效果
实现
新建 UILabel 子类，重写部分 UILabel 方法
RYVerticalAlignmentLabel.h
typedef NS_ENUM(NSUInteger, RYTextVerticalAlignment) {
RYTextVerticalAlignmentTop = 0, // 顶部对齐
RYTextVerticalAlignmentMiddle, // 垂直居中
RYTextVerticalAlignmentBottom // 底部对齐
};
IB_DESIGNABLE
@interface RYVerticalAlignmentLabel : UILabel
#if TARGET_INTERFACE_BUILDER
@property (nonatomic, assign) IBInspectable NSUInteger textVerticalAlignment;
#else
@property (nonatomic, assign) RYTextVerticalAlignment textVerticalAlignment;
#endif
@end
RYVerticalAlignmentLabel.m
@implementation RYVerticalAlignmentLabel
/**
设置文本垂直对齐方式后调用 setNeedsDisplay ，系统会自动调用 drawTextInRect
@param textVerticalAlignment 垂直对齐方式枚举类型
*/
- (void)setVerticalAlignment:(RYTextVerticalAlignment)textVerticalAlignment {
_textVerticalAlignment = textVerticalAlignment;
[self setNeedsDisplay];
}
/**
重写父类 textRectForBounds 方法，修改并返回 textRect
@param bounds 文本 bounds
@param numberOfLines 行数
@return 修改后文本 bounds
*/
- (CGRect)textRectForBounds:(CGRect)bounds limitedToNumberOfLines:(NSInteger)numberOfLines {
CGRect textRect = [super textRectForBounds:bounds limitedToNumberOfLines:numberOfLines];
switch (self.textVerticalAlignment) {
case RYTextVerticalAlignmentTop:
textRect.origin.y = bounds.origin.y;
break;
case RYTextVerticalAlignmentBottom:
textRect.origin.y = bounds.origin.y + bounds.size.height - textRect.size.height;
break;
case RYTextVerticalAlignmentMiddle:
default:
textRect.origin.y = bounds.origin.y + (bounds.size.height - textRect.size.height) / 2.0;
}
return textRect;
}
/**
重写父类 drawTextInRect 方法，调用本类 textRectForBounds 方法
@param requestedRect 文本 bounds
*/
-(void)drawTextInRect:(CGRect)requestedRect {
CGRect actualRect = [self textRectForBounds:requestedRect limitedToNumberOfLines:self.numberOfLines];
[super drawTextInRect:actualRect];
}
@end
IBInspectable
IBInspectable关键字，可以使自定义 UIView 的属性出现在 IB 中的 Attributes inspector
RYVerticalAlignmentLabel.h 中为对应属性添加关键字
#if TARGET_INTERFACE_BUILDER
@property (nonatomic, assign) IBInspectable NSUInteger textVerticalAlignment;
#else
@property (nonatomic, assign) RYTextVerticalAlignment textVerticalAlignment;
#endif
在 xib / storyboard 中拖入 UIlabel 对象视图后，修改 Class
效果
IB_DESIGNABLE
IB_DESIGNABLE关键字 可以让自定义 UIView 在 IB 中预览
RYVerticalAlignmentLabel.h 中为类添加关键字
IB_DESIGNABLE
@interface RYVerticalAlignmentLabel : UILabel
参考
