How do I get a UIButton press to work in a UIColle

问题:

So this is a tvOS project in Swift. I have a custom UICollectionViewCell with a button as one of its subviews. I add a target to the button to allow it to interpret clicks. Here's a simplified version of the relevant code

class CustomCell: UICollectionViewCell {
    var button:UIButton!

    override init(frame: CGRect) {
        super.init(frame: frame)

        button = UIButton(...) // Button is initialized with a frame
        button.userInteractionEnabled = true
        button.enabled = true
        button.addTarget(self, action: "pressed:", forControlEvents: .PrimaryActionTriggered)
        contentView.addSubview(button)
    }

    func pressed(sender: UIButton!) {
        print("button pressed!")
    }
}

For some reason it's not ever printing out my message. I tried adding 'pressedEnded' to the cell class to see if it's getting any and it gets called

func pressesEnded(presses: Set<UIPress>, withEvent event: UIPressesEvent?) {
        // If I put a breakpoint here it's reached
}

Any suggestions? When I run it in the simulator the button can get focus, so I don't know why it can't get any events

回答1:

So, I figured out how to solve this, although it's somewhat of a workaround. Basically for the UICollectionView I need to ensure the cell's can't get focus.

Next I had didUpdateFocusInContext in CustomCell previously. This was what was actually animating the button when the cell, but when I checked the button never got focus. I'm guessing this was intercepting it. So I removed that function from CustomCell and instead, at the bottom of my file I added that function as an extension of UIButton.

This also could've been done by creating a subclass of UIButton and using that instead, but this was less code (that is probably the ideal way). So the full code looks like:

class MyCollection: UICollectionView, UICollectionViewDelegate {
    // Need initializer functions as well as functions for creating CustomCell's. They're omitted because they're not relevant to the answer

    func collectionView(collectionView: UICollectionView, canFocusItemAtIndexPath indexPath: NSIndexPath) -> Bool {
        return false
    }  
}

class CustomCell: UICollectionViewCell {
    var button:UIButton!

    override init(frame: CGRect) {
        super.init(frame: frame)

        button = UIButton(...) // Button is initialized with a frame
        button.userInteractionEnabled = true
        button.enabled = true
        button.addTarget(self, action: "pressed:", forControlEvents: .PrimaryActionTriggered)
        self.addSubview(button)
    }

    func pressed(sender: UIButton!) {
        print("button pressed!")
    }
}

extension UIButton {
    override public func didUpdateFocusInContext(context: UIFocusUpdateContext, withAnimationCoordinator coordinator: UIFocusAnimationCoordinator) {
        super.didUpdateFocusInContext(context, withAnimationCoordinator: coordinator)

        if self.superview is CustomCell {   // This ensures that all UIButtons aren't affected
            if context.nextFocusedView == self {
                // Perform actions for when UIButton is focused
            }else {
                // Perform actions for when UIButton loses focus
            }
        }
    }
}

回答2:

Make sure the User Interaction Enabled checkbox is checked for the UICollectionViewCell.

回答3:

Above answer is correct, and if you are using a custom UICollectionViewCell you could also do this in its subclass for specific cells:

override func canBecomeFocused() -> Bool {
    return false
}

回答4:

It seems the UICollectionViewCell is overlayed automatically by a clear view, which catches taps.

For us just calling bringSubview(toFront: checkButton) worked. Now the checkButton touchUpInside action is called as it should.

import UIKit

class SerieItemCollectionViewCell: UICollectionViewCell {

   var checked : (()->())?


   static let reuseIdentifier = "SerieItemCollectionViewCell"

   @IBOutlet weak var checkButton: UIButton!
   @IBOutlet var imageView: UIImageView!

   override func layoutSubviews() {
       super.layoutSubviews()
       bringSubview(toFront: checkButton)
   }

   @IBAction func buttonClicked(_ sender: Any) {
       checked?()
       print("Hello")
   }
}