嵌入到导航控制器中时，CollectionView 不起作用

Question

我有一个简单的集合视图测试（基于在线教程），它可以很好地独立运行。但是当我将它嵌入导航控制器时，它停止工作。我通过 (1) 创建一个 headerView（64 像素高）并将其添加到顶部的视图中来构建屏幕。(2) 我构建了一个集合视图并将其添加到 headerView。

这是代码：

import UIKit

class ViewController: UIViewController,
UICollectionViewDelegate, UICollectionViewDataSource,
UINavigationControllerDelegate
{
var collectionView : UICollectionView!
var topView: UIView!

override func viewDidLoad() {
    super.viewDidLoad()
    var frame = CGRect(x:0,y:128, width:view.frame.width, height:64)
    topView = UIView(frame:frame)
    self.view.addSubview(topView)

    // CollectionView
    let layout: UICollectionViewFlowLayout = UICollectionViewFlowLayout()
    layout.scrollDirection = .horizontal
    layout.sectionInset = UIEdgeInsets(top: 0, left: 10, bottom: 0, right: 10)
    layout.itemSize = CGSize(width: 50, height: 50)

    frame = CGRect(x: 0, y: 0, width: Int(self.topView.frame.width), height: Int(self.topView.frame.height))
    collectionView = UICollectionView (frame: frame, collectionViewLayout: layout)
    collectionView.dataSource = self
    collectionView.delegate = self
    collectionView.register(UICollectionViewCell.self, forCellWithReuseIdentifier: "collectionCell")
    collectionView.backgroundColor = UIColor.green
    self.topView.addSubview(collectionView)

}

//MARK: - CollectionView

func collectionView(_ collectionView: UICollectionView, numberOfItemsInSection section: Int) -> Int {
    return 14
}



func collectionView(_ collectionView: UICollectionView, cellForItemAt indexPath: IndexPath) -> UICollectionViewCell {
    let cell = collectionView.dequeueReusableCell(withReuseIdentifier: "collectionCell", for: indexPath as IndexPath)
    for v in cell.subviews {
        v.removeFromSuperview()
    }
    cell.backgroundColor = UIColor.orange

    let label = UILabel(frame: CGRect(x:0 , y:0 , width:50 , height:50))
    label.text = "\(indexPath.item)"
    label.textAlignment = .center
    label.textColor = UIColor.white
    cell.addSubview(label)

    return cell
}

func numberOfSections(in collectionView: UICollectionView) -> Int {
    return 1
}


override func didReceiveMemoryWarning() {
    super.didReceiveMemoryWarning()
    // Dispose of any resources that can be recreated.
}

}

Answer 1

我无法按照所述使考沙尔的建议发挥作用。它确实给了我一个线索，由于我不明白的原因，我嵌入集合视图的视图的位置在 viewDidLoad 中被放错了位置。然而，通过将集合视图配置放在 viewDidAppear （而不是 viewDidLoad ）中，效果很好。我将 y 位置偏移了 64 以清除导航栏，并将行高减小到 64。我还放置了代码以仅执行一次代码，以便从页面导航不会添加彼此顶部的多个视图。顺便说一句，我最初的目标是拥有水平滚动的单元格。在我的程序中，我有带有相应部分的表格视图，其想法是使用具有水平滚动单元格的行来移动到相应的部分。

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代码如下所示：

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    //\n//  CustomViewController.swift\n//  DSM Tracker\n//\n//  Created by Syed Tariq on 1/7/17.\n//  Copyright \xc2\xa9 2017 com.syedtariq. All rights reserved.\n//\n\nimport UIKit\n\n\nclass ViewController: UIViewController,\n    UICollectionViewDelegate,\n    UICollectionViewDataSource,\n    UINavigationControllerDelegate\n\n{\n\n    var executeOnce = true\n    var cellDimensions = [String:Int]()\n    var cellHeight = 50\n    var cellWidth = 120\n\n    var collectionContainerView: UICollectionView!\n    var navBar: UINavigationBar = UINavigationBar()\n\n\n    // view constants\n    var viewY = CGFloat()\n    var viewX = CGFloat()\n    var viewWidth = CGFloat()\n    var viewHeight = CGFloat()\n\n\n    // gaps from view edge\n    let leftGap = CGFloat(20)\n    let rightGap = CGFloat(20)\n\n\n    // navbar constants\n    let navBarHeight = CGFloat(64)\n\n    var headerLabels = ["Cell 01","Cell 02","Cell 03","Cell 04","Cell 05","Cell 06","Cell 07","Cell 08","Cell 09","Cell 10","Cell 11","Cell 12","Cell 13","Cell 14","Cell 15","Cell 16"]\n\n\n    override func viewDidLoad() {\n        super.viewDidLoad()\n        navBar.backgroundColor = UIColor.green\n        executeOnce = true\n        viewY = view.frame.origin.y\n        viewX = view.frame.origin.x\n        viewWidth = view.frame.width\n        viewHeight = view.frame.height\n    }\n\n\n\n    func configureCollectionView () {\n        if executeOnce {\n            executeOnce = false\n            let layout: UICollectionViewFlowLayout = UICollectionViewFlowLayout()\n            layout.scrollDirection = .horizontal\n            layout.sectionInset = UIEdgeInsets(top: 0, left: 0, bottom: 0, right: 10)\n            layout.itemSize = CGSize(width: cellWidth, height: cellHeight)\n\n            let colWidth = viewWidth - leftGap - rightGap\n            let colX = viewX + leftGap\n            let colY = viewY + navBarHeight\n            let colHeight = CGFloat(64)\n            let frame = CGRect(x:colX, y:colY, width: colWidth, height: colHeight)\n            //let frame = CGRect.zero\n            collectionContainerView = UICollectionView (frame: frame, collectionViewLayout: layout)\n            collectionContainerView.dataSource = self\n            collectionContainerView.delegate = self\n            collectionContainerView.autoresizingMask = [.flexibleLeftMargin,.flexibleLeftMargin,.flexibleBottomMargin,.flexibleRightMargin, .flexibleHeight, .flexibleWidth]\n            collectionContainerView.register(UICollectionViewCell.self, forCellWithReuseIdentifier: "collectionCell")\n            collectionContainerView.backgroundColor = UIColor.blue\n            collectionContainerView.allowsSelection = true\n            collectionContainerView.isScrollEnabled = true\n            collectionContainerView.setNeedsDisplay()\n            print("collectionContainerView.frame \\(collectionContainerView.frame)")\n            view.addSubview(collectionContainerView)\n        }\n    }\n\n    override func viewDidAppear(_ animated: Bool) {\n        configureCollectionView()\n    }\n\n    func numberOfSections(in collectionView: UICollectionView) -> Int {\n        return 1\n    }\n\n    func collectionView(_ collectionView: UICollectionView, numberOfItemsInSection section: Int) -> Int {\n        print("headerLabels.count \\(headerLabels.count)")\n        return  headerLabels.count\n    }\n\n\n\n    func collectionView(_ collectionView: UICollectionView, cellForItemAt indexPath: IndexPath) -> UICollectionViewCell {\n        let cell = collectionView.dequeueReusableCell(withReuseIdentifier: "collectionCell", for: indexPath as IndexPath)\n\n        for v in cell.subviews {\n            v.removeFromSuperview()\n        }\n\n        let cellTitle = headerLabels[indexPath.row]\n        let cellTitleLines = cellTitle.components(separatedBy: " ")\n        let nLabels = cellTitleLines.count\n\n        cell.layer.borderWidth = 1\n        cell.layer.cornerRadius = 8\n        let labelHeight = cellHeight / cellTitleLines.count\n        for i in (0 ..< nLabels) {\n            let frame = CGRect(x: 0, y: labelHeight * i, width: cellWidth, height: labelHeight)\n            let label1 = UILabel(frame: frame)\n            cell.backgroundColor = UIColor.lightGray\n            label1.numberOfLines = 1\n            label1.text = headerLabels[indexPath.row]\n            label1.textAlignment = .center\n            label1.textColor = UIColor.black\n            label1.clipsToBounds = true\n            label1.adjustsFontSizeToFitWidth = true\n            label1.text = cellTitleLines[i]\n            cell.addSubview(label1)\n        }\n\n        return cell\n    }\n\n    func collectionView(_ collectionView: UICollectionView, shouldSelectItemAt indexPath: IndexPath) -> Bool {\n        collectionContainerView.scrollToItem(at:IndexPath(item: indexPath.item, section: 0), at: .centeredHorizontally, animated: false)\n\n        return true\n    }\n\n    func collectionView(_ collectionView: UICollectionView, didSelectItemAt indexPath: IndexPath) {\n        let cell = collectionContainerView.cellForItem(at: indexPath)\n        print("cell = \\(cell)")\n        collectionContainerView.scrollToItem(at:IndexPath(item: indexPath.item, section: 0), at: .centeredHorizontally, animated: false)\n    }\n\n\n    func collectionView(_ collectionView: UICollectionView, shouldHighlightItemAt indexPath: IndexPath) -> Bool {\n        return true\n    }\n\n\n    func collectionView(_ collectionView: UICollectionView, didHighlightItemAt indexPath: IndexPath) {\n    }\n\n\n\n    override func prepare(for segue: UIStoryboardSegue, sender: Any?) {\n    }\n}\n

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