iOS字体适配

最近项目中，UI要求字体适配屏幕，根据屏幕大小来决定字体大小，因为在大屏手机上字体确实显得小了。因为之前没做过，所以今天抽空研究了一下，还是有一些值得记录的内容

1. 通过代码设置的字体适配
   代码设置字体，因为已经写过很多地方，不可能一个一个的改，所以使用了method swizzle的方法，用自定义方法替换系统设置字体的方法

   //UIFont+Custom.m
   + (void)load {
       static dispatch_once_t fontToken;
       dispatch_once(&fontToken, ^{
           [self exchangeClassMethod:@selector(systemFontOfSize:) withMethod:@selector(adapterSystemFontOfSize:)];
           [self exchangeClassMethod:@selector(systemFontOfSize:weight:) withMethod:@selector(adapterSystemFontOfSize:weight:)];
           [self exchangeClassMethod:@selector(fontWithName:size:) withMethod:@selector(adapterFontWithName:size:)];
       });
   }
   
   + (UIFont *)adapterSystemFontOfSize:(CGFloat)size {
       CGFloat adapterSize = [self getAdapterFontSize:size];
       return [self adapterSystemFontOfSize:adapterSize];
   }
   
   + (UIFont *)adapterSystemFontOfSize:(CGFloat)size weight:(UIFontWeight)weight {
       CGFloat adapterSize = [self getAdapterFontSize:size];
       return [self adapterSystemFontOfSize:adapterSize weight:weight];
   }
   
   + (UIFont *)adapterFontWithName:(NSString *)name size:(CGFloat)size {
       CGFloat adapterSize = [self getAdapterFontSize:size];
       return [self adapterFontWithName:name size:adapterSize];
   }
   
   //获取适配后的字体大小
   + (CGFloat)getAdapterFontSize:(CGFloat)size {
       CGFloat adapterSize = size;
       if (IS_NOTCH_SCREEN) {
           adapterSize = size + 2;
       } else if (IS_BIG_SCREEN) {
           adapterSize = size + 1;
       } else {
           adapterSize = size;
       }
   //    NSLog(@"size %f, adapter %f", size, adapterSize);
       return adapterSize;
   }
   

2. 通过xib/storyboard设置的字体适配
   xib/storyboard里面设置的字体都是固定大小的，想要适配不同的屏幕，可以通过两种方式：1.手动设置字体大小，因为上面我们已经替换了uifont的方法，所以在设置的时候就会适配。2.重写awakefromnib方法，在初始化完成后设置自动字体大小。因为已经写了很多页面，不好一个一个修改，所以这里用第二种方法实现

   //UILabel+Custom.m
   + (void)load {
       static dispatch_once_t fontToken;
       dispatch_once(&fontToken, ^{
           [self exchangeInstanceMethod:@selector(awakeFromNib) withMethod:@selector(awakeFromNibAndSetFont)];
       });
   }
   
   - (void)awakeFromNibAndSetFont {
       CGFloat adapterSize = [UIFont getAdapterFontSize:self.font.pointSize];
       self.font = [UIFont fontWithDescriptor:self.font.fontDescriptor size:adapterSize];
       [self awakeFromNibAndSetFont];
   }
   

   同理需要对其他的可以设置字体的空间添加分类，替换awakefromnib方法。我这里使用了UILabel和UITextField两个分类

3. 遇到的问题及解决
   因为之前写的都是交换实例方法，没写过类方法的交换，所以我直接按着实例方法来写，发现交换不了

   + (void)exchangeClassMethod:(SEL)originSelector withMethod:(SEL)newSelector {
       Class class = self;
       Method originMethod = class_getClassMethod(class, originSelector);
       Method newMethod = class_getClassMethod(class, newSelector);
   
       BOOL addSuccess = class_addMethod(class, originSelector, method_getImplementation(newMethod), method_getTypeEncoding(newMethod));
       if (addSuccess) {
           class_replaceMethod(class, newSelector, method_getImplementation(originMethod), method_getTypeEncoding(originMethod));
       } else {
           method_exchangeImplementations(originMethod, newMethod);
       }
   }
   

   原来是因为添加方法的时候，添加到了类上，而类方法是在元类里面的，所以导致添加成功但是替换之后没效果。在添加方法的时候改成添加到元类上即可。 因为用到的地方比较多所以对方法替换进行了简单的封装，并添加到NSObject的分类中

   //NSObject+Custom.m
   + (void)exchangeClassMethod:(SEL)originSelector withMethod:(SEL)newSelector {
       Class class = self;
       Method originMethod = class_getClassMethod(class, originSelector);
       Method newMethod = class_getClassMethod(class, newSelector);
   
       //类方法需要添加到类对象的父类-元类上
       BOOL addSuccess = class_addMethod(object_getClass(class), originSelector, method_getImplementation(newMethod), method_getTypeEncoding(newMethod));
       if (addSuccess) {
           class_replaceMethod(class, newSelector, method_getImplementation(originMethod), method_getTypeEncoding(originMethod));
       } else {
           method_exchangeImplementations(originMethod, newMethod);
       }
   }
   
   + (void)exchangeInstanceMethod:(SEL)originSelector withMethod:(SEL)newSelector {
       Class class = self;
       Method originMethod = class_getInstanceMethod(class, originSelector);
       Method newMethod = class_getInstanceMethod(class, newSelector);
   
       BOOL addSuccess = class_addMethod(class, originSelector, method_getImplementation(newMethod), method_getTypeEncoding(newMethod));
       if (addSuccess) {
           class_replaceMethod(class, newSelector, method_getImplementation(originMethod), method_getTypeEncoding(originMethod));
       } else {
           method_exchangeImplementations(originMethod, newMethod);
       }
   }
   

4. 参考链接

   • iOS交换类方法
   • 适配xib和storyboard字体