Flutter -如何对卡片小部件的某些百分比进行着色？

import 'package:flutter/material.dart';
import 'package:flutter/painting.dart';

Container(
  width: 200,
  height: 200,
  child: Card(
    child: // 卡片内容
  ),
),

class CustomCard extends StatelessWidget {
  final double percentage;
  
  CustomCard({this.percentage});
  
  @override
  Widget build(BuildContext context) {
    return Container(
      width: 200,
      height: 200,
      child: Card(
        child: CustomPaint(
          painter: _CustomPainter(percentage: percentage),
          child: // 卡片内容
        ),
      ),
    );
  }
}

class _CustomPainter extends CustomPainter {
  final double percentage;
  
  _CustomPainter({this.percentage});
  
  @override
  void paint(Canvas canvas, Size size) {
    final rect = Offset.zero & size;
    
    // 根据百分比计算颜色
    final color = Color.lerp(Colors.green, Colors.red, percentage / 100);
    
    // 绘制矩形
    final paint = Paint()..color = color;
    canvas.drawRect(rect, paint);
  }
  
  @override
  bool shouldRepaint(_CustomPainter oldDelegate) {
    return oldDelegate.percentage != percentage;
  }
}