Custom dotted border in flutter

dotted_border.dart

import 'package:flutter/material.dart';

class DottedBorder extends StatelessWidget {
  final double strokeWidth;
  final Color color;
  final double dashLength;
  final double dashGap;
  final Shape shape;
  final Widget child;

  const DottedBorder({
    super.key,
    this.strokeWidth = 2.0,
    this.color = Colors.black,
    this.dashLength = 4.0,
    this.dashGap = 2.0,
    this.shape = Shape.rectangle,
    required this.child,
  });

  @override
  Widget build(BuildContext context) {
    return CustomPaint(
      painter: DottedBorderPainter(
        shape: shape,
        strokeWidth: strokeWidth,
        color: color,
        dashGap: dashGap,
        dashLength: dashLength,
      ),
      child: child,
    );
  }
}

enum Shape { rectangle, circle }

class DottedBorderPainter extends CustomPainter {
  final double strokeWidth;
  final Color color;
  final double dashLength;
  final double dashGap;
  final Shape shape;

  DottedBorderPainter({
    this.strokeWidth = 2.0,
    this.color = Colors.black,
    this.dashLength = 4.0,
    this.dashGap = 2.0,
    this.shape = Shape.rectangle,
  });

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

    if (shape == Shape.rectangle) {
      drawDottedLine(
          canvas, const Offset(0, 0), Offset(size.width, 0), paint); // Top
      drawDottedLine(canvas, Offset(size.width, 0),
          Offset(size.width, size.height), paint); // Right
      drawDottedLine(canvas, Offset(size.width, size.height),
          Offset(0, size.height), paint); // Bottom
      drawDottedLine(
          canvas, Offset(0, size.height), const Offset(0, 0), paint); // Left
    } else if (shape == Shape.circle) {
      drawDottedCircle(canvas, Offset(size.width / 2, size.height / 2),
          size.width / 2, paint);
    }
  }

  void drawDottedLine(Canvas canvas, Offset start, Offset end, Paint paint) {
    double totalLength = (start - end).distance;
    double dashLengthWithGap = dashLength + dashGap;
    double dashCount = (totalLength / dashLengthWithGap).floorToDouble();
    double dashLengthActual = totalLength / dashCount - dashGap;

    for (int i = 0; i < dashCount; i++) {
      double currentLength = i * dashLengthWithGap;
      Offset from = Offset.lerp(start, end, currentLength / totalLength)!;
      Offset to = Offset.lerp(
          start, end, (currentLength + dashLengthActual) / totalLength)!;
      canvas.drawLine(from, to, paint);
    }
  }

  void drawDottedCircle(
      Canvas canvas, Offset center, double radius, Paint paint) {
    double circumference = 2 * 3.14159265358979323846 * radius;
    double dashCount = (circumference / (dashLength + dashGap)).floorToDouble();
    double dashArcLength = 2 * 3.14159265358979323846 / dashCount;

    for (int i = 0; i < dashCount; i++) {
      double startAngle = i * dashArcLength;
      double endAngle = startAngle + (dashLength / radius);
      canvas.drawArc(Rect.fromCircle(center: center, radius: radius),
          startAngle, endAngle - startAngle, false, paint);
    }
  }

  @override
  bool shouldRepaint(CustomPainter oldDelegate) {
    return false;
  }
}