IOS 中将NSInteger类型的秒，转换为00:00:00格式

NSInteger secCount = [timeDate timeIntervalSinceDate:lastStartTime];
self.contractions.FrequencySec = [NSNumber numberWithInt:secCount];

NSString *tmphh = [NSString stringWithFormat:@"%d",secCount/3600];
if ([tmphh length] == 1)
{
tmphh = [NSString stringWithFormat:@"0%@",tmphh];
}
NSString *tmpmm = [NSString stringWithFormat:@"%d",(secCount/60)%60];
if ([tmpmm length] == 1)
{
tmpmm = [NSString stringWithFormat:@"0%@",tmpmm];
}
NSString *tmpss = [NSString stringWithFormat:@"%d",secCount%60];
if ([tmpss length] == 1)
{
tmpss = [NSString stringWithFormat:@"0%@",tmpss];
}
self.contractions.FrequencyStr = [NSString stringWithFormat:@"%@:%@:%@",tmphh,tmpmm,tmpss];
self.frequencyLabel.text = self.contractions.FrequencyStr;