What class is typically used to customize the appearance of a Dialog in Android?

The class used to customize the appearance of a Dialog in Android is the Dialog class. This class provides the flexibility to create a dialog with a custom layout, allowing developers to define the UI components they want to include. By using Dialog, you can inflate your own layout and set it as the content view of the dialog, which gives you full control over the design and functionalities of the dialog.

While other options like AlertDialog also allow for some customization, it is primarily geared towards showing alerts and predefined button actions. DialogFragment is utilized for managing dialogs in conjunction with fragments, providing lifecycle management and allowing the dialog to be retained across configuration changes. PopupWindow can show content in a floating popup but is not specifically designed for dialog-like interactions.

Therefore, when customization is necessary, particularly for a unique layout with specific behaviors, the Dialog class stands out as the most suitable option to use.