如何在 ios 中显示事件的时间

Question

在我的 iOS 应用程序中，我必须创建一个 HH:MM:SS 格式的数字计时器（不是系统时间），它应该从 00:00:00 开始，点击 [=13] =]，我可以使用任何标准库来这样做吗？或者我应该写我自己的逻辑？

Answer 1

iOS Foundation 框架包括 NSDateFormatter class（和 NSDate 数据类型），它们就是这样做的。

Answer 2

在您的 .m 文件中添加这些属性：

#import "MyVC.h"

@interface MyVC()
    @property (strong, nonatomic) NSTimer* timer; // our timer
    @property (nonatomic) NSInteger secondsPassed; // how many seconds have been passed since the start of the timer
@end

在 viewDidLoad 或 IBAction 方法中 UIButton:

- (void)viewDidLoad {
    [super viewDidLoad];

    self.myLabel.text = @"00:00:00"; // start text 

    // invoke updateTimer every second 
    self.timer = [NSTimer scheduledTimerWithTimeInterval: 1.0
                                              target:self
                                            selector:@selector(updateTimer)
                                            userInfo:nil
                                             repeats: YES];
}

此方法将每秒调用一次以更新 UILabel

-(void) updateTimer{
    NSInteger hours, minutes, seconds;
   // increase the passed seconds
    self.secondsPassed++;

    // calculate the hours, minutes, seconds from the total number of seconds
    hours =  self.secondsPassed / 3600;
    minutes = ( self.secondsPassed % 3600) / 60;
    seconds = ( self.secondsPassed %3600) % 60;

    // update the label with the time
    self.myLabel.text = [NSString stringWithFormat:@"%02zd:%02zd:%02zd", hours, minutes, seconds];
}

或者您可以使用 MZTimerLabel

Answer 3

所以你可以做的一件事就是创建一个计时器并记住你创建它的时间。

@IBAction func buttonTapped() {

    // Store date / time in which you tapped the button
    self.initialDate = NSDate()

    // Create timer that fires every second starting now (scheduled), and repeats
    self.timer = NSTimer.scheduledTimerWithTimeInterval(1.0, target: self, selector: Selector("timerTick"), userInfo: nil, repeats: true)
}

然后，当你有初始的东西时，你可以做timerTick方法。在这里，您可以获得当前日期，将您存储的日期与当前日期进行区分并显示：

func timerTick() {

    // Get calendar and components of the dates in interval <initialDate, currentDate>
    let calendar = NSCalendar.currentCalendar()
    let components = calendar.components(.CalendarUnitSecond | .CalendarUnitMinute | .CalendarUnitHour, fromDate: self.initialDate, toDate: NSDate(), options: NSCalendarOptions.allZeros)

    // In this point you have minutes, seconds and hours, you can just present it
    // "%02d:%02d:%02d" in format means "number, always at least 2 numbers, fill with zeroes if needed")
    self.label.text = String(format: "%02d:%02d:%02d", components.hour, components.minute, components.second)
}

如果你想停止定时器，你可以调用self.timer.invalidate()

希望对您有所帮助！

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