随机数

一个小小的随机数工具。。。。。。。
 1 self.view.backgroundColor = [UIColor yellowColor];
 2     
 3     UILabel *label = [[UILabel alloc] initWithFrame:CGRectMake(40, 40, 240, 60)];
 4     label.font = [UIFont boldSystemFontOfSize:30];
 5     label.text = @"点击开始随机";
 6     label.backgroundColor = [UIColor grayColor];
 7     label.textAlignment = NSTextAlignmentCenter;
 8     label.tag = 1;
 9     [self.view addSubview:label];
10     [label release];
11     
12     UIButton *btn = [UIButton buttonWithType:UIButtonTypeCustom];
13     btn.frame = CGRectMake(120, 180, 80, 40);
14     btn.backgroundColor = [UIColor grayColor];
15     [btn setTitle:@"开始" forState:UIControlStateNormal];
16     [btn setTitle:@"停止" forState:UIControlStateSelected];
17     [btn addTarget:self action:@selector(btnClick:) forControlEvents:UIControlEventTouchUpInside];
18     [self.view addSubview:btn];
19 }
20 
21 - (void)btnClick:(UIButton *)sender
22 {
23     sender.selected = !sender.selected;
24     
25     if (sender.selected) {
26         
27         _timer = [NSTimer scheduledTimerWithTimeInterval:0.01 target:self selector:@selector(timeRun) userInfo:nil repeats:YES];
28         //启动时间器，让self每隔0.01秒执行一次timeRun
29         
30     } else {
31         
32         [_timer invalidate];
33         //关闭时间器
34     }
35 }
36 
37 - (void)timeRun
38 {
39     int row = arc4random_uniform(8)+1;
40     int num = arc4random_uniform(11)+1;
41     
42     UILabel *label = (UILabel *)[self.view viewWithTag:1];
43     //通过tag找view
44     
45     label.text = [NSString stringWithFormat:@"%d%02d",row,num];
46 }