| // Copyright 2014 The Flutter Authors. All rights reserved. |
| // Use of this source code is governed by a BSD-style license that can be |
| // found in the LICENSE file. |
| |
| import 'dart:math' as math; |
| |
| import 'package:flutter/material.dart'; |
| |
| class StockArrowPainter extends CustomPainter { |
| StockArrowPainter({ this.color, this.percentChange }); |
| |
| final Color color; |
| final double percentChange; |
| |
| @override |
| void paint(Canvas canvas, Size size) { |
| final Paint paint = Paint()..color = color; |
| paint.strokeWidth = 1.0; |
| const double padding = 2.0; |
| assert(padding > paint.strokeWidth / 2.0); // make sure the circle remains inside the box |
| final double r = (size.shortestSide - padding) / 2.0; // radius of the circle |
| final double centerX = padding + r; |
| final double centerY = padding + r; |
| |
| // Draw the arrow. |
| const double w = 8.0; |
| double h = 5.0; |
| double arrowY; |
| if (percentChange < 0.0) { |
| h = -h; |
| arrowY = centerX + 1.0; |
| } else { |
| arrowY = centerX - 1.0; |
| } |
| final Path path = Path(); |
| path.moveTo(centerX, arrowY - h); // top of the arrow |
| path.lineTo(centerX + w, arrowY + h); |
| path.lineTo(centerX - w, arrowY + h); |
| path.close(); |
| paint.style = PaintingStyle.fill; |
| canvas.drawPath(path, paint); |
| |
| // Draw a circle that circumscribes the arrow. |
| paint.style = PaintingStyle.stroke; |
| canvas.drawCircle(Offset(centerX, centerY), r, paint); |
| } |
| |
| @override |
| bool shouldRepaint(StockArrowPainter oldDelegate) { |
| return oldDelegate.color != color |
| || oldDelegate.percentChange != percentChange; |
| } |
| } |
| |
| class StockArrow extends StatelessWidget { |
| const StockArrow({ Key key, this.percentChange }) : super(key: key); |
| |
| final double percentChange; |
| |
| int _colorIndexForPercentChange(double percentChange) { |
| const double maxPercent = 10.0; |
| final double normalizedPercentChange = math.min(percentChange.abs(), maxPercent) / maxPercent; |
| return 100 + (normalizedPercentChange * 8.0).floor() * 100; |
| } |
| |
| Color _colorForPercentChange(double percentChange) { |
| if (percentChange > 0) |
| return Colors.green[_colorIndexForPercentChange(percentChange)]; |
| return Colors.red[_colorIndexForPercentChange(percentChange)]; |
| } |
| |
| @override |
| Widget build(BuildContext context) { |
| return Container( |
| width: 40.0, |
| height: 40.0, |
| margin: const EdgeInsets.symmetric(horizontal: 5.0), |
| child: CustomPaint( |
| painter: StockArrowPainter( |
| // TODO(jackson): This should change colors with the theme |
| color: _colorForPercentChange(percentChange), |
| percentChange: percentChange, |
| ), |
| ), |
| ); |
| } |
| } |