objective-c 如何为 cocos2d 创建倒数计时器？

How can I create a count down timer for cocos2d?

提问by Md Nasir Uddin

I am developing a 2D iPhone game by using cocos2d. I need a countdown timer. How can I create a count down timer in cocos2d?

我正在使用 cocos2d 开发 2D iPhone 游戏。我需要一个倒数计时器。如何在 cocos2d 中创建倒数计时器？

回答by JustinB

Not enough rep to upvote Tom, but he's absolutely right. Within the context of this question, NSTimer is the WRONG solution. The Cocos2d framework provides a scheduler that integrates with other game features like Pause/Resume (and most likely uses NSTimer under the hood).

没有足够的代表来支持汤姆，但他是绝对正确的。在这个问题的上下文中， NSTimer 是错误的解决方案。Cocos2d 框架提供了一个调度程序，它与其他游戏功能（如暂停/恢复）集成（并且很可能在幕后使用 NSTimer）。

Example from the above link:

来自上述链接的示例：

-(id) init
{
    if( ! [super init] )
        return nil;

    // schedule timer
    [self schedule: @selector(tick:)];
    [self schedule: @selector(tick2:) interval:0.5];

    return self;
}

-(void) tick: (CCTime) dt
{
    // bla bla bla
}

-(void) tick2: (CCTime) dt
{
    // bla bla bla
}

回答by Md Nasir Uddin

http://www.cocos2d-iphone.org/wiki/doku.php/prog_guide:best_practices

http://www.cocos2d-iphone.org/wiki/doku.php/prog_guide:best_practices

• Try NOTto use Cocoa's NSTimer. Instead use cocos2d's own scheduler.
• If you use cocos2d scheduler, you will have:
  • automatic pause/resume.
  • when the Layer (Scene, Sprite, CocosNode) enters the stage the timer will be automatically activated, and when it leaves the stage it will be automatically deactivated.
  • Your target/selector will be called with a delta time...

• 尽量不要使用 Cocoa 的 NSTimer。而是使用 cocos2d 自己的调度程序。
• 如果您使用 cocos2d 调度程序，您将拥有：
  • 自动暂停/恢复。
  • 当Layer（Scene、Sprite、CocosNode）进入舞台时定时器会自动开启，离开舞台时定时器会自动关闭。
  • 您的目标/选择器将使用增量时间调用...

回答by Sri

In cocos 2d there is default update section for timer.

在 cocos 2d 中，计时器有默认的更新部分。

Try this:

尝试这个：

[self schedule:@selector(update:)];
- (void)update:(ccTime)dt {
}

回答by Ziminji

For those that want to use NSTimer instead of the "schedule" method, you can create a class such as the following:

对于那些想要使用 NSTimer 而不是“schedule”方法的人，您可以创建一个如下所示的类：

ZIMCountdownTicker.h

ZIMCountdownTicker.h

#import <Foundation/Foundation.h>

extern NSString * const ZIMCountdownTickerTickAction;
extern NSString * const ZIMCountdownTickerResetAction;

@protocol ZIMCountdownTickerProtocol;

/*!
 @class             ZIMCountdownTicker
 @discussion        This class creates a countdown ticker.
 @updated           2011-03-05
 */
@interface ZIMCountdownTicker : NSObject {

    @private
        NSTimer *_timer;
        id<ZIMCountdownTickerProtocol> _delegate;
        NSTimeInterval _interval;
        double _period;
        double _value;

}

/*!
 @method                initWithDelegate:withTimeInterval:forTimePeriod:
 @discussion            This method instantiate an instance of this class with the specified parameters.
 @param delegate        A reference to a class that has implemented ZIMCountdownTickerProtocol.
 @param interval        The time interval in seconds to be used when running the countdown ticker.
 @param period          The time period in seconds for which countdown ticker will run.
 @updated               2011-03-05
 */
- (id) initWithDelegate: (id<ZIMCountdownTickerProtocol>)delegate withTimeInterval: (NSTimeInterval)interval forTimePeriod: (double)period;
/*!
 @method                start
 @discussion            This method will start the countdown ticker.
 @updated               2011-03-05
 */
- (void) start;
/*!
 @method                stop
 @discussion            This method will stop the countdown ticker.
 @updated               2011-03-05
 */
- (void) stop;
/*!
 @method                reset
 @discussion            This method will reset the countdown ticker.
 @updated               2011-03-06
 */
- (void) reset;
/*!
 @method                value
 @discussion            This method will return the countdown ticker's current value; however, using this method will cause
                    the ticker to stop.
 @return                The countdown ticker's current value.
 @updated               2011-03-05
 */
- (double) value;

@end

@protocol ZIMCountdownTickerProtocol <NSObject>

@optional
/*!
 @method                countdownTicker:didUpdateValue:withAction:
 @discussion            This method will notify the delegate with the current value.
 @param ticker          A reference to tiggering ticker.
 @param value           The current value.
 @param action          The action that tiggered this method.
 @updated               2011-03-05
 */
- (void) countdownTicker: (ZIMCountdownTicker *)ticker didUpdateValue: (double)value withAction: (NSString *)action;
/*!
 @method                countdownTickerDidFinish:
 @discussion            This method will notify the delegate that the countdown ticker finished.
 @param ticker          A reference to tiggering ticker.
 @updated               2011-03-05
 */
- (void) countdownTickerDidFinish: (ZIMCountdownTicker *)ticker;

@end

ZIMCountdownTicker.m

ZIMCountdownTicker.m

// Ziminji Classes
#import "ZIMCountdownTicker.h"

NSString * const ZIMCountdownTickerTickAction = @"ticker.tick";
NSString * const ZIMCountdownTickerResetAction = @"ticker.reset";

/*!
 @category          ZIMCountdownTicker (Private)
 @discussion        This category defines the prototypes for this class's private methods.
 @updated           2011-03-05
 */
@interface ZIMCountdownTicker (Private)
    /*!
     @method            countdown:
     @discussion        This method is called by the timer to decrement the counter's value and will send
                    the delegate the updated value.
     @param timer       The timer currently in use.
 @updated           2011-03-06
    */
    - (void) countdown: (NSTimer *)timer;
@end

@implementation ZIMCountdownTicker

- (id) initWithDelegate: (id<ZIMCountdownTickerProtocol>)delegate withTimeInterval (NSTimeInterval)interval forTimePeriod: (double)period {
    if (self = [super init]) {
        _delegate = delegate;
        _interval = interval;
        _period = period;
        _value = period;
        _timer = nil;
    }
    return self;
}

- (void) start {
    if (_timer == nil) {
        _timer = [NSTimer scheduledTimerWithTimeInterval: _interval target: self selector: @selector(countdown:) userInfo: nil repeats: YES];
    }
}

- (void) stop {
    if (_timer != nil) {
        [_timer invalidate];
        _timer = nil;
    }
}

- (void) reset {
    [self stop];
    _value = _period;
    if ((_delegate != nil) && [_delegate respondsToSelector: @selector(countdownTicker:didUpdateValue:withAction:)]) {
        [_delegate countdownTicker: self didUpdateValue: _value withAction: ZIMCountdownTickerResetAction];
    }
}

- (double) value {
    [self stop];
    return _value;
}

- (void) countdown: (NSTimer *)timer {
    _value -= 1;
    if ((_delegate != nil) && [_delegate respondsToSelector: @selector(countdownTicker:didUpdateValue:withAction:)]) {
        [_delegate countdownTicker: self didUpdateValue: _value withAction: ZIMCountdownTickerTickAction];
    }
    if (_value <= 0) {
        [self stop];
        if ((_delegate != nil) && [_delegate respondsToSelector: @selector(countdownTickerDidFinish:)]) {
            [_delegate countdownTickerDidFinish: self];
        }
    }
}

- (void) dealloc {
    if (_delegate != nil) {
        [_delegate release];
    }
    if (_timer != nil) {
        [_timer invalidate];
    }
    [super dealloc];
}

@end

回答by Joel Levin

Look at NSTimer, it can most likely provide any needed timer functionality.

看看 NSTimer，它很可能提供任何需要的定时器功能。

NSTimer class reference

NSTimer 类参考

回答by lostInTransit

-(id) init
{
    if( ! [super init] )
        return nil;

    // schedule timer
    [self schedule: @selector(tick:)];
    [self schedule: @selector(tick2:) interval:0.5];

    return self;
}

-(void) tick: (ccTime) dt
{
    //some function here
}

-(void) tick2: (ccTime) dt
{
    //some function here
}