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Flutter進階之實現動畫效果（十）
前面的兩篇文章【動畫效果（八） 、動畫效果（九） 】中，我們只需要統計產品和地區，如果現在增加一個統計項目——銷售渠道，那么使用之前的堆疊條形圖和分組條形圖都不適合。我們可以將兩者結合，使用分組+堆疊條形圖，實際效果如下圖所示：
在金平等地區，都構建了全面的區域性戰略布局，加強發展的系統性、市場前瞻性、產品創新能力，以專注、極致的服務理念，為客戶提供成都網站設計、網站制作 網站設計制作按需定制開發,公司網站建設,企業網站建設,成都品牌網站建設,成都全網營銷,外貿網站建設,金平網站建設費用合理。
如上圖，我們使用同一種顏色的不同透明度表示不同的銷售渠道，為了實現不同的透明度，我們需要先更新一下color_palette.dart文件的代碼：
import 'package:flutter/material.dart';
import 'dart:math';
class ColorPalette {
static final ColorPalette primary = new ColorPalette([
Colors.blue[400],
Colors.red[400],
Colors.green[400],
Colors.yellow[400],
Colors.purple[400],
Colors.orange[400],
Colors.teal[400],
]);
ColorPalette(List 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 _colors;
Color operator [](int index) => _colors[index % length];
int get length => _colors.length;
Color random(Random random) => this[random.nextInt(length)];
} 最后我們再更新一下bar.dart文件的代碼：
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 groups;
factory BarChart.empty(Size size) {
return new BarChart([]);
}
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 _selectRanks(Random random, int cap) {
final ranks = [];
var rank = 0;
while(true) {
rank += random.nextInt(2);
if(cap <= rank) break;
ranks.add(rank);
rank++;
}
return ranks;
}
}
class BarChartTween extends Tween {
BarChartTween(BarChart begin, BarChart end)
: _groupsTween = new MergeTween(begin.groups, end.groups),
super(begin: begin, end: end);
final MergeTween _groupsTween;
@override
BarChart lerp(double t) => new BarChart(_groupsTween.lerp(t));
}
class BarGroup implements MergeTweenable {
BarGroup(this.rank, this.stacks);
final int rank;
final List stacks;
@override
BarGroup get empty => new BarGroup(rank, []);
@override
bool operator <(BarGroup other) => rank < other.rank;
@override
Tween tweenTo(BarGroup other) => new BarGroupTween(this, other);
}
class BarGroupTween extends Tween {
BarGroupTween(BarGroup begin, BarGroup end)
: _stacksTween = new MergeTween(begin.stacks, end.stacks),
super(begin: begin, end: end) {
assert(begin.rank == end.rank);
}
final MergeTween _stacksTween;
@override
BarGroup lerp(double t) => new BarGroup(
begin.rank,
_stacksTween.lerp(t)
);
}
class BarStack implements MergeTweenable {
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 bars;
@override
BarStack get empty => new BarStack(rank, baseColor, x, 0.0, []);
@override
bool operator <(BarStack other) => rank < other.rank;
@override
Tween tweenTo(BarStack other) => new BarStackTween(this, other);
}
class BarStackTween extends Tween {
BarStackTween(BarStack begin, BarStack end)
: _barsTween = new MergeTween(begin.bars, end.bars),
super(begin: begin, end: end) {
assert(begin.rank == end.rank);
}
final MergeTween _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(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 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 {
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 animation)
: animation = animation,
super(repaint: animation);
final Animation 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;
} 關于如何實現動畫效果的教程到這里就暫時告一段落了。
以上就是本文的全部內容，希望對大家的學習有所幫助，也希望大家多多支持創新互聯。
文章名稱：Flutter進階之實現動畫效果（十）
文章URL：http://www.xueling.net.cn/article/iisojc.html