2021年的正确答案。语法改变了。

12岁的答案(甚至是对它的编辑)是坏的。

它只是:

let _font = UIFont.systemFont(ofSize: 10)
UISegmentedControl.appearance()
 .setTitleTextAttributes([NSAttributedString.Key.font: _font], for: .normal)

你很可能会想要正确地改变高度，而你在它:

import UIKit

class SmallerSegmentedControl: UISegmentedControl {

    override init(frame: CGRect) {
        super.init(frame: frame)
        common()
    }

    required init?(coder aDecoder: NSCoder) {
        super.init(coder: aDecoder)
        common()
    }

    func common() {
        let _font = UIFont.systemFont(ofSize: 10)
        UISegmentedControl.appearance()
         .setTitleTextAttributes([NSAttributedString.Key.font: _font], for: .normal)
    }

    override var intrinsicContentSize:CGSize {
        var s = super.intrinsicContentSize
        s.height = 24
        return s
    }

}

另一种选择是对控件应用转换。然而，它将缩小一切，包括控制边界。

segmentedControl.transform = CGAffineTransformMakeScale(.6f, .6f);

丹尼尔指给我正确的路。我是这样用的-

float scaleFactor = 0.8f;

UISegmentedControl *segmentedControl = [[UISegmentedControl alloc]
initWithFrame:CGRectMake(10, 70, 300/scaleFactor,35)];

[segmentedControl insertSegmentWithTitle:@"..." atIndex:0 animated:NO];
[segmentedControl insertSegmentWithTitle:@"..." atIndex:1 animated:NO];
[segmentedControl insertSegmentWithTitle:@"..." atIndex:2 animated:NO];

segmentedControl.transform = CGAffineTransformMakeScale(scaleFactor, 1);
CGPoint segmentedControlCenter = segmentedControl.center;
segmentedControlCenter.x = self.center.x;
segmentedControl.center = segmentedControlCenter;

// Set font-size and font-femily the way you want
UIFont *objFont = [UIFont fontWithName:@"DroidSans" size:18.0f];

// Add font object to Dictionary
NSDictionary *dictAttributes = [NSDictionary dictionaryWithObject:objFont forKey:NSFontAttributeName];

// Set dictionary to the titleTextAttributes
[yourSegment setTitleTextAttributes:dictAttributes forState:UIControlStateNormal];

如果您有任何疑问，请联系我。

在iOS 5.0+中使用Appearance API:

[[UISegmentedControl appearance] setTitleTextAttributes:[NSDictionary dictionaryWithObjectsAndKeys:[UIFont fontWithName:@"STHeitiSC-Medium" size:13.0], UITextAttributeFont, nil] forState:UIControlStateNormal];

链接: http://developer.apple.com/library/ios/#documentation/UIKit/Reference/UIAppearance_Protocol/Reference/Reference.html#//apple_ref/doc/uid/TP40010906

http://www.raywenderlich.com/4344/user-interface-customization-in-ios-5

斯威夫特风格:

UISegmentedControl.appearance().setTitleTextAttributes(NSDictionary(objects: [UIFont.systemFontOfSize(14.0)], forKeys: [NSFontAttributeName]), forState: UIControlState.Normal)