RippleDrawable on different API levels will modulate the alphas differently
for the pressed / focused / hovered states. Therefore, in order to get the
desired alphas for pressed / focused / hovered states, we are using the
mtrl_(low|high)_ripple_(pressed|focused|hovered|default)_alpha values which have
been defined to account for the different implementations of RippleDrawable.
This will allow developers to specify different colors for focused vs. pressed if desired.
PiperOrigin-RevId: 255306749
The OnChangedListener provides a callback that MaterialShapeDrawables can use to invalidate themselves when the associated ShapeAppearanceModel changes. This allows for modifying the ShapeAppearanceModel through the get/setShapeAppearance methods that the Shapeable interface exposes without having to update the client to redraw itself.
PiperOrigin-RevId: 238703600
