UIlabel顶格

新建一个继承uilabel的类，用它定义label，设置属性即可。

#import <UIKit/UIKit.h>

typedefenum : NSUInteger {

    VerticalAlignmentTop =0, // default

    VerticalAlignmentMiddle,

    VerticalAlignmentBottom,

} VerticalAlignment;

@interface MyLabel :UILabel

@property (nonatomic)VerticalAlignment verticalAlignment;

@end

#import "MyLabel.h"

@implementation MyLabel

/*

// Only override drawRect: if you perform custom drawing.

// An empty implementation adversely affects performance during animation.

- (void)drawRect:(CGRect)rect {

    // Drawing code

}

*/

- (id)initWithFrame:(CGRect)frame {

   if (self = [superinitWithFrame:frame]) {

        self.verticalAlignment =VerticalAlignmentMiddle;

    }

    return self;

}

- (void)setVerticalAlignment:(VerticalAlignment)verticalAlignment {

   _verticalAlignment = verticalAlignment;

    [selfsetNeedsDisplay];

}

- (CGRect)textRectForBounds:(CGRect)bounds limitedToNumberOfLines:(NSInteger)numberOfLines {

   CGRect textRect = [supertextRectForBounds:bounds limitedToNumberOfLines:numberOfLines];

    switch (self.verticalAlignment) {

        caseVerticalAlignmentTop:

            textRect.origin.y = bounds.origin.y;

           break;

        caseVerticalAlignmentBottom:

            textRect.origin.y = bounds.origin.y + bounds.size.height - textRect.size.height;

           break;

        caseVerticalAlignmentMiddle:

            // Fall through.

       default:

            textRect.origin.y = bounds.origin.y + (bounds.size.height - textRect.size.height) /2.0;

    }

   return textRect;

}

-(void)drawTextInRect:(CGRect)requestedRect {

   CGRect actualRect = [selftextRectForBounds:requestedRect limitedToNumberOfLines:self.numberOfLines];

    [superdrawTextInRect:actualRect];

}

@end

注意storyboard中label的类要绑定，牵线的属性也要改成自定义的类。

实现：

- (void)awakeFromNib{

    [self.titleLabelsetVerticalAlignment:VerticalAlignmentTop];

}