Flutter之ExpansionTile可展開的列表

 源碼

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,//標題左側要展示的widget
    @required this.title,//要展示的標題widget
    this.backgroundColor,//北京
    this.onExpansionChanged,//列表展開收起的回調函數
    this.children = const <Widget>[],//列表展開時顯示的widget
    this.trailing,//標題右側要展示的widget
    this.initiallyExpanded = false,//是否默認狀態下展開
  }) : assert(initiallyExpanded != null),
}

demo:

import 'package:flutter/material.dart';


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

const CITY_NAMES = {
  '北京':['東城區','西城區','海淀區','朝陽區','石景山區','順義區'],
  '上海':['黃浦區','徐彙區','長寧區','靜安區','普陀區','閘北區'],
  '廣州':['越秀','海珠','荔灣','天河','白雲','黃埔','南沙'],
  '深圳':['南山','福田','羅湖','鹽田','龍崗','寶安','龍華'],
  '杭州':['上城區','下城區','江乾區','拱墅區','西湖區','濱江區'],
  '蘇州':['姑蘇區','吳中區','相城區','高新區','虎丘區','工業園區','吳江區'],
};

class MyApp extends StatelessWidget {



  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      home: Scaffold(
        appBar: AppBar(
          title: Text("列表展開與收起"),
        ),
        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){
    //可以設置撐滿寬度的盒子 稱之爲百分百佈局
    return FractionallySizedBox(
      //寬度因子 1爲百分百撐滿
      widthFactor: 1,
      child: Container(
        height: 50,
        margin: EdgeInsets.only(bottom: 5),
        decoration: BoxDecoration(color: Colors.lightBlueAccent),
        child: Text(subCity),
      ),
    );
  }
}

效果：