opacity property

Animation<double> opacity

The animation that drives this render object's opacity.

An opacity of 1.0 is fully opaque. An opacity of 0.0 is fully transparent (i.e., invisible).

To change the opacity of a child in a static manner, not animated, consider RenderOpacity instead.

Implementation 

Animation<double> get opacity => _opacity;
void opacity= (Animation<double> value)

Implementation 

set opacity(Animation<double> value) {
  assert(value != null);
  if (_opacity == value)
    return;
  if (attached && _opacity != null)
    _opacity.removeListener(_updateOpacity);
  _opacity = value;
  if (attached)
    _opacity.addListener(_updateOpacity);
  _updateOpacity();
}