Explain the lifecycle stages of StatefulWidget in Flutter.

The lifecycle of a StatefulWidget in Flutter consists of several key stages:

1. Creating the StatefulWidget — the widget's constructor is called.
2. Creating the State — the createState() method creates a state object that holds mutable data.
3. Initializing the state — the initState() method is called, where initial setup can be performed.
4. Building the UI — the build() method is called to render the widget on the screen.
5. Updating the state — calling setState() triggers a rebuild via build().
6. Handling updates — the didUpdateWidget() method is called if the widget is updated with new parameters.
7. Cleaning up resources — the dispose() method is called when the widget is removed, to free resources.

Example:

class MyWidget extends StatefulWidget {
  @override
  _MyWidgetState createState() => _MyWidgetState();
}

class _MyWidgetState extends State<MyWidget> {
  @override
  void initState() {
    super.initState();
    // Initialization
  }

  @override
  Widget build(BuildContext context) {
    return Container();
  }

  @override
  void dispose() {
    // Cleanup
    super.dispose();
  }
}