//不重复，只调用一次。timer运行一次就会自动停止运行 myTimer = [NSTimer scheduledTimerWithTimeInterval:1.5 target:self selector:@selector(scrollTimer) userInfo:nil repeats:NO];

//每1秒运行一次function方法。

timer = [NSTimer scheduledTimerWithTimeInterval:1.0 target:self selector:@selector(function:) userInfo:nil repeats:YES];

//取消定时器

[timer invalidate]; timer = nil;

//关闭定时器

[myTimer setFireDate:[NSDate distantFuture]];

//开启定时器

[myTimer setFireDate:[NSDate distantPast]];