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Perception
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import 'package:flutter/material.dart'; | |
void main() => runApp(MyApp()); | |
class MyApp extends StatelessWidget { | |
@override | |
Widget build(BuildContext context) { | |
return MaterialApp( | |
title: 'Perception is Everything', | |
home: MyHomePage(), | |
); | |
} | |
} | |
class MyHomePage extends StatelessWidget { | |
@override | |
Widget build(BuildContext context) { | |
return Material( | |
color: Colors.white, | |
child: FractionallySizedBox( | |
heightFactor: 0.8, | |
child: Container( | |
constraints: BoxConstraints(maxWidth: 500), | |
child: Column( | |
children: <Widget>[ | |
FractionallySizedBox( | |
widthFactor: 0.5, | |
child: Text('Which of the following animations is faster? ' | |
'(This is a trick question. ' | |
'Read the code for the answer.)'), | |
), | |
SizedBox(height: 50), | |
Expanded( | |
child: Row( | |
mainAxisAlignment: MainAxisAlignment.center, | |
children: <Widget>[ | |
MyPerception('A', Curves.linear), | |
SizedBox(width: 50), | |
MyPerception('B', Curves.easeOutCubic), | |
], | |
), | |
), | |
], | |
), | |
), | |
), | |
); | |
} | |
} | |
class MyPerception extends StatefulWidget { | |
final String label; | |
final Curve curve; | |
MyPerception(this.label, this.curve, {Key key}) : super(key: key); | |
@override | |
_MyPerceptionState createState() => _MyPerceptionState(); | |
} | |
class _MyPerceptionState extends State<MyPerception> { | |
Alignment _current = Alignment.bottomCenter; | |
Alignment _next = Alignment.bottomCenter; | |
@override | |
Widget build(BuildContext context) { | |
return Column( | |
children: <Widget>[ | |
FlatButton( | |
onPressed: () => setState(() { | |
_current = _next; | |
_next = _current == Alignment.bottomCenter | |
? Alignment.topCenter | |
: Alignment.bottomCenter; | |
}), | |
color: Colors.black12, | |
child: Text('Tap'), | |
), | |
SizedBox(height: 50), | |
Expanded( | |
child: TweenAnimationBuilder( | |
tween: AlignmentTween( | |
begin: _current, | |
end: _next, | |
), | |
// Oh snap! The duration is exactly the same for both animations. | |
duration: const Duration(milliseconds: 300), | |
// It's all about the curve. | |
// Linear motion generally feels more sluggish than a well chosen | |
// curve (like easeOutCubic in the case of B). | |
curve: widget.curve, | |
builder: (context, alignment, child) { | |
return Align( | |
alignment: alignment, | |
child: child, | |
); | |
}, | |
child: Container( | |
width: 50, | |
height: 50, | |
color: Colors.black, | |
child: Center( | |
child: | |
Text(widget.label, style: TextStyle(color: Colors.white)), | |
), | |
), | |
), | |
), | |
], | |
); | |
} | |
} |
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