Swift iOS -ScrollView w / StackView PageController崩溃

Question

1. 我跟着这个programmatic scrollview-pageview tutorial我一直在Scrollview代表ScrollViewDidScroll(...)
中遇到崩溃

  

主题1：EXC_BREAKPOINT（代码= 1，子代码= 0x1030b0d98）

此行显示崩溃：pageControl.currentPage = Int(round(pageFraction))

为什么这种崩溃不断发生

ViewController类：

class ViewController: UIViewController, UIScrollViewDelegate {

let scrollView: UIScrollView = {
    let scrollView = UIScrollView()
    scrollView.translatesAutoresizingMaskIntoConstraints = false
    scrollView.autoresizingMask = [.flexibleWidth, .flexibleHeight]
    scrollView.isPagingEnabled = true
    scrollView.showsHorizontalScrollIndicator = false
    scrollView.backgroundColor = UIColor.white
    return scrollView
}()

let stackView: UIStackView = {
    let stackView = UIStackView()
    stackView.translatesAutoresizingMaskIntoConstraints = false
    stackView.distribution = .equalSpacing
    return stackView
}()

let pageControl: UIPageControl = {
    let pageControl = UIPageControl()
    pageControl.translatesAutoresizingMaskIntoConstraints = false
    pageControl.currentPage = 0
    pageControl.tintColor = UIColor.white
    pageControl.pageIndicatorTintColor = UIColor.gray
    pageControl.currentPageIndicatorTintColor = UIColor.red
    pageControl.addTarget(self, action: #selector(pageControlTapped(sender:)), for: .valueChanged)
    return pageControl
}()

var views = [UIView]()

override func viewDidLoad() {
    super.viewDidLoad()

    view.backgroundColor = UIColor.white

    scrollView.delegate = self

    configureViewsForViewArray()
    setScrollViewAnchors()
    setStackViewAnchors()
    setPageViewsInsideStackView()
    setPageControlAnchors()
}

func configureViewsForViewArray(){

    let pageView1 = PageView(headerText: "Header 1", paragraphText: "Bla bla bla", backgroundColor: .red)
    views.append(pageView1)
    let pageView2 = PageView(headerText: "Header 2", paragraphText: "Bla bla bla", backgroundColor: .orange)
    views.append(pageView2)
    let pageView3 = PageView(headerText: "Header 3", paragraphText: "Bla bla bla", backgroundColor: .blue)
    views.append(pageView3)
    let pageView4 = PageView(headerText: "Header 4", paragraphText: "Bla bla bla", backgroundColor: .green)
    views.append(pageView4)
}

func setScrollViewAnchors(){

    view.addSubview(scrollView)

    if #available(iOS 11.0, *) {
        scrollView.leadingAnchor.constraint(equalTo: view.safeAreaLayoutGuide.leadingAnchor, constant: 0).isActive = true
    } else {
        scrollView.leadingAnchor.constraint(equalTo: view.leadingAnchor, constant: 0).isActive = true
    }

    if #available(iOS 11.0, *) {
        scrollView.trailingAnchor.constraint(equalTo: view.safeAreaLayoutGuide.trailingAnchor, constant: 0).isActive = true
    } else {
        scrollView.trailingAnchor.constraint(equalTo: view.trailingAnchor, constant: 0).isActive = true
    }

    if #available(iOS 11.0, *) {
        scrollView.topAnchor.constraint(equalTo: view.safeAreaLayoutGuide.topAnchor, constant: 0).isActive = true
    } else {
        scrollView.topAnchor.constraint(equalTo: view.topAnchor, constant: 0).isActive = true
    }

    if #available(iOS 11.0, *) {
        scrollView.bottomAnchor.constraint(equalTo: view.safeAreaLayoutGuide.bottomAnchor, constant: 0).isActive = true
    } else {
        scrollView.bottomAnchor.constraint(equalTo: view.bottomAnchor, constant: 0).isActive = true
    }
}

func setStackViewAnchors(){

    scrollView.addSubview(stackView)
    stackView.leftAnchor.constraint(equalTo: scrollView.leftAnchor).isActive = true
    stackView.rightAnchor.constraint(equalTo: scrollView.rightAnchor).isActive = true
    stackView.topAnchor.constraint(equalTo: scrollView.topAnchor).isActive = true
    stackView.bottomAnchor.constraint(equalTo: scrollView.bottomAnchor).isActive = true
}

func setPageViewsInsideStackView(){

    for eachView in self.views{
        eachView.translatesAutoresizingMaskIntoConstraints = false
        stackView.addArrangedSubview(eachView)
        eachView.heightAnchor.constraint(equalTo: view.heightAnchor).isActive = true
        eachView.widthAnchor.constraint(equalTo: view.widthAnchor).isActive = true
    }
}

func setPageControlAnchors(){

    view.addSubview(pageControl)

    pageControl.numberOfPages = views.count

    if #available(iOS 11.0, *) {
        pageControl.centerXAnchor.constraint(equalTo: view.safeAreaLayoutGuide.centerXAnchor).isActive = true
    } else {
        // Fallback on earlier versions
        pageControl.centerXAnchor.constraint(equalTo: view.centerXAnchor).isActive = true
    }

    if #available(iOS 11.0, *) {
        pageControl.bottomAnchor.constraint(equalTo: view.safeAreaLayoutGuide.bottomAnchor, constant: -20).isActive = true
    } else {
        // Fallback on earlier versions
        pageControl.bottomAnchor.constraint(equalTo: view.bottomAnchor, constant: -20).isActive = true
    }
}

@objc func pageControlTapped(sender: UIPageControl) {

    let pageWidth = scrollView.bounds.width
    let offset = sender.currentPage * Int(pageWidth)
    UIView.animate(withDuration: 0.33, animations: { [weak self] in
        self?.scrollView.contentOffset.x = CGFloat(offset)
    })
}

func scrollViewDidScroll(_ scrollView: UIScrollView) {

    let pageWidth = scrollView.bounds.width
    let pageFraction = scrollView.contentOffset.x/pageWidth

    //I get a crash here?
    pageControl.currentPage = Int(round(pageFraction))
}
}

//这是在

上面的[UIView]数组中添加的视图的模型

浏览量：

import Foundation
import UIKit

class PageView: UIView {

    // Private so that it can only be modified from within the class
    private var headerTextField = UITextField()
    // When this property is set it will update the headerTextField text
    var headerText: String = "" {
        didSet {
            headerTextField.text = headerText
        }
    }

    // Private so that you can only change from within the class
    private var paragraphTextView = UITextView()
    // When this property is set it will update the paragraphTextView text
    var paragraphText: String = "" {
        didSet {
            paragraphTextView.text = paragraphText
        }
    }

    // Designated Init method
    init(headerText: String, paragraphText: String, backgroundColor: UIColor) {
        super.init(frame: .zero)
        setup()
        self.headerTextField.text = headerText
        self.paragraphTextView.text = paragraphText
        self.backgroundColor = backgroundColor

    }

    override init(frame: CGRect) {
        super.init(frame: frame)
        setup()
    }

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

    func setup() {
        // Basic text and view setup
        headerTextField.isUserInteractionEnabled = false
        headerTextField.textColor = .black
        headerTextField.textAlignment = .center
        headerTextField.sizeToFit()

        paragraphTextView.isUserInteractionEnabled = false
        paragraphTextView.textColor = .black
        paragraphTextView.textAlignment = .center
        paragraphTextView.sizeToFit()
        paragraphTextView.isScrollEnabled = false
        paragraphTextView.backgroundColor = .clear

        // Configuring the textfield/view for autoLayout
        headerTextField.translatesAutoresizingMaskIntoConstraints = false
        self.addSubview(headerTextField)
        paragraphTextView.translatesAutoresizingMaskIntoConstraints = false
        self.addSubview(paragraphTextView)

        // Creating and activating the constraints
        NSLayoutConstraint.activate([
            headerTextField.centerXAnchor.constraint(equalTo: self.centerXAnchor),
            headerTextField.centerYAnchor.constraint(equalTo: self.centerYAnchor),
            paragraphTextView.centerXAnchor.constraint(equalTo: self.centerXAnchor),
            paragraphTextView.topAnchor.constraint(equalTo: headerTextField.bottomAnchor, constant: 20),
            paragraphTextView.widthAnchor.constraint(equalTo: self.widthAnchor, multiplier: (2/3))
            ])
    }

}