stacked_bar_chart.dart

import 'package:flutter/material.dart';

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

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

  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      debugShowCheckedModeBanner: false,
      home: Scaffold(
        body: Center(
          child: SizedBox(
            width: 900, // Adjust the width to accommodate more columns
            height: 500, // Adjust the height for the columns
            child: CustomPaint(
              painter: SpacedMultiShadowPainter(),
            ),
          ),
        ),
      ),
    );
  }
}

class SpacedMultiShadowPainter extends CustomPainter {
  @override
  void paint(Canvas canvas, Size size) {
    final barSpacing = size.width / 4; // Divide space for 3 columns
    const barWidth = 30.0;
    const spacerHeight = 4.0; // Vertical space between base bars and shadows
    const spaceWidth = 2.0; // Horizontal space between base bar and shadow
    const borderRadius = Radius.circular(8.0); // Radius for rounded corners

    // Data for all columns
    const columnHeights = [
      [50.0, 15.0, 30.0], // First column (Green, Pink, Blue)
      [60.0, 25.0, 35.0], // Second column
      [70.0, 30.0, 40.0], // Third column
    ];

    // Colors for each base bar
    final baseBarColors = [
      Colors.green.withOpacity(0.8),
      Colors.pink.withOpacity(0.8),
      Colors.blue.withOpacity(0.8),
    ];

    // Draw shadows dynamically for each base bar
    for (int i = 0; i < columnHeights.length - 1; i++) {
      final currentColumn = columnHeights[i];
      final nextColumn = columnHeights[i + 1];

      double currentHeight1 = size.height;
      double currentHeight2 = size.height;

      for (int j = 0; j < currentColumn.length; j++) {
        final shadowPaint = Paint()
          ..color = baseBarColors[j]
              .withOpacity(0.3) // Match shadow color with base bar color
          ..style = PaintingStyle.fill;

        final currentBaseBottom1 = currentHeight1;
        final currentBaseTop1 = currentHeight1 - currentColumn[j];

        final nextBaseBottom2 = currentHeight2;
        final nextBaseTop2 = currentHeight2 - nextColumn[j];

        if (currentColumn[j] > 0 || nextColumn[j] > 0) {
          // Draw shadow for this base bar
          final shadowPath = Path()
            ..moveTo(
              barSpacing * (i + 1) +
                  barWidth / 2 +
                  spaceWidth, // Bottom-right with space
              currentBaseBottom1,
            )
            ..lineTo(
              barSpacing * (i + 1) +
                  barWidth / 2 +
                  spaceWidth, // Top-right with space
              currentBaseTop1,
            )
            ..lineTo(
              barSpacing * (i + 2) -
                  barWidth / 2 -
                  spaceWidth, // Top-left with space
              nextBaseTop2,
            )
            ..lineTo(
              barSpacing * (i + 2) -
                  barWidth / 2 -
                  spaceWidth, // Bottom-left with space
              nextBaseBottom2,
            )
            ..close();

          canvas.drawPath(shadowPath, shadowPaint);
        }

        // Update heights for the next base bar
        currentHeight1 -= (currentColumn[j] + spacerHeight);
        currentHeight2 -= (nextColumn[j] + spacerHeight);
      }
    }

    // Draw all columns
    for (int i = 0; i < columnHeights.length; i++) {
      final column = columnHeights[i];
      double currentHeight = size.height;

      for (int j = 0; j < column.length; j++) {
        final baseBarPaint = Paint()
          ..color = baseBarColors[j]
          ..style = PaintingStyle.fill;

        final barRect = Rect.fromLTWH(
          barSpacing * (i + 1) - barWidth / 2,
          currentHeight - column[j],
          barWidth,
          column[j],
        );

        final barRRect = RRect.fromRectAndRadius(barRect, borderRadius);

        canvas.drawRRect(barRRect, baseBarPaint);
        currentHeight -=
            (column[j] + spacerHeight); // Add space between base bars
      }
    }
  }

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