How do you implement a popup window functionality in your application?

In Flutter, a popup window (dialog) can be implemented using the showDialog function, which displays a widget over the current screen.

Here's an example of a simple popup window with a close button:

showDialog(
  context: context,
  builder: (BuildContext context) {
    return AlertDialog(
      title: Text('Popup Window'),
      content: Text('This is a Flutter dialog example.'),
      actions: [
        TextButton(
          onPressed: () => Navigator.of(context).pop(),
          child: Text('Close'),
        ),
      ],
    );
  },
);

This approach makes it easy to create custom dialogs with any content and control their behavior.