【Flutter】ExpansionTile 可折叠列表

class ExpansionTile extends StatefulWidget {
  /// Creates a single-line [ListTile] with a trailing button that expands or collapses
  /// the tile to reveal or hide the [children]. The [initiallyExpanded] property must
  /// be non-null.
  const ExpansionTile({
    Key? key,
    this.leading,      // 标题左侧的 Widget 组件
    required this.title,    // 展示的列表标题 Widget 
    this.subtitle,      // 子标题 
    this.onExpansionChanged,    // 列表 展开/折叠 回调函数
    this.children = const <Widget>[], // 列表展示时显示的 Widget 组件集合
    this.trailing,      // 标题右侧的 Widget 组件
    this.initiallyExpanded = false,  // 默认状态下是否展开 , 默认不展开 
    this.maintainState = false,
    this.tilePadding,
    this.expandedCrossAxisAlignment,
    this.expandedAlignment,
    this.childrenPadding,
    this.backgroundColor,    // 背景沿着
    this.collapsedBackgroundColor,
    this.textColor,
    this.collapsedTextColor,
    this.iconColor,
    this.collapsedIconColor,
  }) : assert(initiallyExpanded != null),
       assert(maintainState != null),
       assert(
       expandedCrossAxisAlignment != CrossAxisAlignment.baseline,
       'CrossAxisAlignment.baseline is not supported since the expanded children '
           'are aligned in a column, not a row. Try to use another constant.',
       ),
       super(key: key);
}

import 'package:flutter/cupertino.dart';
import 'package:flutter/material.dart';
const NAMES = {
  '三十六天罡' : [ '宋江', '卢俊义', '吴用', '公孙胜', '关胜' ],
  '七十二地煞' : [ '陈继真', '黄景元', '贾成', '呼颜', '鲁修德' ]
};
void main() {
  runApp(MyApp());
}
class MyApp extends StatefulWidget {
  const MyApp({Key? key}) : super(key: key);
  @override
  _MyAppState createState() => _MyAppState();
}
class _MyAppState extends State<MyApp> {
  @override
  Widget build(BuildContext context) {
    /// 材料设计主题
    return MaterialApp(
      home: Scaffold(
        appBar: AppBar(
          /// 标题组件
          title: Text("ListView 示例"),
        ),
        /// 列表组件
        body: ListView(
          children: _buildList(),
        ),
      ),
    );
  }
  /// 创建列表 , 每个元素都是一个 ExpansionTile 组件
  List<Widget> _buildList(){
    List<Widget> widgets = [];
    NAMES.keys.forEach((key) {
      widgets.add(_generateExpansionTileWidget(key, NAMES[key]));
    });
    return widgets;
  }
  /// 生成 ExpansionTile 组件 , children 是 List<Widget> 组件
  Widget _generateExpansionTileWidget(tittle, List<String>? names){
    return ExpansionTile(
      title: Text(
        tittle,
        style: TextStyle(
          color: Colors.black54,
          fontSize: 20
        ),
      ),
      children: names!.map((name) => _generateWidget(name)).toList(),
    );
  }
  /// 生成 ExpansionTile 下的 ListView 的单个组件
  Widget _generateWidget(name){
    /// 使用该组件可以使宽度撑满
    return FractionallySizedBox(
      widthFactor: 1,
      child: Container(
        height: 80,
        //width: 80,
        margin: EdgeInsets.only(bottom: 5),
        //margin: EdgeInsets.only(right: 5),
        alignment: Alignment.center,
        decoration: BoxDecoration(color: Colors.black),
        child: Text(
          name,
          style: TextStyle(
              color: Colors.yellowAccent,
              fontSize: 20
          ),
        ),
      ),
    );
  }
}