flutter|flutter 动手撸一个城市选择citypicker功能 flutter动手撸一个城市选择cit

城市选择器在项目开发中一般都会用到，基于flutter版本的也有一个city_pickers但是已经很久没有人维护了，项目中之前也用的是这个,最近升级到flutter1.17.x后，发现有一定的概率闪退，无奈之下，只能自动动手撸一个了

文章图片

demo下载地址：https://github.com/qqcc1388/city_picker
CityPickerView能够实现以下功能

显示省市区地址，市或者区可以为空白数据
省市区数据支持自定义，但是格式要按照city.json中个格式来，如果需要外部传入省市区数据，直接使用params参数即可
支持选中之后回调选中内容以及对于的省市区code码

思路利用cupertino.dart中的CupertinoPicker来实现单层数据显示，通过row实现3层数据的滚动显示，然后让3个CupertinoPicker实现联动即可实现地址选择器，
代码

import 'dart:convert'; import 'package:city_picker/city_result.dart'; import 'package:flutter/cupertino.dart'; import 'package:flutter/material.dart'; import 'package:flutter/services.dart'; typedef ResultBlock = void Function(CityResult result); class CityPickerView extends StatefulWidget {// json数据可以从外部传入，如果外部有值，取外部值final List params; // 结果返回final ResultBlock onResult; CityPickerView({this.onResult, this.params}); @override_CityPickerViewState createState() => _CityPickerViewState(); }class _CityPickerViewState extends State {List datas = []; int provinceIndex; int cityIndex; int areaIndex; FixedExtentScrollController provinceScrollController; FixedExtentScrollController cityScrollController; FixedExtentScrollController areaScrollController; CityResult result = CityResult(); bool isShow = false; List get provinces {if (datas.length > 0) {if (provinceIndex == null) {provinceIndex = 0; result.province = provinces[provinceIndex]['label']; result.provinceCode = provinces[provinceIndex]['value'].toString(); }return datas; }return []; }List get citys {if (provinces.length > 0) {return provinces[provinceIndex]['children'] ?? []; }return []; }List get areas {if (citys.length > 0) {if (cityIndex == null) {cityIndex = 0; result.city = citys[cityIndex]['label']; result.cityCode = citys[cityIndex]['value'].toString(); }List list = citys[cityIndex]['children'] ?? []; if (list.length > 0) {if (areaIndex == null) {areaIndex = 0; result.area = list[areaIndex]['label']; result.areaCode = list[areaIndex]['value'].toString(); }}return list; }return []; }// 保存选择结果_saveInfoData() {var prs = provinces; var cts = citys; var ars = areas; if (provinceIndex != null && prs.length > 0) {result.province = prs[provinceIndex]['label']; result.provinceCode = prs[provinceIndex]['value'].toString(); } else {result.province = ''; result.provinceCode = ''; }if (cityIndex != null && cts.length > 0) {result.city = cts[cityIndex]['label']; result.cityCode = cts[cityIndex]['value'].toString(); } else {result.city = ''; result.cityCode = ''; }if (areaIndex != null && ars.length > 0) {result.area = ars[areaIndex]['label']; result.areaCode = ars[areaIndex]['value'].toString(); } else {result.area = ''; result.areaCode = ''; }}@overridevoid dispose() {provinceScrollController.dispose(); cityScrollController.dispose(); areaScrollController.dispose(); super.dispose(); }@overridevoid initState() {super.initState(); //初始化控制器provinceScrollController = FixedExtentScrollController(); cityScrollController = FixedExtentScrollController(); areaScrollController = FixedExtentScrollController(); //读取city.json数据if (widget.params == null) {_loadCitys().then((value) {setState(() {isShow = true; }); }); } else {datas = widget.params; setState(() {isShow = true; }); }}Future _loadCitys() async {var cityStr = await rootBundle.loadString('assets/city.json'); datas = json.decode(cityStr) as List; //result默认取第一组值return Future.value(true); }@overrideWidget build(BuildContext context) {return Material(child: Container(child: Column(crossAxisAlignment: CrossAxisAlignment.start,mainAxisSize: MainAxisSize.min,children: [_firstView(),_contentView(),],),),); }Widget _firstView() {return Container(height: 44,child: Row(mainAxisAlignment: MainAxisAlignment.spaceBetween,children: [FlatButton(child: Text('取消'),onPressed: () {Navigator.pop(context); },),FlatButton(child: Text('确定'),onPressed: () {if (widget.onResult != null) {widget.onResult(result); }Navigator.pop(context); },),]),decoration: BoxDecoration(border: Border(bottom: BorderSide(color: Colors.grey.withOpacity(0.1), width: 1)),),); }Widget _contentView() {return Container(// color: Colors.orange,height: 200,child: isShow? Row(children: [Expanded(child: _provincePickerView()),Expanded(child: _cityPickerView()),Expanded(child: _areaPickerView()),],): Center(child: CupertinoActivityIndicator(animating: true,),),); }Widget _provincePickerView() {return Container(child: CupertinoPicker(scrollController: provinceScrollController,children: provinces.map((item) {return Center(child: Text(item['label'],style: TextStyle(color: Colors.black87, fontSize: 16),maxLines: 1,),); }).toList(),onSelectedItemChanged: (index) {provinceIndex = index; if (cityIndex != null) {cityIndex = 0; if (cityScrollController.positions.length > 0) {cityScrollController.jumpTo(0); }}if (areaIndex != null) {areaIndex = 0; if (areaScrollController.positions.length > 0) {areaScrollController.jumpTo(0); }}_saveInfoData(); setState(() {}); },itemExtent: 36,),); }Widget _cityPickerView() {return Container(child: citys.length == 0? Container(): CupertinoPicker(scrollController: cityScrollController,children: citys.map((item) {return Center(child: Text(item['label'],style: TextStyle(color: Colors.black87, fontSize: 16),maxLines: 1,),); }).toList(),onSelectedItemChanged: (index) {cityIndex = index; if (areaIndex != null) {areaIndex = 0; if (areaScrollController.positions.length > 0) {areaScrollController.jumpTo(0); }}_saveInfoData(); setState(() {}); },itemExtent: 36,),); }Widget _areaPickerView() {return Container(width: double.infinity,child: areas.length == 0? Container(): CupertinoPicker(scrollController: areaScrollController,children: areas.map((item) {return Center(child: Text(item['label'],style: TextStyle(color: Colors.black87, fontSize: 16),maxLines: 1,),); }).toList(),onSelectedItemChanged: (index) {areaIndex = index; _saveInfoData(); setState(() {}); },itemExtent: 36,),); }}class CityResult {/// 省市区String province = ''; String city = ''; String area = ''; /// 对应的编码String provinceCode = ''; String cityCode = ''; String areaCode = ''; CityResult({this.province,this.city,this.area,this.provinceCode,this.cityCode,this.areaCode,}); CityResult.fromJson(Map json) {province = json['province']; city = json['city']; area = json['area']; provinceCode = json['provinceCode']; cityCode = json['cityCode']; areaCode = json['areaCode']; }Map toJson() {final Map datas = new Map(); datas['province'] = this.province; datas['city'] = this.city; datas['area'] = this.area; datas['provinceCode'] = this.provinceCode; datas['cityCode'] = this.cityCode; datas['areaCode'] = this.areaCode; return datas; }}

用法

// var cityStr = await rootBundle.loadString('assets/city.json'); // List datas = json.decode(cityStr) as List; showModalBottomSheet(context: context,isScrollControlled: true,builder: (ctx) {return CityPickerView(// params: datas,onResult: (res) {print(res.toJson()); setState(() {citySelect = res.toJson().toString(); }); },); },);

demo下载地址：https://github.com/qqcc1388/city_picker

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