问题:

I have a question about UIView, what's the difference between views hidden, alpha and opaque?

The effect of setting view: hidden = yes and view.alpha = 0.0f is the same.

回答1:

The differences are subtle. According to the UIView class reference:

opaque tells the system that the view has no transparency and is thus faster to render because calculations for blending can be skipped
hidden is boolean property that changes only the visibility of the current view and hides it from ui events.
alpha is an animatable property

Setting alpha = 0.0f or hidden = YES has the same visual effect. However using hidden to actually hide a view not only in a graphical sense but also from ui events might result in a more efficient responder chain when you have lots of nested views.

回答2:

setting view.hidden = yes will hide the view and view.alpha = 0.0f will set the colors of view alpha 0.0 which will make the view invisible, so both are not same.... :)