painter_line_chart.dart

painter_line_chart.dart

import 'package:flutter/material.dart';
class ChartData {
  final double x;
  final double y;

  ChartData(this.x, this.y);
}

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

class MyApp extends StatefulWidget {
  const MyApp({super.key});

  @override
  State<MyApp> createState() => _MyAppState();
}

class _MyAppState extends State<MyApp> {
   final List<ChartData> _data = [
    ChartData(0.1, 0.3),
    ChartData(0.2, 0.5),
    ChartData(0.3, 0.7),
    ChartData(0.4, 0.4),
    ChartData(0.5, 0.6),
    ChartData(0.6, 0.8),
    ChartData(0.7, 0.5),
    ChartData(0.8, 0.9),
    ChartData(0.9, 0.7),
  ];

  double _selectedX = -1;
  
  
  @override
  Widget build(BuildContext context) {
    return const MaterialApp(
      debugShowCheckedModeBanner: false,
      home: Scaffold(
        body: GestureDetector(
      onPanUpdate: (details) {
        setState(() {
          _selectedX = details.localPosition.dx;
        });
      },
      onPanEnd: (_) {
        setState(() {
          _selectedX = -1;
        });
      },
      child: CustomPaint(
        size: Size(double.infinity, 300),
        painter: LineChartPainter(_data, _selectedX),
      ),
    )
      ),
    );
  }
}
class LineChartPainter extends CustomPainter {
  final List<ChartData> dataPoints;
  final double selectedX;

  LineChartPainter(this.dataPoints, this.selectedX);

  @override
  void paint(Canvas canvas, Size size) {
    final paint = Paint()
      ..color = Colors.blue
      ..style = PaintingStyle.stroke
      ..strokeWidth = 2;

    // Draw axes
    final axisPaint = Paint()
      ..color = Colors.black
      ..strokeWidth = 1;

    canvas.drawLine(Offset(0, size.height), Offset(size.width, size.height), axisPaint); // X-axis
    canvas.drawLine(Offset(0, 0), Offset(0, size.height), axisPaint); // Y-axis

    // Draw lines connecting data points
    final path = Path();
    for (var i = 0; i < dataPoints.length; i++) {
      final point = dataPoints[i];
      final x = point.x * size.width;
      final y = size.height - (point.y * size.height); // Invert Y for correct orientation
      if (i == 0) {
        path.moveTo(x, y);
      } else {
        path.lineTo(x, y);
      }
    }
    canvas.drawPath(path, paint);

    // Highlight selected point
    if (selectedX != -1) {
      for (var point in dataPoints) {
        final x = point.x * size.width;
        if ((x - selectedX).abs() < 10) {
          final y = size.height - (point.y * size.height);
          final highlightPaint = Paint()
            ..color = Colors.red
            ..style = PaintingStyle.fill;
          canvas.drawCircle(Offset(x, y), 6, highlightPaint);
          break;
        }
      }
    }
  }

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