SOLVED: how to call function when keyboard disappears

@kikashi59

Aug '21

Another beginner's question! I use this code, which I picked up from someone helpful (perhaps here), so that a tap anywhere dismisses the keyboard being shown:

extension UIApplication {
    func addTapGestureRecognizer() {
        guard let window = windows.first else { return }
        let tapGesture = UITapGestureRecognizer(target: window, action: #selector(UIView.endEditing))
        tapGesture.cancelsTouchesInView = false
        tapGesture.delegate = self
        tapGesture.name = "MyTapGesture"
        window.addGestureRecognizer(tapGesture)
    }
}

It works very nicely. I'd like to be able to call a function when the keyboard is dismissed, but my knowledge of iOS outside SwiftUI is pretty much zero. Can I add a function call to this code somehow?

3

@njansari

Aug '21

You have a UITapGestureRecognizer which has an action associated with it. This gets called when there is a tap. You can specify a custom function to run here.

Here is an example of what you can add:

@objc func dismissKeyboard(_ sender: UITapGestureRecognizer) {
  // do what you need to do here
}

You will need to change the action parameter to #selector(dismissKeyboard).

3

@kikashi59

Aug '21

Thanks - I'd tried changing the #selector to a function, but no matter how I define the function, I get a crash immediately:

    let tapGesture = UITapGestureRecognizer(target: window, action: #selector(dismissKeyboard))

-[UIWindow dismissKeyboard:]: unrecognized selector sent to instance 0x7fd716909110

I've tried various declarations of dismissKeyboard, but the result is always the same.

Jeremy

3

@njansari

Aug '21

What your error message is saying is that the UIWindow object has no function called dismissKeyboard. The target of the tap gesture is the first window in the application, but you have added the dismissKeyboard function to an instance of UIApplication. There is nothing wrong with dismissKeyboard itself: it's just how you have defined your UITapGestureRecognizer.

To fix this, make sure the target you pass into the tap gesture has the dismissKeyboard function. There are two ways that I would go about this:

Either change the target to be self
Or add the dismissKeyboard function to the instance of UIWindow

3

@kikashi59

Aug '21

This reminds me of learning how to write for MacOS in the 1980s, when it was said that in order to understand any one of the five volumes of Inside Mac, one had first to have read and understood the other four.

I'm afraid I'm going to parade my ignorance again: how do I do what you suggest?

At present, with the code as it stands, @objc func hideKeyboard() lives inside extension UIApplication, and my @main function (largely supplied by XCode) reads

@main
struct fooApp: App {
    var body: some Scene {
        WindowGroup {
            Calculator()
                .onAppear(perform: UIApplication.shared.addTapGestureRecognizer)
        }
    }
}

and with #selector(UIView.endEditing) it works fine (Calculator() is a NavigationView with a variety of destinations). When I change it to #selector(dismissKeyboard), the crash happens as soon as I tap on a link in the NavigationView, presumably because a new window is opened which doesn't have dismissKeyboard() attached. How do I accomplish either attaching to self or adding it to each new window?

3

@njansari

Aug '21

Maybe this will help:

extension UIApplication: UIGestureRecognizerDelegate {
    func addTapGestureRecognizer() {
        guard let window = windows.first else { return }
        let tapGesture = UITapGestureRecognizer(target: window, action: #selector(UIWindow.dismissKeyboard))
        tapGesture.cancelsTouchesInView = false
        tapGesture.delegate = self // requires conformance to UIGestureRecognizerDelegate
        tapGesture.name = "MyTapGesture"
        window.addGestureRecognizer(tapGesture)
    }
}

extension UIWindow {
    @objc func dismissKeyboard(_ sender: UITapGestureRecognizer) {
        print("Tapped")
    }
}

I've tested this and it seems to work. Every time I tap on the screen, the "Tapped" message is printed out. I'm guessing this is what you want.

3

@kikashi59

Aug '21

It does work, and it is exactly what I was looking for. Thanks very much. I've learned something as well as having a problem fixed.

Jeremy

3

	@kikashi59 Aug '21 Another beginner's question! I use this code, which I picked up from someone helpful (perhaps here), so that a tap anywhere dismisses the keyboard being shown: `extension UIApplication { func addTapGestureRecognizer() { guard let window = windows.first else { return } let tapGesture = UITapGestureRecognizer(target: window, action: #selector(UIView.endEditing)) tapGesture.cancelsTouchesInView = false tapGesture.delegate = self tapGesture.name = "MyTapGesture" window.addGestureRecognizer(tapGesture) } }` It works very nicely. I'd like to be able to call a function when the keyboard is dismissed, but my knowledge of iOS outside SwiftUI is pretty much zero. Can I add a function call to this code somehow? 3
	@njansari Aug '21 You have a `UITapGestureRecognizer` which has an action associated with it. This gets called when there is a tap. You can specify a custom function to run here. Here is an example of what you can add: `@objc func dismissKeyboard(_ sender: UITapGestureRecognizer) { // do what you need to do here }` You will need to change the action parameter to `#selector(dismissKeyboard)`. 3
	@kikashi59 Aug '21 Thanks - I'd tried changing the #selector to a function, but no matter how I define the function, I get a crash immediately: `let tapGesture = UITapGestureRecognizer(target: window, action: #selector(dismissKeyboard))` -[UIWindow dismissKeyboard:]: unrecognized selector sent to instance 0x7fd716909110 I've tried various declarations of dismissKeyboard, but the result is always the same. Jeremy 3
	@njansari Aug '21 What your error message is saying is that the `UIWindow` object has no function called `dismissKeyboard`. The target of the tap gesture is the first window in the application, but you have added the `dismissKeyboard` function to an instance of `UIApplication`. There is nothing wrong with `dismissKeyboard` itself: it's just how you have defined your `UITapGestureRecognizer`. To fix this, make sure the target you pass into the tap gesture has the `dismissKeyboard` function. There are two ways that I would go about this: Either change the target to be `self` Or add the `dismissKeyboard` function to the instance of `UIWindow` 3
	@kikashi59 Aug '21 This reminds me of learning how to write for MacOS in the 1980s, when it was said that in order to understand any one of the five volumes of Inside Mac, one had first to have read and understood the other four. I'm afraid I'm going to parade my ignorance again: how do I do what you suggest? At present, with the code as it stands, `@objc func hideKeyboard()` lives inside `extension UIApplication`, and my `@main` function (largely supplied by XCode) reads `@main struct fooApp: App { var body: some Scene { WindowGroup { Calculator() .onAppear(perform: UIApplication.shared.addTapGestureRecognizer) } } }` and with `#selector(UIView.endEditing)` it works fine (Calculator() is a NavigationView with a variety of destinations). When I change it to `#selector(dismissKeyboard)`, the crash happens as soon as I tap on a link in the NavigationView, presumably because a new window is opened which doesn't have `dismissKeyboard()` attached. How do I accomplish either attaching to self or adding it to each new window? 3
	@njansari Aug '21 Maybe this will help: extension UIApplication: UIGestureRecognizerDelegate { func addTapGestureRecognizer() { guard let window = windows.first else { return } let tapGesture = UITapGestureRecognizer(target: window, action: #selector(UIWindow.dismissKeyboard)) tapGesture.cancelsTouchesInView = false tapGesture.delegate = self // requires conformance to UIGestureRecognizerDelegate tapGesture.name = "MyTapGesture" window.addGestureRecognizer(tapGesture) } } extension UIWindow { @objc func dismissKeyboard(_ sender: UITapGestureRecognizer) { print("Tapped") } } I've tested this and it seems to work. Every time I tap on the screen, the `"Tapped"` message is printed out. I'm guessing this is what you want. 3
	@kikashi59 Aug '21 It does work, and it is exactly what I was looking for. Thanks very much. I've learned something as well as having a problem fixed. Jeremy 3

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