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March 14, 2020 13:10
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import 'dart:ui'; | |
import 'package:flutter/material.dart'; | |
void main() { | |
runApp(MyApp()); | |
} | |
class MyApp extends StatelessWidget { | |
// This widget is the root of your application. | |
@override | |
Widget build(BuildContext context) { | |
return MaterialApp( | |
title: 'Flutter Demo', | |
theme: ThemeData( | |
// This is the theme of your application. | |
// | |
// Try running your application with "flutter run". You'll see the | |
// application has a blue toolbar. Then, without quitting the app, try | |
// changing the primarySwatch below to Colors.green and then invoke | |
// "hot reload" (press "r" in the console where you ran "flutter run", | |
// or simply save your changes to "hot reload" in a Flutter IDE). | |
// Notice that the counter didn't reset back to zero; the application | |
// is not restarted. | |
primarySwatch: Colors.blue, | |
), | |
home: MyHomePage(title: 'Flutter Demo Home Page'), | |
); | |
} | |
} | |
class MyHomePage extends StatefulWidget { | |
MyHomePage({Key key, this.title}) : super(key: key); | |
// This widget is the home page of your application. It is stateful, meaning | |
// that it has a State object (defined below) that contains fields that affect | |
// how it looks. | |
// This class is the configuration for the state. It holds the values (in this | |
// case the title) provided by the parent (in this case the App widget) and | |
// used by the build method of the State. Fields in a Widget subclass are | |
// always marked "final". | |
final String title; | |
@override | |
_MyHomePageState createState() => _MyHomePageState(); | |
} | |
class _MyHomePageState extends State<MyHomePage> { | |
List<Offset> _offsets = <Offset>[]; | |
@override | |
Widget build(BuildContext context) { | |
final mediaSize = MediaQuery.of(context).size; | |
return Scaffold( | |
appBar: AppBar( | |
title: Text(widget.title), | |
), | |
body: Center( | |
child: GestureDetector( | |
onPanUpdate: (details) { | |
setState(() { | |
_offsets.add(details.localPosition); | |
}); | |
}, | |
onPanStart: (details) { | |
setState(() { | |
_offsets.add(details.localPosition); | |
}); | |
}, | |
onPanEnd: (details) { | |
setState(() { | |
_offsets.add(null); | |
}); | |
}, | |
child: CustomPaint( | |
painter: FlipbookPainter(_offsets), | |
child: Container( | |
height: mediaSize.height, | |
width: mediaSize.width, | |
color: Color(0x88ffccdd), | |
), | |
), | |
), | |
), | |
); | |
} | |
} | |
enum PathState { start, middle, end } | |
class FlipbookPainter extends CustomPainter { | |
final List<Offset> offsets; | |
var offsetsChanged = true; | |
final _paint = Paint() | |
..style = PaintingStyle.stroke | |
..color = Colors.black | |
..strokeWidth = 6 | |
..strokeCap = StrokeCap.round | |
..strokeJoin = StrokeJoin.round | |
..strokeMiterLimit = 4; | |
FlipbookPainter(this.offsets) : super(); | |
@override | |
void paint(Canvas canvas, Size size) { | |
var path = Path(); | |
var state = PathState.start; | |
for (var i = 0; i < offsets.length - 1; i++) { | |
final oi = offsets[i]; | |
print(oi.toString()); | |
switch (state) { | |
case PathState.start: | |
path.moveTo(oi.dx, oi.dy); | |
state = PathState.middle; | |
break; | |
case PathState.middle: | |
if (oi != null) { | |
path.lineTo(oi.dx, oi.dy); | |
} else { | |
state = PathState.end; | |
} | |
break; | |
case PathState.end: | |
canvas.drawPath(path, _paint); | |
path = Path(); | |
state = PathState.start; | |
break; | |
} | |
} | |
} | |
@override | |
bool shouldRepaint(CustomPainter oldDelegate) { | |
return true; | |
} | |
} |
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