How to add line dash in Flutter

class DashedLinePainter extends CustomPainter {
  @override
  void paint(Canvas canvas, Size size) {
    double dashWidth = 9, dashSpace = 5, startX = 0;
    final paint = Paint()
      ..color = Colors.grey
      ..strokeWidth = 1;
    while (startX < size.width) {
      canvas.drawLine(Offset(startX, 0), Offset(startX + dashWidth, 0), paint);
      startX += dashWidth + dashSpace;
    }
  }

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

// garis putus putus
Row(
children: List.generate(150~/10, (index) => Expanded(
 child: Container(
  color: index%2==0?Colors.transparent
  :Colors.grey,
  height: 2,
 ),
 )),
),

As a workaround, in your case, you can do something like this

class MySeparator extends StatelessWidget {
  const MySeparator({Key? key, this.height = 1, this.color = Colors.black})
      : super(key: key);
  final double height;
  final Color color;

  @override
  Widget build(BuildContext context) {
    return LayoutBuilder(
      builder: (BuildContext context, BoxConstraints constraints) {
        final boxWidth = constraints.constrainWidth();
        const dashWidth = 10.0;
        final dashHeight = height;
        final dashCount = (boxWidth / (2 * dashWidth)).floor();
        return Flex(
          children: List.generate(dashCount, (_) {
            return SizedBox(
              width: dashWidth,
              height: dashHeight,
              child: DecoratedBox(
                decoration: BoxDecoration(color: color),
              ),
            );
          }),
          mainAxisAlignment: MainAxisAlignment.spaceBetween,
          direction: Axis.horizontal,
        );
      },
    );
  }
}

and use it const MySeparator()

class App extends StatelessWidget {
  const App({Key? key}) : super(key: key);

  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      home: Material(
        child: Container(
          color: Colors.blue,
          child: Center(
            child: Container(
              height: 600,
              width: 350,
              decoration: BoxDecoration(
                color: Colors.white,
                borderRadius: BorderRadius.all(Radius.circular(16.0)),
              ),
              child: Flex(
                direction: Axis.vertical,
                children: [
                  Expanded(child: Container()),
                  const MySeparator(color: Colors.grey),
                  Container(height: 200),
                ],
              ),
            ),
          ),
        ),
      ),
    );
  }
}