Dynamically changing font size of UILabel

Here is the fill code of a UILabel subclass that implements animated font size change:

@interface SNTextLayer : CATextLayer

@end

@implementation SNTextLayer

- (void)drawInContext:(CGContextRef)ctx {
// We override this to make text appear at the same vertical positon as in UILabel
// (otherwise it's shifted tdown)
CGFloat height = self.bounds.size.height;
float fontSize = self.fontSize;
// May need to adjust this somewhat if it's not aligned perfectly in your implementation
float yDiff = (height-fontSize)/2 - fontSize/10;

CGContextSaveGState(ctx);
CGContextTranslateCTM(ctx, 0.0, yDiff);
[super drawInContext:ctx];
CGContextRestoreGState(ctx);
}

@end

@interface SNAnimatableLabel ()

@property CATextLayer* textLayer;

@end

@interface SNAnimatableLabel : UILabel

- (void)animateFontToSize:(CGFloat)fontSize withDuration:(double)duration;

@end



@implementation SNAnimatableLabel


- (void)awakeFromNib {
[super awakeFromNib];
_textLayer = [SNTextLayer new];
_textLayer.backgroundColor = self.backgroundColor.CGColor;
_textLayer.foregroundColor = self.textColor.CGColor;
_textLayer.font = CGFontCreateWithFontName((CFStringRef)self.font.fontName);
_textLayer.frame = self.bounds;
_textLayer.string = self.text;
_textLayer.fontSize = self.font.pointSize;
_textLayer.contentsScale = [UIScreen mainScreen].scale;
[_textLayer setPosition: CGPointMake(CGRectGetMidX(_textLayer.frame), CGRectGetMidY(_textLayer.frame))];
[_textLayer setAnchorPoint: CGPointMake(0.5, 0.5)];
[_textLayer setAlignmentMode: kCAAlignmentCenter];
self.textColor = self.backgroundColor;
// Blend text with background, so that it doens't interfere with textlayer text
[self.layer addSublayer:_textLayer];
self.layer.masksToBounds = NO;
}

- (void)setText:(NSString *)text {
_textLayer.string = text;
super.text = text;
}

- (void)layoutSubviews {
[super layoutSubviews];
// Need to enlarge the frame, otherwise the text may get clipped for bigger font sizes
_textLayer.frame = CGRectInset(self.bounds, -5, -5);
}

- (void)animateFontToSize:(CGFloat)fontSize withDuration:(double)duration {
[CATransaction begin];
[CATransaction setAnimationDuration:duration];
_textLayer.fontSize = fontSize;
[CATransaction commit];
}

**Single line**- There are two ways, you can simply change.

1- Pragmatically **(Swift 3)**

Just add the following code

yourLabel.numberOfLines = 1;
yourLabel.minimumScaleFactor = 0.7;
yourLabel.adjustsFontSizeToFitWidth = true;

2 - Using UILabel Attributes inspector

i- Select your label- Set number of lines 1.
ii- Autoshrink- Select Minimum Font Scale from drop down
iii- Set Minimum Font Scale value as you wish , I have set 0.7 as in below image. (default is 0.5)



[![enter image description here][1]][1]


[1]:

*Single line:*

factLabel.numberOfLines = 1;
factLabel.minimumFontSize = 8;
factLabel.adjustsFontSizeToFitWidth = YES;

The above code will adjust your text's font size down to (for example) `8` trying to fit your text within the label.
`numberOfLines = 1` is mandatory.

*Multiple lines:*

For `numberOfLines > 1` there is a method to figure out the size of final text through [NSString's sizeWithFont:... UIKit addition](

[To see links please register here]

) methods, for example:

CGSize lLabelSize = [yourText sizeWithFont:factLabel.font
forWidth:factLabel.frame.size.width
lineBreakMode:factLabel.lineBreakMode];

After that you can just resize your label using resulting `lLabelSize`, for example (assuming that you will change only label's height):

factLabel.frame = CGRectMake(factLabel.frame.origin.x, factLabel.frame.origin.y, factLabel.frame.size.width, lLabelSize.height);


**iOS6**

*Single line:*

Starting with iOS6, `minimumFontSize` has been deprecated. The line

factLabel.minimumFontSize = 8.;

can be changed to:

factLabel.minimumScaleFactor = 8./factLabel.font.pointSize;


**iOS7**

*Multiple lines:*

Starting with iOS7, `sizeWithFont` becomes deprecated.
Multiline case is reduced to:

factLabel.numberOfLines = 0;
factLabel.lineBreakMode = NSLineBreakByWordWrapping;
CGSize maximumLabelSize = CGSizeMake(factLabel.frame.size.width, CGFLOAT_MAX);
CGSize expectSize = [factLabel sizeThatFits:maximumLabelSize];
factLabel.frame = CGRectMake(factLabel.frame.origin.x, factLabel.frame.origin.y, expectSize.width, expectSize.height);

**iOS 13 (Swift 5):**

label.adjustsFontSizeToFitWidth = true
label.minimumScaleFactor = 0.5