Allowing interaction with a UIView under another UIView

user_109009 0
Viewed 67775

Is there a simple way of allowing interaction with a button in a UIView that lies under another UIView - where there are no actual objects from the top UIView on top of the button?

For instance, at the moment I have a UIView (A) with an object at the top and an object at the bottom of the screen and nothing in the middle. This sits on top of another UIView that has buttons in the middle (B). However, I cannot seem to interact with the buttons in the middle of B.

I can see the buttons in B - I've set the background of A to clearColor - but the buttons in B do not seem to receive touches despite the fact that there are no objects from A actually on top of those buttons.

EDIT - I still want to be able to interact with the objects in the top UIView

Surely there is a simple way of doing this?

objective-c cocoa-touch ios
19 Answers

Swift 3

override func point(inside point: CGPoint, with event: UIEvent?) -> Bool {
    for subview in subviews {
        if subview.frame.contains(point) {
            return true
        }
    }
    return false
}
user_21883680

Swift 4 Implementation for HitTest based solution

let hitView = super.hitTest(point, with: event)
if hitView == self { return nil }
return hitView
user_77007630

Derived from Stuart's excellent, and mostly foolproof answer, and Segev's useful implementation, here is a Swift 4 package that you can drop into any project:

extension UIColor {
    static func colorOfPoint(point:CGPoint, in view: UIView) -> UIColor {

        var pixel: [CUnsignedChar] = [0, 0, 0, 0]

        let colorSpace = CGColorSpaceCreateDeviceRGB()
        let bitmapInfo = CGBitmapInfo(rawValue: CGImageAlphaInfo.premultipliedLast.rawValue)

        let context = CGContext(data: &pixel, width: 1, height: 1, bitsPerComponent: 8, bytesPerRow: 4, space: colorSpace, bitmapInfo: bitmapInfo.rawValue)

        context!.translateBy(x: -point.x, y: -point.y)

        view.layer.render(in: context!)

        let red: CGFloat   = CGFloat(pixel[0]) / 255.0
        let green: CGFloat = CGFloat(pixel[1]) / 255.0
        let blue: CGFloat  = CGFloat(pixel[2]) / 255.0
        let alpha: CGFloat = CGFloat(pixel[3]) / 255.0

        let color = UIColor(red:red, green: green, blue:blue, alpha:alpha)

        return color
    }
}

And then with hitTest: 

override func hitTest(_ point: CGPoint, with event: UIEvent?) -> UIView? {
    guard UIColor.colorOfPoint(point: point, in: self).cgColor.alpha > 0 else { return nil }
    return super.hitTest(point, with: event)
}
user_12148000
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