The z-coordinate at which to place this button relative to its parent.
This controls the size of the shadow below the raised button.
Defaults to 2, the appropriate elevation for raised buttons. The value is always non-negative.
- FlatButton, a button with no elevation or fill color.
- focusElevation, the elevation when the button is focused.
- 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 elevation