使用Snapkit的约束问题

Question

所以我只是有点困惑为什么这不能按照我想要的方式在这个VC中工作。 基本上我有一个滚动视图设置，其中包含一些项目。顶部项是imageContainer，其中包含一个图像，然后在下面是collectionView。但是，当我尝试将collectionView绑定到scrollView的底部时，没有任何内容出现。它只在我给它高度后出现。 但是不应该将它固定在它上面的项目的底部，并且滚动视图的底部定义它的高度。当我定义高度并滚动到底部时，我可以看到我不想要的scrollView的背面。

我在创建此屏幕时试图模仿本教程 https://medium.freecodecamp.org/tutorial-creating-stretchy-layouts-on-ios-using-auto-layout-3fa974fa5e28

import Foundation
import UIKit

class NewProfileVC: UIViewController,UIScrollViewDelegate {
    private let scrollView = UIScrollView()
    private let imageView = UIImageView()
    private let imageContainer = UIView()
    let cellID = "cellID"
    let headerID = "headerID"

    lazy var myCollectionView : UICollectionView = {
        let layout = UICollectionViewFlowLayout()
        let cv = UICollectionView(frame: CGRect.zero, collectionViewLayout: layout)
        cv.translatesAutoresizingMaskIntoConstraints = false
        cv.delegate = self
        cv.dataSource = self
        cv.backgroundColor = .yellow
        return cv
    }()

    lazy var currentImage : UIImageView = {
        let currentImage = UIImageView()
        currentImage.clipsToBounds = true
        currentImage.translatesAutoresizingMaskIntoConstraints = false
        currentImage.contentMode = .scaleToFill
        currentImage.layer.masksToBounds = true
        currentImage.image = UIImage(named: "lbj")
        return currentImage
    }()

    override func viewDidLoad() {
        super.viewDidLoad()
        myCollectionView.register(NewUserHeader.self, forSupplementaryViewOfKind: UICollectionElementKindSectionHeader, withReuseIdentifier: headerID)
        myCollectionView.register(NewUserEventAttendingCell.self, forCellWithReuseIdentifier: cellID)
        setupVC()
    }
    @objc func setupVC(){
    //will be responsible for setting up vc
        self.navigationController?.navigationBar.isTranslucent = false
        let bounds = self.navigationController!.navigationBar.bounds

        self.navigationController?.navigationBar.frame = CGRect(x: 0, y: 0, width: bounds.width, height: bounds.height - 400)

        view.addSubview(scrollView)
        scrollView.contentInsetAdjustmentBehavior = .never
        scrollView.delegate = self
        scrollView.showsVerticalScrollIndicator = false

        //Pin the edges of the scroll view to
        // our view controller’s view
        scrollView.backgroundColor = .white
        scrollView.snp.makeConstraints { (make) in
            make.edges.equalTo(view.safeAreaLayoutGuide)
        }
        imageContainer.backgroundColor = .darkGray
        scrollView.addSubview(imageContainer)
        //Pin the top of our image view to the scroll view
        // pin the left and right to the view controller’s view
        // give it an aspect ratio constraint by constraining
        // its height to its width with a multiplier
        imageContainer.snp.makeConstraints {(make) in
            make.top.equalTo(scrollView)
            make.left.right.equalTo(view)
            make.height.equalTo(imageContainer.snp.width).multipliedBy(0.95)
        }

        scrollView.addSubview(currentImage)
        currentImage.snp.makeConstraints {(make) in
            make.left.right.equalTo(imageContainer)
            //** Note the priorities
            make.top.equalTo(view).priority(.high)
            //** We add a height constraint too
            make.height.greaterThanOrEqualTo(imageContainer.snp.height).priority(.required)
            //** And keep the bottom constraint
            make.bottom.equalTo(imageContainer.snp.bottom)
        }

        scrollView.addSubview(myCollectionView)
        myCollectionView.snp.makeConstraints {(make) in
            make.top.equalTo(imageContainer.snp.bottom)
            make.left.right.equalTo(view)
            make.bottom.equalTo(scrollView)
            make.height.equalTo(view.bounds.height/1.5)
        }

    }

    override func viewDidLayoutSubviews() {
        super.viewDidLayoutSubviews()
        //** We want the scroll indicators to use all safe area insets
        scrollView.scrollIndicatorInsets = view.safeAreaInsets
        //** But we want the actual content inset to just respect the bottom safe inset
        scrollView.contentInset = UIEdgeInsets(top: 0, left: 0, bottom: view.safeAreaInsets.bottom, right: 0)
    }

    private var previousStatusBarHidden = false

    func scrollViewDidScroll(_ scrollView: UIScrollView) {
        if previousStatusBarHidden != shouldHideStatusBar {

            UIView.animate(withDuration: 0.2, animations: {
                self.setNeedsStatusBarAppearanceUpdate()
            })

            previousStatusBarHidden = shouldHideStatusBar
        }
    }

    private var shouldHideStatusBar: Bool {
        let frame = myCollectionView.convert(myCollectionView.bounds, to: nil)
        return frame.minY < view.safeAreaInsets.top
    }


    override var preferredStatusBarUpdateAnimation: UIStatusBarAnimation {
        return .slide
    }

    override var prefersStatusBarHidden: Bool {
        return shouldHideStatusBar
    }

    override var preferredStatusBarStyle: UIStatusBarStyle {
        return .lightContent
    }


}

extension NewProfileVC: UICollectionViewDataSource, UICollectionViewDelegate,UICollectionViewDelegateFlowLayout {

    func numberOfSections(in collectionView: UICollectionView) -> Int {
        return 1
    }
    func collectionView(_ collectionView: UICollectionView, numberOfItemsInSection section: Int) -> Int {
    return 5
    }

    func collectionView(_ collectionView: UICollectionView, cellForItemAt indexPath: IndexPath) -> UICollectionViewCell {
        let cell = collectionView.dequeueReusableCell(withReuseIdentifier: cellID, for: indexPath) as! NewUserEventAttendingCell
        return cell
    }

    func collectionView(_ collectionView: UICollectionView, layout collectionViewLayout: UICollectionViewLayout, insetForSectionAt section: Int) -> UIEdgeInsets {
        return UIEdgeInsets(top: 10.0, left: 1.0, bottom: 1.0, right: 1.0)
    }

    func collectionView(_ collectionView: UICollectionView,
                        layout collectionViewLayout: UICollectionViewLayout,
                        sizeForItemAt indexPath: IndexPath) -> CGSize {
        let kWhateverHeightYouWant = 149
        return CGSize(width: collectionView.bounds.size.width - 60, height: CGFloat(kWhateverHeightYouWant))
    }
//    func collectionView(_ collectionView: UICollectionView, layout collectionViewLayout: UICollectionViewLayout, referenceSizeForHeaderInSection section: Int) -> CGSize {
//        return CGSize(width: view.frame.width/6, height: 100)
//    }

    func collectionView(_ collectionView: UICollectionView, viewForSupplementaryElementOfKind kind: String, at indexPath: IndexPath) -> UICollectionReusableView {
        let header = collectionView.dequeueReusableSupplementaryView(ofKind: kind, withReuseIdentifier: headerID, for: indexPath) as! NewUserHeader
        return header
    }


}