So right now I have a UIView with a UILabel in it. I want the background to have an opacity < 1.0 and the label to have an opacity of 1.0. However since alphas propagate down the view hierarchy, the label ends up with an opacity < 1.0 as well.
Is there anyway to do what I want without making the UILabel a subview of another view??
Just set the background color to be semitransparent:
view.backgroundColor = [[UIColor blackColor] colorWithAlphaComponent:0.5f];
100% opacity UILabel over a 50% opacity background (UIView?) UIView是百分之50透明而上面的UILable是100%不透明
原文：http://www.cnblogs.com/ghgyj/p/4059028.html