getFocusElevation method Null safety

double getFocusElevation(
  1. MaterialButton button
)

The button's elevation when it is enabled and has focus.

Returns the button's MaterialButton.focusElevation if it is non-null, otherwise the highlight elevation is 4.0.

Implementation

double getFocusElevation(MaterialButton button) => button.focusElevation ?? 4.0;