Question

我需要显示有关通过CAKeyframeAnimation显示的当前fey帧图像的信息。因此，当显示“值”索引0处的图像时，在某些NSTextField中显示关于该图像的信息，并且当它动画到索引1时显示关于该图像的信息。是否有可能做到这一点？

CAKeyframeAnimation *theAnimation=[CAKeyframeAnimation animationWithKeyPath:@"contents"];
theAnimation.values = myView.productImages;
theAnimation.duration = 5.0;
theAnimation.repeatCount = HUGE_VALF;
theAnimation.calculationMode = kCAAnimationDiscrete;
theAnimation.fillMode = kCAFillModeRemoved;
[myView.exampleCALayer addAnimation:theAnimation forKey:@"contents"];
[myView.exampleCALayer setNeedsDisplay];

Answer 1

通常情况下，您可以观察位置等属性，例如，在动画运行时很容易使用计时器或显示链接，但是，因为它是您要监视的内容属性，所以事情变得更加棘手。我建议您为自己的自定义属性设置动画。然后，您可以在组中为其添加动画以及现有内容动画，并在自定义属性更改时获取更新。

步骤如下：

声明CALayer派生类
覆盖这些方法：

- (id)initWithLayer:(id)layer

+ (BOOL)needsDisplayForKey:(NSString*)key

- (void)drawInContext:(CGContextRef)ctx
在标题
创建动画属性的关键帧动画

以下是您的图层在其实现中的外观：

@implementation MLImageLayer

- (id)initWithLayer:(id)layer
{
    if(self = [super initWithLayer:layer]) {
        if([layer isKindOfClass:[MLImageLayer class]]) {
            MLImageLayer *other = (MLImageLayer*)layer;
      [self setCounter:[other counter]];
        }
    }
    return self;
}

+ (BOOL)needsDisplayForKey:(NSString*)key
{
  if ([key isEqualToString:@"counter"]) {
    return YES;
  } else {
    return [super needsDisplayForKey:key];
  }
}

- (void)drawInContext:(CGContextRef)ctx
{
  DLog(@"Counter is: %d", _counter);
}

@end

然后，要实际为该属性设置动画，请执行以下操作：

  CAKeyframeAnimation *counterAnimation = [CAKeyframeAnimation 
                                              animationWithKeyPath:@"counter"];
  [counterAnimation setDelegate:self];
  NSArray *values = @[@(0), @(1), @(2), @(3), @(4), @(5)];
  [counterAnimation setValues:values];
  [counterAnimation setDuration:5.0];
  [counterAnimation setRepeatCount:HUGE_VALF];
  [counterAnimation setCalculationMode:kCAAnimationDiscrete];

现在，回到派生图层的-drawInContext：方法中，您可以监视计数器值，然后做出相应的响应。

但是，这可能有点棘手，因为您同时为两个属性设置了动画。您必须使用一组来使其正常工作：

- (void)viewDidLoad
{
  [super viewDidLoad];

  _animationLayer = [MLImageLayer layer];
  [_animationLayer setBounds:CGRectMake(0.0f, 0.0f, 400.0f, 320.0f)];
  [_animationLayer setPosition:[[self view] center]];

  UIImage *image = [UIImage imageNamed:@"Countryside.jpg"];
  [_animationLayer setContents:(__bridge id)[image CGImage]];

  [[[self view] layer] addSublayer:_animationLayer];

  CAKeyframeAnimation *slideShowAnimation = [CAKeyframeAnimation animationWithKeyPath:@"contents"];
  [slideShowAnimation setValues:@[(id)[[UIImage imageNamed:@"Countryside.jpg"] CGImage],
   (id)[[UIImage imageNamed:@"Countryside-1.jpg"] CGImage],
   (id)[[UIImage imageNamed:@"Countryside-2.jpg"] CGImage],
   (id)[[UIImage imageNamed:@"Countryside-3.jpg"] CGImage],
   (id)[[UIImage imageNamed:@"Countryside-4.jpg"] CGImage],
   (id)[[UIImage imageNamed:@"Countryside-5.jpg"] CGImage]]];

  [slideShowAnimation setDuration:5.0];
  [slideShowAnimation setDelegate:self];
  [slideShowAnimation setRepeatCount:HUGE_VALF];
  [slideShowAnimation setCalculationMode:kCAAnimationDiscrete];

  CAKeyframeAnimation *counterAnimation = [CAKeyframeAnimation animationWithKeyPath:@"counter"];
  [counterAnimation setDelegate:self];
  NSArray *values = @[@(0), @(1), @(2), @(3), @(4), @(5)];
  [counterAnimation setValues:values];
  [counterAnimation setDuration:5.0];
  [counterAnimation setRepeatCount:HUGE_VALF];
  [counterAnimation setCalculationMode:kCAAnimationDiscrete];

  CAAnimationGroup *group = [CAAnimationGroup animation];
  [group setDuration:5.0];
  [group setRepeatCount:HUGE_VALF];
  [group setAnimations:@[slideShowAnimation, counterAnimation]];

  [_animationLayer addAnimation:group forKey:nil];
}

我发布了一个项目up on github。它是为iOS编写的，但您应该能够在OSX应用程序中调整Core Animation特定代码。

Answer 2

哇，这太棒了!!!我会用它......

只有一个注释，我在Xcode 5上，我注意到只有第一个动画“slideShowAnimation”被触发。

我可以通过添加以下两行来修复它：

[slideShowAnimation setBeginTime:0];
[counterAnimation setBeginTime:0];

感谢分享。 - nIc

检测CAKeyframeAnimation中显示的帧

2 个答案: