title: Scroll multiple scrollable widgets in sync
body: <p>to put it simply:</p>
  
  <p><strong>is there a way to have multiple sccrollable widgets (say, <code>SingleSchildScrollView</code>) together in sync?</strong></p>
  
  <hr>
  
  <p>i just want 2 scrollables that can scroll the other as i scroll one.</p>
  
  <p>this way i can use <code>Stack</code> to put them on top of each other and the one behind can scroll following the front one.</p>
  
  <p>or maybe put them in another set of <code>Column</code> or <code>Row</code> so that they are separate, but still scrolls by just scrolling either one.</p>
  
  <p>i tried using <code>controller</code> but it does not seems to be doing what i think it is.</p>
  
  <hr>
  
  <p>Try the code below for example,
  the "RIGHT" will be in front of the "LEFT" and if i try to scroll them, only the RIGHT will move. so how do i move them both together at the same time??</p>
  
  <p><em>please dont tell me to put the stack inside a <code>ListView</code>, that is not what i need.</em></p>
  
  <pre><code>class _MyHomePageState extends State&lt;MyHomePage&gt; {
  
    final ScrollController _mycontroller = new ScrollController();
  
    @override
    Widget build(BuildContext context) {
      body:
        Container(
          height: 100,
          child:
            Stack( children: &lt;Widget&gt;[
              SingleChildScrollView(
                controller: _mycontroller,
                child: Column( children: &lt;Widget&gt;[
                  Text('LEFT            '),
                  Text('LEFT            '),
                  Text('LEFT            '),
                  Text('LEFT            '),
                  Text('LEFT            '),
                  Text('LEFT            '),
                ],)
              ),
              SingleChildScrollView(
                controller: _mycontroller,
                child: Column(children: &lt;Widget&gt;[
                  Text('          RIGHT'),
                  Text('          RIGHT'),
                  Text('          RIGHT'),
                  Text('          RIGHT'),
                  Text('          RIGHT'),
                  Text('          RIGHT'),
                ],)
              ),
            ])
        )
  }}
  </code></pre>
  
  <p>i believe this question has been asked before in multiple forums before but nobody has put a conclusion or solution to this at all. (see <a href="https://stackoverflow.com/questions/52170779/scrollcontroller-attached-to-multiple-scroll-views">here</a>)</p>