Swift-在KeyWindow的subView中无法识别点击手势

Question

I made a view that used as black overlay by adding itself to keyWindow. It shows as intended but tap gesture is not triggered.

class Menu{
let backView = UIView()
let menuWidth:CGFloat = 150
let menuView: UICollectionView = {
    let layout = UICollectionViewFlowLayout()
    let cv = UICollectionView(frame: .zero, collectionViewLayout: layout)
    cv.backgroundColor = .white
    return cv
}()

init(){
    if let window = UIApplication.shared.keyWindow{
        backView.frame = window.frame
        backView.addGestureRecognizer(UITapGestureRecognizer(target: self, action: #selector(dismissHandler)))
        backView.backgroundColor = UIColor(white: 0, alpha: 0.5)
        backView.alpha = 0

        menuView.frame = CGRect(x: -1*menuWidth, y: 0, width: menuWidth, height: window.frame.height)
    }
}

func show(){
    if let window = UIApplication.shared.keyWindow{
        window.addSubview(backView)
        //window.addSubview(menuView)

        UIView.animate(withDuration: 0.5, delay: 0, usingSpringWithDamping: 1, initialSpringVelocity: 1, options: .curveEaseIn, animations: {
            self.backView.alpha = 1
            self.menuView.frame = CGRect(x: 0, y: 0, width: self.menuWidth, height: window.frame.height)
        }, completion: nil)
    }
}

@objc func dismissHandler(){
    if let window = UIApplication.shared.keyWindow{
        UIView.animate(withDuration: 0.5, animations: {
            self.backView.alpha = 0
            self.menuView.frame = CGRect(x: -1*self.menuWidth, y: 0, width: self.menuWidth, height: window.frame.height)
        }){(isSuccess) in
            if(isSuccess){
                self.backView.removeFromSuperview()
                self.menuView.removeFromSuperview()
            }
        }
    }
}

I checked frame size of window and backview but they are same. Any idea why it is not working?

Solved: Problem was that I was making its instance in local scope. Thanks matt for providing me the answer.

Answer 1

In your original question, you didn't show how you use the Menu class itself to make anything happen. But that could be where the problem is.

For example, suppose you create the Menu class instance but you don't maintain it somehow. Then you might be able to create the overlay, but after that, the Menu instance is gone, so the tap gesture recognizer subsequently has no target to talk to.

In other words, you've got this tap gesture configuration code:

backView.addGestureRecognizer(UITapGestureRecognizer(target: self, action: #selector(dismissHandler)))

...but when the user taps and the tap gesture recognizer tries to send its message, your self has gone out of existence.