How to detect when user used Password AutoFill on a UITextField

Question

I\'ve implemented all the app and server changes necessary to support Password Autofill on iOS 11, and it works well. I\'d like it to work a little better.

My usern

Answer 1

Not sure if the previous answer stopped working at some point, but I can't get it to work—I only get a single didBeginEditing call when AutoFill is used.

However, I did find a way to detect AutoFill. And keep in mind that it is possible for AutoFill to be used after some characters have already been entered, for example if the user has already typed some numbers in the phone number, then they AutoFill the full number.

For Swift 4/5:

private var fieldPossibleAutofillReplacementAt: Date?

private var fieldPossibleAutofillReplacementRange: NSRange?

func textField(_ textField: UITextField, shouldChangeCharactersIn range: NSRange, replacementString string: String) -> Bool {
    // To detect AutoFill, look for two quick replacements. The first replaces a range with a single space
    // (or blank string starting with iOS 13.4).
    // The next replaces the same range with the autofilled content.
    if string == " " || string == "" {
        self.fieldPossibleAutofillReplacementRange = range
        self.fieldPossibleAutofillReplacementAt = Date()
    } else {
        if fieldPossibleAutofillReplacementRange == range, let replacedAt = self.fieldPossibleAutofillReplacementAt, Date().timeIntervalSince(replacedAt) < 0.1 {
            DispatchQueue.main.async {
                // Whatever you use to move forward.
                self.moveForward()
            }
        }
        self.fieldPossibleAutofillReplacementRange = nil
        self.fieldPossibleAutofillReplacementAt = nil
    }

    return true
}

Answer 2

I don't think there is a better solution.

One thing I noticed is that autofill is only enabled when the text field is empty.

So if the text field went from empty to a length greater than the minimum password/username, then it is most likely autofill/paste.

I am using shouldChangeCharactersIn to detect the change in the UITextField. I'm not for sure if there is a case where text from the keyboard could be batched together before the delegate method is called.

Answer 3

I'd like to trigger this on behalf of the user.

If this is your primary goal, I'm doing a little different approach here.

Upon showing the login form, I first check iCloud Keychain with SecRequestSharedWebCredential. If the closure returns a credentials, which means user's intent is to login with it, then I automatically login for him/her. Otherwise, make the login text filed becomeFirstResponder().

This approach does not support third-party password manager, but most people use iCloud Keychain I believe.

Answer 4

Swift 5:

The following delegate method gets triggered every time that the user types something in the textfield. That string count is usually one, so any number great than that is either autofill or the user pasting some text into the field. I am only using this delegate on this password field.

extension LoginView: UITextFieldDelegate {

    func textField(_ textField: UITextField, shouldChangeCharactersIn range: NSRange, replacementString string: String) -> Bool {
        if string.count > 1 {
            DispatchQueue.main.asyncAfter(deadline: .now() + .seconds(1)) { [weak self] in
                self?.endEditing(true)
            }
        }
        return true
    }
}

Answer 5

Found a solution.

When the password manager is used to autofill username + password, it will trigger didBeginEditing twice, faster than a human ever could.

So, I calculate the time between the events. If the time is extremely fast, then I assume that autofill (e.g. FaceID or TouchID) was used to enter credentials and auto-trigger whatever UI is next -- in my case, the User tapping "Sign-in".

Obviously, you have to set up the correct delegation of the UITextFields you want to monitor, but once you do that:

var biometricAutofillTime: Date!

func textFieldDidBeginEditing(_ textField: UITextField) {
    if biometricAutofillTime != nil {
        if Date().timeIntervalSince(biometricAutofillTime) < 0.1 {
            // NOTE: Need to hesitate for a very short amount of time,
            //        because, otherwise, the second UITextField (password)
            //        won't yet be populated
            DispatchQueue.main.asyncAfter(deadline: .now() + 0.2) { self.didTapSignin() }
        }
        biometricAutofillTime = nil
    }
    biometricAutofillTime = Date()
}

Answer 6

This detects when user has autofilled via passwords. It may also trigger when user pastes text from their clipboard. (If textfield is empty)

You can probably handle the logic to remove user pasted cases with this link.. how to know when text is pasted into UITextView

  private var didAutofillTextfield: Bool = false {
    didSet {
      if didAutofillTextfield {
        // Fire analytics for user autofilling
      }
    }
  }


 func textField(_ textField: UITextField, shouldChangeCharactersIn range: NSRange, replacementString string: String) -> Bool {
    // If the range is {0,0} and the string count > 1, then user copy paste text or used password autofill.
    didAutofillTextfield = range == NSRange(location: 0, length: 0) && string.count > 1
    return true
  }