flutter fl_chart 柱状图柱条数量较多实现左右滑动固定y轴

一、引入插件

pub.dev：fl_chart package - All Versions

根据项目版本，安装可适配的 fl_chart 版本

二、官网柱状图示例

github参数配置：（x轴、y轴、边框、柱条数据、tooltip等）

https://github.com/imaNNeo/fl_chart/blob/master/repo_files/documentations/bar_chart.md

BarChart(BarChartData(// read about it in the BarChartData section),swapAnimationDuration: Duration(milliseconds: 150), // OptionalswapAnimationCurve: Curves.linear, // Optional
);

官方给的例子：（柱条数量多时，不能左右滚动）https://github.com/imaNNeo/fl_chart/blob/master/example/lib/presentation/samples/bar/bar_chart_sample1.dart

三、自定义实现左右滑动固定y轴

思路：

1、在 BarChart 外层添加一层 Container，Container外面包裹一层 SingleChildScrollView，scrollDirection 属性设置为 Axis.horizontal，即可实现水平滚动；

2、但是y轴也会跟着一起滚动，所以我们在 SingleChildScrollView 外手写一个y轴，用Row包裹；

1、手写的y轴

这里没什么技巧，主要是y轴数据的分配：此例中最大值大于5时，也是5等分，四舍五入；小于5则根据最大值分，间隔为1；

            // 手写y轴Column(children: [const Text('人数',style: TextStyle(color: Color(0xFF999999), fontSize: 11)),Row(children: [Column(children: totalNum >= 5 ? List.generate(5, (index) {return Column(children: [Text('${(totalNum / 4 * (4 - index)).round()}',style: const TextStyle(color: Color(0xFF999999),fontSize: 11)),index < 4 ? const SizedBox(height: 25) : const SizedBox()],);}): List.generate(totalNum + 1, (index) {return Column(children: [Text('${totalNum - index}',style: const TextStyle(color: Color(0xFF999999),fontSize: 11)),index < totalNum ? SizedBox(height: (100 / totalNum).toDouble()) : const SizedBox()],);})),const SizedBox(width: 4),//垂直分割线const SizedBox(width: 1,height: 161,child: DecoratedBox(decoration: BoxDecoration(color: Color(0xFFEEEEEE)),),),],),],),

2、实现左右滑动

💎💎注意层级结构，Expanded — SingleChildScrollView — Container — BarChart

            Expanded(child: SingleChildScrollView(scrollDirection: Axis.horizontal,child: Container(padding: const EdgeInsets.only(top: 10, bottom: 10),width: barList.length * 35 + 220,height: 220,child: BarChart(BarChartData(alignment: BarChartAlignment.spaceEvenly,titlesData: FlTitlesData(show: true,topTitles: AxisTitles(sideTitles: SideTitles(showTitles: false),),bottomTitles: AxisTitles(sideTitles: SideTitles(showTitles: true,reservedSize: 32,// getTitlesWidget: bottomTitles,  x轴配置),),leftTitles: AxisTitles(sideTitles: SideTitles(showTitles: false,),),rightTitles: AxisTitles(sideTitles: SideTitles(showTitles: false),),),gridData: FlGridData(show: false),borderData: FlBorderData(border: const Border(bottom: BorderSide(color: AppColors.colorFFEEEEEE),)),// barGroups: showingGroups()  柱条数据配置),),)),),

完整代码结构（x轴、图表数据等需要自己去完善）

import 'package:fl_chart/fl_chart.dart';
import 'package:flutter/material.dart';
import 'package:oamic_project/common/values/colors.dart';// 柱状图
class SubjectClassficationBarChart extends StatelessWidget {const SubjectClassficationBarChart({super.key});@overrideWidget build(BuildContext context) {List<int> barList = [10,20,30,4,0,5,50,50,78,45,23,6,21,10];  // 数据列表int totalNum = 0;  // 总人数return LayoutBuilder(builder: (context, constraints) {final maxWidth = constraints.maxWidth;return SizedBox(width: maxWidth,height: 220,child: Row(children: [// 手绘y轴Column(children: [const Text('人数',style: TextStyle(color: Color(0xFF999999), fontSize: 11)),Row(children: [Column(children: totalNum >= 5 ? List.generate(5, (index) {return Column(children: [Text('${(totalNum / 4 * (4 - index)).round()}',style: const TextStyle(color: Color(0xFF999999),fontSize: 11)),index < 4 ? const SizedBox(height: 25) : const SizedBox()],);}): List.generate(totalNum + 1, (index) {return Column(children: [Text('${totalNum - index}',style: const TextStyle(color: Color(0xFF999999),fontSize: 11)),index < totalNum ? SizedBox(height: (100 / totalNum).toDouble()) : const SizedBox()],);})),const SizedBox(width: 4),//垂直分割线const SizedBox(width: 1,height: 161,child: DecoratedBox(decoration: BoxDecoration(color: Color(0xFFEEEEEE)),),),],),],),Expanded(child: SingleChildScrollView(scrollDirection: Axis.horizontal,child: Stack(children: [Container(padding: const EdgeInsets.only(top: 10, bottom: 10),width: barList.length * 35 + 220,height: 220,child: BarChart(BarChartData(alignment: BarChartAlignment.spaceEvenly,titlesData: FlTitlesData(show: true,topTitles: AxisTitles(sideTitles: SideTitles(showTitles: false),),bottomTitles: AxisTitles(sideTitles: SideTitles(showTitles: true,reservedSize: 32,// getTitlesWidget: bottomTitles,  x轴配置),),leftTitles: AxisTitles(sideTitles: SideTitles(showTitles: false,),),rightTitles: AxisTitles(sideTitles: SideTitles(showTitles: false),),),gridData: FlGridData(show: false),borderData: FlBorderData(border: const Border(bottom: BorderSide(color: AppColors.colorFFEEEEEE),)),// barGroups: showingGroups()  柱条数据配置),),)],),),),],),);});}
}