UIKit Gestures in SwiftUI

ExampleUIKitGestures.swift

import SwiftUI


struct ExampleUIKitGestureViewA: View {
    var body: some View {
        Color.blue
            .overlay { ExampleUIKitGestureViewRepresentableA() }
        /*
            can also place it behind if hits are disabled on attaching view,
            or you have other views you want to receive gestures that it would block
         
            .background { ExampleUIKitGestureViewRepresentable() }
        */
    }
}


struct ExampleUIKitGestureViewRepresentableA: UIViewRepresentable {
    func makeUIView(context: Context) -> some UIView {
        let v = UIView()
        
        /*
            declare necessary gestures here, and attach them to callbacks in a "Coordinator", or delegate object that implements recognizer functions, or other delegate functions for interactions (like UIDragInteraction)
         */
        let tap = UITapGestureRecognizer(target: context.coordinator, action: #selector(Coordinator.tap))
        
        v.addGestureRecognizer(tap)
        return v
    }
    
    func updateUIView(_ uiView: UIViewType, context: Context) {}
    
    func makeCoordinator() -> Coordinator {
        Coordinator()
    }
    
    class Coordinator: NSObject, UIGestureRecognizerDelegate {
       
        @objc func tap(gesture: UITapGestureRecognizer) {
            // do something with tap here
        }
    }
}



/*
    If you'd rather handle the gesture callbacks in a SwiftUI view, you can use a callback function and simply pass along the gesture parameters
 
 */
struct ExampleUIKitGestureViewB: View {
    var body: some View {
        Color.blue
            .overlay { ExampleUIKitGestureViewRepresentableB(event: handle) }
    }
    
    func handle(_ event: ExampleUIKitGestureEvent) {
        // handle gesture callback in SwiftUI view
    }
    

}




enum ExampleUIKitGestureEvent {
    case tap(UITapGestureRecognizer)
}


struct ExampleUIKitGestureViewRepresentableB: UIViewRepresentable {
    let event: (ExampleUIKitGestureEvent) -> ()
    
    func makeUIView(context: Context) -> some UIView {
        let v = UIView()
        let tap = UITapGestureRecognizer(target: context.coordinator, action: #selector(Coordinator.tap))
        
        v.addGestureRecognizer(tap)
        return v
    }
    
    func updateUIView(_ uiView: UIViewType, context: Context) {}
    
    func makeCoordinator() -> Coordinator {
        Coordinator(event: event)
    }
    
    class Coordinator: NSObject, UIGestureRecognizerDelegate {
        let event: (ExampleUIKitGestureEvent) -> ()
        
        init(event: @escaping (ExampleUIKitGestureEvent) -> Void) {
            self.event = event
        }
        
        @objc func tap(gesture: UITapGestureRecognizer) {
            event(.tap(gesture))
        }
    }
}


/*
    For handling raw touches, you'll need to define your own custom UIView
 
 */

class TouchHandlingUIView: UIView {
    override func touchesBegan(_ touches: Set<UITouch>, with event: UIEvent?) {
        // do something with touches
    }
}

/*
 
 can use this in place of a standard UIView
 
 func makeUIView(context: Context) -> some UIView {
     let v = TouchHandlingUIView()
     return v
 }
 */