实现原理比较简单,这里不做过多介绍.

#import "ViewController.h"    @interface ViewController ()  @property (weak, nonatomic) IBOutlet UILabel *titleLabel;  @property (copy , nonatomic)NSString *contentStr;    @end

- (void)viewDidLoad  {      [super viewDidLoad];        NSThread *thread = [[NSThread alloc]initWithTarget:self selector:@selector(animationLabel) object:nil];      [thread start];      self.contentStr = @"人生最宝贵的是生命，生命属于人只有一次。一个人的生命应当这样度过：当他回忆往事的时候，他不致因虚度年华而悔恨，也不致因碌碌无为而羞愧；在临死的时候，他能够说：“我的整个生命和全部精力，都已献给世界上最壮丽的事业——为人类的解放而斗争。”";          }

- (void)animationLabel  {      for (NSInteger i = 0; i < self.contentStr.length; i++)      {          [self performSelectorOnMainThread:@selector(refreshUIWithContentStr:) withObject:[self.contentStr substringWithRange:NSMakeRange(0, i+1)] waitUntilDone:YES];          [NSThread sleepForTimeInterval:0.3];      }  }

- (void)refreshUIWithContentStr:(NSString *)contentStr  {      self.titleLabel.text = contentStr;  }

最终效果:

来自：http://blog.csdn.net/qq_31810357/article/details/49486509