如何观察图像旋转？

Question

I have an ImageView called - (woowwww): ImageView

@IBOutlet weak var ImageView: UIImageView!

... and I'd like to fire an event every time the transform -property of the ImageView changed.

An event should get called every time the ImageView get's rotated by maybe something like this:

self.ImageView.transform = CGAffineTransform(rotationAngle: CGFloat(10))

---

To achieve this I tried to use some kind of KVO but obviously it is not working as expected...

override func viewDidLoad() {
    super.viewDidLoad()
    self.ImageView.addObserver(self.ImageView.transform, forKeyPath: "test", options: .new, context: nil)
}


func observeValueForKeyPath(keyPath: String?, ofObject object: AnyObject?, change: [String : AnyObject]?, context: UnsafeMutableRawPointer) {
    print("changed")
}

Any help would be very appreciated! Thanks.

Answer 1

Set "transform" in keyPath like below:

imgView.addObserver(self, forKeyPath: "transform", options: .new, context: nil)

then add below code:

 override func observeValue(forKeyPath keyPath: String?, of object: Any?, change: [NSKeyValueChangeKey : Any]?, context: UnsafeMutableRawPointer?) {
        if let newValue = change?[.newKey] as? NSObject {

            print("Changed \(newValue)")
        }

Hope it will help you.

Answer 2

keyPath should be nameOfObject.property so if imageView name is dd to listen to transform it's should dd.transform

Try this

class ViewController: UIViewController {

@IBOutlet weak var dd: UIImageView!
override func viewDidLoad() {
    super.viewDidLoad()
    // Do any additional setup after loading the view, typically from a nib.

   self.addObserver(self, forKeyPath: "dd.transform", options: .new, context: nil)


   self.dd.transform = CGAffineTransform(rotationAngle: CGFloat(10))

}


override func observeValue(forKeyPath keyPath: String?, of object: Any?, change: [NSKeyValueChangeKey : Any]?, context: UnsafeMutableRawPointer?) {
    if let newValue = change?[.newKey] as? NSObject {

        print("Changed \(newValue)")
    }

}}