首先在Xcode中新建.h文件,將以下代碼複製進去
//
// myUILabel.h
//
//
// Created by yexiaozi_007 on 3/4/13.
// Copyright (c) 2013 yexiaozi_007. All rights reserved.
//
#import <UIKit/UIKit.h>
typedef enum
{
VerticalAlignmentTop = 0, // default
VerticalAlignmentMiddle,
VerticalAlignmentBottom,
} VerticalAlignment;
@interface myUILabel : UILabel
{
@private
VerticalAlignment _verticalAlignment;
}
@property (nonatomic) VerticalAlignment verticalAlignment;
@end
再新建一個.m文件,拷入以下代碼
//
// myUILabel.m
//
//
// Created by yexiaozi_007 on 3/4/13.
// Copyright (c) 2013 yexiaozi_007. All rights reserved.
//
#import "myUILabel.h"
@implementation myUILabel
@synthesize verticalAlignment = verticalAlignment_;
- (id)initWithFrame:(CGRect)frame {
if (self = [super initWithFrame:frame]) {
self.verticalAlignment = VerticalAlignmentMiddle;
}
return self;
}
- (void)setVerticalAlignment:(VerticalAlignment)verticalAlignment {
verticalAlignment_ = verticalAlignment;
[self setNeedsDisplay];
}
- (CGRect)textRectForBounds:(CGRect)bounds limitedToNumberOfLines:(NSInteger)numberOfLines {
CGRect textRect = [super textRectForBounds:bounds limitedToNumberOfLines:numberOfLines];
switch (self.verticalAlignment) {
case VerticalAlignmentTop:
textRect.origin.y = bounds.origin.y;
break;
case VerticalAlignmentBottom:
textRect.origin.y = bounds.origin.y + bounds.size.height - textRect.size.height;
break;
case VerticalAlignmentMiddle:
// 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 = [self textRectForBounds:requestedRect limitedToNumberOfLines:self.numberOfLines];
[super drawTextInRect:actualRect];
}
@end
如果這是你導入的第一個.m文件Xcode會提示你要不要創建Bridging-Header,選Ok
在新創建的Bridging-Header文件裏拷入下方代碼
#import "myUILabel.h"
然後右鍵拖動Label或者按住Control鍵左鍵拖動連線到Label所在的父View的Class中生成Outlet,如果之前已經連線好,則改完Custom Class後,將連線生成代碼中的UILabel改爲myUILabel,示意圖如下
然後就可以調用該label的類方法
label.verticalAlignment = VerticalAlignmentBottom
按上方代碼可以實現居下對其,居中 居上 分別將代碼中的Bottom改爲Middle和Top,默認爲居上