How can I use a UIButton in a UICollection supplem

问题:

I am attempting to place a UIButton in a UICollectionView supplementary view (footer). I have connected the UIButton using storyboards to a subclass of UICollectionViewCell and can change it's properties programmatically including the background image. However, when I wire up the touch up inside event of the button to a method, it does not fire. In fact, the button does not even appear to be responding visually to the user's touch. In troubleshooting, I attempted to add a UIButton to the collection view's header and see identical behavior. Adding the button to an unrelated view produces interaction effects when pressed.

Is there something special I need to do to implement a UIButton in a UICollection supplementary view?

回答1:

A supplementary view should be a UICollectionReusableView (or subclass thereof), not a UICollectionViewCell.

Anyway, if the button's not responding, the first thing to do is check that all of its ancestor views have userInteractionEnabled set to YES. Pause in the debugger once the button is on screen and do this:

(lldb) po [[UIApp keyWindow] recursiveDescription]

Find the button in the list and copy its address. Then you can check it and each superview. Example:

(lldb) p (BOOL)[0xa2e4800 isUserInteractionEnabled]
(BOOL) $4 = YES
(lldb) p (BOOL)[[0xa2e4800 superview] isUserInteractionEnabled]
(BOOL) $5 = YES
(lldb) p (BOOL)[[[0xa2e4800 superview] superview] isUserInteractionEnabled]
(BOOL) $6 = YES
(lldb) p (BOOL)[[[[0xa2e4800 superview] superview] superview] isUserInteractionEnabled]
(BOOL) $8 = YES
(lldb) p (BOOL)[[[[[0xa2e4800 superview] superview] superview] superview] isUserInteractionEnabled]
(BOOL) $9 = YES
(lldb) p (BOOL)[[[[[[0xa2e4800 superview] superview] superview] superview] superview] isUserInteractionEnabled]
(BOOL) $10 = NO
(lldb) po [[[[[0xa2e4800 superview] superview] superview] superview] superview]
(id) $11 = 0x00000000 <nil>

Here I found that all views up to the root (the UIWindow) return YES from isUserInteractionEnabled. The window's superview is nil.

回答2:

I have a custom button which subclasses UIControl and put it inside a UICollectionReusableView. To make it work, I made every single subview of the control and its subviews' subviews handle no user interaction.

func disableUserInteractionInView(view: UIView) {
    view.userInteractionEnabled = false
    for view in view.subviews {
        self.disableUserInteractionInView(view)
    }
}

// My control has a subview called contentView which serves as a container
// of all my custom button's subviews.
self.disableUserInteractionInView(self.contentView)

Since adding that code, all event listeners to .TouchUpInside would fire, and the control will visually highlight when pressed down.