我如何在 xcode 4.5 中创建倒数计时器 [英] How do i create a countdown timer in xcode 4.5

问题描述

好的，我想创建多个计时器，它们都在不同的时间(25、50,1 分钟、1 分钟 30 秒...)开始，但我不知道如何让它在达到 0 和达到零时停止，将播放器"带到另一个视图.

Ok i want to create MULTIPLE timers that all start at a different time (25, 50,1 min, 1min 30s...) but i dont know how to make it stop when it reaches 0 and when it does reach zero, bring the "Player" to another view.

这是我的 .h 文件

@interface ViewController :UIViewController {

IBOutlet UILabel *seconds;

NSTimer *timer;

int MainInt;
}

@end

这是我的 .m 文件

@implementation ViewController

-(void)countDownDuration {

MainInt -= 1;

seconds.text = [NSString stringWithFormat:@"%i", MainInt];

}

-(IBAction)start:(id)sender {

MainInt = 25;

timer = [NSTimer scheduledTimerWithTimeInterval:1.0

                                         target:self
                                       selector:@selector(countDownDuration)
                                       userInfo:nil
                                        repeats:YES];
}

@end

推荐答案

NSTimer 不会自动执行此操作，但将其添加到您的 countDownDuration 方法中很简单.例如:

NSTimer doesn't do this automatically, but it's trivial to add it to your countDownDuration method. For example:

-(void)countDownDuration {
  MainInt -= 1;
  seconds.text = [NSString stringWithFormat:@"%i", MainInt];
  if (MainInt <= 0) {
    [timer invalidate];
    [self bringThePlayerToAnotherView];
  }
}

当然要创建多个计时器.您可以将每个存储在不同的变量中，并为每个变量提供不同的选择器.但是如果你查看 NSTimer 的文档，回调方法实际上将计时器对象作为选择器；你忽略了它，但你不应该.

Of course you want to create multiple timers. You could store each one in a different variable and give each one a different selector. But if you look at the documentation for NSTimer, the callback method actually takes the timer object as a selector; you're ignoring it, but you shouldn't be.

同时，您可以将任何类型的对象存储为计时器的 userInfo，因此这是为每个计时器存储单独的当前倒计时值的好地方.

And meanwhile, you can store an object of any type you want as the userInfo for the timer, so that's a good place to stash a separate current countdown value for each timer.

所以，你可以这样做:

-(void)countDownDuration:(NSTimer *)timer {
  int countdown = [[timer userInfo] reduceCountdown];
  seconds.text = [NSString stringWithFormat:@"%i", countdown];
  if (countdown <= 0) {
    [timer invalidate];
    [self bringThePlayerToAnotherView];
  }
}

-(IBAction)start:(id)sender {
  id userInfo = [[MyCountdownClass alloc] initWithCountdown:25];
  timer = [NSTimer scheduledTimerWithTimeInterval:1.0
                                           target:self
                                         selector:@selector(countDownDuration:)
                                         userInfo:userInfo
                                          repeats:YES];
}

我没有写一些细节(比如 MyCountdownClass 的定义——它必须包括方法 initWithCountdown: 和 reduceCountdown正确的事情)，但它们都应该非常简单.(另外，大概你想要一个 userInfo 来存储的不仅仅是倒计时值——例如，如果每个计时器将玩家发送到不同的视图，你也必须将视图存储在那里.)

I've left a few details unwritten (like the definition of MyCountdownClass—which has to include method initWithCountdown: and reduceCountdown that do the right thing), but they should all be pretty simple. (Also, presumably you want a userInfo that stores more than just the countdown value—e.g., if each timer sends the player to a different view, you've got to stash the view there as well.)

PS，注意你现在需要@selector(countDownDuration:).ObjC 的新手总是把这搞砸.countDownDuration: 和 countDownDuration 是完全不相关的选择器.

PS, notice that you now need @selector(countDownDuration:). Newcomers to ObjC screw this up all the time. countDownDuration: and countDownDuration are completely unrelated selectors.

PPS，MyCountdownClass 的完整定义必须在 countDownDuration: 中可见(除非您有其他具有相同选择器的类).您可能希望将 userInfo 的结果显式转换为 MyCountdownClass * 以使事情更清楚.

PPS, the full definition of MyCountdownClass will have to be visible in countDownDuration: (unless you have some other class with the same selectors). You may want to explicitly cast the result of userInfo to MyCountdownClass * to make things clearer.

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