做电商类的朋友经常会用到一个东西,那就是网购倒计时.所以今天就简单的实现了一下这个功能.用UILabel去显示时间.
封装了一个CountDownView.m文件

#import "CountDownView.h"
#define TIMELABELWIDTH 40
#define HEIGHT 40
#define COLONLABELWIDTH 10
#define Y 0

@interface CountDownView ()
{
    NSTimer *timer ; //定时器
}
// 我们用七个Label来显示 (冒号也算在内)---  天数 : 小时 : 分 : 秒
@property (nonatomic,retain)UILabel *dayLabel ; // 显示天数的Label
@property (nonatomic,retain)UILabel *colonAfterDayLabel ; // 跟在小时后便的冒号
@property (nonatomic,retain)UILabel *hourLabel ; // 显示小时的Label
@property (nonatomic,retain)UILabel *colonAfterHourLabel ; // 跟在小时后便的冒号
@property (nonatomic,retain)UILabel *minuteLabel ; // 显示分钟的Label
@property (nonatomic,retain)UILabel *colonAfterMinuteLabel ; // 跟在分钟后便的label
@property (nonatomic,retain)UILabel *secondLabel ; // 显示秒数的Label

@end

@implementation CountDownView

- (instancetype)initWithFrame:(CGRect)frame
{
    CGRect myFrame = CGRectMake(0, frame.origin.y, [[UIScreen mainScreen] bounds].size.width, 50) ;
    if ([super initWithFrame:myFrame])
    {
        [self addSubview:self.colonAfterDayLabel] ;
        [self addSubview:self.colonAfterHourLabel] ;
        [self addSubview:self.colonAfterMinuteLabel] ;
    }
    return self ;
}
// 每个时间Label宽度 50 高度40  每个冒号Label宽度10 高度40 相连放置即可
// 懒加载
- (UILabel *)dayLabel
{
    if (!_dayLabel)
    {
        _dayLabel = [[UILabel alloc] initWithFrame:CGRectMake(50, Y, TIMELABELWIDTH, HEIGHT)] ;
        _dayLabel.textAlignment = NSTextAlignmentCenter ;
        [self addSubview:_dayLabel] ;
    }
    return _dayLabel ;
}

- (UILabel *)colonAfterDayLabel
{
    if (!_colonAfterDayLabel)
    {
        _colonAfterDayLabel = [[UILabel alloc] initWithFrame:CGRectMake(50+TIMELABELWIDTH, Y, COLONLABELWIDTH, HEIGHT)] ;
        _colonAfterDayLabel.text = @":" ;
        _colonAfterDayLabel.textAlignment = NSTextAlignmentCenter ;
    }
    return _colonAfterDayLabel ;
}

- (UILabel *)hourLabel
{
    if (!_hourLabel)
    {
        _hourLabel = [[UILabel alloc] initWithFrame:CGRectMake(50 + TIMELABELWIDTH + COLONLABELWIDTH, Y, TIMELABELWIDTH, HEIGHT)] ;
        _hourLabel.textAlignment = NSTextAlignmentCenter ;
        [self addSubview:_hourLabel] ;
    }
    return _hourLabel ;
}

- (UILabel *)colonAfterHourLabel
{
    if (!_colonAfterHourLabel)
    {
        _colonAfterHourLabel = [[UILabel alloc] initWithFrame:CGRectMake(50 + TIMELABELWIDTH*2 + 10, Y, COLONLABELWIDTH, HEIGHT)] ;
        _colonAfterHourLabel.text = @":" ;
        _colonAfterHourLabel.textAlignment = NSTextAlignmentCenter ;
    }
    return _colonAfterHourLabel ;
}

- (UILabel *)minuteLabel
{
    if (!_minuteLabel)
    {
        _minuteLabel = [[UILabel alloc] initWithFrame:CGRectMake(50+(TIMELABELWIDTH + COLONLABELWIDTH)*2, Y, TIMELABELWIDTH, HEIGHT)] ;
        _minuteLabel.textAlignment = NSTextAlignmentCenter ;
        [self addSubview:_minuteLabel] ;
    }
    return _minuteLabel ;
}

- (UILabel *)colonAfterMinuteLabel
{
    if (!_colonAfterMinuteLabel)
    {
        _colonAfterMinuteLabel = [[UILabel alloc] initWithFrame:CGRectMake(50 + TIMELABELWIDTH*3 + COLONLABELWIDTH *2, Y, COLONLABELWIDTH, HEIGHT)] ;
        _colonAfterMinuteLabel.text = @":" ;
        _colonAfterMinuteLabel.textAlignment = NSTextAlignmentCenter ;
        
    }
    return _colonAfterMinuteLabel ;
}

- (UILabel *)secondLabel
{
    if (!_secondLabel)
    {
        _secondLabel = [[UILabel alloc] initWithFrame:CGRectMake(50 + (TIMELABELWIDTH + COLONLABELWIDTH)*3, Y, TIMELABELWIDTH, HEIGHT)] ;
        _secondLabel.textAlignment = NSTextAlignmentCenter ;
        [self addSubview:_secondLabel] ;
    }
    return _secondLabel ;
}

// 当我们给时间间隔赋值时,生成定时器
- (void)setTimeInterval:(NSInteger)timeInterval
{
    _timeInterval = timeInterval ;
    if (_timeInterval!=0)
    {
        timer = [NSTimer scheduledTimerWithTimeInterval:1 target:self selector:@selector(timerAction) userInfo:nil repeats:YES] ;
    }
}

// 获取时间间隔
- (NSTimeInterval)timeIntervalWithFormatterString : (NSString *)formatterString andFutureDataString : (NSString *)futureDataString
{
    // 获取当前时间
    NSDate *date = [NSDate date] ;
    // 创建时间格式对象
    NSDateFormatter *dateFormatter = [[NSDateFormatter alloc] init] ;
    // 设置时间格式
    [dateFormatter setDateFormat:formatterString] ;
    // 将你需要的时间格式字符串转化为日期对象
    NSDate *futureDate = [dateFormatter dateFromString:futureDataString] ;
    // 获取当前时间距你所需要时间的时间间隔
    NSTimeInterval timerInterval = [futureDate timeIntervalSinceDate:date] ;
    return timerInterval ;
}

// 每间隔一秒定时器触发执行该方法
- (void)timerAction
{
    // 定时器每次触发 时间间隔减一 也就是说时间间隔依次递减
    _timeInterval -- ;
    [self getTimeFromTimeInterval:_timeInterval] ;
    // 当时间间隔为0时干掉定时器
    if (_timeInterval == 0)
    {
        [timer invalidate] ;
        timer = nil ;
    }
}

// 通过时间间隔计算具体时间(天,小时,分,秒)
- (void)getTimeFromTimeInterval : (NSInteger)timeInterval
{
    // 通过时间间隔获取天数 小时数 分钟数 秒数
    NSInteger ms = timeInterval;
    NSInteger ss = 1;
    NSInteger mi = ss * 60;
    NSInteger hh = mi * 60;
    NSInteger dd = hh * 24;
    
    // 剩余的
    NSInteger day = ms / dd;// 天
    NSInteger hour = (ms - day * dd) / hh;// 时
    NSInteger minute = (ms - day * dd - hour * hh) / mi;// 分
    NSInteger second = (ms - day * dd - hour * hh - minute * mi) / ss;// 秒
    
    self.dayLabel.text = [NSString stringWithFormat:@"%zd天",day];
    self.hourLabel.text = [NSString stringWithFormat:@"%zd时",hour];
    self.minuteLabel.text = [NSString stringWithFormat:@"%zd分",minute];
    self.secondLabel.text = [NSString stringWithFormat:@"%zd秒",second];
}

@end

- (void)viewWillAppear:(BOOL)animated
{
// 初始化后添加 显示时间倒计时
    CountDownView *countDownView = [[CountDownView alloc] initWithFrame:CGRectMake(0, 50, 0, 0)] ;
    countDownView.timeInterval = [countDownView timeIntervalWithFormatterString:@"yyyy年-MM月-dd日 HH时-mm分-ss秒" andFutureDataString:@"2016年-1月-1日 00时-00分--00秒"] ;
    [self.view addSubview:countDownView] ;
}