如何同时成功地为多个 CALayers 设置动画？

Question

我成功地为单个图层设置动画，以沿屏幕上的任意路径更改其位置。我现在尝试多次复制这个动画，以产生某种东西在拐角处弯曲的错觉。我将代码放在 CATransaction 中，并将其放入循环中，为循环的每次迭代递增起始位置，然后在循环后提交 CATransaction。如果代码不在循环中（也就是说，只有一个图层被动画），那么我看到的效果是相同的，然后在动画结束时所有图层都会出现（在我的代表在动画结束时删除它们之前 animationDidStop )

我写的代码是这样的：

NSArray* path = [board caclulatePath:s];
    [CATransaction begin];
    [CATransaction setValue:[NSNumber numberWithFloat:([path count] * 0.25)] forKey:kCATransactionAnimationDuration];
    for (int i = 0; i < 20; i++)
    {
        CALayer* laserLayer = [CALayer layer];
        laserLayer.bounds = CGRectMake(s.frame.origin.x, s.frame.origin.y + (10*i), 20, 10);
        laserLayer.position = CGPointMake(s.frame.origin.x + (s.frame.size.width / 2), s.frame.origin.y + (s.frame.size.height / 2) + (10*i));
        laserLayer.contents = (id)[UIImage imageNamed:@"Laser.png"].CGImage;
        [self.layer addSublayer:laserLayer];

        CAKeyframeAnimation* anim = [CAKeyframeAnimation animationWithKeyPath:@"position"];
        anim.values = path;
        anim.duration = ([path count] * 0.25);
        anim.removedOnCompletion = NO;
        anim.delegate = self;
        anim.rotationMode = kCAAnimationRotateAuto;
        [anim setValue:@"Fire" forKey:@"Action"];
        [anim setValue:laserLayer forKey:@"Layer"];
        [laserLayer addAnimation:anim forKey:nil];
    }
    [CATransaction commit];

其中 [board caclulatePath:s] 返回代表 CGPoints 的 NSValues 的 NSArray*。

我怎样才能达到我想要的效果（哪个是laser.png的多个副本遵循相同的路径）？ [Laser.png 是一个 20px x 20px 的红色正方形];

Answer 1

实际的问题是每个层都在同一时间遵循相同的路径...解决方案是在 i 递增的 (someSmallFractionOfTime * i) 延迟后触发每个层/动画。

所以我将动画部分提取为一个新的函数/方法/消息（不管它叫什么）

- (void) kickoffLaserAnimationWithPath: (NSArray *) path  {
CGPoint start = [(NSValue*)[path objectAtIndex:0] CGPointValue];
CALayer* laserLayer = [CALayer layer];
laserLayer.bounds = CGRectMake(start.x, start.y, 20, 10);
laserLayer.position = CGPointMake(start.x, start.y);
laserLayer.contents = (id)[UIImage imageNamed:@"Laser.png"].CGImage;
[self.layer addSublayer:laserLayer];

CAKeyframeAnimation* anim = [CAKeyframeAnimation animationWithKeyPath:@"position"];
anim.values = path;
anim.duration = ([path count] * laserSpeed);
anim.removedOnCompletion = NO;
anim.delegate = self;
anim.rotationMode = kCAAnimationRotateAuto;
[anim setValue:@"Fire" forKey:@"Action"];
[anim setValue:laserLayer forKey:@"Layer"];
[laserLayer addAnimation:anim forKey:nil];
isAnimating = YES;

}

并像这样在循环中调用它：

NSArray* path = [board caclulatePath:s];
    [CATransaction begin];
    [CATransaction setValue:[NSNumber numberWithFloat:([path count] * laserSpeed)] forKey:kCATransactionAnimationDuration];
    float numBetweenPoints = (float)((float)s.frame.size.height / (float)10) * 2;
    float delay = (laserSpeed / numBetweenPoints);
    for (int i = 0; i < [path count]; i++)
    {
        [self performSelector:@selector(kickoffLaserAnimationWithPath:) withObject:path afterDelay:(delay*i)];

    }
    [CATransaction commit];

瞧……

Answer 2

看看CAAnimationGroup。我认为它可能适合您的问题。