我试图在collectionView单元内部实现searchBar，在无法使搜索栏与重新加载单元作为标头一起工作之后，我在第一个出队单元中实现了searchBar。如何为该单元格赋予类似于粘性页眉的属性，当用户向上滚动时，该标题保留在屏幕顶部，而向下滚动时则隐藏该标题？可以吗？
下面是有问题的代码
import UIKit
class ViewController: UIViewController, UICollectionViewDelegateFlowLayout, UICollectionViewDataSource, UICollectionViewDelegate, UISearchBarDelegate {
lazy var collectionView : UICollectionView = {
let layout = UICollectionViewFlowLayout()
let cv = UICollectionView(frame: .zero, collectionViewLayout: layout)
cv.backgroundColor = .white
cv.delegate = self
cv.dataSource = self
return cv
}()
var genericTagsArray:[String] = ["tag1","tag2","tag3","tag4","tag5","tag6","tag7","tag8","tag9","tag10","tag11","tag12","A","B","C","D","E","F","G","Ab","Abc","za","tag1","tag2","tag3","tag4","tag5","tag6","tag7","tag8","tag9","tag10","tag11","tag12","A","B","C","D","E","F","G","Ab","Abc","za"]
var currentTagsArray:[String] = [String]() {
didSet {
collectionView.reloadData()
}
}
override func viewDidLoad() {
super.viewDidLoad()
self.view.addSubview(collectionView)
collectionView.register(Cell.self, forCellWithReuseIdentifier: "cell")
currentTagsArray = genericTagsArray
collectionView.register(Header.self, forCellWithReuseIdentifier: "\(Header.self)")
collectionView.translatesAutoresizingMaskIntoConstraints = false
collectionView.topAnchor.constraint(equalTo: view.safeAreaLayoutGuide.topAnchor).isActive = true
collectionView.leadingAnchor.constraint(equalTo: self.view.leadingAnchor).isActive = true
collectionView.bottomAnchor.constraint(equalTo: self.view.bottomAnchor).isActive = true
collectionView.trailingAnchor.constraint(equalTo: self.view.trailingAnchor).isActive = true
collectionView.contentInset = UIEdgeInsetsMake(0, 0, 0, 0)
}
func collectionView(_ collectionView: UICollectionView, numberOfItemsInSection section: Int) -> Int {
return currentTagsArray.count + 1
}
func numberOfSections(in collectionView: UICollectionView) -> Int {
return 1
}
func collectionView(_ collectionView: UICollectionView, layout collectionViewLayout: UICollectionViewLayout, referenceSizeForHeaderInSection section: Int) -> CGSize {
return CGSize(width: self.view.frame.width, height: 50)
}
var searchCell:Header!
func collectionView(_ collectionView: UICollectionView, cellForItemAt indexPath: IndexPath) -> UICollectionViewCell {
if indexPath.section == 0 && indexPath.item == 0 {
let cell = collectionView.dequeueReusableCell(withReuseIdentifier: "\(Header.self)", for: indexPath) as! Header
cell.searchBar.delegate = self
searchCell = cell
DispatchQueue.main.async {
if self.currentTagsArray.count != 0 {
self.searchCell?.searchBar.becomeFirstResponder()
}
}
return cell
}
let cell = collectionView.dequeueReusableCell(withReuseIdentifier: "cell", for: indexPath) as! Cell
cell.label.text = currentTagsArray[indexPath.item - 1]
return cell
}
func collectionView(_ collectionView: UICollectionView, layout collectionViewLayout: UICollectionViewLayout, sizeForItemAt indexPath: IndexPath) -> CGSize {
return CGSize(width: self.view.frame.size.width, height: 50)
}
func collectionView(_ collectionView: UICollectionView, layout collectionViewLayout: UICollectionViewLayout, minimumInteritemSpacingForSectionAt section: Int) -> CGFloat {
return 5
}
func collectionView(_ collectionView: UICollectionView, layout collectionViewLayout: UICollectionViewLayout, minimumLineSpacingForSectionAt section: Int) -> CGFloat {
return 5
}
func searchBar(_ searchBar: UISearchBar, textDidChange searchText: String) {
self.currentTagsArray = self.genericTagsArray.filter { (text) -> Bool in
return text.contains(searchText.lowercased())
}
}
var lastContentOffset:CGFloat = 0
func scrollViewDidScroll(_ scrollView: UIScrollView) {
if self.lastContentOffset > self.collectionView.contentOffset.y && self.collectionView.contentOffset.y > 0 && self.collectionView.contentOffset.y < collectionView.frame.maxY {
self.lastContentOffset = scrollView.contentOffset.y
searchCell.isHidden = false
}
else if (self.lastContentOffset < self.collectionView.contentOffset.y) && (self.collectionView.contentOffset.y < self.collectionView.frame.maxY) && (self.collectionView.contentOffset.y > 0) {
self.lastContentOffset = scrollView.contentOffset.y
searchCell.isHidden = true
}
else{
self.lastContentOffset = scrollView.contentOffset.y
print("content offSet: \(scrollView.contentOffset.y)")
print("Nothing happened")
// self.headerDelegate?.hideHeaderView(hide: true)
}
}
}
class Cell : UICollectionViewCell {
let label = UILabel()
override init(frame: CGRect) {
super.init(frame: frame)
setupViews()
}
required init?(coder aDecoder: NSCoder) {
fatalError("init(coder:) has not been implemented")
}
func setupViews() {
self.backgroundColor = .gray
self.addSubview(label)
label.translatesAutoresizingMaskIntoConstraints = false
label.topAnchor.constraint(equalTo: self.topAnchor).isActive = true
label.bottomAnchor.constraint(equalTo: self.bottomAnchor).isActive = true
label.trailingAnchor.constraint(equalTo: self.trailingAnchor).isActive = true
label.leadingAnchor.constraint(equalTo: self.leadingAnchor).isActive = true
}
}
class Header : UICollectionViewCell {
let searchBar = UISearchBar()
override init(frame: CGRect) {
super.init(frame: frame)
setupViews()
}
required init?(coder aDecoder: NSCoder) {
fatalError("init(coder:) has not been implemented")
}
func setupViews() {
self.backgroundColor = .gray
self.addSubview(searchBar)
searchBar.translatesAutoresizingMaskIntoConstraints = false
searchBar.topAnchor.constraint(equalTo: self.topAnchor).isActive = true
searchBar.bottomAnchor.constraint(equalTo: self.bottomAnchor).isActive = true
searchBar.trailingAnchor.constraint(equalTo: self.trailingAnchor).isActive = true
searchBar.leadingAnchor.constraint(equalTo: self.leadingAnchor).isActive = true
}
}