如何在特定索引处添加动画层 [英] How to add an animated layer at a specific index

问题描述

我在视图中添加了两个CAText层，并对其中的一个进行了动画处理。我想为一层动画，但要在动画制作完成之前在层层次结构中正确定位。谁能看到我做错了吗？动画有效，它一直在 topcharlayer2后面运行，直到动画完成。

I am adding two CAText layers to a view and animating one of them. I want to animate one layer above the other but it doesn't get positioned correctly in the layer hierarchy until the animation has finished. Can anyone see what I have done wrong? The animation works, it is just running behind 'topcharlayer2' until the animation has finished.

- (CABasicAnimation *)topCharFlap
{
CABasicAnimation *flipAnimation;


flipAnimation = [CABasicAnimation animationWithKeyPath:@"transform"]; 
flipAnimation.toValue      = [NSValue valueWithCATransform3D:CATransform3DMakeRotation(1.57f, 1, 0, 0)];
flipAnimation.fromValue    = [NSValue valueWithCATransform3D:CATransform3DMakeRotation(0.0, 1, 0, 0)]; 
flipAnimation.autoreverses = NO; 
flipAnimation.duration     = 0.5f;
flipAnimation.repeatCount  = 10;


return flipAnimation;
}

- (id)initWithFrame:(CGRect)frame {
if ((self = [super initWithFrame:frame])) {
    [self setBackgroundColor:[UIColor clearColor]]; //makes this view transparent other than what is drawn.

    [self initChar];
}

return self;
}

static CATransform3D CATransform3DMakePerspective(CGFloat z)
{
CATransform3D t = CATransform3DIdentity;
t.m34 = - 1. / z;
return t;
}



-(void) initChar 
{
UIFont *theFont = [UIFont fontWithName:@"AmericanTypewriter" size:FONT_SIZE];

self.layer.sublayerTransform = CATransform3DMakePerspective(-1000.0f);

topHalfCharLayer2 = [CATextLayer layer];

topHalfCharLayer2.bounds = CGRectMake(0.0f, 0.0f, CHARACTERS_WIDTH, 100.0f);
topHalfCharLayer2.string = @"R";    
topHalfCharLayer2.font = theFont.fontName;
topHalfCharLayer2.fontSize = FONT_SIZE;
topHalfCharLayer2.backgroundColor = [UIColor blackColor].CGColor;
topHalfCharLayer2.position = CGPointMake(CGRectGetMidX(self.bounds),CGRectGetMidY(self.bounds));

topHalfCharLayer2.wrapped = NO;


topHalfCharLayer1 = [CATextLayer layer];


topHalfCharLayer1.bounds = CGRectMake(0.0f, 0.0f, CHARACTERS_WIDTH, 100.0f);
topHalfCharLayer1.string = @"T";


topHalfCharLayer1.font = theFont.fontName;
topHalfCharLayer1.fontSize = FONT_SIZE;

topHalfCharLayer1.backgroundColor = [UIColor redColor].CGColor;
topHalfCharLayer1.position = CGPointMake(CGRectGetMidX(self.bounds),CGRectGetMidY(self.bounds));
topHalfCharLayer1.wrapped = NO;
//topHalfCharLayer1.zPosition = 100;

[topHalfCharLayer1 setAnchorPoint:CGPointMake(0.5f,1.0f)];

[[self layer] addSublayer:topHalfCharLayer1 ];
[[self layer] insertSublayer:topHalfCharLayer2 atIndex:0];

[topHalfCharLayer1 addAnimation:[self topCharFlap] forKey:@"anythingILikeApparently"];

}

包含此代码的View由视图控制器加载在loadView中。视图的initWithFrame方法中调用了initChar方法。目标是iOS4。我没有使用setWantsLayer，因为我已经知道iOS中的UIView是自动支持图层的，不需要此。

The View which contains this code is loaded by a view controller in loadView. The initChar method is called in the view's initWithFrame method. The target is iOS4. I'm not using setWantsLayer as I've read that UIView in iOS is automatically layer backed and doesn't require this.

推荐答案

从crystal-dev苹果邮件列表中：

From the quartz-dev apple mailing list:

通常在2D情况下，addSublayer会在先前的
上方绘制新层。但是，我相信这种实现机制是独立于zPosition的
，并且可能仅使用了
画家的算法。但是，当您添加zPositions和3D时，我不认为您可以完全依靠图层排序。但是实际上我不清楚
是否在您未在图层上设置
zPositions却设置了3D变换矩阵的情况下由Apple保证。

Generally in a 2D case, addSublayer will draw the new layer above the previous. However, I believe this implementation mechanism is independent of zPosition and probably just uses something like painter's algorithm. But the moment you add zPositions and 3D, I don't think you can solely rely on layer ordering. But I am actually unclear if Apple guarantees anything in the case where you have not set zPositions on your layers but have a 3D transform matrix set.

因此，似乎我在将3D变换应用于图层时必须显式设置zPosition。

So, it seems I have to set the zPosition explicitly when applying 3D transforms to layers.

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