将CALayers作为子视图合并并翻转到CATransformLayer

Question

基于前面的stackoverflow建议，我正在尝试使用添加到CATransformLayer中的CALayers创建一张扑克牌。这个想法是创建正面和背面CALayers，并将它们组合在CATransformLayer中，然后可以旋转、翻转等，并自动显示正确的一面。下面的示例代码尝试创建一张正面为绿色，背面为红色的单张卡片。

红色背面围绕Y轴翻转，因此它背对着绿色正面。绿色前轮的Z位置比红色后轮的Z位置高。

但是，当我进行转换时，我只是看到卡片处于未翻转的状态。你知道我在哪里做错了吗？

#define DEGREES_TO_RADIANS(angle) (angle * M_PI / 180.0)

- (void)viewDidLoad
{
    [super viewDidLoad];

    CATransformLayer *cardContainer = [CATransformLayer layer];

    cardContainer.bounds = CGRectMake(0,0, 150,200);


    CALayer *cardFront  = [CALayer layer];
    cardFront.frame     = cardContainer.bounds;

    cardFront.backgroundColor = [UIColor greenColor].CGColor;
    cardFront.borderColor = [UIColor blackColor].CGColor;
    cardFront.borderWidth = 2.0;
    cardFront.cornerRadius = 30.0;
    cardFront.zPosition = 2; // Put front of card on top relative to back of card
    cardFront.doubleSided = NO;
    [cardContainer addSublayer:cardFront];

    CALayer *cardBack  = [CALayer layer];
    cardBack.frame     = cardContainer.bounds;
    cardBack.backgroundColor = [UIColor redColor].CGColor;
    cardBack.zPosition = 1;
    cardBack.doubleSided = NO;

    // Flip cardBack image so it is facing outward and visible when flipped
    cardBack.transform = CATransform3DMakeRotation(DEGREES_TO_RADIANS(180),0.0,1.0,0.0);
    [cardContainer addSublayer:cardBack];

    UIView* cardView = [[UIView alloc] initWithFrame:cardContainer.bounds];
    cardView.center = CGPointMake(self.view.center.x, self.view.center.y);
    [cardView.layer addSublayer:cardContainer];
    [self.view addSubview:cardView];

    // Show the card flipped over (desired the red side to be showing, but instead shows green)
    cardView.layer.transform = CATransform3DMakeRotation(DEGREES_TO_RADIANS(180),0.0,1.0,0.0);

}

Answer 1

发现问题后，必须将转换应用于sublayerTransform属性，如下所示：

cardView.layer.sublayerTransform = ...