luojigou_battle/lib/button/button_painter.dart

import 'dart:ui';

import 'package:battle/button/button_controller.dart';
import 'package:flutter/material.dart';
import 'package:widget/widget.dart';

class ButtonPainter extends CustomPainter {
  final GameController controller;

  ButtonPainter({required this.controller}) : super(repaint: controller);

  @override
  void paint(Canvas canvas, Size size) {
    final paint = Paint()
      ..style = PaintingStyle.fill
      ..strokeWidth = 4;

    for (var button in controller.buttonList) {
      var path = fromBottomToCenter(size, button.startIndex, button.endIndex);
      var pms = path.computeMetrics();
      for (var pm in pms) {
        Tangent? tangent = pm.getTangentForOffset(pm.length * button.process);
        if (tangent == null) continue;
        paint.color = button.color;
        canvas.drawCircle(tangent.position, getButtonSize(size) / 2, paint);
        paint.color = button.color.withOpacity(0.2);
        canvas.drawCircle(tangent.position, getButtonSize(size) / 2 + getButtonSize(size) * 0.1, paint);
      }
    }
  }

  @override
  bool shouldRepaint(covariant CustomPainter oldDelegate) => true;
}