How to make scrollable Drag and Drop in Flutter?

I am trying to make a scrollable and zoomable Stack using SingleChildScrollView in order to implement a canvas editor.

The Drag and Drop works perfectly when I put my dragabble item in the initial view but when I scroll down the view and I tried to drop my container is coming back in the initial view.

I'm new to the Flutter development so maybe I missunderstood in the implementation of a such thing.

Here's the code I currently have.

void main() => runApp(new MyApp());

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      home: Scaffold(
        body: App(),
      ),
    );
  }
}

class App extends StatefulWidget {
  @override
  AppState createState() => AppState();
}

class AppState extends State<App> {
  Color caughtColor = Colors.grey;

  @override
  Widget build(BuildContext context) {
    return SingleChildScrollView(
      child: Stack(
        children: <Widget>[
          Container(
            height: 2000,
          ),
          DragBox(Offset(0.0, 0.0), 'Box One', Colors.blueAccent),
        ],
      ),
    );

  }
}

class DragBox extends StatefulWidget {
  final Offset initPos;
  final String label;
  final Color itemColor;

  DragBox(this.initPos, this.label, this.itemColor);

  @override
  DragBoxState createState() => DragBoxState();
}

class DragBoxState extends State<DragBox> {
  Offset position = Offset(0.0, 0.0);

  @override
  void initState() {
    super.initState();
    position = widget.initPos;
  }

  @override
  Widget build(BuildContext context) {
    return Positioned(
        left: position.dx,
        top: position.dy,
        child: Draggable(
          data: widget.itemColor,
          child: Container(
            width: 100.0,
            height: 100.0,
            color: widget.itemColor,
            child: Center(
              child: Text(
                widget.label,
                style: TextStyle(
                  color: Colors.white,
                  decoration: TextDecoration.none,
                  fontSize: 20.0,
                ),
              ),
            ),
          ),
          onDraggableCanceled: (velocity, offset) {
            setState(() {
              position = offset;
            });
          },
          feedback: Container(
            width: 120.0,
            height: 120.0,
            color: widget.itemColor.withOpacity(0.5),
            child: Center(
              child: Text(
                widget.label,
                style: TextStyle(
                  color: Colors.white,
                  decoration: TextDecoration.none,
                  fontSize: 18.0,
                ),
              ),
            ),
          ),
        ));
  }
}

Any suggestions or code samples would be really helpful to me.