Flutter之ExpansionTile可展开的列表

 源码

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,//标题左侧要展示的widget
    @required this.title,//要展示的标题widget
    this.backgroundColor,//北京
    this.onExpansionChanged,//列表展开收起的回调函数
    this.children = const <Widget>[],//列表展开时显示的widget
    this.trailing,//标题右侧要展示的widget
    this.initiallyExpanded = false,//是否默认状态下展开
  }) : assert(initiallyExpanded != null),
}

demo:

import 'package:flutter/material.dart';


void main() => runApp(MyApp());

const CITY_NAMES = {
  '北京':['东城区','西城区','海淀区','朝阳区','石景山区','顺义区'],
  '上海':['黄浦区','徐汇区','长宁区','静安区','普陀区','闸北区'],
  '广州':['越秀','海珠','荔湾','天河','白云','黄埔','南沙'],
  '深圳':['南山','福田','罗湖','盐田','龙岗','宝安','龙华'],
  '杭州':['上城区','下城区','江干区','拱墅区','西湖区','滨江区'],
  '苏州':['姑苏区','吴中区','相城区','高新区','虎丘区','工业园区','吴江区'],
};

class MyApp extends StatelessWidget {



  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      home: Scaffold(
        appBar: AppBar(
          title: Text("列表展开与收起"),
        ),
        body: Container(
          child: ListView(
            children: _buildList(),
          ),
        ),
      ),

    );
  }
  List<Widget> _buildList(){
    List<Widget> widgets = [];
    CITY_NAMES.keys.forEach((key){
      widgets.add(_item(key, CITY_NAMES[key]));
    });
    return widgets;
  }
  Widget _item(String city,List<String> subCities){
    return ExpansionTile(
      title: Text(
        city,
        style: TextStyle(color: Colors.black54,fontSize: 20),
      ),
      children: subCities.map((subCity)=>_buildSub(subCity)).toList(),
    );
  }

  Widget _buildSub(String subCity){
    //可以设置撑满宽度的盒子 称之为百分百布局
    return FractionallySizedBox(
      //宽度因子 1为百分百撑满
      widthFactor: 1,
      child: Container(
        height: 50,
        margin: EdgeInsets.only(bottom: 5),
        decoration: BoxDecoration(color: Colors.lightBlueAccent),
        child: Text(subCity),
      ),
    );
  }
}

效果：