Flutter:使用 CustomClipper 绘制 N 角星
// This custom clipper help us achieve n-pointed star shape
class StarClipper extends CustomClipper
/// The number of points of the star
final int points;
StarClipper(this.points);
// Degrees to radians conversion
double _degreeToRadian(double deg) => deg * (math.pi / 180.0);
@override
Path getClip(Size size) {
Path path = Path();
double max = 2 * math.pi;
double width = size.width;
double halfWidth = width / 2;
double wingRadius = halfWidth;
double radius = halfWidth / 2;
double degreesPerStep = _degreeToRadian(360 / points);
double halfDegreesPerStep = degreesPerStep / 2;
path.moveTo(width, halfWidth);
for (double step = 0; step < max; step += degreesPerStep) {
path.lineTo(halfWidth + wingRadius * math.cos(step),
halfWidth + wingRadius * math.sin(step));
path.lineTo(halfWidth + radius * math.cos(step + halfDegreesPerStep),
halfWidth + radius * math.sin(step + halfDegreesPerStep));
}
path.close();
return path;
}
// If the new instance represents different information than the old instance, this method will return true, otherwise it should return false.
@override
bool shouldReclip(CustomClipper
StarClipper starClipper = oldClipper as StarClipper;
return points != starClipper.points;
}
}
- 现在您可以轻松绘制星星了,如下所示:
SizedBox(
height: 360,
width: 360,
child: ClipPath(
clipper: StarClipper(6),
child: Container(
height: 300,
color: Colors.amber,
),
),
),
预览
此示例生成 4 种不同的星形:5 角星、6 角星、10 角星和 20 角星。
![[外链图片转存失败,源站可能有防盗链机制,建议将图片保存下来直接上传(img-VF2prauV-1634091109338)(D:\study_manger\hugo_LoveIt_blog\content\post\flutter_tips\Flutter:使用 CustomClipper 绘制 N 角星.assets\Screen-Shot-2021-10-11-at-14.30.25.jpg)]](https://i-blog.csdnimg.cn/blog_migrate/bcd7069ef303ff61cffc873cc94933c6.png)
编码
main.dart 中的完整源代码和解释:
// main.dart
import ‘package:flutter/material.dart’;
import ‘dart:math’ as math;
// This custom clipper help us achieve n-pointed star shape
class StarClipper extends CustomClipper
/// The number of points of the star
final int points;
StarClipper(this.points);
// Degrees to radians conversion
double _degreeToRadian(double deg) => deg * (math.pi / 180.0);
@override
Path getClip(Size size) {
Path path = Path();
double max = 2 * math.pi;
double width = size.width;
double halfWidth = width / 2;
double wingRadius = halfWidth;
double radius = halfWidth / 2;
double degreesPerStep = _degreeToRadian(360 / points);
double halfDegreesPerStep = degreesPerStep / 2;
path.moveTo(width, halfWidth);
for (double step = 0; step < max; step += degreesPerStep) {
path.lineTo(halfWidth + wingRadius * math.cos(step),
halfWidth + wingRadius * math.sin(step));
path.lineTo(halfWidth + radius * math.cos(step + halfDegreesPerStep),
halfWidth + radius * math.sin(step + halfDegreesPerStep));
}
path.close();
return path;
}
// If the new instance represents different information than the old instance, this method will return true, otherwise it should return false.
@override
bool shouldReclip(CustomClipper
StarClipper starClipper = oldClipper as StarClipper;
return points != starClipper.points;
}
}
void main() {
runApp(const MyApp());
}
class MyApp extends StatelessWidget {
const MyApp({Key? key}) : super(key: key);
@override
Widget build(BuildContext context) {
return MaterialApp(
debugShowCheckedModeBanner: false,
title: ‘KindaCode.com’,
theme: ThemeData(
primarySwatch: Colors.indigo,
),
home: const MyHomePage(),
);
}
}
class MyHomePage extends StatefulWidget {
const MyHomePage({Key? key}) : super(key: key);
@override
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