在Flutter中实现轮子效果的省市区级联组件，当然也可以是任意的选择器，该Widget已经加入到ym_flutter_widget 0.0.2中，可以直接引入，你也可以拷贝下面的源码实现。

最终效果如图：

首先看下该组件的使用方法：

///
/// Cascader级联选择器
///
class CascaderPage extends StatefulWidget {

  CascaderPage({Key? key}) : super(key: key);

  final String title = "Cascader";

  @override
  _CascaderPageState createState() => _CascaderPageState();
}

class _CascaderPageState extends State {

  //显示底部弹窗
  bool _showPickerDialog = false;

  //计算拼接地址字符串的
  List _pickerSelected = [0,0,0];
  String  _address3 = "请选择";

  //{"label": "请选择", "value": ""},
  List> _regionData = [[],[],[]];    //数据
  List _regionValue = ["0","0","0"];   //默认值

  @override
  void initState() {
    super.initState();
    //加载数据
    _loadData(0,0);
  }

  ///返回
  Future _goBack() async{Navigator.pop(context);
  }

  ///请求数据
  Future _loadData(int pid,int index) async {

    List

下面是封装好的级联组件代码：

///
/// Cascader级联选择器
///

class YmCascader extends StatefulWidget {

  //数据
  late List> data;

  //默认Value
  late List value;

  final double width;
  final double height;
  final Function onChanged;
  final Function onOkClick;
  final Function onCancelClick;
  final Color backgroundColor;
  final double itemHeight;

  YmCascader(
      this.data,
      this.value,
      {
        Key? key,
        required this.onChanged,
        required this.onOkClick,
        required this.onCancelClick,
        this.itemHeight = 36,
        this.backgroundColor = const Color(0xffffffff),
        this.height = 150.0,
        this.width = 150.0
      }
  ): super(key: key);

  @override
  _YmCascaderState createState() => _YmCascaderState();

}

class _YmCascaderState extends State {

  @override
  void initState() {
    super.initState();
  }

  Widget _getPickerWidget(int position){
    double pickerItemWidth = (MediaQuery.of(context).size.width)/widget.data.length;
    return YmPicker(
      widget.data.elementAt(position),
      widget.value[position],
      width: pickerItemWidth,
      itemHeight: 40,
      height: 180,
      onChanged: (index,val) {
        print("Picker onChanged  position=" + position.toString() + ",index=" + index.toString() + ",val=" + val);
        widget.onChanged(position,index,val);
      },
    );
  }

  @override
  Widget build(BuildContext context) {
    return Container(
      height:220,
      child: Column(
        mainAxisAlignment: MainAxisAlignment.center,
        crossAxisAlignment: CrossAxisAlignment.center,
        children:[
          Divider(
            height: 1,
            color: Color(0xffEFEFEF),
            thickness: 1,
          ),
          Container(
            height:38,
            child: Row(
                mainAxisAlignment: MainAxisAlignment.spaceBetween,
                crossAxisAlignment: CrossAxisAlignment.center,
                children: [
                  YmTextButton("取消", Color(0xFF666666), (){
                    widget.onCancelClick();
                  },isOutlined: true,size: Size(60,30),borderColor: Color(0x00666666),),

                  YmTextButton("确定", Color(0xFF3446F2), (){
                    widget.onOkClick();
                  },isOutlined: true,size:Size(60,30),borderColor: Color(0x00666666),),
                ]
            ),
          ),

          Row(
            children:List.generate(widget.data.length, (index) {
              return _getPickerWidget(index);
            }),
          )
        ],
      ),
    );
  }

  @override
  void dispose() {
    super.dispose();
  }

}

///
/// 单个选择器picker
///
class YmPicker extends StatefulWidget {

  //默认值
  late String value;

  //数据格式：{"label": "请选择", "value": ""}
  late List