iPhone中的倒數計時器

Question

我有兩個時間..一個直接取得字符串（@「21:00」）和其他是當前時間。我想顯示一個倒計時計時器，顯示從現在開始到21:00的剩餘時間。

例如：如果當前時間爲17:30，則我使用的標籤應顯示「您有3小時30分鐘..」。 謝謝..

Answer 1

確定已完全修改我的答案，並創建了一個完整的解決方案，在github上提供完整測試示例代碼。

享受:)

Answer 2

您創建的NSTimer將觸發每一秒：

NSTimer *timer = [NSTimer scheduledTimerWithTimeInterval:1.0 target:self selector:@selector(tickClock) userInfo:nil repeats:YES]; 

火災時，你輸入一個方法：

- (void)tickClock; 

在那裏

，您比較日期你已經對現在的日期[NSData currentDate];

喜歡其中distanceBetweenDates以秒爲單位指定

NSTimeInterval distanceBetweenDates = [currentDate timeIntervalSinceDate:yourDate]; 

。

若要從您的字符串的日期創建的NSDate相應

NSInteger year = 2011; 
NSInteger month = 8; 
NSInteger day = 26; 
NSInteger hour = 21; 
NSInteger minute = 0; 
NSInteger second = 0;  


NSCalendar *calendar = [NSCalendar currentCalendar]; 
NSDateComponents *components = [[NSDateComponents alloc] init]; 
[components setYear:year]; 
[components setMonth:month]; 
[components setDay:day]; 
[components setHour:hour]; 
[components setMinute:minute]; 
[components setSecond:second]; 
    NSDate *date = [calendar dateFromComponents:components]; 
[components release]; 

Answer 3

像這樣的東西應該這樣做。這會在幾秒鐘內給你剩餘的時間。然後你只需要標準的定時器的東西，如其他答案中所示。

//assumption: targetTime is after now 
NSString *targetTime = @"21:00"; 

//split our time into components 
NSArray *timeSplit = [targetTime componentsSeparatedByString:@":"]; 

NSUInteger hours = [[timeSplit objectAtIndex:0] intValue]; 
NSUInteger minutes = [[timeSplit objectAtIndex:1] intValue]; 

NSDate *now = [NSDate date]; 

//split now into year month day components 
NSCalendar *currentCalendar = [NSCalendar currentCalendar]; 
NSDateComponents *dateComponents = [currentCalendar components:NSYearCalendarUnit | NSMonthCalendarUnit | NSDayCalendarUnit fromDate:now]; 

//set our time components from above 
[dateComponents setHour:hours]; 
[dateComponents setMinute:minutes]; 

NSDate *targetDate = [currentCalendar dateFromComponents:dateComponents]; 

//ensure target is after now 
if ([targetDate timeIntervalSinceDate:now] < 0) 
{ 
    NSDateComponents *day = [[NSDateComponents alloc] init]; 
    [day setDay:1]; 

    targetDate = [currentCalendar dateByAddingComponents:day toDate:targetDate options:0]; 
} 

NSTimeInterval timeRemaining = [targetDate timeIntervalSinceDate:now];