanding AppBar in Flutter
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import 'package:flutter/material.dart'; | |
void main() => runApp(new MyApp()); | |
class MyApp extends StatelessWidget { | |
@override | |
Widget build(BuildContext context) { | |
return new MaterialApp( | |
title: 'Expanding AppBar Example', | |
theme: new ThemeData( | |
primarySwatch: Colors.teal, | |
), | |
home: new AnimatedScaffold(), | |
); | |
} | |
} | |
class AnimatedScaffold extends StatefulWidget { | |
@override | |
createState() => new AnimatedScaffoldState(); | |
} | |
class AnimatedScaffoldState extends State<AnimatedScaffold> | |
with SingleTickerProviderStateMixin { | |
AnimatedScaffoldState() { | |
controller = new AnimationController( | |
duration: new Duration(milliseconds: 500), vsync: this); | |
animation = new CurvedAnimation(parent: controller, curve: Curves.easeIn); | |
} | |
AnimationController controller; | |
Animation animation; | |
bool expanded = false; | |
_animateAppBar() { | |
expanded ? controller.reverse() : controller.forward(); | |
expanded = !expanded; | |
} | |
Widget build(BuildContext context) { | |
return new AnimatedScaffoldBottom( | |
animation: animation, onPress: _animateAppBar); | |
} | |
} | |
class AnimatedScaffoldBottom extends AnimatedWidget { | |
AnimatedScaffoldBottom({Key key, Animation<double> animation, this.onPress}) | |
: super(key: key, listenable: animation); | |
final Function onPress; | |
static final _sizeTween = new Tween<double>(begin: 0.0, end: 300.0); | |
@override | |
Widget build(BuildContext context) { | |
return new Scaffold( | |
body: new Center( | |
child: new Text( | |
'Hello World!', | |
style: Theme.of(context).textTheme.display1, | |
)), | |
appBar: new AppBar( | |
title: const Text('Expanding AppBar Example'), | |
actions: [ | |
new IconButton( | |
icon: new Icon(Icons.expand_more), | |
onPressed: onPress, | |
), | |
], | |
bottom: new PreferredSize( | |
preferredSize: new Size.fromHeight(_sizeTween.evaluate(listenable)), | |
child: new Container( | |
height: _sizeTween.evaluate(listenable), | |
child: const Center( | |
child: const FlutterLogo(size: 300.0), | |
), | |
), | |
), | |
), | |
); | |
} | |
} |
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