iOS中将毫秒转换成时长

+ (NSString *)ConvertStrToTime:(NSString *)timeStr
//timeStr毫秒字段
{

long long time=[timeStr longLongValue];

NSDate *d = [[NSDate alloc]initWithTimeIntervalSince1970:time/1000.0];

NSDateFormatter *formatter = [[NSDateFormatter alloc]init];

[formatter setDateFormat:@"mm:ss"];//根据自己需要yyyy/MM/dd HH:mm:ss 截取自己需要的

NSString*timeString=[formatter stringFromDate:d];

return timeString;

}