iOS runtime之--动态修改字体大小

创建NSObject分类，并增加一个可进行“Method交换”的方法。Method交换的本质，其实就是imp指针的交换。系统给我们提供了一个C语言的函数method_exchangeImplementations可以进行交换。流程如下：

1.根据原方法和目标方法的selector，获取方法的method。如果是类方法用class_getClassMethod获取method，如是对象方法则用class_getInstanceMethod获取method

2.获取到method后，调用method_exchangeImplementations函数进行两个method的imp指针的交换

#import "NSObject+Category.h"
#import 

@implementation NSObject (Category)

/**
 @brief 方法替换
 @param originselector 替换的原方法
 @param swizzleSelector 替换后的方法
 @param isClassMethod 是否为类方法，YES为类方法，NO为对象方法
 */
+ (void)runtimeReplaceFunctionWithSelector:(SEL)originselector
                           swizzleSelector:(SEL)swizzleSelector
                             isClassMethod:(BOOL)isClassMethod
{
    Method originMethod;
    Method swizzleMethod;
if (isClassMethod == YES) {
        originMethod = class_getClassMethod([self class], originselector);
        swizzleMethod = class_getClassMethod([self class], swizzleSelector);
    }else{
        originMethod = class_getInstanceMethod([self class], originselector);
        swizzleMethod = class_getInstanceMethod([self class], swizzleSelector);
    }
    method_exchangeImplementations(originMethod, swizzleMethod);
}
@end

UIFont设置font的类方法替换

#import "UIFont+Category.h"
#import "NSObject+Category.h"

@implementation UIFont (Category)

//+(void)load方法会在main函数之前自动调用，不需要手动调用
+ (void)load
{
    //交换systemFontOfSize: 方法
    [[self class] runtimeReplaceFunctionWithSelector:@selector(systemFontOfSize:) swizzleSelector:@selector(customSystemFontOfSize:) isClassMethod:YES];
    //交换fontWithName:size:方法
    [[self class] runtimeReplaceFunctionWithSelector:@selector(fontWithName:size:) swizzleSelector:@selector(customFontWithName:size:) isClassMethod:YES];
}

//自定义的交换方法
+ (UIFont *)customSystemFontOfSize:(CGFloat)fontSize
{
    CGFloat size = [UIFont transSizeWithFontSize:fontSize];
    ///这里并不会引起递归，方法交换后，此时调用customSystemFontOfSize方法，其实是调用了原来的systemFontOfSize方法
    return [UIFont customSystemFontOfSize:size];
}

//自定义的交换方法
+ (UIFont *)customFontWithName:(NSString *)fontName size:(CGFloat)fontSize
{
    CGFloat size = [UIFont transSizeWithFontSize:fontSize];
    return [UIFont customFontWithName:fontName size:size];
}

///屏幕宽度大于320的，字体加10。(此处可根据不同的需求设置字体大小)
+ (CGFloat)transSizeWithFontSize:(CGFloat)fontSize
{
    CGFloat size = fontSize;
    CGFloat width = [UIFont getWidth];
    if (width > 320) {
        size += 10;
    }
    return size;
}

///获取竖屏状态下的屏幕宽度
+ (CGFloat)getWidth
{
    for (UIScreen *windowsScenes in UIApplication.sharedApplication.connectedScenes) {
        UIWindowScene * scenes = (UIWindowScene *)windowsScenes;
        UIWindow *window = scenes.windows.firstObject;
        if (scenes.interfaceOrientation == UIInterfaceOrientationPortrait) {
            return window.frame.size.width;
        }
        return window.frame.size.height;
    }
    return 0;
}

@end

至此就实现了，动态改变字体大小的目的，那xib和storyboard拖的控件怎么修改呢？我们接着看

动态修改xib和storyboard控件的字体大小

#import "UILabel+Category.h"
#import "NSObject+Category.h"

@implementation UILabel (Category)

+ (void)load
{
    [[self class] runtimeReplaceFunctionWithSelector:@selector(initWithCoder:) swizzleSelector:@selector(customInitWithCoder:) isClassMethod:NO];
}

- (instancetype)customInitWithCoder:(NSCoder *)coder
{
if ([self customInitWithCoder:coder]) {
///此时调用fontWithName:size:方法，实际上调用的是方法交换后的customFontWithName:size:
        self.font = [UIFont fontWithName:self.font.familyName size:self.font.pointSize];
    }
    return self;
}

@end

#import "UIButton+Category.h"
#import "NSObject+Category.h"

@implementation UIButton (Category)

+ (void)load
{
    [[self class] runtimeReplaceFunctionWithSelector:@selector(initWithCoder:) swizzleSelector:@selector(customInitWithCoder:) isClassMethod:NO];
}

- (instancetype)customInitWithCoder:(NSCoder *)coder
{
if ([self customInitWithCoder:coder]) {
if (self.titleLabel != nil) {
            self.titleLabel.font = [UIFont fontWithName:self.titleLabel.font.familyName size:self.titleLabel.font.pointSize];
        }
    }
return self;
}

@end

#import "UITextField+Category.h"
#import "NSObject+Category.h"

@implementation UITextField (Category)

+ (void)load
{
    [[self class] runtimeReplaceFunctionWithSelector:@selector(initWithCoder:) swizzleSelector:@selector(customInitWithCoder:) isClassMethod:NO];
}

- (instancetype)customInitWithCoder:(NSCoder *)coder
{
if ([self customInitWithCoder:coder]) {
        self.font = [UIFont fontWithName:self.font.familyName size:self.font.pointSize];
    }
return self;
}

@end

#import "UITextView+Category.h"
#import "NSObject+Category.h"

@implementation UITextView (Category)

+ (void)load
{
    [[self class] runtimeReplaceFunctionWithSelector:@selector(initWithCoder:) swizzleSelector:@selector(customInitWithCoder:) isClassMethod:NO];
}

- (instancetype)customInitWithCoder:(NSCoder *)coder
{
if ([self customInitWithCoder:coder]) {
        self.font = [UIFont fontWithName:self.font.familyName size:self.font.pointSize];
    }
return self;
}

@end