title: Flutter (Dart): Highlight or select a widget (Tile or any element) onLongPress event
body: <p>Does anyone know how to implement a selection of the elements located inside a <code>ListView Class</code> in Flutter. All elements present in my list are constructed as </p>
  
  <pre><code>@override
    Widget build(BuildContext context) {
      return new GestureDetector(
        onTap: () {
           Navigator.of(context).push(
                    new MaterialPageRoute(builder: (BuildContext context) =&gt; new SomePage(someId))
                  );
        }, 
        onLongPress: () {
           //how to implement this to highlight that particular widget as selected
        }
    }
  </code></pre>
  
  <p>When I tap over it I open a new page showing/preforming some operations and is all good. But when long pressed I need to select it and then provide a comparison in between all selected elements. Because my elements are objects is easy to process them but I can not select or mark it as selected on long press.</p>
  
  <p>The selected widget can be anything from tile, row, shape...any widget in general.</p>
  
  <p>thanks in advance...</p>