Double Tap Recognition over UIWebView - Swift 3 - ios

Question

I'm trying to implement Gesture recognizer over UIWebView to detect double taps. But there is no recognition.
I have looked over web for a few tutorials and I could compile to this. Code below. But there is no success.
class PageContentViewController: UIViewController, UIGestureRecognizerDelegate, UIWebViewDelegate {
#IBOutlet weak var webView: UIWebView!
var pageIndex: Int = 0
var strTitle: String!
var flag : Int = 0
override func viewDidLoad() {
super.viewDidLoad()
webView.delegate = self
DispatchQueue.main.async {
let req = URLRequest(url: URL(fileURLWithPath: Bundle.main.path(forResource: self.strTitle+"/index" , ofType: "html")!))
self.webView.loadRequest(req)
self.view.addSubview(self.webView)
}
let tapGestureRecognizer = UITapGestureRecognizer(target:self, action:#selector(self.goToback))
tapGestureRecognizer.delegate? = self
tapGestureRecognizer.numberOfTapsRequired = 2
webView.isUserInteractionEnabled = true
webView.addGestureRecognizer(tapGestureRecognizer)
webView.scrollView.addGestureRecognizer(tapGestureRecognizer)
webView.gestureRecognizerShouldBegin(tapGestureRecognizer)
}
func gestureRecognizer(_: UIGestureRecognizer, shouldRecognizeSimultaneouslyWith:UIGestureRecognizer) -> Bool {
return true
}
func gestureRecognizer(_: UIGestureRecognizer, shouldReceive:UITouch) -> Bool {
return true
}
func goToback(){
print("On the Back")
}
}
What is wrong in the code.?
I'm noob to swift.
Thanks in advance

Answer 1

I think you will need to add
webView.delegate = self
Also add UIWebViewDelegate to your class
Edit:
Your shouldRecognizeSimultaneouslyWith and shouldReceive look a bit weird maybe a copy paste mistake? It should look like:
func gestureRecognizer(_: UIGestureRecognizer, shouldRecognizeSimultaneouslyWith:UIGestureRecognizer) -> Bool {
return true
}
func gestureRecognizer(_: UIGestureRecognizer, shouldReceive:UITouch) -> Bool {
return true
}
Edit 2:
I copied your exact code and removed gestureRecognizerShould begin and it worked, I was able to remove some other code as well, not sure if you needed it in your project but here is what works with me:
class ViewController: UIViewController, UIGestureRecognizerDelegate, UIWebViewDelegate {
#IBOutlet weak var webView: UIWebView!
override func viewDidLoad() {
super.viewDidLoad()
webView.delegate = self
DispatchQueue.main.async {
let req = URLRequest(url: URL(fileURLWithPath: Bundle.main.path(forResource: self.strTitle+"/index" , ofType: "html")!))
self.webView.loadRequest(req)
}
let tapGestureRecognizer = UITapGestureRecognizer(target:self, action:#selector(self.goToback))
tapGestureRecognizer.delegate = self
tapGestureRecognizer.numberOfTapsRequired = 2
webView.isUserInteractionEnabled = true
webView.addGestureRecognizer(tapGestureRecognizer)
}
func gestureRecognizer(_: UIGestureRecognizer, shouldRecognizeSimultaneouslyWith:UIGestureRecognizer) -> Bool {
return true
}
func goToback() {
print("On the Back")
}

Answer 2

Why are you using same gesture UIGestureRecognizer for webview and webview.scrollview.
Instead you need to create two separate UIGestureRecognizer for both like this...
// for webView
let tapGestureRecognizer = UITapGestureRecognizer(target:self, action:#selector(self.goToback))
tapGestureRecognizer.delegate? = self
tapGestureRecognizer.numberOfTapsRequired = 2
webView.isUserInteractionEnabled = true
webView.addGestureRecognizer(tapGestureRecognizer)
// for webView.scrollView
let tapGestureRecognizer1 = UITapGestureRecognizer(target:self, action:#selector(self.goToback))
tapGestureRecognizer1.delegate? = self
tapGestureRecognizer1.numberOfTapsRequired = 2
webView.scrollView.addGestureRecognizer(tapGestureRecognizer1)
If you you assign same gesture recognizer to two object then one of the object doesn't have it...see log

Answer 3

I have a double tap gesture working in my app by doing the following:
I created a subclass of UIWebView that is the UIGestureRecognizerDelegate
class MyWebView: UIWebView, UIGestureRecognizerDelegate {
func gestureRecognizer(_: UIGestureRecognizer, shouldRecognizeSimultaneouslyWith:UIGestureRecognizer) -> Bool {
return true
}
func gestureRecognizer(_: UIGestureRecognizer, shouldReceive:UITouch) -> Bool {
return true
}
}
Then in my View Controller class I reference my subclass (make sure it is referenced in Interface Builder also)
#IBOutlet weak var webView: MyWebView!
And in viewDidLoad add the recognizer
let tapGestureRecognizer = UITapGestureRecognizer(target:self, action:#selector(self.goToback))
tapGestureRecognizer.delegate? = self.webView //set the delegate to the custom UIWebView
tapGestureRecognizer.numberOfTapsRequired = 2
webView.isUserInteractionEnabled = true
webView.addGestureRecognizer(tapGestureRecognizer)
Hope this helps, my original code was in Objective-C code so had to do a quick translation here so hope there are no syntax issues.

Answer 4

I have used this code and it works for me flawlessly
override func viewDidLoad() {
super.viewDidLoad()
let tapLockGesture = UITapGestureRecognizer(target: self, action: #selector(tapLock))
tapLockGesture.delegate = self
tapLockGesture.numberOfTapsRequired = 2
webView.addGestureRecognizer(tapLockGesture)
}
func gestureRecognizer(_ gestureRecognizer: UIGestureRecognizer, shouldRecognizeSimultaneouslyWith otherGestureRecognizer: UIGestureRecognizer) -> Bool {
return true
}
make sure you conform to UIGestureRecognizerDelegate and UIScrollViewDelegate.