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 *)sender22 {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timeRun29         30     } else {31         32         [_timer invalidate];33         //关闭时间器34     }35 }36 37 - (void)timeRun38 {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view44     45     label.text = [NSString stringWithFormat:@"%d%02d",row,num];46 }