How can I find out whether the user pressed the Call or the Cancel button when making a call from my app?

Question

I need to return to my app after making a call from my app, so I use this code:

NSURL *url = [NSURL URLWithString:@"telprompt://123-4567-890"]; 
[[UIApplication  sharedApplication] openURL:url]; 

When the user presses a button to execute this code, an alert is shown with 2 buttons, "Call" and "Cancel".

How can I find out if the user pressed the "Call" button?

Answer 1

Here is an iOS 10+ solution for Swift 4.2, tested with iOS 12 that detects both the Cancel and the Call button.

Don't forget to import CallKit and conform your class to CXCallObserverDelegate!

let callObserver = CXCallObserver()

var didDetectOutgoingCall = false

func showCallAlert() {
    guard let url = URL(string: "tel:+36201234567"),
        UIApplication.shared.canOpenURL(url) else {
            return
    }

    callObserver.setDelegate(self, queue: nil)

    didDetectOutgoingCall = false

    //we only want to add the observer after the alert is displayed,
    //that's why we're using asyncAfter(deadline:)
    UIApplication.shared.open(url, options: [:]) { [weak self] success in
        if success {
            DispatchQueue.main.asyncAfter(deadline: .now() + 0.3) {
                self?.addNotifObserver()
            }
        }
    }
}

func addNotifObserver() {
    let selector = #selector(appDidBecomeActive)
    let notifName = UIApplication.didBecomeActiveNotification
    NotificationCenter.default.addObserver(self, selector: selector, name: notifName, object: nil)
}

@objc func appDidBecomeActive() {
    //if callObserver(_:callChanged:) doesn't get called after a certain time,
    //the call dialog was not shown - so the Cancel button was pressed
    DispatchQueue.main.asyncAfter(deadline: .now() + 0.3) { [weak self] in
        if !(self?.didDetectOutgoingCall ?? true) {
            print("Cancel button pressed")
        }
    }
}

func callObserver(_ callObserver: CXCallObserver, callChanged call: CXCall) {
    if call.isOutgoing && !didDetectOutgoingCall {
        didDetectOutgoingCall = true

        print("Call button pressed")
    }
}