为什么我的某些锚约束不起作用，而其他锚约束却对同一个项目起作用？

Question

I am trying to put anchor constraints on a textField contained within a subView. For the leading and top anchors the anchors work but for the bottom and trailing anchors they dont. Im not sure what it could be, I would like some space between the keyboard and the items in my subview as well as some space between the UITextField and the trailing anchor edge of the screen. Below is the code in question

Layout Code:

func setUpLayout(){

    //myView
    self.myView.translatesAutoresizingMaskIntoConstraints = false
    self.myView.leadingAnchor.constraint(equalTo: self.view.safeAreaLayoutGuide.leadingAnchor, constant: 0).isActive = true
  self.myView.trailingAnchor.constraint(equalTo: self.view.safeAreaLayoutGuide.trailingAnchor, constant: 0).isActive = true
    self.myView.heightAnchor.constraint(equalToConstant: 98).isActive = true
    self.myView.bottomAnchor.constraint(equalTo: self.view.safeAreaLayoutGuide.bottomAnchor, constant: 4).isActive = true


    //CollectionView
    self.collectionView.translatesAutoresizingMaskIntoConstraints = false
    self.collectionView.leadingAnchor.constraint(equalTo: self.myView.leadingAnchor, constant: 0).isActive = true
    self.collectionView.trailingAnchor.constraint(equalTo: self.myView.trailingAnchor, constant: 0).isActive = true
    self.collectionView.bottomAnchor.constraint(equalTo: self.myView.bottomAnchor, constant: 4).isActive = true
    self.collectionView.topAnchor.constraint(equalTo: self.searchBar.bottomAnchor, constant: 4).isActive = true

    //searchbar
    self.searchBar.translatesAutoresizingMaskIntoConstraints = false
    self.searchBar.topAnchor.constraint(equalTo: self.myView.topAnchor, constant: 0).isActive = true
    self.searchBar.leadingAnchor.constraint(equalTo: self.myView.leadingAnchor, constant: 4).isActive = true
    self.searchBar.trailingAnchor.constraint(equalTo: self.myView.trailingAnchor, constant: 4).isActive = true
    self.searchBar.heightAnchor.constraint(equalToConstant: 45).isActive = true
    searchBar.backgroundColor = .white
    searchBar.layer.borderWidth = 2
    searchBar.layer.borderColor = UIColor.black.cgColor
    //PictureView
    self.PictureView.translatesAutoresizingMaskIntoConstraints = false
    self.PictureView.topAnchor.constraint(equalTo: self.view.safeAreaLayoutGuide.topAnchor, constant: 0).isActive = true
    self.PictureView.bottomAnchor.constraint(equalTo: self.view.safeAreaLayoutGuide.bottomAnchor, constant: 0).isActive = true
    self.PictureView.leadingAnchor.constraint(equalTo: self.view.safeAreaLayoutGuide.leadingAnchor, constant: 0).isActive = true
    self.PictureView.trailingAnchor.constraint(equalTo: self.view.safeAreaLayoutGuide.trailingAnchor, constant: 0).isActive = true
    self.PictureView.backgroundColor = .green
}

Code in its entirety

import UIKit

class SearchCollectionViewController: UIViewController,UICollectionViewDelegate,UICollectionViewDelegateFlowLayout, UITextFieldDelegate, UICollectionViewDataSource,UIGestureRecognizerDelegate {

    var myView: UIView!
    var searchBar: UITextField!
    var collectionView: UICollectionView!

    var PictureView: UIView!


    var genericArray:[String] = ["A","B","C","D","E","F","G","Ab","Abc","za"]
    var currentGenericArray:[String] = [String]()
    var tagsSelected:[String] = [String]()


    let keyboardSlider = KeyboardSlider()

    override func viewDidLoad() {
        super.viewDidLoad()
        keyboardSlider.subscribeToKeyboardNotifications(view: view)

        myView = UIView(frame: CGRect(x: 0, y: self.view.frame.height, width: self.view.frame.width, height: self.view.frame.height))
        searchBar = UITextField(frame: CGRect(x: 0, y: 0, width: self.myView.frame.width, height: self.myView.frame.height))
        PictureView = UIView(frame: self.view.frame)
         self.view.addSubview(PictureView)

        let layout: UICollectionViewFlowLayout = UICollectionViewFlowLayout()
        layout.sectionInset = UIEdgeInsets(top: 0, left: 0, bottom: 10, right: 0)
        layout.itemSize = CGSize(width: (UIScreen.main.bounds.width-1)/2, height: (UIScreen.main.bounds.width-1)/2)
        layout.scrollDirection = .horizontal
        self.collectionView = UICollectionView(frame: CGRect(x: 0, y: self.myView.frame.height, width: self.myView.frame.width, height: 100), collectionViewLayout: layout)
        collectionView.backgroundColor = .clear
        collectionView.contentInset = UIEdgeInsets(top: 4, left: 4, bottom: 4, right: 4)
        myView.backgroundColor = .clear
        collectionView.delegate = self
        collectionView.dataSource = self
        self.myView.addSubview(collectionView)
        self.view.addSubview(myView)

        collectionView.register(CollectionCell.self, forCellWithReuseIdentifier: "collectionViewCell")
        currentGenericArray = genericArray




        searchBar.delegate = self
        searchBar.autocorrectionType = .no
        searchBar.keyboardType = .default
        searchBar.addTarget(self, action: #selector(SearchCollectionViewController.textFieldDidChange), for: .editingChanged)



        self.myView.addSubview(searchBar)


        let viewTapGestureRecognizer = UITapGestureRecognizer(target: self, action: #selector(viewTapped(gestureRecognizer:)))
        viewTapGestureRecognizer.cancelsTouchesInView = false
        self.PictureView.addGestureRecognizer(viewTapGestureRecognizer)
        self.PictureView.backgroundColor = .purple
        self.view.backgroundColor = .green
        self.searchBar.becomeFirstResponder()

        self.collectionView.allowsSelection = true
        setUpLayout()
    }

    func setUpLayout(){

        //myView
        self.myView.translatesAutoresizingMaskIntoConstraints = false
        self.myView.leadingAnchor.constraint(equalTo: self.view.safeAreaLayoutGuide.leadingAnchor, constant: 0).isActive = true
      self.myView.trailingAnchor.constraint(equalTo: self.view.safeAreaLayoutGuide.trailingAnchor, constant: 0).isActive = true
        self.myView.heightAnchor.constraint(equalToConstant: 98).isActive = true
        self.myView.bottomAnchor.constraint(equalTo: self.view.safeAreaLayoutGuide.bottomAnchor, constant: 4).isActive = true


        //CollectionView
        self.collectionView.translatesAutoresizingMaskIntoConstraints = false
        self.collectionView.leadingAnchor.constraint(equalTo: self.myView.leadingAnchor, constant: 0).isActive = true
        self.collectionView.trailingAnchor.constraint(equalTo: self.myView.trailingAnchor, constant: 0).isActive = true
        self.collectionView.bottomAnchor.constraint(equalTo: self.myView.bottomAnchor, constant: 4).isActive = true
        self.collectionView.topAnchor.constraint(equalTo: self.searchBar.bottomAnchor, constant: 4).isActive = true

        //searchbar
        self.searchBar.translatesAutoresizingMaskIntoConstraints = false
        self.searchBar.topAnchor.constraint(equalTo: self.myView.topAnchor, constant: 0).isActive = true
        self.searchBar.leadingAnchor.constraint(equalTo: self.myView.leadingAnchor, constant: 4).isActive = true
        self.searchBar.trailingAnchor.constraint(equalTo: self.myView.trailingAnchor, constant: 4).isActive = true
        self.searchBar.heightAnchor.constraint(equalToConstant: 45).isActive = true
        searchBar.backgroundColor = .white
        searchBar.layer.borderWidth = 2
        searchBar.layer.borderColor = UIColor.black.cgColor
        //PictureView
        self.PictureView.translatesAutoresizingMaskIntoConstraints = false
        self.PictureView.topAnchor.constraint(equalTo: self.view.safeAreaLayoutGuide.topAnchor, constant: 0).isActive = true
        self.PictureView.bottomAnchor.constraint(equalTo: self.view.safeAreaLayoutGuide.bottomAnchor, constant: 0).isActive = true
        self.PictureView.leadingAnchor.constraint(equalTo: self.view.safeAreaLayoutGuide.leadingAnchor, constant: 0).isActive = true
        self.PictureView.trailingAnchor.constraint(equalTo: self.view.safeAreaLayoutGuide.trailingAnchor, constant: 0).isActive = true
        self.PictureView.backgroundColor = .green
    }



    override func viewDidAppear(_ animated: Bool) {
        super.viewDidAppear(animated)

    }



    override func viewWillDisappear(_ animated: Bool) {
        super.viewWillDisappear(animated)
        keyboardSlider.unsubscribeFromKeyboardNotifications()

    }

    func textFieldShouldReturn(_ textField: UITextField) -> Bool {
        textField.resignFirstResponder()

        collectionView.reloadData()
        return true
    }

    /// Helper to dismiss keyboard
    @objc func didStopEditing() {
    }

    func textFieldDidEndEditing(_ textField: UITextField) {
        UIView.setAnimationCurve(UIViewAnimationCurve.easeInOut)
        UIView.animate(withDuration: 0.2) {
            self.view.frame.origin.y = 0
        }
    }

    @objc func textFieldDidChange(){
        guard(!(searchBar.text?.isEmpty)!) else{
            currentGenericArray = genericArray
            collectionView.reloadData()
            return
        }

        currentGenericArray = genericArray.filter({letter -> Bool in
            if searchBar.text!.count > letter.count{
                return false
            }
            let stringRange = letter.index(letter.startIndex, offsetBy: searchBar.text!.count)
            let subword = letter[..<stringRange]
            return subword.lowercased().contains(searchBar.text!.lowercased())
        })

        if currentGenericArray.isEmpty{
            print("text being inserted \(searchBar.text!)")
            currentGenericArray.append(searchBar.text!)
        }

        collectionView.reloadData()
    }

    func gestureRecognizer(_ gestureRecognizer: UIGestureRecognizer, shouldReceive touch: UITouch) -> Bool {
        if (touch.view?.isDescendant(of: self.collectionView))!{
            return false
        }
        return true
    }

    var keyboardIsOpen:Bool = false

    @objc func viewTapped(gestureRecognizer:UIGestureRecognizer){

        if keyboardIsOpen{
            myView.isHidden = true
            keyboardIsOpen = !keyboardIsOpen
            searchBar.resignFirstResponder()
        }

        else{
            myView.isHidden = false
            keyboardIsOpen = !keyboardIsOpen
            searchBar.becomeFirstResponder()
        }


    }

    func numberOfSections(in collectionView: UICollectionView) -> Int {
        return 2
    }

    func collectionView(_ collectionView: UICollectionView, numberOfItemsInSection section: Int) -> Int {
        if section == 0{
            return tagsSelected.count
        }
        else {
            return currentGenericArray.count
        }
    }

    func collectionView(_ collectionView: UICollectionView, cellForItemAt indexPath: IndexPath) -> UICollectionViewCell {

        let cell = collectionView.dequeueReusableCell(withReuseIdentifier: "collectionViewCell", for: indexPath) as! CollectionCell
        if indexPath.section == 0{
            cell.collectionLabel.text = tagsSelected[indexPath.item]
            cell.backgroundColor = .blue
            cell.collectionLabel.textColor = .white
        }
        else if indexPath.section == 1{
            cell.backgroundColor = .white
            cell.collectionLabel.textColor = UIColor.black
            cell.collectionLabel.text = currentGenericArray[indexPath.row]
        }
        cell.layer.masksToBounds = true
        cell.layer.cornerRadius = cell.bounds.width/20
        return cell
    }

    func collectionView(_ collectionView: UICollectionView, layout collectionViewLayout: UICollectionViewLayout, minimumLineSpacingForSectionAt section: Int) -> CGFloat {
        return 6
    }

    func collectionView(_ collectionView: UICollectionView, didSelectItemAt indexPath: IndexPath) {

        if indexPath.section == 1{\
            if(tagsSelected.contains(currentGenericArray[indexPath.item])){
            }

            tagsSelected.append(currentGenericArray[indexPath.item])
            for i in 0...genericArray.count-1{
                if(currentGenericArray[indexPath.item] == genericArray[i]){
                    genericArray.remove(at: i)
                    break
                }
            }
            currentGenericArray.remove(at: indexPath.item)
            searchBar.text = ""
            collectionView.reloadData()
            if collectionView.numberOfItems(inSection: 1)>0{
            collectionView.scrollToItem(at: IndexPath(item: 0, section: 1), at: .right, animated: true)
            }
        }
        else if indexPath.section == 0{
            currentGenericArray.append(tagsSelected[indexPath.item])
            tagsSelected.remove(at: indexPath.item)
            collectionView.reloadData()
        }
    }

    var offsetY:CGFloat = 0

    override func viewWillAppear(_ animated: Bool) {
        super.viewWillAppear(animated)
        NotificationCenter.default.addObserver(self, selector: #selector(SearchCollectionViewController.keyboardFrameChangeNotification(notification:)), name: NSNotification.Name.UIKeyboardWillChangeFrame, object: nil)
    }



    @objc func keyboardFrameChangeNotification(notification: Notification) {
        if let userInfo = notification.userInfo {
            let endFrame = userInfo[UIKeyboardFrameEndUserInfoKey] as? CGRect
            let animationDuration = userInfo[UIKeyboardAnimationDurationUserInfoKey] as? Double ?? 0
            let animationCurveRawValue = (userInfo[UIKeyboardAnimationCurveUserInfoKey] as? Int) ?? Int(UIViewAnimationOptions.curveEaseInOut.rawValue)
            let animationCurve = UIViewAnimationOptions(rawValue: UInt(animationCurveRawValue))
            if let _ = endFrame, endFrame!.intersects(self.myView.frame) {
                self.offsetY = self.myView.frame.maxY - endFrame!.minY
            } else {
                if self.offsetY != 0 {
                    UIView.animate(withDuration: animationDuration, delay: TimeInterval(0), options: animationCurve, animations: {
                        self.myView.frame.origin.y = self.myView.frame.origin.y + self.offsetY
                        self.offsetY = 0
                    }, completion: nil)
                }
            }
        }
    }

}


class CollectionCell:UICollectionViewCell{


    var collectionLabel: UILabel!
    var view:UIView!
    override init(frame: CGRect) {
        super.init(frame: frame)
         collectionLabel = UILabel(frame: CGRect(x: 0, y: 0, width: self.bounds.width, height: self.bounds.height))
        self.addSubview(collectionLabel)
        collectionLabel.textAlignment = .center
        collectionLabel.translatesAutoresizingMaskIntoConstraints = false
        collectionLabel.topAnchor.constraint(equalTo: self.topAnchor, constant: 0).isActive = true
        collectionLabel.bottomAnchor.constraint(equalTo: self.bottomAnchor, constant: 0).isActive = true
        collectionLabel.leadingAnchor.constraint(equalTo: self.leadingAnchor, constant: 0).isActive = true
        collectionLabel.trailingAnchor.constraint(equalTo: self.trailingAnchor, constant: 0).isActive = true
    }

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

extension UIView {
    func currentFirstResponder() -> UIResponder? {
        if self.isFirstResponder {
            return self
        }

        for view in self.subviews {
            if let responder = view.currentFirstResponder() {
                return responder
            }
        }

        return nil
    }
}

extension Notification.Name{
    static let showKeyboard = Notification.Name("showKeyboard")
}
class KeyboardSlider: NSObject {
    // variables to hold and process information from the view using this class
    weak var view: UIView?

    @objc func keyboardWillShow(notification: NSNotification) {
        // method to move keyboard up
        view?.frame.origin.y = 0 - getKeyboardHeight(notification as Notification)
    }

    func getKeyboardHeight(_ notification:Notification) -> CGFloat {
        // get exact height of keyboard on all devices and convert to float value to return for use
        let userInfo = notification.userInfo
        let keyboardSize = userInfo![UIKeyboardFrameEndUserInfoKey] as! NSValue
        return keyboardSize.cgRectValue.height
    }

    func subscribeToKeyboardNotifications(view: UIView) {
        // assigning view to class' counterpart
        self.view = view
        // when UIKeyboardWillShow do keyboardWillShow function
        NotificationCenter.default.addObserver(self, selector: #selector(keyboardWillShow(notification:)), name: .UIKeyboardWillShow, object: nil)
    }

    func unsubscribeFromKeyboardNotifications() {
        NotificationCenter.default.removeObserver(self, name: .UIKeyboardWillShow, object: nil)
    }


}

Answer 1

For trailing and bottom anchor constraints, it is common that you have to use negative numbers for the constants to achieve what you want.

For example:

searchBar.bottomAnchor.constraint(equalTo: myView.bottomAnchor, constant: 4).isActive = true

Becomes:

searchBar.bottomAnchor.constraint(equalTo: myView.bottomAnchor, constant: -4).isActive = true