Resize a UITextField while typing (by using Autolayout)

Question

I have a UITableViewCell which has two UITextFields (without borders). The following constraints are used to set up the horizontal layout.

@"|-10-[leftTextField(>=80)]-(>=10)-[rightTextField(>=40)]-10-|"

Nothing fancy, and works as expected.

As you can see the upper textField has the correct size. The lower textField started with an empty text, and because of the empty text it is 80 points wide. When I type text into the editing textField the text scrolls to the left, it does not change its width.

I don't like that, the width of the textField should adjust while the user types into that textField.

In my opinion that should work out of the box. By implementing a IBAction for the UIControlEventEditingChanged event I can confirm that typing actually changes the intrinsicContentSize of the UITextField.

But well, the width does not change until the textField is no longer the first responder. If I put the cursor into another textField the width of the edited textField is set. That's a bit late for what I want.

These commented out lines is what I tried without any success:

- (IBAction)textFieldDidChange:(UITextField *)textField {
    [UIView animateWithDuration:0.1 animations:^{
//        [self.contentView removeConstraints:horizontalConstraints];
//        [self.contentView addConstraints:horizontalConstraints];
//        [self.contentView layoutIfNeeded];

//        [self.contentView setNeedsLayout];

//        [self.contentView setNeedsUpdateConstraints];
    }];
    NSLog(@"%@", NSStringFromCGSize(textField.intrinsicContentSize));
}

Does anybody know what I am missing? What could I try to make this work?

Answer 1

This is what works for me:

- (IBAction) textFieldDidChange: (UITextField*) textField
{
    [UIView animateWithDuration:0.1 animations:^{
        [textField invalidateIntrinsicContentSize];
    }];
}

What's interesting is that it seems as if it SHOULD work out of the box, given this text from the docs:

In addition, if a property of a view changes and that change affects the intrinsic content size, the view must call invalidateIntrinsicContentSize so that the layout system notices the change and can re-layout. In the implementation of your view class, you must ensure that if the value of any property upon which the intrinsic size depends changes, you invoke invalidateIntrinsicContentSize. For example, a text field calls invalidateIntrinsicContentSize if the string value changes.

My best guess is that the textfield only calls invalidateIntrinsicContentSize once editing has finished, not during.

Edit: A bunch of "This is not working for me". I think the confusion here is perhaps the triggering event that is tied to the textFieldDidChange: handler. The event needs to be UIControlEventEditingChanged. If you're using IB, double check that you're handling the right event.

The UITextField also cannot be constrained in size. You can lock it into position with constraints, but any width constraint, or set of left+right positioning constraints will prevent it from resizing to its intrinsic content size.

Answer 2

I don't know why UITextField only updates its intrinsicContentSize when it resigns its first responder status. This happens for both iOS 7 and iOS 8.

As a temporary solution, I override intrinsicContentSize and determine the size using typingAttributes. This accounts for leftView and rightView as well

// This method is target-action for UIControlEventEditingChanged
func textFieldEditingChanged(textField: UITextField) {
  textField.invalidateIntrinsicContentSize()
}


override var intrinsicContentSize: CGSize {
    if isEditing {
      let string = (text ?? "") as NSString
      let size = string.size(attributes: typingAttributes)
      return CGSize(width: size.width + (rightView?.bounds.size.width ?? 0) + (leftView?.bounds.size.width ?? 0) + 2,
                    height: size.height)
    }

    return super.intrinsicContentSize
  }

Here I make the it wider to account for the caret

Answer 3

Here's the answer in Swift. As a bonus, this snippet doesn't collapse the text field if there is a placeholder.

// UITextField subclass

override func awakeFromNib() {
    super.awakeFromNib()
    self.addTarget(self, action: #selector(textFieldTextDidChange), forControlEvents: .EditingChanged)
}

func textFieldTextDidChange(textField: UITextField) {
    textField.invalidateIntrinsicContentSize()
}

override func intrinsicContentSize() -> CGSize {
    if self.editing {
        let textSize: CGSize = NSString(string: ((text ?? "" == "") ? self.placeholder : self.text) ?? "").sizeWithAttributes(self.typingAttributes)
        return CGSize(width: textSize.width + (self.leftView?.bounds.size.width ?? 0) + (self.rightView?.bounds.size.width ?? 0) + 2, height: textSize.height)
    } else {
        return super.intrinsicContentSize()
    }
}

Answer 4

First things first: in Swift 4, UITextField's intrinsicContentSize is a computed variable, not a method.

Below is a Swift4 solution with a specialized use case. A right justified textfield can resize and extend leftward up to a certain pixel boundary. The textfield is assigned to the CurrencyTextField class which inherits from UITextField. CurrencyTextField is then extended to provide custom behavior for returning the object's intrinsicContentSize, a computed variable. .
The "editing changed" event of the CurrencyTextField instance is mapped to the repositionAndResize IBAction method in its host UIViewController class. This method simply invalidates the current intrinsic content size of the CurrencyTextField instance. Invoking the CurrencyTextField's invalidateIntrinsicContentSize method ( inherited form UITextField ) triggers an attempt to get the object's intrinsic content size.

The custom logic in CurrencyTextField's intrinsicContentSize getter method has to convert the CurrentTextField's text property to NSString in order ascertain its size, which it returns as the intrinsicContentSize if the x coordinate of the CurrencyTextField is greater than the stipulated pixel boundary.

class CurrencyTextField:UITextField {

}

extension CurrencyTextField {


     override open var intrinsicContentSize: CGSize {

        if isEditing {
            let string = (text ?? "") as NSString
            let stringSize:CGSize = string.size(withAttributes: 
             [NSAttributedStringKey.font: UIFont.systemFont(ofSize: 
             19.0)])
             if self.frame.minX > 71.0 {
                return stringSize
             }
       }

       return super.intrinsicContentSize
    }


}

class TestController: UIViewController {

    @IBAction func repositionAndResize(_ sender: CurrencyTextField) {
        sender.invalidateIntrinsicContentSize()
    }


    override func viewDidLoad() {
        super.viewDidLoad()

    }

}