import 'dart:math';

import 'package:flutter/material.dart';

class BackGroundClipper extends CustomClipper<Path> {
  ///取值为 -1 ~ 1.0
  double moveFlag = 0;

  BackGroundClipper(this.moveFlag);

  @override
  Path getClip(Size size) {
    //创建 Path
    Path path = Path();
    //移动到点 P0点 也是曲线的起点
    path.lineTo(0, size.height * 0.2);
    //计算控制点 P1 的坐标
    double xCenter = size.width * 0.5 +
        (size.width * 0.6 + 1) * sin(moveFlag * pi);
    double yCenter = size.height * 0.2 + 69 * cos(moveFlag*pi);
    //构建 二阶贝塞尔曲线
    path.quadraticBezierTo(xCenter, yCenter, size.width, size.height * 0.2);

    path.lineTo(size.width, 0);
    return path;
  }

  @override
  bool shouldReclip(CustomClipper<Path> oldClipper) {
    return true;
  }
}