使用 iCarousel 缩放项目

Question

我正在尝试使用 iCarousel 作为我的解决方案之一，我需要实现如下图

应该是这样的

iCarouselOptionFadeMin iCarouselOptionFadeMax iCarouselOptionFadeRange iCarouselOptionFadeMinAlpha 使用

- (CGFloat)carousel:(iCarousel *)carousel valueForOption:(iCarouselOption)option withDefault:(CGFloat)value

我试图创建一个完全一样的函数

- (CGFloat)alphaForItemWithOffset:(CGFloat)offset

我发现它可以使用offset 值来完成，但事情对我不起作用，任何人都可以帮助我实现这一目标吗？

谢谢。

Answer 1

您可以通过委托方法中的iCarousel 的iCarouselTypeCustom 类型来做到这一点

- (CATransform3D)carousel:(iCarousel *)carousel itemTransformForOffset:(CGFloat)offset baseTransform:(CATransform3D)transform

只需设置轮播的类型（例如在轮播的视图控制器的viewDidLoad中）：

self.carousel.type = iCarouselTypeCustom;

并根据需要计算转换。我将物体放在双曲线上，并在它们远离中心时将它们缩小一点。我认为这与您的图像非常相似：

- (CATransform3D)carousel:(iCarousel *)carousel itemTransformForOffset:(CGFloat)offset baseTransform:(CATransform3D)transform
{
    const CGFloat offsetFactor = [self carousel:carousel valueForOption:iCarouselOptionSpacing withDefault:1.0f]*carousel.itemWidth;

    //The larger these values, as the items move away from the center ...

    //... the faster they move to the back
    const CGFloat zFactor = 150.0f;

    //... the faster they move to the bottom of the screen
    const CGFloat normalFactor = 50.0f;

    //... the faster they shrink
    const CGFloat shrinkFactor = 3.0f;

    //hyperbola
    CGFloat f = sqrtf(offset*offset+1)-1;

    transform = CATransform3DTranslate(transform, offset*offsetFactor, f*normalFactor, f*(-zFactor));
    transform = CATransform3DScale(transform, 1/(f/shrinkFactor+1.0f), 1/(f/shrinkFactor+1.0f), 1.0);
    return transform;
}

结果：

您可以根据自己的喜好调整浮点常量。

要围绕一个圆圈移动项目，同时缩放它们，只需使用测角函数进行平移，然后旋转和缩放：

- (CGFloat)carousel:(iCarousel *)carousel valueForOption:(iCarouselOption)option withDefault:(CGFloat)value
{
    if (option == iCarouselOptionSpacing)
    {
        return value * 2.0f;
    }
    if(option == iCarouselOptionVisibleItems)
    {
        return 11;
    }
    if(option == iCarouselOptionWrap) return YES;
    return value;
}

- (CATransform3D)carousel:(iCarousel *)carousel itemTransformForOffset:(CGFloat)offset baseTransform:(CATransform3D)transform
{
    const CGFloat radius = [self carousel:carousel valueForOption:iCarouselOptionRadius withDefault:200.0];
    const CGFloat offsetFactor = [self carousel:carousel valueForOption:iCarouselOptionSpacing withDefault:1.0f]*carousel.itemWidth;
    const CGFloat angle = offset*offsetFactor/radius;

    //... the faster they shrink
    const CGFloat shrinkFactor = 2.0f;
    //hyperbola (now only for shrinking purposes)
    CGFloat f = sqrtf(offset*offset+1)-1;


    transform = CATransform3DTranslate(transform, radius*sinf(angle), radius*(1-cosf(angle)), 0.0);
    transform = CATransform3DRotate(transform, angle, 0, 0, 1);
    transform = CATransform3DScale(transform, 1/(f*shrinkFactor+1.0f), 1/(f*shrinkFactor+1.0f), 1.0);
    return transform;
} 

再一次，结果：

您可以在carousel:valueForOption:withDefault:方法中调整间距和半径。

享受吧！ :)

Answer 2

稍作修改并在 SWIFT 中复制粘贴 ;) - 非常适合我

func carousel(carousel: iCarousel, valueForOption option: iCarouselOption, withDefault value: CGFloat) -> CGFloat {
    if option == iCarouselOption.Spacing {
        return value * 1.8
    }
    return value
}

func carousel(carousel: iCarousel, itemTransformForOffset offset: CGFloat, baseTransform transform: CATransform3D) -> CATransform3D {
    let offsetFactor = self.carousel(carousel, valueForOption: iCarouselOption.Spacing, withDefault: 1) * carousel.itemWidth

    let zFactor: CGFloat = 150
    let normalFactor: CGFloat = 0
    let shrinkFactor: CGFloat = 1
    let f = sqrt(offset*offset+1)-1

    var transform = CATransform3DTranslate(transform, offset*offsetFactor, f*normalFactor, f*(-zFactor));
    transform = CATransform3DScale(transform, 1/(f/shrinkFactor+1), 1/(f/shrinkFactor+1), 1);
    return transform;
}

Answer 3

我没有足够的声誉来发表评论，所以我必须再问一个问题作为回复:(

@burax 是否可以在线性线上而不是双曲线上布局项目但保持调整大小？

问候，很抱歉这样问

编辑：通过随机尝试我实现了这个：

- (CATransform3D)carousel:(iCarousel *)carousel itemTransformForOffset:(CGFloat)offset baseTransform:(CATransform3D)transform
{
const CGFloat radius = [self carousel:carousel valueForOption:iCarouselOptionRadius withDefault:5050.0];
const CGFloat offsetFactor = [self carousel:carousel valueForOption:iCarouselOptionSpacing withDefault:0.8f]*carousel.itemWidth;
const CGFloat angle = offset*offsetFactor/radius;

//... the faster they shrink
const CGFloat shrinkFactor = 2.0f;
//hyperbola (now only for shrinking purposes)
CGFloat f = sqrtf(offset*offset+1)-1;


transform = CATransform3DTranslate(transform, radius*sinf(angle), radius*(1-cosf(angle)), 0.0);
transform = CATransform3DRotate(transform, angle, 0, 0, 1);
transform = CATransform3DScale(transform, 1/(f*shrinkFactor+1.0f), 1/(f*shrinkFactor+1.0f), 1.0);
return transform;
}

可能有更好的方法，但我对转换不熟悉 :)