iOS实现倒计时显示 时 分 秒

1.创建一个类继承自UILabel.（用来显示 时 分 秒）
.h文件
#import

@interface TimeLable : UILabel

@property (nonatomic,assign)NSInteger second;
@property (nonatomic,assign)NSInteger minute;
@property (nonatomic,assign)NSInteger hour;

@end
.m文件
#import "TimeLable.h"
@interface TimeLable ()
@property (nonatomic, strong)NSTimer *timer;
@end

@implementation TimeLable

- (id)initWithFrame:(CGRect)frame{
    self = [super initWithFrame:frame];
    if (self) {
        self.textAlignment = NSTextAlignmentCenter;
        self.timer = [NSTimer scheduledTimerWithTimeInterval:1 target:self selector:@selector(timeHeadle) userInfo:nil repeats:YES];
    }
    return self;
}

- (void)timeHeadle{
   
    self.second--;
    if (self.second==-1) {
        self.second=59;
        self.minute--;
        if (self.minute==-1) {
            self.minute=59;
            self.hour--;
        }
    }
   
    self.text = [NSString stringWithFormat:@"%ld:%ld:%ld",(long)self.hour,(long)self.minute,(long)self.second];
    if (self.second==0 && self.minute==0 && self.hour==0) {
        [self.timer invalidate];
        self.timer = nil;
    }
}

2.在需要倒计时器的类中导入头文件即可使用，示例：

 TimeLable *lable = [[TimeLable alloc]initWithFrame:CGRectMake(100, 100, 100, 100)];
    lable.hour = 10;
    lable.minute = 38;
    lable.second = 29;

    [self.view addSubview:lable];

-----------------------分割线----------------------------

整个label内部倒计时所显示的内容可以看做一个字符串

头部代码#import "YQHomeViewController.h"@interface YQHomeViewController ()//将sb中的label进行拖拽过来@property (weak, nonatomic) IBOutlet UILabel *timeLbl;//创建定时器(因为下面两个方法都使用,所以定时器拿出来设置为一个属性)@property(nonatomic,strong)NSTimer*countDownTimer;@end@implementation YQHomeViewController//倒计时总的秒数static NSInteger  secondsCountDown = 86400;- (void)viewDidLoad {    [super viewDidLoad];

实现步骤:

1.设置定时器(给定24小时)

一个定时器,定时器里面做设置间隔多少时间执行什么方法(countDownAction)

- (void)viewDidLoad {    [super viewDidLoad];    //设置定时器   _countDownTimer = [NSTimer scheduledTimerWithTimeInterval:1 target:self selector:@selector(countDownAction) userInfo:nil repeats:YES];    //启动倒计时后会每秒钟调用一次方法 countDownAction    //设置倒计时显示的时间    NSString *str_hour = [NSString stringWithFormat:@"%02ld",secondsCountDown/3600];//时    NSString *str_minute = [NSString stringWithFormat:@"%02ld",(secondsCountDown%3600)/60];//分    NSString *str_second = [NSString stringWithFormat:@"%02ld",secondsCountDown%60];//秒    NSString *format_time = [NSString stringWithFormat:@"%@:%@:%@",str_hour,str_minute,str_second];    self.timeLbl.text = [NSString stringWithFormat:@"倒计时   %@",format_time];    //设置文字颜色    self.timeLbl.textColor = [UIColor  blackColor ];    [self.view addSubview:_timeLbl];}

2.方法(countDownAction)(来自创建定时器时需要执行的方法)内部:总秒数递减

1.先递减
2.给时分秒字符串通过递减过后的秒数,重新计算数值,并输出显示

//实现倒计时动作-(void)countDownAction{    //倒计时-1    secondsCountDown--;    //重新计算 时/分/秒    NSString *str_hour = [NSString stringWithFormat:@"%02ld",secondsCountDown/3600];    NSString *str_minute = [NSString stringWithFormat:@"%02ld",(secondsCountDown%3600)/60];    NSString *str_second = [NSString stringWithFormat:@"%02ld",secondsCountDown%60];    NSString *format_time = [NSString stringWithFormat:@"%@:%@:%@",str_hour,str_minute,str_second];    //修改倒计时标签及显示内容    self.timeLbl.text=[NSString stringWithFormat:@"实训倒计时   %@",format_time];    //当倒计时到0时做需要的操作，比如验证码过期不能提交    if(secondsCountDown==0){        [_countDownTimer invalidate];    }    }

屏幕输出结果:

程序输出结果:灰色的两个scrollView可以忽略,不要让它干扰到你