title: Prevent a NestedScrollView from scrolling
body: <p>I have a widget that is a NestedScrollView and some text in the body. There are cases where I want to "lock" the user and not allow him to scroll. I have tried using the physics property and set it to NeverScrollableScrollPhysics()as the docs seem to indicate this is what it is for: <a href="https://api.flutter.dev/flutter/widgets/NeverScrollableScrollPhysics-class.html" rel="noreferrer">https://api.flutter.dev/flutter/widgets/NeverScrollableScrollPhysics-class.html</a> however this does not seem to be working and the screen still scrolls. </p>
  
  <p>Is there a way to prevent the scroll?</p>
  
  <pre><code>  @override
    Widget build(BuildContext context) {
      return DefaultTabController(
          length: 2,
          child: NestedScrollView(
            physics: NeverScrollableScrollPhysics(),
            headerSliverBuilder: (BuildContext context, bool innerBoxIsScrolled) {
              return &lt;Widget&gt;[
                SliverAppBar(
                  expandedHeight: 150.0,
                  floating: false,
                  pinned: true,
                  forceElevated: true,
                  flexibleSpace: FlexibleSpaceBar(
                    centerTitle: true,
                    title: Text('I am a header'),
                  ),
                )
              ];
            },
            body: Text(' I am scrolling'),
          ));
    }
  </code></pre>