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August 10, 2021 22:05
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Paint demo with a simple animation. Creates a loading bar.
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| import 'dart:math'; | |
| import 'package:flutter/material.dart'; | |
| void main() => runApp(const MyApp()); | |
| class MyApp extends StatelessWidget { | |
| const MyApp({Key? key}) : super(key: key); | |
| @override | |
| Widget build(BuildContext context) { | |
| return MaterialApp( | |
| showPerformanceOverlay: false, | |
| title: 'Paint Demo', | |
| home: Scaffold( | |
| appBar: AppBar( | |
| title: const Text('Paint Demo'), | |
| ), | |
| body: const Center( | |
| child: PaintDemo(), | |
| ), | |
| ), | |
| ); | |
| } | |
| } | |
| class PaintDemo extends StatefulWidget { | |
| const PaintDemo({Key? key}) : super(key: key); | |
| @override | |
| _PaintDemoState createState() => _PaintDemoState(); | |
| } | |
| class _PaintDemoState extends State<PaintDemo> | |
| with SingleTickerProviderStateMixin { | |
| late AnimationController _controller; | |
| late CurvedAnimation _animation; | |
| @override | |
| void initState() { | |
| _controller = | |
| AnimationController(vsync: this, duration: const Duration(seconds: 3)); | |
| _animation = CurvedAnimation(parent: _controller, curve: Curves.slowMiddle); | |
| _controller.repeat(); | |
| super.initState(); | |
| } | |
| @override | |
| void dispose() { | |
| _controller.dispose(); | |
| super.dispose(); | |
| } | |
| @override | |
| Widget build(BuildContext context) { | |
| return AnimatedBuilder( | |
| animation: _animation, | |
| builder: (_, child) { | |
| return CustomPaint( | |
| painter: LinePainter(progress: _animation.value), | |
| child: child, | |
| ); | |
| }, | |
| child: const SizedBox( | |
| width: 200, | |
| height: 75, | |
| child: Text('Loading...'), | |
| ), | |
| ); | |
| } | |
| } | |
| class LinePainter extends CustomPainter { | |
| LinePainter({this.progress = 0.5}); | |
| final double progress; | |
| static final linePaint = Paint() | |
| ..color = const Color(0xFFF4AC45) | |
| ..style = PaintingStyle.stroke | |
| ..strokeWidth = 6 | |
| ..strokeCap = StrokeCap.round; | |
| static const _gap = 12.0; | |
| @override | |
| void paint(Canvas canvas, Size size) { | |
| final height = size.height / 2; | |
| final widthProgress = size.width * progress; | |
| final point1 = max(0.0, widthProgress - _gap); | |
| final point2 = min(widthProgress + _gap, size.width); | |
| canvas | |
| ..drawLine(Offset(0, height), Offset(point1, height), linePaint) | |
| ..drawLine(Offset(point2, height), Offset(size.width, height), linePaint); | |
| } | |
| @override | |
| bool shouldRepaint(LinePainter oldDelegate) { | |
| if (progress != oldDelegate.progress) { | |
| return true; | |
| } | |
| return false; | |
| } | |
| } |
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