UISegmentedControl的扩展，用于设置字体大小。

extension UISegmentedControl {
    @available(iOS 8.2, *)
    func setFontSize(fontSize: CGFloat) {
            let normalTextAttributes: [NSObject : AnyObject]!
            if #available(iOS 9.0, *) {
                normalTextAttributes = [
                    NSFontAttributeName: UIFont.monospacedDigitSystemFontOfSize(fontSize, weight: UIFontWeightRegular)
                ]
            } else {
                normalTextAttributes = [
                    NSFontAttributeName: UIFont.systemFontOfSize(fontSize, weight: UIFontWeightRegular)
                ]
            }

        self.setTitleTextAttributes(normalTextAttributes, forState: .Normal)
    }
 }

斯威夫特4

let font = UIFont.systemFont(ofSize: 16)
UISegmentedControl.setTitleTextAttributes([NSFontAttributeName: font], for: .normal)

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);

UISegmentedControl的扩展，用于设置字体大小。

extension UISegmentedControl {
    @available(iOS 8.2, *)
    func setFontSize(fontSize: CGFloat) {
            let normalTextAttributes: [NSObject : AnyObject]!
            if #available(iOS 9.0, *) {
                normalTextAttributes = [
                    NSFontAttributeName: UIFont.monospacedDigitSystemFontOfSize(fontSize, weight: UIFontWeightRegular)
                ]
            } else {
                normalTextAttributes = [
                    NSFontAttributeName: UIFont.systemFontOfSize(fontSize, weight: UIFontWeightRegular)
                ]
            }

        self.setTitleTextAttributes(normalTextAttributes, forState: .Normal)
    }
 }

// 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。

这是为objective - c添加你的分段控件名称来代替mysegmentedcontrol

UIFont *font = [UIFont systemFontOfSize:11.0f];

NSDictionary *attributes = [NSDictionary dictionaryWithObject:font
                                                            forKey:UITextAttributeFont];

[mySegmentedcontrol setTitleTextAttributes:attributes                                    forState:UIControlStateNormal];

希望能有所帮助