focusElevation property Null safety
The elevation for the button's Material when the button is enabled and has the input focus.
Defaults to 4.0. The value is always non-negative.
- elevation, the default elevation.
- hoverElevation, the elevation when a pointer is hovering over the button.
- disabledElevation, the elevation when the button is disabled.
- highlightElevation, the elevation when the button is pressed.
final double? focusElevation;