我想要一个从当前时间到特定日期的倒计时，并在标签中显示该值。我看了一些NSTimer教程，但我不知道如何将它们应用于我的情况。
NSTimeInterval TimeInterval = [aString doubleValue];
NSDate* upperDate = [aDate dateByAddingTimeInterval:TimeInterval];
NSDate* Today = [NSDate date];
//cell.myLabel.text = here i should write a countdown.
抱歉代码不足。在这里提问之前，我通常会尝试写一些自己的代码，但这次我不知道该写什么。
编辑因此，有了PartiallyFinite的答案，我想好了如何设置计时器。但是因为我使用的是tableview，所以我无法实现MyTimerLabel的重复消息。我刚刚做了什么：
- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath
{
static NSString *CellIdentifier = @"MyCell";
MekanListesiViewCell *cell = (MyCell *)[tableView dequeueReusableCellWithIdentifier:CellIdentifier forIndexPath:indexPath];
if (cell == nil)
{
NSArray *nib = [[NSBundle mainBundle] loadNibNamed:@"MyCell" owner:self options:nil];
cell = [nib objectAtIndex:0];
}
aClass *aC = [myArray objectAtIndex:indexPath.row];
NSTimeInterval TimeInterval = [aC.aTimeIntervalwithString doubleValue];
NSDate* UpperDate = [aC.aNSDate dateByAddingTimeInterval:TimeInterval];
NSDateFormatter *dateFormatter = [[NSDateFormatter alloc] init];
[dateFormatter setDateFormat:@"YYYY-MM-dd"];
NSCalendar *calendar = [NSCalendar currentCalendar];
NSUInteger unitFlags = NSYearCalendarUnit|NSMonthCalendarUnit|NSDayCalendarUnit|NSHourCalendarUnit|NSMinuteCalendarUnit|NSSecondCalendarUnit;
NSDateComponents *dateComponents = [calendar components:unitFlags fromDate:[NSDate date] toDate:UpperDate options:0];
NSInteger days = [dateComponents day];
NSInteger months = [dateComponents month];
NSInteger years = [dateComponents year];
NSInteger hours = [dateComponents hour];
NSInteger minutes = [dateComponents minute];
NSInteger seconds = [dateComponents second];
NSString *countdownText = [NSString stringWithFormat:@"%d Days %d:%d:%d", days, hours, minutes, seconds];
cell.countdownText= countdownText;
[self performSelector:@selector(updateCoundown)]; // The delay is in seconds, make it whatever you want.
return cell;
}
At myCellView.h
@interface MekanListesiViewCell : UITableViewCell
@property (nonatomic, weak) IBOutlet UILabel *MyTimerLabel;
@property(weak)NSString *countdownText;
at myCellView.m
-(void)updateCoundown{
MyTimerLabel.text = countdownText;
[self performSelector:@selector(updateCoundown) withObject:nil afterDelay:1];
}
我在MyTimerLabel中什么也没得到。
使用这个答案中的代码(为了示例的完整性，复制粘贴在下面(来获得倒计时周期的各个组件：
- (void)updateCountdown {
NSDateFormatter *dateFormatter = [[NSDateFormatter alloc] init];
[dateFormatter setDateFormat:@"YYYY-MM-dd"];
NSDate *startingDate = [dateFormatter dateFromString:@"2005-01-01"];
NSDate *endingDate = [NSDate date];
NSCalendar *calendar = [NSCalendar currentCalendar];
NSUInteger unitFlags = NSYearCalendarUnit|NSMonthCalendarUnit|NSDayCalendarUnit|NSHourCalendarUnit|NSMinuteCalendarUnit|NSSecondCalendarUnit;
NSDateComponents *dateComponents = [calendar components:unitFlags fromDate:startingDate toDate:endingDate options:0];
NSInteger days = [dateComponents day];
NSInteger months = [dateComponents month];
NSInteger years = [dateComponents year];
NSInteger hours = [dateComponents hour];
NSInteger minutes = [dateComponents minute];
NSInteger seconds = [dateComponents second];
然后我们可以创建一个包含所有这些数字的字符串：
NSString *countdownText = [NSString stringWithFormat:@"%d Years %d Months %d Days %d Hours %d Minutes %d Seconds", days, months, years, hours, minutes, seconds];
cell.myLabel.text = countdownText;
然后，我们可以使用performSelector:withObject:afterDelay:使该方法在指定的延迟后再次被调用(注意，延迟以秒为单位(：
[self performSelector:@selector(updateCountdown) withObject:nil afterDelay:1];
}
声明成员变量，如NSDate*开始日期，*结束日期；无符号长countDownSeconds；
根据您的要求
-(void)setUpCountDown{
startDate = [NSDate date]; //Current time
NSDate *endDate = [startDate dateByAddingTimeInterval:10000]; //some future date
NSTimeInterval milliseconds = [endDate timeIntervalSinceDate:startDate];/////will give time in milliseconds
countDownSeconds = (unsigned long)milliseconds/1000;
[NSTimer scheduledTimerWithTimeInterval:1 target:self selector:@selector(countDown:) userInfo:nil repeats:YES];
}
-(void)countDown:(NSTimer *)timer{
if (countDownSeconds<=0) {
[timer invalidate];
timer = nil;
}
NSLog(@"Time Elapsed in seconds %d", countDownSeconds);
countDownSeconds--;
}
let formatter = NSDateFormatter()
let userCalendar = NSCalendar.currentCalendar()
let requestedComponent: NSCalendarUnit = [
//NSCalendarUnit.Month,
//NSCalendarUnit.Day,
NSCalendarUnit.Hour,
NSCalendarUnit.Minute,
NSCalendarUnit.Second
]
func printTime() {
formatter.dateFormat = "MM/dd/yy hh:mm:ss a"
let startTime = NSDate()
let endTime = formatter.dateFromString("12/25/16 8:00:00 a")
let timeDifference = userCalendar.components(requestedComponent, fromDate: startTime, toDate: endTime!, options: [])
self.TimeLabel.text = " (timeDifference.hour)Hours (timeDifference.minute)Minutes (timeDifference.second) Seconds"
}
//Put this in your initialiser
let timer = NSTimer.scheduledTimerWithTimeInterval(1, target: self, selector: #selector(myProject.printTime), userInfo: nil, repeats: true)
timer.fire()
我知道这个线程很旧，但这就是我在Swift 中的做法
保留一个实例变量以保存日期
//Fire Timer
_savedDate = [[NSDate date]dateByAddingTimeInterval:30];
[NSTimer scheduledTimerWithTimeInterval:1.0f target:self selector:@selector(countDown:) userInfo:nil repeats:YES];
- (void)countDown:(NSTimer *)timer
{
NSDate *date = [NSDate date];
if ([date isEqualToDate:_savedDate]) {
[timer invalidate];
}
NSDateComponents *dateComponents = [[NSCalendar currentCalendar]components:NSHourCalendarUnit|NSMinuteCalendarUnit|NSSecondCalendarUnit fromDate:date toDate:_savedDate options:0];
NSLog(@"%02d:%02d:%02d",dateComponents.hour,dateComponents.minute,dateComponents.second);
}