Adjusting UILabel text with Autoshrink - ios

Question

Background
I am creating an application, and inside it I have an animation that repositions a UILabel and a UITextField when the keyboard is presented. It is set up like this:
NSNotificationCenter.defaultCenter().addObserver(self, selector: #selector(raiseTextField), name: UIKeyboardWillShowNotification, object: nil)
And this is the function:
func raiseTextField(sender: NSNotification){
UIView.animateWithDuration(0.25, animations: { () -> Void in
self.userInputTextFieldBottomContstraint.constant = sender.userInfo![UIKeyboardFrameEndUserInfoKey]!.CGRectValue().size.height
self.view.layoutIfNeeded()
})
}
My storyboard looks like this:
I have constraints set up so that the friendInputView is the right size, and it has Autoshrink so the font adjusts accordingly.
Problem
When I call raiseTextField(), everything works fine, except the font-size of the friendInputView takes a long time to change. Instead of updating while the animation is happening, it updates afterwards.
It does eventually adjust, just not at the preferred speed.
I tried adding self.friendInputLabel.adjustsFontSizeToFitWidth = true inside of animateWithDuration(), but it did't seem to change anything.
Examples
Before raising keyboard:
(text adjusted correctly)
Immediately after raising keyboard:
(text-size too big)
A second or so after raising keyboard:
(text adjusted correctly)
The Bottom Line
Is there any way to make a UILabel resize its text programmatically, rather than just waiting for it to update itself? Similarly to how layoutIfNeeded() re-adjusts constraints, is there any function like that for re-adjusting Autoshrink?
Edit 1
I ended up getting it to work based on an answer I got that said to use a UITextFieldDelegate instead of NSNotificationCenter. I replaced the raiseTextField() function with the following code:
func textFieldShouldBeginEditing(textField: UITextField) -> Bool {
self.userInputTextFieldBottomContstraint.constant = 250
self.view.setNeedsUpdateConstraints()
UIView.animateWithDuration(0.25, animations: { () -> Void in
self.view.layoutIfNeeded()
})
return true
}
func textFieldShouldReturn(textField: UITextField) -> Bool {
textField.resignFirstResponder()
self.userInputTextFieldBottomContstraint.constant = 10
self.view.setNeedsUpdateConstraints()
UIView.animateWithDuration(0.25, animations: { () -> Void in
self.view.layoutIfNeeded()
})
return true
}
However, now I have a new question: How can I get it to use the real keyboard size? Assuming that the keyboard size is always 250 isn't very helpful.
I tried doing so by creating this variable:
var keyboardHeight: CGFloat?
Putting this in viewDidLoad():
NSNotificationCenter.defaultCenter().addObserver(self, selector: #selector(setTheKeyboardHeight), name: UIKeyboardWillShowNotification, object: nil)
And creating this function:
func setTheKeyboardHeight(sender: NSNotification){
keyboardHeight = sender.userInfo![UIKeyboardFrameEndUserInfoKey]?.CGRectValue().height
}
Then I added it to textFieldShouldBeginEditing() like this:
self.userInputTextFieldBottomContstraint.constant = keyboardHeight!
self.view.setNeedsUpdateConstraints()
UIView.animateWithDuration(0.25, animations: { () -> Void in
self.view.layoutIfNeeded()
})
return true
However, it ends up just giving the error:
fatal error: unexpectedly found nil while unwrapping an Optional value
I think it happens because the keyboardHeight gets set after textFieldShouldBeginEditing() is called, but I don't know how to fix it.
Is there any way that I can access the keyboard height while using textFieldShouldBeginEditing(), or do I have to use NSNotificationCenter?

Answer 1

I have done same demo what you have done, and have observed some weird behaviour of UIKeyboardNotification, i'm not sure that it is weird or it is like that only,
What i have observed is when you change any constraint in UIKeyboardNotification it changes the constraint constant (or frame) with animation, even though you have not used UIView animationWithDuration block. So i think this delay might be due to that animation effect added by KeyboardNotification,
func raiseTextField(sender: NSNotification){
self.bottomConstraintTextField.constant = 250//sender.userInfo![UIKeyboardFrameEndUserInfoKey]!.CGRectValue().size.height
self.view.setNeedsUpdateConstraints()
//As you can see i have commented the animation block, still it changes the constraint with animation.
//UIView.animateWithDuration(0.25, animations: { () -> Void in
self.view.layoutIfNeeded()
//})
}
So in your scenario i have added the animation code in textFields delegates and it it working as expected,
func textFieldShouldBeginEditing(textField: UITextField) -> Bool {
self.bottomConstraintTextField.constant = 250//sender.userInfo![UIKeyboardFrameEndUserInfoKey]!.CGRectValue().size.height
self.view.setNeedsUpdateConstraints()
UIView.animateWithDuration(0.25, animations: { () -> Void in
self.view.layoutIfNeeded()
})
return true
}
func textFieldShouldReturn(textField: UITextField) -> Bool {
textField.resignFirstResponder()
self.bottomConstraintTextField.constant = 10
self.view.setNeedsUpdateConstraints()
UIView.animateWithDuration(0.25, animations: { () -> Void in
self.view.layoutIfNeeded()
})
return true
}
Here is the result,
Hope it helps you.
Update:
I have played arround it and found one workaround, so instead of taking a variable to hold keyboard height you can do it as below,
func raiseTextField(sender: NSNotification){
self.bottomConstraintTextField.constant = sender.userInfo![UIKeyboardFrameEndUserInfoKey]!.CGRectValue().size.height
self.view.setNeedsUpdateConstraints()
self.view.layoutIfNeeded()
}
func textFieldShouldBeginEditing(textField: UITextField) -> Bool {
self.bottomConstraintTextField.constant = 200
self.view.setNeedsUpdateConstraints()
UIView.animateWithDuration(0.25, animations: { () -> Void in
self.view.layoutIfNeeded()
})
return true
}
So have both textField delegate and KeyboardNotification and change the bottom constraint in textField delegate it will get called before keyboard notification and by doing this you will not observe the delay in shrinking the label text.
See the updated effect below,