UILabel文本垂直頂部對齊的方法

也不知道爲何UILabel自己沒有提供文本垂直頂部對齊的方法，真的有點暈。咱們建立一個簡單的UILabel來看看：

[box type="info"]

UILabel *myLabel = [[UILabel alloc]initWithFrame:CGRectMake(10, 10, 300, 100)];

[myLabel setText:@"蘋果iOS(iphone Operation System)是由蘋果公司開發的手持設備操做系統。蘋果公司最先於2007年1月9日的Macworld大會上公佈這個系統，最初是設計給iPhone使用的"];

[myLabel setFont:[UIFont fontWithName:@"Arial" size:14.0]];

[myLabel setBackgroundColor:[UIColor blueColor]];

[myLabel setTextColor:[UIColor whiteColor]];

[self.view addSubview:myLabel];

[/box]

在ios模擬器上看到的效果以下圖：

 

這顯然不是咱們要的效果，咱們再添加一行代碼：

myLabel.numberOfLines = 0;

結果是：

 

顯示有點正常了，但如何使文字頂部對齊呢？

實現代碼：

[box type="info"]

UILabel *myLabel = [[UILabel alloc]init];//WithFrame:CGRectMake(10, 10, 300, 100)];

 

UIFont *strFont = [UIFont fontWithName:@"Arial" size:14.0];

 

[myLabel setFont:strFont];

[myLabel setBackgroundColor:[UIColor blueColor]];

[myLabel setTextColor:[UIColor whiteColor]];

myLabel.numberOfLines = 0;

 

CGSize maximumSize = CGSizeMake(300, 999);

NSString *string = @」蘋果iOS(iphone Operation System)是由蘋果公司開發的手持設備操做系統。蘋果公司最先於2007年1月9日的Macworld大會上公佈這個系統，最初是設計給iPhone使用的」;

CGSize stringSize = [string sizeWithFont:strFont

constrainedToSize:maximumSize

lineBreakMode:myLabel.lineBreakMode];

[myLabel setText:string];

CGRect strFrame = CGRectMake(10, 10, 300, stringSize.height);

myLabel.frame = strFrame;

[self.view addSubview:myLabel];

 

[/box]

運行結果以下圖：

 

盆友們，若是有更好的方法使UILabel垂直頂部對齊，必定要分享出來哦

 

在iOS中默認的UILabel中的文字在豎直方向上只能居中對齊，從UILabel繼承了一個新類，實現了居上對齊，居中對齊，居下對齊。具體以下：

//
//  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

 

在使用時：

 

lbl_mylabel = [[myUILabel alloc] initWithFrame:CGRectMake(20, 50, 150, 600)];
UIColor *color = [UIColor colorWithPatternImage:[UIImage imageNamed:@"halfTransparent.png"]];//使用半透明圖片做爲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];