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）

效果如下：

ViewController.h

1 #import <UIKit/UIKit.h>

2 

3 @interface ViewController : UIViewController

4 @end

ViewController.m

 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

KMLabel.h

1 #import <UIKit/UIKit.h>

2 

3 @interface KMLabel : UILabel

4 - (id)initWithTextAlignment:(NSTextAlignment)textAlignment;

5 

6 @end

KMLabel.m

 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