(NSTimer)创建计时器倒数 [英] (NSTimer) creating a Timer Countdown

问题描述

我正在尝试创建一个简单的倒数计时器，以便当玩家进入我的游戏时，计时器从60倒数到0.这看似简单，但是我对如何编写它感到困惑.

I am trying to create a simple Countdown Timer so that when a player enters my game the timer begins from 60 down to 0. It seems simple but I am getting confused at how I write this.

到目前为止，我已经在GameController.m中创建了一个如下所示的方法:

So far I have created a method within my GameController.m that looks like this:

-(int)countDownTimer:(NSTimer *)timer {
    [NSTimer scheduledTimerWithTimeInterval:-1
                                 invocation:NULL
                                    repeats:YES];
    reduceCountdown = -1;
    int countdown = [[timer userInfo] reduceCountdown];
    if (countdown <= 0) {
        [timer invalidate];
    }
    return time;
}

在游戏开始时，我将整数Time初始化为60.然后在ViewController中设置标签.但是在我编译代码的那一刻，它只在60处显示标签，而丝毫不减.

At the start of the game I initialise the integer Time at 60. The label is then being set within ViewController. But at the moment when I compile the code it just shows the label at 60 and doesn't decrement at all.

任何帮助将不胜感激-我是Objective-C的新手.

Any help would be greatly appreciated - I am new to Objective-C.

编辑

在我的帮助下，我现在将代码分为2个单独的方法.现在的代码如下所示:

With some assistance from I have now separated the code into 2 separate methods. The code now looks like this:

-(void)countDown:(NSTimer *)timer {
    if (--time == 0) {
        [timer invalidate];
        NSLog(@"It's working!!!");
    }
}

-(void)countDownTimer:(NSTimer *)timer {
    NSLog(@"Hello");
    [NSTimer scheduledTimerWithTimeInterval:1
                                      target:self
                             selector:@selector(countDown:)
                                      userInfo:nil
                                      repeats:YES];
}

但是，该代码仍无法正常运行，当我从View Controller调用方法[game countDownTimer]时，它会中断说:无法识别的选择器已发送至实例".谁能解释这里出什么问题了?

HOWEVER, the code is still not running properly and when I call the method [game countDownTimer] from my View Controller it breaks saying: "unrecognized selector sent to instance". Can anybody explain what is wrong here?

推荐答案

您的代码有些错误:

• 您在时间间隔中传递了错误的参数-负数被解释为0.1毫秒
• 您正在调用错误的重载-您应该传递一个调用对象，但您传递的是NULL
• 您将要在计时器上执行的代码与计时器初始化一起放置-需要在计时器上执行的代码应放入单独的方法中.

• You are passing a wrong parameter for the time interval - negative numbers are interpreted as the 0.1 ms
• You are calling the wrong overload - you are expected to pass an invocation object, yet you are passing a NULL
• You put the code that you want executed on timer together with timer initialization - the code that needs to be executed on timer should go into a separate method.

您应该调用带有选择器的重载，并在间隔内传递1而不是-1.

You should call the overload that takes a selector, and pass 1 for the interval, rather than -1.

声明NSTimer *timer和int remainingCounts，然后添加

timer = [NSTimer scheduledTimerWithTimeInterval:1
                                         target:self
                                       selector:@selector(countDown)
                                       userInfo:nil
                                        repeats:YES];
remainingCounts = 60;

到您要开始倒计时的地方.然后添加countDown方法本身:

to the place where you want to start the countdown. Then add the countDown method itself:

-(void)countDown {
    if (--remainingCounts == 0) {
        [timer invalidate];
    }
}

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