grid_paper_example.dart

grid_paper_example.dart

import 'package:flutter/material.dart';

void main() {
  runApp(const ExampleApp());
}

class ExampleApp extends StatelessWidget {
  const ExampleApp({super.key});
  
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      home: GridPaper(),
    );
  }  
}

class GridPaper extends StatelessWidget {
  const GridPaper({super.key});
  
  @override
  Widget build(BuildContext context) {
    return Scaffold(
      backgroundColor: Colors.white,
      body: Container(
        color: Colors.white,
        width: double.infinity,
        height: double.infinity,
        child: GridWidget(GridPainter()),
      ),
    );
  }
}

class GridWidget extends StatelessWidget {
  final CustomPainter foreground;

  const GridWidget(this.foreground, {Key? key}) : super(key: key);

  @override
  Widget build(BuildContext context) {
    return Padding(
      padding: const EdgeInsets.all(5),
      child: SafeArea(
        child: CustomPaint(
          foregroundPainter: foreground,
          painter: GridPainter(),
        ),
      ),
    );
  }
}

class GridPainter extends CustomPainter {
  final double boxSize = 50;

  @override
  void paint(Canvas canvas, Size size) {
    final vLines = (size.width ~/ boxSize) + 1;
    final hLines = (size.height ~/ boxSize) + 1;

    final paint = Paint()
      ..strokeWidth = 1
      ..color = Colors.red
      ..style = PaintingStyle.stroke;

    final path = Path();

    // Draw vertical lines
    for (var i = 0; i < vLines; ++i) {
      final x = boxSize * i;
      path.moveTo(x, 0);
      path.relativeLineTo(0, size.height);
    }

    // Draw horizontal lines
    for (var i = 0; i < hLines; ++i) {
      final y = boxSize * i;
      path.moveTo(0, y);
      path.relativeLineTo(size.width, 0);
    }
    canvas.drawPath(path, paint);
  }

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