iphone - 如何成功地同时为多个 CALayer 制作动画？

Question

我成功地对单个图层进行了动画处理，以改变其沿屏幕上任意路径的位置。我现在尝试多次复制此动画，以产生某种东西在拐角处弯曲的错觉。我将代码放入 CATransaction 中，并将其放入一个循环中，递增循环每次迭代的起始位置，然后在循环后提交 CATransaction。如果代码不在循环中(即，只有一层被动画化)，那么在动画结束时所有层都会出现(在我的委托(delegate)在animationDidStop中的动画结束时删除它们之前)，我看到的效果是相同的)

我编写的代码如下所示:

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] 返回表示 CGPoints 的 NSValues 的 NSArray*。

如何才能达到我想要的效果(即沿同一路径复制 Laser.png 的多个副本)？ [Laser.png 是一个 20px x 20px 的红色正方形]；

Answer 1

实际问题是每个层同时遵循相同的路径...解决方案是在延迟 (someSmallFractionOfTime * i) 后触发每个层/动画，其中 i 递增。

所以我将动画部分提取为新函数/方法/消息(无论它叫什么)

- (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;

}

并在循环中调用它，如下所示:

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...