iPhone SDK：定時器失效后，如何再次使用？

Question

我已經使用 NSTimer 在 Xcode 中設置了一個 animation，它一遍又一遍地重復，所以我使用了這個命令：

else if(gordon.image == pigImage11)
    [animationTimer invalidate];

因此，當 gordon（一個 UIImageView）圖像設置為 pigImage11 時，計時器失效，這達到了停止 animation 不斷重復的預期效果，但停止了再次使用計時器，那么我如何讓計時器再次可用，但是有它在那個框架上使自己失效？ 為了進一步說明，這是我的全部代碼：

- (IBAction)startClick:(id)sender{
    animationTimer = [NSTimer scheduledTimerWithTimeInterval:(1.00/30.00) target:self selector:@selector(tick) userInfo:nil repeats:YES];
}
- (void)tick{
    [self animatePig];
}
- (void)animatePig{
    UIImage *pigImage1=[UIImage imageNamed:@"gordonapple0004.png"];
    UIImage *pigImage2=[UIImage imageNamed:@"gordonapple0005.png"];
    UIImage *pigImage3=[UIImage imageNamed:@"gordonapple0006.png"];
    UIImage *pigImage4=[UIImage imageNamed:@"gordonapple0007.png"];
    UIImage *pigImage5=[UIImage imageNamed:@"gordonapple0008.png"];
    UIImage *pigImage6=[UIImage imageNamed:@"gordonapple0009.png"];
    UIImage *pigImage7=[UIImage imageNamed:@"gordonapple0010.png"];
    UIImage *pigImage8=[UIImage imageNamed:@"gordonapple0011.png"];
    UIImage *pigImage9=[UIImage imageNamed:@"gordonapple0012.png"];
    UIImage *pigImage10=[UIImage imageNamed:@"gordonapple0013.png"];
    UIImage *pigImage11=[UIImage imageNamed:@"gordonapple0014.png"];
    UIImage *pigImage12=[UIImage imageNamed:@"gordonapple0015.png"];
    UIImage *pigImage13=[UIImage imageNamed:@"gordonapple0016.png"];


    if(gordon.image == pigImage1)
        gordon.image = pigImage2;
    else if(gordon.image == pigImage2)
        gordon.image = pigImage3;
    else if(gordon.image == pigImage3)
        gordon.image = pigImage4;
    else if(gordon.image == pigImage4)
        gordon.image = pigImage5;
    else if(gordon.image == pigImage5)
        gordon.image = pigImage6;
    else if(gordon.image == pigImage6)
        gordon.image = pigImage7;
    else if(gordon.image == pigImage7)
        gordon.image = pigImage8;
    else if(gordon.image == pigImage8)
        gordon.image = pigImage9;
    else if(gordon.image == pigImage9)
        gordon.image = pigImage10;
    else if(gordon.image == pigImage10)
        gordon.image = pigImage11;
    else if(gordon.image == pigImage11)
        [animationTimer invalidate];
    else
        gordon.image = pigImage1;
}

- (void)stopTimer
{
    [animationTimer invalidate];
    [animationTimer release];
}

Answer 1

您可以像這樣重用計時器：

- (void) startTimer {
    if ( myTimer == nil ) {
        myTimer = [NSTimer scheduledTimerWithTimeInterval: 5.0f
                   target: self
                   selector: @selector(myTimerAction:)
                   userInfo: nil
                   repeats: NO];
    }
}

- (void) stopTimer {
    if ( myTimer || [myTimer isValid])
    {
        [myTimer invalidate];
        myTimer = nil;
    }
}

Answer 2

不使計時器無效而只設置一個“不動畫”標志怎么樣？

Answer 3

[[NSRunLoop currentRunLoop] addTimer:animationTimer
                             forMode:NSDefaultRunLoopMode];

但是你當然不能在無效后釋放定時器。

Answer 4

為什么不使用 animation 中內置的 UIImageView：

UIImageView* gordonView = [[UIImage alloc]init];
gordonview.animationImages = [NSArray arrayWithObjects: pigImage1, pigimage2, etc., nil];
gordonView.animationDuration = 0.5f; // about 30fps with your 13 images. 
//Set gordon's frame here
[gordonView startAnimating];

披露，我在 SO 中輸入了這個，而不是 Xcode 我確定它不會編譯，但至少你知道在 SDK 中尋找什么。