倒计时是一个常用的功能页面, 该功能可以分解成3步: ①倒计时UI的展示 ②定时数据的格式与解析 ③定时器的选择
下面通过3个知识点来完成整个功能
1. UIDatePicker
UIDatePicker 是一个系统封装好控制器类，封装了 UIPickerView，但是他是UIControl的子类，专门用于接受日期、时间和持续时长的输入，我们对于时间选择的UI可以直接使用该类去完成，下面贴出具体使用代码
@property (nonatomic, strong) UIDatePicker *datePicker; //设置为属性
- (void)configPickerView{ //创建
UIDatePicker *datePicker = [[UIDatePicker alloc] initWithFrame:CGRectMake(0, 100, self.view.frame.size.width, 200)];
//设置地区: zh-中国
datePicker.locale = [NSLocale localeWithLocaleIdentifier:@"zh"];
//设置日期模式(Displays month, day, and year depending on the locale setting)
datePicker.datePickerMode = UIDatePickerModeCountDownTimer;
//设置当前显示时间
//需要转换的字符串
NSString *dateString = @"5"; //格式2018-11-22 08:08:08对应yyyy-MM-dd HH:mm:ss 初始化为5
//设置转换格式
NSDateFormatter *formatter = [[NSDateFormatter alloc] init] ;
[formatter setDateFormat:@"mm"]; //对应设置的5为分钟
//NSString转NSDate
NSDate *date=[formatter dateFromString:dateString];
[datePicker setDate:date animated:YES];
//监听DataPicker的滚动
[datePicker addTarget:self action:@selector(dateChange:) forControlEvents:UIControlEventValueChanged];
self.datePicker = datePicker;
[self.view addSubview:self.datePicker];
}
这里需要注意datePickerMode方法，系统提供了多种形态的UI可供选择
typedef NS_ENUM(NSInteger, UIDatePickerMode) {
UIDatePickerModeTime, // Displays hour, minute, and optionally AM/PM designation depending on the locale setting (e.g. 6 | 53 | PM)
UIDatePickerModeDate, // Displays month, day, and year depending on the locale setting (e.g. November | 15 | 2007)
UIDatePickerModeDateAndTime, // Displays date, hour, minute, and optionally AM/PM designation depending on the locale setting (e.g. Wed Nov 15 | 6 | 53 | PM)
UIDatePickerModeCountDownTimer, // Displays hour and minute (e.g. 1 | 53)
} __TVOS_PROHIBITED;
对应样式如下
1.1 UIDatePickerModeTime
UIDatePickerModeTime
1.2 UIDatePickerModeDate
UIDatePickerModeDate
1.3 UIDatePickerModeDateAndTime
UIDatePickerModeDateAndTime
1.4 UIDatePickerModeCountDownTimer
UIDatePickerModeCountDownTimer
2. Cron表达式
cron表达式就是对时间数据的一种处理，可以和后台商量好都使用这个方式去解析时间数据，举个例子:8 27 22 1 3 ? 2019，代表时间2019年3月1日22点27点8秒，具体代码如下
获取当前时间值(秒为单位)
NSDate* nowDate = [NSDate date];
NSTimeZone* zone = [NSTimeZone timeZoneWithName:@"Asia/Shanghai"];
NSTimeInterval time = [zone secondsFromGMTForDate:nowDate];// 以秒为单位返回当前时间与系统格林尼治时间的差
int newTime = ([nowDate timeIntervalSince1970]+time);
int nowhour = newTime / 3600;
int nowminite = newTime / 60 % 60;
int newsecond = newTime % 60;
nowhour %= 24;
newTime = 3600*nowhour+60*nowminite+newsecond;
在将newTime传入下面参数，即可获得当前时间的cron表达式
+(NSString*)cronStringWithtime:(long long)time
week:(NSInteger)week
weekday:(NSInteger)weekday
{
NSString* cron;
long hour = time / 3600;
long min = time / 60 % 60;
long second = time % 60;
//执行一次 应该设置 日月年, tbd.
NSString* weekDesp=@"";
if(week == 0){ //once
weekDesp = @"?";
NSDate* date = [NSDate date];
NSCalendar * calendar = [NSCalendar currentCalendar]; // 指定日历的算法
NSDateComponents *comps = [calendar components:kCFCalendarUnitSecond|NSCalendarUnitMinute|NSCalendarUnitHour|NSCalendarUnitDay|NSCalendarUnitMonth|NSCalendarUnitYear fromDate:date];
long long currentTime=comps.hour*60*60+comps.minute*60+comps.second;
if (currentTime>=time) {
NSDate *tomorrowDate = [NSDate dateWithTimeIntervalSinceNow:(24*60*60)];
comps=[calendar components:kCFCalendarUnitSecond|NSCalendarUnitMinute|NSCalendarUnitHour|NSCalendarUnitDay|NSCalendarUnitMonth|NSCalendarUnitYear fromDate:tomorrowDate];
}
cron = [NSString stringWithFormat:@"%ld %ld %ld %ld %ld %@ %ld",second,min,hour,comps.day,comps.month,weekDesp,comps.year];
return cron;
}else if(week == 127){ //every day
weekDesp = @"*";
}else{
NSMutableString *weekString = [NSMutableString new];
NSInteger weekIndex = 0;
while (week) {
if (week & 0x1) {
if (0 != weekString.length) {
[weekString appendString:@","];
}
[weekString appendFormat:@"%ld", weekIndex+1]; //cron from 1-7
}
week >>= 1;
++weekIndex;
}
weekDesp = weekString;
}
//Seconds Minutes Hours Day-of-Month Month Day-of-Week Year
cron = [NSString stringWithFormat:@"%ld %ld %ld ? * %@ *",second,min,hour,weekDesp]; //cron = @"0 0 8 ? * 2,3,4,5,6 *";
return cron;
}
倒计时的本质也就是对比时间差，所以小伙伴要根据实际项目中的数据做处理，cron表达式只是其中一种，下面介绍另一种时间数据处理
#pragma mark - 定时器Hander
- (void)timerHander {
NSString *redEffectiveTime = @"2019-3-1 16:00:00";
NSDate *nowDate = [NSDate date];
NSDateFormatter *dateFomatter = [[NSDateFormatter alloc] init];
dateFomatter.dateFormat = @"yyyy-MM-dd HH:mm:ss";
// 截止时间字符串格式
NSString *expireDateStr = redEffectiveTime;
// 当前时间字符串格式
NSString *nowDateStr = [dateFomatter stringFromDate:nowDate];
// 截止时间data格式
NSDate *expireDate = [dateFomatter dateFromString:expireDateStr];
// 当前时间data格式
nowDate = [dateFomatter dateFromString:nowDateStr];
// 当前日历
NSCalendar *calendar = [NSCalendar currentCalendar];
// 需要对比的时间数据
NSCalendarUnit unit = NSCalendarUnitYear | NSCalendarUnitMonth | NSCalendarUnitDay | NSCalendarUnitHour | NSCalendarUnitMinute | NSCalendarUnitSecond;
// 对比时间差
NSDateComponents *dateCom = [calendar components:unit fromDate:nowDate toDate:expireDate options:0];
NSString *day = [NSString stringWithFormat:@"%d",(int)dateCom.day];
NSString *hours = [NSString stringWithFormat:@"%02d",(int)dateCom.hour];
NSString *minutes = [NSString stringWithFormat:@"%02d",(int)dateCom.minute];
NSString *seconds = [NSString stringWithFormat:@"%02d",(int)dateCom.second];
NSString *time = @"";
if ([day intValue]>0) {
time = [NSString stringWithFormat:@"剩余时间：%@天%@:%@:%@",day,hours,minutes,seconds];
}else{
time = [NSString stringWithFormat:@"剩余时间：%@:%@:%@",hours,minutes,seconds];
}
}
3. dispatch_source_t
定时器选择了GCD的dispatch_source_t，没有选择平时最常用的定时器NSTime，因为Timer有很多缺点，如
①循环引用导致内存泄漏
②因为受runloop影响定时可能不准确
③代码繁多
使用dispatch_source_t有效的避免上面问题
①将self作为传入方法，避免了循环引用
②底层语言实现，不依赖runloop不会出现线程拥堵导致的定时不准确问题
③block块代码看起来更简洁，方便管理
具体代码如下
#pragma mark 开启定时器
- (void)createGCDTimer:(NSString *)schedule{
//获得服务器传输过来的cron时间
NSString* desc = [HYCronTimerUtils displaySecondStringWithcronString:schedule]; //得到12:27
NSArray *tempArr = [desc componentsSeparatedByString:@":"]; //得到12 和 27
NSString* hour = tempArr[0];
NSString* min = tempArr[1];
NSString* second = tempArr[2];
int mins = [hour intValue]*3600+[min intValue]*60+[second intValue];
//得到当前时间
NSDate* nowDate = [NSDate date];
NSTimeZone* zone = [NSTimeZone timeZoneWithName:@"Asia/Shanghai"];
NSTimeInterval time = [zone secondsFromGMTForDate:nowDate];// 以秒为单位返回当前时间与系统格林尼治时间的差
int newTime = ([nowDate timeIntervalSince1970]+time);
int nowhour = newTime / 3600;
int nowminite = newTime / 60 % 60;
int newsecond = newTime % 60;
nowhour %= 24;
newTime = 3600*nowhour+60*nowminite+newsecond;
//得到倒计时时间
__block int timeout = mins-newTime;
//定时器的创建
dispatch_queue_t queue = dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0);
self.timer = dispatch_source_create(DISPATCH_SOURCE_TYPE_TIMER, 0, 0,queue);
dispatch_source_set_timer(self.timer,dispatch_walltime(NULL, 0),1.0*NSEC_PER_SEC, 0); //每秒执行
dispatch_source_set_event_handler(self.timer, ^{
if(timeout <= 0){ //倒计时结束，关闭
dispatch_source_cancel(self.timer);
dispatch_async(dispatch_get_main_queue(), ^{
//设置界面的按钮显示 根据自己需求设置
NSLog(@"倒计时结束");
});
}else{
int hour = timeout / 3600;
int minute = timeout / 60 % 60;
int second = timeout % 60;
dispatch_async(dispatch_get_main_queue(), ^{
//设置界面的按钮显示 根据自己需求设置
self.timerLabel.text = [NSString stringWithFormat:@"%02d:%02d:%02d",hour,minute,second];
});
timeout -= 1;
}
});
dispatch_resume(self.timer);
}
定时器肯定需要注意释放问题，需要在项目中合适的时机释放该定时器
#pragma mark 生命周期
- (void)viewWillDisappear:(BOOL)animated {
[super viewWillDisappear:animated];
dispatch_source_cancel(_timer); //关闭定时器
}
- (void)dealloc
{
NSLog(@"释放了我就放心了!!!"); //可以在dealloc看一下有没有log的打印
}
完整定时功能Demo下载地址:
https://github.com/gaoyuGood/UIDatePicker-Cron-dispatch_source_t
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