title: When drag the GestureDetector in vertical direction in the ListView, can not trigger the GestureDetector onPanUpdate event
body: <p>When drag vertical the GestureDetector in the ListView, can not trigger the GestureDetector onPanUpdate event.</p>
  
  <p><a href="https://i.imgur.com/lvYPXmL.gif" rel="nofollow noreferrer">I made a gif</a>.</p>
  
  <p>The GestureDetector onPanUpdate event just can only be triggered by dragging in the horizontal direction.</p>
  
  <p>I know Flutter has a GestureArenaManager, but how to let the GestureDetector win in the arena?</p>
  
  <p>I want to when dragging the GestureDetector, can </p>
  
  <p>The code like this.</p>
  
  <pre class="lang-dart prettyprint-override"><code>import 'package:flutter/cupertino.dart';
  import 'package:flutter/gestures.dart';
  import 'package:flutter/material.dart';
  
  void main() =&gt; runApp(MaterialApp(
        title: 'hi',
        home: DemoWidget(),
      ));
  
  class DemoWidget extends StatelessWidget {
    Widget build(BuildContext context) {
      return Scaffold(
        appBar: AppBar(title: Text('GestureDetector in ListView')),
        body: ListView(children: &lt;Widget&gt;[
          Card(
            child: Container(
              height: 500,
              child: Stack(
                children: &lt;Widget&gt;[
                  Drag(),
                ],
              ),
            ),
          ),
          Card(
            child: Container(
              height: 1000,
            ),
          ),
        ]),
      );
    }
  }
  
  class Drag extends StatefulWidget {
    @override
    DragState createState() =&gt; DragState();
  }
  
  class DragState extends State&lt;Drag&gt; {
    double x = 0, y = 0;
  
    @override
    Widget build(BuildContext context) {
      return Positioned(
        left: x,
        top: y,
        child: GestureDetector(
          behavior: HitTestBehavior.opaque,
          dragStartBehavior: DragStartBehavior.down,
          child: Container(
            width: 100,
            height: 100,
            color: Colors.lightBlue,
            child: Icon(
              Icons.games,
              color: Colors.white,
              size: 30,
            ),
          ),
          onPanUpdate: (details) {
            x += details.delta.dx;
            y += details.delta.dy;
            setState(() {});
          },
        ),
      );
    }
  }
  </code></pre>