title: How do I call a sliding up panel in Flutter?
body: <p>I am using <a href="https://pub.dev/packages/sliding_up_panel" rel="nofollow noreferrer">https://pub.dev/packages/sliding_up_panel</a> and I want to trigger the opening of a new panel once a button is pressed on my existing panel. </p>
  
  <pre><code>    @override
      Widget build(BuildContext context) {
        BorderRadiusGeometry radius = BorderRadius.only(
          topLeft: Radius.circular(24.0),
          topRight: Radius.circular(24.0),
        );
  
        return Scaffold(
          appBar: AppBar(
            title: Text("SlidingUpPanelExample"),
          ),
          body: SlidingUpPanel(
            panel: Center(
              child: RaisedButton(
                    child: Text('Show new panel'),
                    onPressed: () {
  
                      **///want to add code 
  here to trigger the callback of the new panel.** 
  
                    },
               ),
            ),
  
            collapsed: Container(
              decoration: BoxDecoration(
                color: Colors.blueGrey,
                borderRadius: radius
              ),
              child: Center(
                child: Text(
                  "This is the collapsed Widget",
                  style: TextStyle(color: Colors.white),
                ),
              ),
            ),
  
            body: Center(
              child: Text("This is the Widget behind the sliding panel"),
            ),
  
            borderRadius: radius,
          ),
        );
      }
  </code></pre>
  
  <p>This dependency has the capability to call an open() method with the help of a controller but I am unable to understand how to call a new sliding up panel with it (and obviously closing the existing one). 
  This is the code for the open() operation: </p>
  
  <pre><code>PanelController _pc = new PanelController();
  ...
    RaisedButton(
            child: Text("Open"),
            onPressed: () =&gt; _pc.open(),
          ),
  </code></pre>