Flutter-我正在寻找一种制作脉冲动画的方法 [英] Flutter - I am looking for a way to do a pulse animation
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问题描述
我正在努力实现类似的目标
i am trying to achieved some thing like this in flutter
推荐答案
一种方法是使用 CustomPainter
和动画。另请参阅 SpriteWidget 。
One way is with CustomPainter
and an animation. Also look at SpriteWidget.
import 'dart:math';
import 'package:flutter/material.dart';
class SpritePainter extends CustomPainter {
final Animation<double> _animation;
SpritePainter(this._animation) : super(repaint: _animation);
void circle(Canvas canvas, Rect rect, double value) {
double opacity = (1.0 - (value / 4.0)).clamp(0.0, 1.0);
Color color = new Color.fromRGBO(0, 117, 194, opacity);
double size = rect.width / 2;
double area = size * size;
double radius = sqrt(area * value / 4);
final Paint paint = new Paint()..color = color;
canvas.drawCircle(rect.center, radius, paint);
}
@override
void paint(Canvas canvas, Size size) {
Rect rect = new Rect.fromLTRB(0.0, 0.0, size.width, size.height);
for (int wave = 3; wave >= 0; wave--) {
circle(canvas, rect, wave + _animation.value);
}
}
@override
bool shouldRepaint(SpritePainter oldDelegate) {
return true;
}
}
class SpriteDemo extends StatefulWidget {
@override
SpriteDemoState createState() => new SpriteDemoState();
}
class SpriteDemoState extends State<SpriteDemo>
with SingleTickerProviderStateMixin {
AnimationController _controller;
@override
void initState() {
super.initState();
_controller = new AnimationController(
vsync: this,
);
//_startAnimation();
}
@override
void dispose() {
_controller.dispose();
super.dispose();
}
void _startAnimation() {
_controller.stop();
_controller.reset();
_controller.repeat(
period: Duration(seconds: 1),
);
}
@override
Widget build(BuildContext context) {
return new Scaffold(
appBar: new AppBar(title: const Text('Pulse')),
body: new CustomPaint(
painter: new SpritePainter(_controller),
child: new SizedBox(
width: 200.0,
height: 200.0,
),
),
floatingActionButton: new FloatingActionButton(
onPressed: _startAnimation,
child: new Icon(Icons.play_arrow),
),
);
}
}
void main() {
runApp(
new MaterialApp(
home: new SpriteDemo(),
),
);
}
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