import 'package:flutter/material.dart';import 'dart:math';class ColorPalette { static final ColorPalette primary = new ColorPalette(<Color>[ Colors.blue[400], Colors.red[400], Colors.green[400], Colors.yellow[400], Colors.purple[400], Colors.orange[400], Colors.teal[400], ]); ColorPalette(List<Color> colors) : _colors = colors { assert(colors.isNotEmpty); } factory ColorPalette.monochrome(Color base, int length) { return new ColorPalette(  new List.generate(  length,  (i) => _brighterColor(base, i, length)  ) ); } static Color _brighterColor(Color base, int i, int n) { /* const Color.fromARGB(  int a,  int r,  int g,  int b ) 從四個整數的低8位構造一個顏色  a：a是alpha值，0是透明的，255是完全不透明的  r：r為紅色，從0到255  g：g為紅色，從0到255  b：b為紅色，從0到255  */ return new Color.fromARGB(  /*  int alpha  這個顏色的alpha通道是8位值  值為0表示此顏色完全透明。值為255表示此顏色完全不透明  */  base.alpha,  _brighterComponent(base.red, i, n),  _brighterComponent(base.green, i, n),  _brighterComponent(base.blue, i, n) ); } static int _brighterComponent(int base, int i, int n) { return (base + i * (255 - base) / n).floor(); } final List<Color> _colors; Color operator [](int index) => _colors[index % length]; int get length => _colors.length; Color random(Random random) => this[random.nextInt(length)];}

import 'package:flutter/material.dart';import 'package:flutter/animation.dart';import 'dart:ui' show lerpDouble;import 'dart:math';import 'color_palette.dart';import 'tween.dart';class BarChart { BarChart(this.groups); final List<BarGroup> groups; factory BarChart.empty(Size size) { return new BarChart(<BarGroup>[]); } factory BarChart.random(Size size, Random random) { const groupWidthFraction = 0.75; const stackWidthFraction = 0.9; final groupRanks = _selectRanks(random, 5); final groupCount = groupRanks.length; final groupDistance = size.width / (1+groupCount); final groupWidth = groupDistance * groupWidthFraction; final startX = groupDistance - groupWidth/2; final stackRanks = _selectRanks(random, ColorPalette.primary.length ~/ 2); final stackCount = stackRanks.length; final stackDistance = groupWidth / stackCount; final stackWidth = stackDistance * stackWidthFraction; final groups = new List.generate(  groupCount,  (i) {  final stacks = new List.generate(   stackCount,   (j) {   final baseColor = ColorPalette.primary[stackRanks[j]];   final barRanks = _selectRanks(random, 4);   final monochrome = new ColorPalette.monochrome(baseColor, 4);   final bars = new List.generate(    barRanks.length,    (k) => new Bar(    barRanks[k],    random.nextDouble() * size.height / 2,    monochrome[barRanks[k]],    )   );   return new BarStack(    stackRanks[j],    baseColor,    startX + i * groupDistance + j * stackDistance,    stackWidth,    bars,   );   }  );  return new BarGroup(   groupRanks[i],   stacks  );  } ); return new BarChart(groups); } static List<int> _selectRanks(Random random, int cap) { final ranks = <int>[]; var rank = 0; while(true) {  rank += random.nextInt(2);  if(cap <= rank) break;  ranks.add(rank);  rank++; } return ranks; }}class BarChartTween extends Tween<BarChart> { BarChartTween(BarChart begin, BarChart end) : _groupsTween = new MergeTween<BarGroup>(begin.groups, end.groups), super(begin: begin, end: end); final MergeTween<BarGroup> _groupsTween; @override BarChart lerp(double t) => new BarChart(_groupsTween.lerp(t));}class BarGroup implements MergeTweenable<BarGroup> { BarGroup(this.rank, this.stacks); final int rank; final List<BarStack> stacks; @override BarGroup get empty => new BarGroup(rank, <BarStack>[]); @override bool operator <(BarGroup other) => rank < other.rank; @override Tween<BarGroup> tweenTo(BarGroup other) => new BarGroupTween(this, other);}class BarGroupTween extends Tween<BarGroup> { BarGroupTween(BarGroup begin, BarGroup end) : _stacksTween = new MergeTween<BarStack>(begin.stacks, end.stacks), super(begin: begin, end: end) {  assert(begin.rank == end.rank); } final MergeTween<BarStack> _stacksTween; @override BarGroup lerp(double t) => new BarGroup( begin.rank, _stacksTween.lerp(t) );}class BarStack implements MergeTweenable<BarStack> { BarStack(this.rank, this.baseColor, this.x, this.width, this.bars); final int rank; final Color baseColor; final double x; final double width; final List<Bar> bars; @override BarStack get empty => new BarStack(rank, baseColor, x, 0.0, <Bar>[]); @override bool operator <(BarStack other) => rank < other.rank; @override Tween<BarStack> tweenTo(BarStack other) => new BarStackTween(this, other);}class BarStackTween extends Tween<BarStack> { BarStackTween(BarStack begin, BarStack end) : _barsTween = new MergeTween<Bar>(begin.bars, end.bars), super(begin: begin, end: end) { assert(begin.rank == end.rank); } final MergeTween<Bar> _barsTween; @override BarStack lerp(double t) => new BarStack( begin.rank, Color.lerp(begin.baseColor, end.baseColor, t), lerpDouble(begin.x, end.x, t), lerpDouble(begin.width, end.width, t), _barsTween.lerp(t) );}class Bar extends MergeTweenable<Bar> { Bar(this.rank, this.height, this.color); final int rank; final double height; final Color color; @override Bar get empty => new Bar(rank, 0.0, color); @override bool operator <(Bar other) => rank < other.rank; @override Tween<Bar> tweenTo(Bar other) => new BarTween(this, other); static Bar lerp(Bar begin, Bar end, double t) { assert(begin.rank == end.rank); return new Bar(  begin.rank,  lerpDouble(begin.height, end.height, t),  Color.lerp(begin.color, end.color, t) ); }}class BarTween extends Tween<Bar> { BarTween(Bar begin, Bar end) : super(begin: begin, end: end) { assert(begin.rank == end.rank); } @override Bar lerp(double t) => Bar.lerp(begin, end, t);}class BarChartPainter extends CustomPainter { BarChartPainter(Animation<BarChart> animation)  : animation = animation,  super(repaint: animation); final Animation<BarChart> animation; @override void paint(Canvas canvas, Size size) { final barPaint = new Paint()..style = PaintingStyle.fill; final linePaint = new Paint()  ..style = PaintingStyle.stroke  ..color = Colors.white  ..strokeWidth = 1.0; final linePath = new Path(); final chart = animation.value; for(final group in chart.groups) {  for(final stack in group.stacks) {  var y = size.height;  for(final bar in stack.bars) {   barPaint.color = bar.color;   canvas.drawRect(   new Rect.fromLTWH(    stack.x,    y - bar.height,    stack.width,    bar.height   ),   barPaint   );   if(y < size.height) {   linePath.moveTo(stack.x, y);   linePath.lineTo(stack.x + stack.width, y);   }   y -= bar.height;  }  canvas.drawPath(   linePath,   linePaint  );  linePath.reset();  } } } @override bool shouldRepaint(BarChartPainter old) => false;}