IOS 设置定时器

IOS 设置定时器  自动滚动视图 定时发送坐标信息 即时显示 时钟

NSTimer *timer;
- (void)start
{//1second 调用一次
    timer = [NSTimer scheduledTimerWithTimeInterval:1.0 target:self selector:@selector(updateClock:) userInfo:nil repeats:YES];
}
-(NSString *)updateClock:(NSTimer *)theTimer //精确到分系统时间
{
    NSDate * senddate=[NSDate date];
    
    NSDateFormatter *dateformatter=[[NSDateFormatter alloc] init];
    
    //  [dateformatter setDateFormat:@"ss:SS"];//hh:mm:ss:SSS
    [dateformatter setDateFormat:@"hh:mm"];
    NSString * locationString=[dateformatter stringFromDate:senddate];
   // NSLog(@"==%@==",locationString);
    label_System_hour.text=locationString;
    return locationString;
}

- (void)stop
{
    [timer invalidate];
    timer = nil;
}