141设置屏幕中文本的横向对齐方式（扩展知识：设置标签行间距）

1 #import <UIKit/UIKit.h>
2 
3 @interface ViewController : UIViewController
4 @end

 1 #import "ViewController.h"
 2 #import "KMLabel.h"
 3 
 4 @interface ViewController ()
 5 - (void)layoutUI;
 6 @end
 7 
 8 @implementation ViewController
 9 
10 - (void)viewDidLoad {
11     [super viewDidLoad];
12     
13     [self layoutUI];
14 }
15 
16 - (void)didReceiveMemoryWarning {
17     [super didReceiveMemoryWarning];
18     // Dispose of any resources that can be recreated.
19 }
20 
21 - (void)layoutUI {
22     self.title = @"设置屏幕中文本的横向对齐方式";
23     
24     CGRect newRect = CGRectMake(20.0, 40.0, 320.0, 160.0);
25     KMLabel *lblLeft = [[KMLabel alloc] initWithTextAlignment:NSTextAlignmentLeft];
26     lblLeft.frame = newRect;
27     lblLeft.textColor = [UIColor blueColor];
28     lblLeft.lineBreakMode = NSLineBreakByWordWrapping;
29     [self.view addSubview:lblLeft];
30     
31     KMLabel *lblCenter = [[KMLabel alloc] initWithTextAlignment:NSTextAlignmentCenter];
32     newRect.origin.y += 170;
33     lblCenter.frame = newRect;
34     lblCenter.textColor = [UIColor brownColor];
35     lblCenter.lineBreakMode = NSLineBreakByWordWrapping;
36     [self.view addSubview:lblCenter];
37     
38     KMLabel *lblRight = [[KMLabel alloc] initWithTextAlignment:NSTextAlignmentRight];
39     newRect.origin.y += 170;
40     lblRight.frame = newRect;
41     lblRight.textColor = [UIColor darkGrayColor];
42     lblRight.lineBreakMode = NSLineBreakByWordWrapping;
43     [self.view addSubview:lblRight];
44 }
45 
46 @end

1 #import <UIKit/UIKit.h>
2 
3 @interface KMLabel : UILabel
4 - (id)initWithTextAlignment:(NSTextAlignment)textAlignment;
5 
6 @end

 1 #import "KMLabel.h"
 2 
 3 @interface KMLabel ()
 4 @end
 5 
 6 @implementation KMLabel
 7 
 8 - (id)initWithTextAlignment:(NSTextAlignment)textAlignment {
 9     if (self = [super init]) {
10         self.textAlignment = textAlignment;
11         self.backgroundColor = [UIColor whiteColor];
12         self.autoresizingMask = UIViewAutoresizingFlexibleTopMargin |
13                                 UIViewAutoresizingFlexibleLeftMargin |
14                                 UIViewAutoresizingFlexibleBottomMargin |
15                                 UIViewAutoresizingFlexibleRightMargin;
16         self.layer.masksToBounds = YES;
17         self.layer.cornerRadius = 10.0;
18         self.layer.borderColor = [UIColor grayColor].CGColor;
19         self.layer.borderWidth = 1.0;
20     }
21     return self;
22 }
23 
24 - (void)drawRect:(CGRect)rect {
25     NSString *strMsg;
26     switch (self.textAlignment) {
27         case NSTextAlignmentLeft: {
28             strMsg = @"左对齐\n左对齐\n左对齐";
29             break;
30         }
31         case NSTextAlignmentCenter: {
32             strMsg = @"居中对齐\n居中对齐\n居中对齐";
33             break;
34         }
35         case NSTextAlignmentRight: {
36             strMsg = @"右对齐\n右对齐\n右对齐";
37             break;
38         }
39         default: {
40             break;
41         }
42     }
43     
44     //进行绘制
45     NSMutableParagraphStyle *paragraphStyle = [[NSParagraphStyle defaultParagraphStyle] mutableCopy];
46     // Set line break mode
47     paragraphStyle.lineBreakMode = self.lineBreakMode;
48     // Set text alignment
49     paragraphStyle.alignment = self.textAlignment;
50     paragraphStyle.lineSpacing = 5.0; //设置行间距
51     
52     NSDictionary *dicAttribute = @{
53                                    NSForegroundColorAttributeName : self.textColor,
54                                    NSFontAttributeName : [UIFont systemFontOfSize:18.0],
55                                    NSBaselineOffsetAttributeName : [NSNumber numberWithFloat:-10.0], //每行内容最顶基线开始垂直偏移量（会增加行间距），正浮点表示上方移动，负浮点表示下方移动
56                                    NSParagraphStyleAttributeName : paragraphStyle
57                                    };
58     
59     [strMsg drawInRect:rect withAttributes:dicAttribute];
60     //效果跟上面语句差不多；但对宽度和垂直布局高度不能限制，而且横行对齐方式也不能限制，只能一行显示内容
61     //[strMsg drawAtPoint:rect.origin withAttributes:dicAttribute]; //The width (height for vertical layout) of the rendering area is unlimited, unlike drawInRect:withAttributes:, which uses a bounding rectangle. As a result, this method renders the text in a single line.
62 }
63 
64 @end