iOS利用时间戳获得两个字符串时间差，并闪动提示用户剩余时间

- (void)ExamPaperDict:(NSDictionary *)examPaperDict{
//设置答题剩余时间
NSString *subMitTime = [examPaperDict objectForKey:@"SUBMITTIME"];
NSString *str1 = [subMitTime substringFromIndex:11];
NSString *str2 = [str1 substringToIndex:8];

NSDateFormatter *formatter = [[NSDateFormatter alloc] init];
[formatter setDateStyle:NSDateFormatterMediumStyle];
[formatter setTimeStyle:NSDateFormatterShortStyle];
[formatter setDateFormat:@"HH:mm:ss"];
NSDate* date = [formatter dateFromString:str2];

//把时间转化成时间戳
int timeSp1 =  [date timeIntervalSince1970];
self.timeSp1 = timeSp1;

//创建定时器
NSTimer *timer = [NSTimer scheduledTimerWithTimeInterval:1.0f target:self selector:@selector(showTime) userInfo:nil repeats:YES];
[[NSRunLoop currentRunLoop]addTimer:timer forMode:NSRunLoopCommonModes];
[timer fire];

}

/*
* 定时器开始，此方法每隔1秒执行一次，显示剩余考试时间
*/
- (void)showTime{
//获取当前时间
NSDate *myDate = [NSDate date];
NSTimeZone *zone = [NSTimeZone systemTimeZone];
NSInteger interval = [zone secondsFromGMTForDate: myDate];
NSDate *localeDate = [myDate  dateByAddingTimeInterval: interval];
NSString *myDataStr = [NSString stringWithFormat:@"%@",localeDate];

NSString *mystr1 = [myDataStr substringFromIndex:11];
NSString *mystr2 = [mystr1 substringToIndex:8];

NSDateFormatter *formatter1 = [[NSDateFormatter alloc] init];
[formatter1 setDateStyle:NSDateFormatterMediumStyle];
[formatter1 setTimeStyle:NSDateFormatterShortStyle];
[formatter1 setDateFormat:@"HH:mm:ss"];
NSDate* date1 = [formatter1 dateFromString:mystr2];
int timeSp2 = [date1 timeIntervalSince1970];

int sp = self.timeSp1 - timeSp2;
if (sp >=0 ) {

// 时间戳转时间的方法
NSDate *confromTimesp = [NSDate dateWithTimeIntervalSince1970:sp];
NSString *labStr = [NSString stringWithFormat:@"%@",confromTimesp];
NSString *labstr1 = [labStr substringFromIndex:11];
NSString *labstr2 = [labstr1 substringToIndex:8];

self.endTimeLable1.text =[NSString stringWithFormat:@"离交卷时间:%@",labstr2];

}

}