dash_animation_line.dart

class Home extends StatefulWidget {
  @override
  _HomeState createState() => _HomeState();
}

class _HomeState extends State<Home> with SingleTickerProviderStateMixin {
  AnimationController controller;

  @override
  void initState() {
    controller = AnimationController(
      vsync: this,
      duration: const Duration(seconds: 2),
    );
    controller.addListener(() {
      setState(() {});
    });
    super.initState();
  }

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        actions: <Widget>[
          IconButton(
            icon: Icon(Icons.add_a_photo),
            onPressed: () {
              controller.forward(from: 0.0);
            },
          ),
        ],
      ),
      body: Center(
        child: CustomPaint(
          painter: MyPainter(controller.value),
          child: Container(),
        ),
      ),
    );
  }
}

class MyPainter extends CustomPainter {
  double value;
  MyPainter(this.value);

  @override
  void paint(Canvas canvas, Size size) {
    double counter = 0.0;
    final dotWidth = 20.0;
    for (int i = 0; i < size.width; i++) {
      final paint = Paint()
        ..color = Colors.red
        ..style = PaintingStyle.stroke
        ..strokeWidth = 10.0;
      canvas.drawLine(
        Offset(counter, size.height / 2),
        Offset((counter + dotWidth) * value, size.height / 2),
        paint,
      );
      counter += (dotWidth * 2);
    }
    /*
    canvas.drawLine(
      Offset(0.0, 0.0),
      Offset(size.width * value, size.height * value),
      paint,
    );*/
  }

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