iOS中UILabel设置居上对齐、居中对齐、居下对齐及文字置顶显示

2020-07-26 02:35:11

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iOS中UILabel设置居上对齐、居中对齐、居下对齐

在iOS中默认的UILabel中的文字在竖直方向上只能居中对齐，博主参考国外网站，从UILabel继承了一个新类，实现了居上对齐，居中对齐，居下对齐。

具体如下：

// // 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

// // 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

在使用时：

lbl_mylabel = [[myUILabel alloc] initWithFrame:CGRectMake(20, 50, 150, 600)]; UIColor *color = [UIColor colorWithPatternImage:[UIImage imageNamed:@"halfTransparent.png"]];//使用半透明图片作为label的背景色 lbl_mylabel.backgroundColor = color; lbl_mylabel.textAlignment = UITextAlignmentLeft; lbl_mylabel.textColor = UIColor.whiteColor; lbl_mylabel.lineBreakMode = UILineBreakModeWordWrap; lbl_mylabel.numberOfLines = 0; [lbl_mylabel setVerticalAlignment:VerticalAlignmentTop]; [self addSubview:lbl_mylabel];

UILabel 让文字置顶显示

我们经常会遇到将Label中文字置顶，也就是将文字顶到Lable框的最顶端显示的需求，UILabel是无法对内容文字进行置顶处理的，所以，如果我们不对Label加以额外的设置，就会出现如下情况：

置顶前

解决办法：我们可以通过sizeToFit方法解决它：

- (void)viewDidLoad { [super viewDidLoad]; UILabel *label = [[UILabel alloc] initWithFrame:CGRectMake((self.view.bounds.size.width - 200)/2, 100, 200, 150)]; label.backgroundColor = [UIColor yellowColor]; NSString *labelText = @"我不知道如何置顶，谁来告诉我？"; [label setText:labelText]; [label setNumberOfLines:0];   //让内容置顶 [label sizeToFit]; [self.view addSubview:label];}

效果图：