flutter如何实现省市区选择器

在Flutter中，你可以使用CupertinoPicker或ListWheelScrollView来实现一个省市区的选择器。以下是一个简单的例子，使用CupertinoPicker来创建三个轮询选择器，分别代表省、市、区。

import 'package:flutter/material.dart';
 
void main() => runApp(MyApp());
 
class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      home: CityPickerPage(),
    );
  }
}
 
class CityPickerPage extends StatefulWidget {
  @override
  _CityPickerPageState createState() => _CityPickerPageState();
}
 
class _CityPickerPageState extends State<CityPickerPage> {
  String selectedProvince = '省';
  String selectedCity = '市';
  String selectedArea = '区';
 
  final List<String> provinces = ['省1', '省2', '省3'];
  final List<String> cities = ['城市1', '城市2', '城市3'];
  final List<String> areas = ['区域1', '区域2', '区域3'];
 
  void _onProvinceSelected(String province) {
    setState(() {
      selectedProvince = province;
    });
  }
 
  void _onCitySelected(String city) {
    setState(() {
      selectedCity = city;
    });
  }
 
  void _onAreaSelected(String area) {
    setState(() {
      selectedArea = area;
    });
  }
 
  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: Text('省市区选择器'),
      ),
      body: Column(
        children: <Widget>[
          Row(
            children: <Widget>[
              Expanded(
                child: CupertinoPicker(
                  itemExtent: 32.0,
                  onSelectedItemChanged: _onProvinceSelected,
                  children: provinces.map((String province) {
                    return Text(province);
                  }).toList(),
                ),
              ),
              Expanded(
                child: CupertinoPicker(
                  itemExtent: 32.0,
                  onSelectedItemChanged: _onCitySelected,
                  children: cities.map((String city) {
                    return Text(city);
                  }).toList(),
                ),
              ),
              Expanded(
                child: CupertinoPicker(
                  itemExtent: 32.0,
                  onSelectedItemChanged: _onAreaSelected,
                  children: areas.map((String area) {
                    return Text(area);
                  }).toList(),