kmpdfkit_demo/lib/widgets/function/attrwidget/signature_draw_board_widget.dart

import 'package:flutter/material.dart';


class SignatureDrawBoard extends StatefulWidget {
  @override
  _SignatureDrawBoardState createState() => _SignatureDrawBoardState();
}

class _SignatureDrawBoardState extends State<SignatureDrawBoard> {
  List<Offset> points = [];

  @override
  Widget build(BuildContext context) {
    return GestureDetector(
      onPanUpdate: (DragUpdateDetails details) {
        setState(() {
          RenderBox renderBox = context.findRenderObject() as RenderBox;
          Offset localPosition = renderBox.globalToLocal(details.globalPosition);
          points = List.from(points)..add(localPosition);
        });
      },
      onPanEnd: (DragEndDetails details) {
        // points.add(Offset.zero);
      },
      child: CustomPaint(
        painter: SignaturePainter(
          color: Colors.black,
          strokeWidth: 5.0,
          points: points,
        ),
        size: Size.infinite,
      ),
    );
  }
}






class SignaturePainter extends CustomPainter {
  Color color;
  double strokeWidth;
  List<Offset> points;

  SignaturePainter({required this.color, required this.strokeWidth, required this.points});

  @override
  void paint(Canvas canvas, Size size) {
    Paint paint = Paint()
      ..color = color
      ..strokeWidth = strokeWidth
      ..strokeCap = StrokeCap.round;

    for (int i = 0; i < points.length - 1; i++) {
      canvas.drawLine(points[i], points[i + 1], paint);
    }
  }

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