Animating UILabel Font Size Change

You can change the size and font of your UILabel with animation like bellow .. here I just put the example of how to change the font of UILabel with transform Animation ..

    yourLabel.font = [UIFont boldSystemFontOfSize:35]; // set font size which you want instead of 35
    yourLabel.transform = CGAffineTransformScale(yourLabel.transform, 0.35, 0.35); 
    [UIView animateWithDuration:1.0 animations:^{
        yourLabel.transform = CGAffineTransformScale(yourLabel.transform, 5, 5);
    }];

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For 2017 onwards....

Swift 3.0, 4.0

UIView.animate(withDuration: 0.5) {
     label.transform = CGAffineTransform(scaleX: 1.1, y: 1.1) //Scale label area
 }

Critical:

The critical point to avoid blurring is you must begin with the biggest size, and shrink it. Then expand to "1" when needed.

For quick "pops" (like a highlight animation) it's OK to expand beyond 1 but if you are transitioning between two sizes, make the larger size the "correct" normal one.

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I've created UILabel extension in Swift.

import UIKit

extension UILabel {
    func animate(font: UIFont, duration: TimeInterval) {
        // let oldFrame = frame
        let labelScale = self.font.pointSize / font.pointSize
        self.font = font
        let oldTransform = transform
        transform = transform.scaledBy(x: labelScale, y: labelScale)
        // let newOrigin = frame.origin
        // frame.origin = oldFrame.origin // only for left aligned text
        // frame.origin = CGPoint(x: oldFrame.origin.x + oldFrame.width - frame.width, y: oldFrame.origin.y) // only for right aligned text
        setNeedsUpdateConstraints()
        UIView.animate(withDuration: duration) {
            //L self.frame.origin = newOrigin
            self.transform = oldTransform
            self.layoutIfNeeded()
        }
    }
}

Uncomment lines if the label text is left or right aligned.

---

You could also use CATextLayer which has fontSize as an animatable property.

let startFontSize: CGFloat = 20
let endFontSize: CGFloat = 80

let textLayer = CATextLayer()
textLayer.string = "yourText"
textLayer.font = yourLabel.font.fontName as CFTypeRef?
textLayer.fontSize = startFontSize
textLayer.foregroundColor = UIColor.black.cgColor
textLayer.contentsScale = UIScreen.main.scale //for some reason CATextLayer by default only works for 1x screen resolution and needs this line to work properly on 2x, 3x, etc. ...
textLayer.frame = parentView.bounds
parentView.layer.addSublayer(textLayer)

//animation:
let duration: TimeInterval = 1
textLayer.fontSize = endFontSize //because upon completion of the animation CABasicAnimation resets the animated CALayer to its original state (as opposed to changing its properties to the end state of the animation), setting fontSize to endFontSize right BEFORE the animation starts ensures the fontSize doesn't jump back right after the animation.
let fontSizeAnimation = CABasicAnimation(keyPath: "fontSize")
fontSizeAnimation.fromValue = startFontSize
fontSizeAnimation.toValue = endFontSize
fontSizeAnimation.duration = duration
fontSizeAnimation.timingFunction = CAMediaTimingFunction(name: kCAMediaTimingFunctionEaseInEaseOut)
textLayer.add(fontSizeAnimation, forKey: nil)

I used it in my project: https://github.com/yinanq/AngelListJobs

This animation keeps the font top left aligned (unlike CGAffineTransformScale scaling the label from center), pro or con depending on your needs. A disadvantage of CATextLayer is that CALayers don't work with autolayout constraint animation (which I happened to need and solved it by making a UIView containing just the CATextLayer and animating its constraints).

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For those not looking for a transform, but actual value change:

UIView.transition(with: label, duration: 0.25, options: .transitionCrossDissolve, animations: {
    self.label.font = UIFont.systemFont(ofSize: 15)
}) { isFinished in }

https://i.stack.imgur.com/UDLhF.gif

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For someone who wants to adjust direction of animation

I have created an extension for UILabel to animate font size change

extension UILabel {
  func animate(fontSize: CGFloat, duration: TimeInterval) {
    let startTransform = transform
    let oldFrame = frame
    var newFrame = oldFrame
    let scaleRatio = fontSize / font.pointSize

    newFrame.size.width *= scaleRatio
    newFrame.size.height *= scaleRatio
    newFrame.origin.x = oldFrame.origin.x - (newFrame.size.width - oldFrame.size.width) * 0.5
    newFrame.origin.y = oldFrame.origin.y - (newFrame.size.height - oldFrame.size.height) * 0.5
    frame = newFrame

    font = font.withSize(fontSize)

    transform = CGAffineTransform.init(scaleX: 1 / scaleRatio, y: 1 / scaleRatio);
    layoutIfNeeded()

    UIView.animate(withDuration: duration, animations: {
      self.transform = startTransform
      newFrame = self.frame
    }) { (Bool) in
      self.frame = newFrame
    }
  }

If you want to adjust direction of animation, use below method and put a suitable anchor point.

SWIFT

struct LabelAnimateAnchorPoint {
  // You can add more suitable archon point for your needs
  static let leadingCenterY         = CGPoint.init(x: 0, y: 0.5)
  static let trailingCenterY        = CGPoint.init(x: 1, y: 0.5)
  static let centerXCenterY         = CGPoint.init(x: 0.5, y: 0.5)
  static let leadingTop             = CGPoint.init(x: 0, y: 0)
}

extension UILabel {
  func animate(fontSize: CGFloat, duration: TimeInterval, animateAnchorPoint: CGPoint) {
    let startTransform = transform
    let oldFrame = frame
    var newFrame = oldFrame
    let archorPoint = layer.anchorPoint
    let scaleRatio = fontSize / font.pointSize

    layer.anchorPoint = animateAnchorPoint

    newFrame.size.width *= scaleRatio
    newFrame.size.height *= scaleRatio
    newFrame.origin.x = oldFrame.origin.x - (newFrame.size.width - oldFrame.size.width) * animateAnchorPoint.x
    newFrame.origin.y = oldFrame.origin.y - (newFrame.size.height - oldFrame.size.height) * animateAnchorPoint.y
    frame = newFrame

    font = font.withSize(fontSize)

    transform = CGAffineTransform.init(scaleX: 1 / scaleRatio, y: 1 / scaleRatio);
    layoutIfNeeded()

    UIView.animate(withDuration: duration, animations: {
      self.transform = startTransform
      newFrame = self.frame
    }) { (Bool) in
      self.layer.anchorPoint = archorPoint
      self.frame = newFrame
    }
  }
}

OBJECTIVE-C

// You can add more suitable archon point for your needs
#define kLeadingCenterYAnchorPoint         CGPointMake(0.f, .5f)
#define kTrailingCenterYAnchorPoint        CGPointMake(1.f, .5f)
#define kCenterXCenterYAnchorPoint         CGPointMake(.5f, .5f)
#define kLeadingTopAnchorPoint             CGPointMake(0.f, 0.f)

@implementation UILabel (FontSizeAnimating)

- (void)animateWithFontSize:(CGFloat)fontSize duration:(NSTimeInterval)duration animateAnchorPoint:(CGPoint)animateAnchorPoint {
  CGAffineTransform startTransform = self.transform;
  CGRect oldFrame = self.frame;
  __block CGRect newFrame = oldFrame;
  CGPoint archorPoint = self.layer.anchorPoint;
  CGFloat scaleRatio = fontSize / self.font.pointSize;

  self.layer.anchorPoint = animateAnchorPoint;

  newFrame.size.width *= scaleRatio;
  newFrame.size.height *= scaleRatio;
  newFrame.origin.x = oldFrame.origin.x - (newFrame.size.width - oldFrame.size.width) * animateAnchorPoint.x;
  newFrame.origin.y = oldFrame.origin.y - (newFrame.size.height - oldFrame.size.height) * animateAnchorPoint.y;
  self.frame = newFrame;

  self.font = [self.font fontWithSize:fontSize];
  self.transform = CGAffineTransformScale(self.transform, 1.f / scaleRatio, 1.f / scaleRatio);
  [self layoutIfNeeded];

  [UIView animateWithDuration:duration animations:^{
    self.transform = startTransform;
    newFrame = self.frame;
  } completion:^(BOOL finished) {
    self.layer.anchorPoint = archorPoint;
    self.frame = newFrame;
  }];
}

@end

For example, to animate changing label font size to 30, duration 1s from center and scale bigger. Simply call

SWIFT

YOUR_LABEL.animate(fontSize: 30, duration: 1, animateAnchorPoint: LabelAnimateAnchorPoint.centerXCenterY)

OBJECTIVE-C

[YOUR_LABEL animateWithFontSize:30 
                       duration:1 
             animateAnchorPoint:kCenterXCenterYAnchorPoint];

---

Swift 3.0 & Swift 4.0

 UIView.animate(withDuration: 0.5, delay: 0.1, options: .curveLinear, animations: { 

    label.transform = label.transform.scaledBy(x:4,y:4) //Change x,y to get your desired effect. 

    } ) { (completed) in

         //Animation Completed      

    }

---

I found each of the suggestions here inadequate for these reasons:

They don't actually change the font size. They don't play well with frame sizing & auto layout. Their interface is non-trivial and/or doesn't play nice inside animation blocks.

In order to retain all of these features & still get a smooth animation transition I've combined the transform approach and the font approach.

The interface is simple. Just update the fontSize property and you'll update the font's size. Do this inside an animation block and it'll animate.

@interface UILabel(MPFontSize)

@property(nonatomic) CGFloat fontSize;

@end

As for the implementation, there's the simple way, and there's the better way.

Simple:

@implementation UILabel(MPFontSize)

- (void)setFontSize:(CGFloat)fontSize {

    CGAffineTransform originalTransform = self.transform;
    UIFont *targetFont = [self.font fontWithSize:fontSize];

    [UIView animateWithDuration:0 delay:0 options:0 animations:^{
        self.transform = CGAffineTransformScale( originalTransform,
                fontSize / self.fontSize, fontSize / self.fontSize );
    }                completion:^(BOOL finished) {
        self.transform = originalTransform;
        if (finished)
            self.font = targetFont;
    }];
}

- (CGFloat)fontSize {

    return self.font.pointSize;
};

@end

Now, the problem with this is that the layout can stutter upon completion, because the view's frame is sized based on the original font all the way until the animation completion, at which point the frame updates to accommodate the target font without animation.

Fixing this problem is a little harder because we need to override intrinsicContentSize. You can do this either by subclassing UILabel or by swizzling the method. I personally swizzle the method, because it lets me keep a generic fontSize property available to all UILabels, but that depends on some library code I can't share here. Here is how you would go about this using subclassing.

Interface:

@interface AnimatableLabel : UILabel

@property(nonatomic) CGFloat fontSize;

@end

Implementation:

@interface AnimatableLabel()

@property(nonatomic) UIFont *targetFont;
@property(nonatomic) UIFont *originalFont;

@end

@implementation AnimatableLabel

- (void)setFontSize:(CGFloat)fontSize {

    CGAffineTransform originalTransform = self.transform;
    self.originalFont = self.font;
    self.targetFont = [self.font fontWithSize:fontSize];
    [self invalidateIntrinsicContentSize];

    [UIView animateWithDuration:0 delay:0 options:0 animations:^{
        self.transform = CGAffineTransformScale( originalTransform,
                fontSize / self.fontSize, fontSize / self.fontSize );
    }                completion:^(BOOL finished) {
        self.transform = originalTransform;

        if (self.targetFont) {
            if (finished)
                self.font = self.targetFont;
            self.targetFont = self.originalFont = nil;
            [self invalidateIntrinsicContentSize];
        }
    }];
}

- (CGFloat)fontSize {

    return self.font.pointSize;
};

- (CGSize)intrinsicContentSize {

    @try {
        if (self.targetFont)
            self.font = self.targetFont;
        return self.intrinsicContentSize;
    }
    @finally {
        if (self.originalFont)
            self.font = self.originalFont;
    }
}

@end

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If you want to animate the text size from another anchor point, here is the Swift 5 solution:

How to apply:

yourLabel.setAnimatedFont(.systemFont(ofSize: 48), duration: 0.2, anchorPointX: 0, anchorPointY: 1)

Extensions:

extension UILabel {
  /// Animate font size from a given anchor point of the label.
  /// - Parameters:
  ///   - duration: Animation measured in seconds
  ///   - anchorPointX: 0 = left, 0.5 = center, 1 = right
  ///   - anchorPointY: 0 = top, 0.5 = center, 1 = bottom
  func setAnimatedFont(_ font: UIFont, duration: TimeInterval, anchorPointX: CGFloat, anchorPointY: CGFloat) {
    guard let oldFont = self.font else { return }

    setAnchorPoint(CGPoint(x: anchorPointX, y: anchorPointY))
    self.font = font

    let scaleFactor = oldFont.pointSize / font.pointSize
    let oldTransform = transform
    transform = transform.scaledBy(x: scaleFactor, y: scaleFactor)
    setNeedsUpdateConstraints()

    UIView.animate(withDuration: duration) {
      self.transform = oldTransform
      self.layoutIfNeeded()
    }
  }
}

extension UIView {
  /// Change the anchor point without moving the view's position.
  /// - Parameters:
  ///   - point: The layer's bounds rectangle.
  func setAnchorPoint(_ point: CGPoint) {
    let oldOrigin = frame.origin
    layer.anchorPoint = point
    let newOrigin = frame.origin

    let translation = CGPoint(x: newOrigin.x - oldOrigin.x, y: newOrigin.y - oldOrigin.y)
    translatesAutoresizingMaskIntoConstraints = true
    center = CGPoint(x: center.x - translation.x, y: center.y - translation.y)
  }
}

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