Call hitTest inside of touchesMoved - ios

Question

I have an UIView which is on top of all other views and has overridden hitTest() method which always return itself:
override func hitTest(_ point: CGPoint, with event: UIEvent?) -> UIView? {
return self
}
Then, when I make some operations using points from touchesBegan(), I need to pass hitTest() to the views below of the our UIView:
override public func touchesMoved(_ touches: Set<UITouch>, with event: UIEvent?) {
// Do some operations
// ...
// ...
// ...
// pass touch event handling to views below or change hitTest()
}
So basically, on the top UIView I'm overriding touchesBegan(), touchesMoved() and touchesEnded() methods. Then I need to handle touches, perform some operations and then, if needed, to pass to views below. Is it possible?

Answer 1

It is probably simpler and better to solve your problem differently.
UIKit delivers a touch event by sending it to the window (the root of the view hierarchy) in a sendEvent(_:) message. The window's sendEvent(_:) method is responsible for finding the gesture recognizers interested in the touches, and sending the appropriate touchesBegan, touchesMoved, etc. messages to the recognizers and/or the hit view.
This means that you can subclass UIWindow and override sendEvent(_:) to get a look at every touch event in the window, before the event reaches any gesture recognizers or views, without overriding any view's hitTest(_:with:) method. Then you pass the event along to super.sendEvent(event) for normal routing.
Example:
class MyWindow: UIWindow {
override func sendEvent(_ event: UIEvent) {
if event.type == .touches {
if let count = event.allTouches?.filter({ $0.phase == .began }).count, count > 0 {
print("window found \(count) touches began")
}
if let count = event.allTouches?.filter({ $0.phase == .moved }).count, count > 0 {
print("window found \(count) touches moved")
}
if let count = event.allTouches?.filter({ $0.phase == .ended }).count, count > 0 {
print("window found \(count) touches ended")
}
if let count = event.allTouches?.filter({ $0.phase == .cancelled }).count, count > 0 {
print("window found \(count) touches cancelled")
}
}
super.sendEvent(event)
}
}
You can use this window subclass in your app by initializing your app delegate's window outlet to an instance of it, like this:
#UIApplicationMain
class AppDelegate: UIResponder, UIApplicationDelegate {
var window: UIWindow? = MyWindow()
// other app delegate members...
}
Note that UIKit uses hitTest(_:with:) to set the view property of a touch when the touch begins, before it delivers the touch-began event to the window. UIKit also sets each touch's gestureRecognizers property to the set of recognizers that might want the touch (recognizer state .possible) or are actively using the touch (states began, changed, ended, cancelled) before passing the event to the window's sendEvent(_:). So your sendEvent(_:) override can look at each touch's view property if it needs to know where the touch is going.