下面是在CustomPainter中绘制从点p1到点p2的虚线的函数：

void drawDashedLine(
      {required Canvas canvas,
      required Offset p1,
      required Offset p2,
      required int dashWidth,
      required int dashSpace,
      required Paint paint}) {
  // Get normalized distance vector from p1 to p2
  var dx = p2.dx - p1.dx;
  var dy = p2.dy - p1.dy;
  final magnitude = sqrt(dx * dx + dy * dy);
  dx = dx / magnitude;
  dy = dy / magnitude;

  // Compute number of dash segments
  final steps = magnitude ~/ (dashWidth + dashSpace);

  var startX = p1.dx;
  var startY = p1.dy;

  for (int i = 0; i < steps; i++) {
    final endX = startX + dx * dashWidth;
    final endY = startY + dy * dashWidth;
    canvas.drawLine(Offset(startX, startY), Offset(endX, endY), paint);
    startX += dx * (dashWidth + dashSpace);
    startY += dy * (dashWidth + dashSpace);
  }
}

示例用法：从（0，0）到（100，100）绘制一条红色虚线，虚线宽度为6，间距为4。

drawDashedLine(
    canvas: canvas,
    start: Offset(0, 0),
    end: Offset(100, 100),
    dashWidth: 6,
    dashSpace: 4,
    paint: Paint()..color = Colors.red..strokeWidth = 1);

• 编辑 *

这是一个使用一个Canvas绘制方法调用的版本：

void drawDashedLine({
  required Canvas canvas,
  required Offset p1,
  required Offset p2,
  required double dashWidth,
  required double dashSpace,
  required Paint paint,
}) {
  final points = <Offset>[];
  final distance = (p2 - p1).distance;
  dashWidth /= distance;
  dashSpace /= distance;
  double t = 0;
  while (t < 1) {
    points.add(Offset.lerp(p1, p2, t)!);
    t += dashWidth;
    points.add(Offset.lerp(p1, p2, t.clamp(0, 1))!);
    t += dashSpace;
  }
  canvas.drawPoints(ui.PointMode.lines, points, paint);
}