Ios UICollectionViewController页脚/页眉未显示

我正在实现一个单节

UICollectionViewController

，我想在其中添加页眉和页脚。 我已经阅读了RayWenderlich教程来实现逻辑，除了没有显示的页眉和页脚外，其他一切都很好

我在序列图像板检查器中选中了“节头”和“节尾”，并为每个

UICollectionReusableView

添加了带有“headerView”和“footerView”的标识符

我实现了supplementalelementofkind的

视图（见下面的代码），但在
引用了IzeForFooterInsection和
引用IzeForHeaderInstruction
时没有触发（调试时没有触发断点）。当应用程序启动时，我看不到页眉和页脚的背景色，但我可以看到一个应该是页眉和页脚的空间

提前谢谢你



以下是我的ViewController的摘录：

class VoteNextCityViewController : UICollectionViewController, UICollectionViewDelegateFlowLayout {
fileprivate let sectionInsets = UIEdgeInsets(top: 50.0, left: 20.0, bottom: 50.0, right: 20.0)
fileprivate let itemsPerRow: CGFloat = 2

private let cellID = "cellID"
var pendingCityArray: [City] = []

override func viewDidLoad() {
    super.viewDidLoad()
    fetchVotedCities()
}


override func collectionView(_ collectionView: UICollectionView, cellForItemAt indexPath: IndexPath) -> UICollectionViewCell {
    let cell = collectionView.dequeueReusableCell(withReuseIdentifier: cellID, for: indexPath) as! VoteNextCityCell
    let city = pendingCityArray[indexPath.row] //cannot not be nil, else numberOfItemsInSection would return 0
    cell.setupView(city: city)
    return cell
}

override func numberOfSections(in collectionView: UICollectionView) -> Int {
    return 1
}
override func collectionView(_ collectionView: UICollectionView, numberOfItemsInSection section: Int) -> Int {
        return pendingCityArray.count
}



  func collectionView(_ collectionView: UICollectionView,
                        layout collectionViewLayout: UICollectionViewLayout,
                        sizeForItemAt indexPath: IndexPath) -> CGSize {
        //2
        let paddingSpace = sectionInsets.left * (itemsPerRow + 1)
        let availableWidth = view.frame.width - paddingSpace
        let widthPerItem = availableWidth / itemsPerRow

        return CGSize(width: widthPerItem, height: widthPerItem+50)
    }



func collectionView(_ collectionView: UICollectionView,
                    layout collectionViewLayout: UICollectionViewLayout,
                    insetForSectionAt section: Int) -> UIEdgeInsets {
    return sectionInsets
}

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


func collectionView(_ collectionView: UICollectionView, layout collectionViewLayout: UICollectionViewLayout, referenceSizeForFooterInSection section: Int) -> CGSize {

    return CGSize(width: (self.collectionView?.frame.size.width)!, height: 50)
}

func collectionView(_ collectionView: UICollectionView, layout collectionViewLayout: UICollectionViewLayout, referenceSizeForHeaderInSection section: Int) -> CGSize {
    return CGSize(width: (self.collectionView?.frame.size.width)!, height: 50)

}
func collectionView(collectionView: UICollectionView, viewForSupplementaryElementOfKind kind: String, atIndexPath indexPath: NSIndexPath) -> UICollectionReusableView {
    switch kind {
    case UICollectionElementKindSectionFooter :
        let view = collectionView.dequeueReusableSupplementaryView(ofKind: kind, withReuseIdentifier: "footerView", for: indexPath as IndexPath)
            view.backgroundColor = UIColor.blue

            return view
    case UICollectionElementKindSectionHeader:
            let view = collectionView.dequeueReusableSupplementaryView(ofKind: kind, withReuseIdentifier: "headerView", for: indexPath as IndexPath)
            view.backgroundColor = UIColor.red

            return view

    default:
            assert(false, "Unexpected element kind")
    }
}

我认为根据新语法，只有
\u
（带空格的下划线）缺少

因此，请尝试替换函数定义

func collectionView(collectionView: UICollectionView, viewForSupplementaryElementOfKind kind: String, atIndexPath indexPath: NSIndexPath) -> UICollectionReusableView {

用下面的一个

func collectionView(_ collectionView: UICollectionView, viewForSupplementaryElementOfKind kind: String, atIndexPath indexPath: NSIndexPath) -> UICollectionReusableView {

我认为根据新语法，只有
\u
（带空格的下划线）缺少

因此，请尝试替换函数定义

func collectionView(collectionView: UICollectionView, viewForSupplementaryElementOfKind kind: String, atIndexPath indexPath: NSIndexPath) -> UICollectionReusableView {

用下面的一个

func collectionView(_ collectionView: UICollectionView, viewForSupplementaryElementOfKind kind: String, atIndexPath indexPath: NSIndexPath) -> UICollectionReusableView {

尝试将
func collectionView（collectionView:UICollectionView，viewforsupplmentalelementofkind-kind:String，atIndexPath indexPath:NSIndexPath）->UICollectionReusableView{
替换为
func collectionView（\ucollectionview:UICollectionView，viewforsupplmentalelementofkind-kind:String，atIndexPath indexPath:nsindexath）->UICollectionReusableView{
我认为，根据新版本，缺少
{/code>（下划线）syntax@iRiziya天哪，就是这样！如何因为下划线而浪费3个小时的时间。非常感谢：）回答我的问题，这样我就可以接受itTry替换
func collectionView了（collectionView:UICollectionView，ViewForSupplmentalElementOfKind:String，atIndexPath indexPath:NSIndexPath）->UICollectionReusableView{
with
func collectionView（collectionView:UICollectionView，ViewForSupplmentalElementOfKind:String，atIndexPath indexPath:NSIndexPath）->UICollectionReusableView{
我认为，
\
（下划线）根据新的syntax@iRiziya天哪，就是这样！如何因为下划线而浪费我3个小时的生命。非常感谢：）回答我的问题，这样我就可以接受了