xcode - Does UIButton become disabled when its alpha is set to 0.0?

Question

I have a few buttons in my app whose alpha is currently set to zero. These buttons are completely non-responsive, but as soon as I increase their alpha, they begin to respond. Is this expected behavior?

Answer 1

As per Apple's documentation for UIView's hitTest:withEvent: method:

This method ignores view objects that are hidden, that have disabled user interactions, or have an alpha level less than 0.01.

So any UIView that has alpha lower than 0.01 will be ignored by the touch events processing system, i.e. will not receive touch.