According to the documentation for
UIVIew @property(nonatomic) CGFloat alpha
The value of this property is a floating-point number in the range 0.0
to 1.0, where 0.0 represents totally transparent and 1.0 represents
This value affects only the current view and does not affect any of its embedded subviews.
self.myView.backgroundColor = [UIColor blackColor];
self.myView.alpha = 0.5;
[myView addSubView anotherView];
anotherView.alpha = 1;
NSLog(@"anotherView alpha = %f",anotherView.alpha); // prints 1.0000 as expected
I think this is a bug in the documentation. You should file it at bugreport.apple.com.
Everything I can see after a bit of quick research suggests what you are seeing is how it always has behaved, and my own testing shows it too.
The alpha of a view is applied to all subviews.
Perhaps all you need is
[[UIColor blackColor] colorWithAlphaComponent:0.5] but if not you will need to make the view a sibling instead of a child.