import 'package:flutter/material.dart';import 'package:flutter_app/common/common_bar.dart';class Point{  double x,y;  Point(this.x,this.y);}class EventWidget extends StatefulWidget {  @override  State
    
      createState() => new EventState();}class EventState extends State
     
       {  var point_1=new Point(100.0, 50.0);  ChangePointX(double x){    setState(() {      this.point_1.x=x;    });  }  ChangePointY(double y){    setState(() {      this.point_1.y=y;    });  }  @override  Widget build(BuildContext context) {    double width=MediaQuery.of(context).size.width;     return new Scaffold(      appBar:commonBar('点击、拖动和其它手势', Icons.home),      body: new Column(        children: 
      
       [          new Expanded(            child: new Stack(              children: 
       
        [                new Positioned(                    left: 0.0,                    top: 15.5,                    child: new Container(                      width: 50.0,                      height: 50.0,                      color: Colors.blue,                    )),                    new Positioned(                      left: this.point_1.x,                      top: this.point_1.y,                      child: new GestureDetector( // 只能再GestureDetector 内使用时间                        child: new Container(                          width: 50.0,                          height: 50.0,                          color: Colors.blue,                        ),                        //鼠标按下移动事件                        onVerticalDragUpdate:(e){                          var x=e.globalPosition.dx-20.0;                          var y=e.globalPosition.dy-100.0;//                          print(e.globalPosition.dy);                          this.ChangePointX(x);                          this.ChangePointY(y);                        },                      )                    ),                  new Positioned(                      left: 0.0,                      top: 155.5,                      child: new Container(                        width: 50.0,                        height: 50.0,                        color: Colors.blue,                      ))              ],            ),          )        ],      ),    );  }}