The actual font used for the purpose described by a text style can vary based on a number of dynamic considerations,including the user’s content size category preference,which is represented by the UIApplication property preferredContentSizeCategory.

我注意到属性preferredContentSizeCategory响应于设置中的文本大小而改变.

It’s also important to observe the UIContentSizeCategoryDidChangeNotification so that you can re-layout the text when the user changes the content size category. When your app receives that notification,it should send the invalidateIntrinsicContentSize message to views positioned by Auto Layout or send setNeedsLayout to user interface elements positioned manually. And it should invalidate preferred fonts or font descriptors and acquire new ones as needed.

所以,我的想法是观察适当的通知,根据preferredContentSizeCategory属性计算大小增量,并将增量应用于文本视图的默认字体大小(以IB或编程方式设置).

PreferredFontLabel.h

@interface PreferredFontLabel : UILabel

@property (nonatomic) UIFontDescriptor *defaultFontDescriptor;

@end

PreferredFontLabel.m

#import "PreferredFontLabel.h"
#import "UIApplication+ContentSize.h"

@implementation PreferredFontLabel

- (id)init
{
    self = [super init];
    if (self) {
        [self setup];
    }
    return self;
}

- (id)initWithFrame:(CGRect)frame
{
    self = [super initWithFrame:frame];
    if (self) {
        [self setup];
    }
    return self;
}

- (id)initWithCoder:(NSCoder *)aDecoder
{
    self = [super initWithCoder:aDecoder];
    if (self) {
        [self setup];
    }
    return self;
}

- (void)setup
{
    self.defaultFontDescriptor = self.font.fontDescriptor;

    [[NSNotificationCenter defaultCenter]
     addObserver:self
     selector:@selector(contentSizeCategoryDidChange)
     name:UIContentSizeCategoryDidChangeNotification
     object:nil];

    [self contentSizeCategoryDidChange];
}

- (void)setDefaultFontDescriptor:(UIFontDescriptor *)defaultFontDescriptor
{
    _defaultFontDescriptor = defaultFontDescriptor;

    [self contentSizeCategoryDidChange];
}

- (void)contentSizeCategoryDidChange
{
    CGFloat preferredSize = [self.defaultFontDescriptor.fontAttributes[UIFontDescriptorSizeAttribute] floatValue];
    preferredSize += [UIApplication sharedApplication].contentSizeDelta;

    self.font = [UIFont fontWithDescriptor:self.defaultFontDescriptor size:preferredSize];
    [self invalidateIntrinsicContentSize];
}

- (void)dealloc
{
    [[NSNotificationCenter defaultCenter] removeObserver:self name:UIContentSizeCategoryDidChangeNotification object:nil];
}

@end

UIApplication ContentSize.h

@interface UIApplication (ContentSize)

@property (nonatomic,readonly) NSInteger contentSizeDelta;

@end

UIApplication ContentSize.m

#import "UIApplication+ContentSize.h"

@implementation UIApplication (ContentSize)

- (NSInteger)contentSizeDelta
{
    static NSArray *contentSizeCategories;
    static dispatch_once_t onceToken;
    dispatch_once(&onceToken,^{
        contentSizeCategories = @[UIContentSizeCategoryExtraSmall,UIContentSizeCategorySmall,UIContentSizeCategoryMedium,UIContentSizeCategoryLarge,UIContentSizeCategoryExtraLarge,UIContentSizeCategoryExtraExtraLarge,UIContentSizeCategoryExtraExtraExtraLarge
                                  UIContentSizeCategoryAccessibilityMedium,UIContentSizeCategoryAccessibilityLarge,UIContentSizeCategoryAccessibilityExtraLarge,UIContentSizeCategoryAccessibilityExtraExtraLarge,UIContentSizeCategoryAccessibilityExtraExtraExtraLarge];
    });

    // assume UIContentSizeCategoryLarge is default category
    NSInteger contentSizeDelta = [contentSizeCategories indexOfObject:self.preferredContentSizeCategory];

    if(contentSizeDelta != NSNotFound) {
        contentSizeDelta -= [contentSizeCategories indexOfObject:UIContentSizeCategoryLarge];

        return contentSizeDelta;
    } else {
        return 0;
    }
}

@end

我添加了归因字符串支持,演示可在GitHub