Question

最近我从Android世界切换到iOS。我已经看到了两种创建水平滑块的选项。我的目标是在此图像上创建一个水平的卡片滑块。我很困惑哪个元素需要iOS中最好的选项。我应该使用CollectionView还是应该使用PageViewController？由于我是初学者，因此我不能在现阶段使用图书馆，因为我的知识有限。请建议我该怎么办

Answer 1

简短回答

您应该使用UICollectionView。

更详细的答案

1）使用UICollectionViewFlowLayout

设置水平布局

let layout = UICollectionViewFlowLayout()
// The size of each item. Pick a suitable height so that the items do not get stacked:
layout.itemSize = CGSize(width: view.frame.width / 2, height: view.frame.height)
// The most important part:
layout.scrollDirection = .horizontal
// Then initialize collectionView
let collectionView = UICollectionView(frame: frame, collectionViewLayout: layout)

2）设置缩放（伪代码）

我是self实施UIScrollViewDelegate方法scrollViewDidScroll(UIScrollView)

ii。设置collectionView.delgate = self

iii。在scrollViewDidScroll(UIScrollView)中，通过转换scrollView as! UICollectionView并获取visibleCells属性来获取所有可见单元格。

iv。对于可见细胞中的细胞，设置适当的比例（细胞内容，不是细胞本身），CGAffineTransform给定细胞距离屏幕水平中心的距离。这可能需要一些算术;这应该工作得很好：

s = −0.00005 * pow(cell.center.x, 2) + 1.5

希望这有帮助！如果需要，请随时要求澄清。

Answer 2

我已经为轮播幻灯片尝试了 CollectionView，但它对我不起作用。我不喜欢我必须做的让它在一行中显示图像的黑客方式，我也不喜欢它无法返回活动图像的事实（这里也有一些解决方法，但他们没有看起来很可靠）。因此，很自然地，我最终为我的目的构建了一个自定义幻灯片轮播。我将在这里分享代码，希望它可以帮助（或至少指导某人）解决类似的问题。

注意：我的旋转木马是全宽、singleImagePerScreen 旋转木马，带有滑动识别器来滑动图像和在图像处于活动状态时触发的委托功能（我用它来显示活动图像 - “1 of 5”）。< /p>

已测试：SWIFT 5、XCode 12.2、iOS 14.2

// ImageCarouselView class

import UIKit

class ImageCarouselView: UIView {
    private let images: [UIImage?]
    private var index = 0
    private let screenWidth = UIScreen.main.bounds.width

    var delegate: ImageCarouselViewDelegate?

    lazy var previousImageView = imageView(image: nil, contentMode: .scaleAspectFit)
    lazy var currentImageView = imageView(image: nil, contentMode: .scaleAspectFit)
    lazy var nextImageView = imageView(image: nil, contentMode: .scaleAspectFit)

    lazy var previousImageLeadingConstraint: NSLayoutConstraint = {
        return previousImageView.leadingAnchor.constraint(equalTo: leadingAnchor, constant: -screenWidth)
    }()

    lazy var currentImageLeadingConstraint: NSLayoutConstraint = {
        return currentImageView.leadingAnchor.constraint(equalTo: leadingAnchor, constant: 0)
    }()

    lazy var nextImageLeadingConstraint: NSLayoutConstraint = {
        return nextImageView.leadingAnchor.constraint(equalTo: leadingAnchor, constant: screenWidth)
    }()

    init(_ images: [UIImage?]) {
        self.images = images

        super.init(frame: .zero)

        self.translatesAutoresizingMaskIntoConstraints = false

        setupLayout()
        setupImages()
        setupSwipeRecognizer()
    }

    required init?(coder: NSCoder) {
        fatalError("init(coder:) has not been implemented")
    }

    private func setupLayout() {
        self.subviews.forEach({ $0.removeFromSuperview() })

        addSubview(previousImageView)
        addSubview(currentImageView)
        addSubview(nextImageView)

        previousImageLeadingConstraint = previousImageView.leadingAnchor.constraint(equalTo: leadingAnchor, constant: -screenWidth)
        currentImageLeadingConstraint = currentImageView.leadingAnchor.constraint(equalTo: leadingAnchor, constant: 0)
        nextImageLeadingConstraint = nextImageView.leadingAnchor.constraint(equalTo: leadingAnchor, constant: screenWidth)

        NSLayoutConstraint.activate([
            previousImageLeadingConstraint,
            previousImageView.centerYAnchor.constraint(equalTo: centerYAnchor),
            previousImageView.widthAnchor.constraint(equalToConstant: screenWidth),

            currentImageLeadingConstraint,
            currentImageView.centerYAnchor.constraint(equalTo: centerYAnchor),
            currentImageView.widthAnchor.constraint(equalToConstant: screenWidth),

            nextImageLeadingConstraint,
            nextImageView.centerYAnchor.constraint(equalTo: centerYAnchor),
            nextImageView.widthAnchor.constraint(equalToConstant: screenWidth),
        ])
    }

    private func setupImages() {
        currentImageView.image = images[self.index]

        guard images.count > 1 else { return }

        if (index == 0) {
            previousImageView.image = images[images.count - 1]
            nextImageView.image = images[index + 1]
        }

        if (index == (images.count - 1)) {
            previousImageView.image = images[index - 1]
            nextImageView.image = images[0]
        }
    }

    private func setupSwipeRecognizer() {
        guard images.count > 1 else { return }

        let leftSwipe = UISwipeGestureRecognizer(target: self, action: #selector(handleSwipes))
        let rightSwipe = UISwipeGestureRecognizer(target: self, action: #selector(handleSwipes))

        leftSwipe.direction = .left
        rightSwipe.direction = .right

        self.addGestureRecognizer(leftSwipe)
        self.addGestureRecognizer(rightSwipe)
    }

    @objc private func handleSwipes(_ sender: UISwipeGestureRecognizer) {
        if (sender.direction == .left) {
            showNextImage()
        }

        if (sender.direction == .right) {
            showPreviousImage()
        }
    }

    private func showPreviousImage() {
        previousImageLeadingConstraint.constant = 0
        currentImageLeadingConstraint.constant = screenWidth

        UIView.animate(withDuration: 0.2, delay: 0.0, options: .curveEaseIn, animations: {
            self.layoutIfNeeded()
        }, completion: { _ in
            self.nextImageView = self.currentImageView
            self.currentImageView = self.previousImageView
            self.previousImageView = self.imageView(image: nil, contentMode: .scaleAspectFit)

            self.index = self.index == 0 ? self.images.count - 1 : self.index - 1
            self.delegate?.imageCarouselView(self, didShowImageAt: self.index)
            self.previousImageView.image = self.index == 0 ? self.images[self.images.count - 1] : self.images[self.index - 1]

            self.setupLayout()
        })
    }

    private func showNextImage() {
        nextImageLeadingConstraint.constant = 0
        currentImageLeadingConstraint.constant = -screenWidth

        UIView.animate(withDuration: 0.2, delay: 0.0, options: .curveEaseIn, animations: {
            self.layoutIfNeeded()
        }, completion: { _ in
            self.previousImageView = self.currentImageView
            self.currentImageView = self.nextImageView
            self.nextImageView = self.imageView(image: nil, contentMode: .scaleAspectFit)

            self.index = self.index == (self.images.count - 1) ? 0 : self.index + 1
            self.delegate?.imageCarouselView(self, didShowImageAt: self.index)
            self.nextImageView.image = self.index == (self.images.count - 1) ? self.images[0] : self.images[self.index + 1]

            self.setupLayout()
        })
    }

    func imageView(image: UIImage? = nil, contentMode: UIImageView.ContentMode) -> UIImageView {
        let view = UIImageView()

        view.image = image
        view.contentMode = contentMode
        view.translatesAutoresizingMaskIntoConstraints = false

        return view
    }
}

// ImageCarouselViewDelegate

import UIKit

protocol ImageCarouselViewDelegate: NSObjectProtocol {
    func imageCarouselView(_ imageCarouselView: ImageCarouselView, didShowImageAt index: Int)
}

// Usage

let slideshowView = ImageCarouselView(images) // initialize

self.slideshowView.delegate = self // set delegate in viewDidLoad()

extension YourViewController: ImageCarouselViewDelegate {
    func imageCarouselView(_ imageCarouselView: ImageCarouselView, didShowImageAt index: Int) {
        // do something with index
    }
}

如何在iOS 10 Swift 3中创建水平轮播

2 个答案:

简短回答

更详细的答案