问题
I'm using a UIAlertController
to present the user with a dialog to enter a 5 digit CRN. I want the Add
button to be disabled until there are 5 and only 5 digit in the UITextField
.
Here's what the UI looks like :
Here's the properties setup for the UIAlertController
:
var alertController: UIAlertController!
var addAlertAction: UIAlertAction! {
return UIAlertAction(title: "Add", style: .default)
}
Here's how I'm initializing them in the viewDidLoad
method :
self.alertController = UIAlertController(title: "Add Class", message: "Input CRN", preferredStyle: .alert)
self.alertController.addAction(addAlertAction)
self.alertController.addAction(UIAlertAction(title: "Cancel", style: .destructive))
self.alertController.addTextField { (textField) in
textField.delegate = self
textField.keyboardType = .numberPad
}
Here's how I'm trying to disable/enable the button using the UITextFieldDelegate
method :
func textFieldDidEndEditing(_ textField: UITextField) {
if ((textField.text?.characters.count)! == 5) {
self.alertController.actions[0].isEnabled = true
} else {
self.alertController.actions[0].isEnabled = false
}
}
However, the button remains disabled (or enabled) all the time. It never gets enabled. What's going wrong ?
回答1:
Implement the logic in the shouldChangeCharactersIn
delegate method of UITextField
. This method gets fired on change in each character of textfield.
You can build the logic taking the range parameter into consideration.
Here is the code that works perfectly.
func textField(_ textField: UITextField, shouldChangeCharactersIn range: NSRange, replacementString string: String) -> Bool {
if ((range.location == 4 && range.length == 0) || (range.location == 5 && range.length == 1)) {
self.alertController.actions[0].isEnabled = true
}else{
self.alertController.actions[0].isEnabled = false
}
return true;
}
Tested successfully in Swift 3
, XCode 8
and iOS 10
Hope that helps. Happy coding ...
回答2:
Try using the textfield's EditingChanged event as follow:
let addAction:UIAlertAction = UIAlertAction(title: "Add", style: .default)
addAction.isEnabled = false; //to make it disable while presenting
self.alertController = UIAlertController(title: "Add Class", message: "Input CRN", preferredStyle: .alert)
self.alertController.addAction(addAction)
self.alertController.addAction(UIAlertAction(title: "Cancel", style: .destructive))
self.alertController.addTextField { (textField) in
textField.keyboardType = .numberPad
textField.addTarget(self, action: #selector(self.alertTextFieldDidChange(field:)), for: UIControlEvents.editingChanged)
}
And the listener for text field should look like this:
func alertTextFieldDidChange(field: UITextField){
let alertController:UIAlertController = self.presentedViewController as! UIAlertController;
let textField :UITextField = alertController.textFields![0];
let addAction: UIAlertAction = alertController.actions[0];
addAction.isEnabled = (textField.text?.characters.count)! >= 5;
}
Tested with Xcode 8 and swift 3. Worked for me.
来源:https://stackoverflow.com/questions/39538098/how-to-disable-uialertaction-depending-on-uitextfield-in-uialertcontroller