Question

我的故事板中有以下segue，它连接到ViewController，其根视图是UICollectionView

遵循本教程：https://www.youtube.com/watch?v=L9cZrAbxN1E

我使用自定义dataSource创建了UICollectionViewController的类似设置。他的代码与我自己的代码之间的主要区别在于，他立即设置了对象的dataArray，这些对象在每个collectionView单元格中一对一地映射到viewDidLoad，而我从异步回调中抓取它们并设置结果我的dataSource数组中的对象用于我的视图单元格。

问题是，在我按照开头显示的segue后，我的视图中没有添加任何内容。故事板中描绘的视图的主ViewController类型为FeedController，所以我知道这不是原因。我觉得这是因为我的contentSize可能没有正确设置。这很奇怪，因为根据我的知识，视频中的人从未明确地设置了他的collectionView的大小。

 import UIKit

let cellId = "cellId"


class FeedController: UICollectionViewController, UICollectionViewDelegateFlowLayout {

var recipes = [BrowsableRecipe]()

var recipeIndex = 1
var pageSize = 10



override func viewDidLoad() {
    super.viewDidLoad()


    navigationItem.title = "Homepage"

    collectionView?.alwaysBounceVertical = true

    collectionView?.backgroundColor = UIColor(white: 0.95, alpha: 1)

    collectionView?.registerClass(RecipeCell.self, forCellWithReuseIdentifier: cellId)


    ServerMessenger.sharedInstance.getRecipesForHomePage(recipeIndex, pageSize: pageSize){
        responseObject, error in
        if let data = responseObject{

            self.recipes = data
            print(self.recipes)


        }

    }
}


override func collectionView(collectionView: UICollectionView, numberOfItemsInSection section: Int) -> Int {
    return recipes.count
}

override func collectionView(collectionView: UICollectionView, cellForItemAtIndexPath indexPath: NSIndexPath) -> UICollectionViewCell {
    let recipeCell = collectionView.dequeueReusableCellWithReuseIdentifier(cellId, forIndexPath: indexPath) as! RecipeCell
    print("cellForItem called")
    recipeCell.recipe = recipes[indexPath.item]

    return recipeCell
}



override func viewWillTransitionToSize(size: CGSize, withTransitionCoordinator coordinator: UIViewControllerTransitionCoordinator) {
    super.viewWillTransitionToSize(size, withTransitionCoordinator: coordinator)

    collectionView?.collectionViewLayout.invalidateLayout()
}

}

class RecipeCell: UICollectionViewCell {

var recipe: BrowsableRecipe? {
    didSet {

        if let name = recipe?.recipeName {

            let attributedText = NSMutableAttributedString(string: name, attributes: [NSFontAttributeName: UIFont.boldSystemFontOfSize(14)])
            nameLabel.textColor = UIColor.blackColor()
            print("in did set")
            nameLabel.attributedText = attributedText

        }


    }
}

override init(frame: CGRect) {
    super.init(frame: frame)

    setupViews()
}

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

let nameLabel: UILabel = {
    let label = UILabel()
    label.numberOfLines = 2



    return label
}()



func setupViews() {
    backgroundColor = UIColor.blueColor()

    addSubview(nameLabel)

    addConstraintsWithFormat("V:|-12-[v0]", views: nameLabel)

}

}

 extension UIColor {

static func rgb(red: CGFloat, green: CGFloat, blue: CGFloat) -> UIColor {
    return UIColor(red: red/255, green: green/255, blue: blue/255, alpha: 1)
}

}

extension UIView {

func addConstraintsWithFormat(format: String, views: UIView...) {
    var viewsDictionary = [String: UIView]()
    for (index, view) in views.enumerate() {
        let key = "v\(index)"
        viewsDictionary[key] = view
        view.translatesAutoresizingMaskIntoConstraints = false
    }

    addConstraints(NSLayoutConstraint.constraintsWithVisualFormat(format, options: NSLayoutFormatOptions(), metrics: nil, views: viewsDictionary))
}

}

我确信这个collectionView中没有显示任何内容的原因直接源于cellForItemAtIndexPath永远不会被调用的事实（我使用print语句进行了测试）

任何帮助赞赏。

供参考，这是我用作起点的项目 https://github.com/purelyswift/facebook_feed_dynamic_cell_content

更新：

我尝试在异步回调中使用reloadItemsAtIndexPaths执行此操作：

我得到了

reason: 'attempt to delete item 9 from section 0 which only contains 0 items before the update'

这表明我需要先在第0部分添加内容。所以我试试：

     self.collectionView!.insertItemsAtIndexPaths(myArrayOfIndexPaths)

我得到了：

 reason: 'no UICollectionViewLayoutAttributes instance for -layoutAttributesForItemAtIndexPath:

Answer 1

设置数据阵列后调用重新加载数据。在设置数据数组之前，Coz系统调用realod将调用

if let data = responseObject{

        self.recipes = data
        print(self.recipes)

        dispatch_async(dispatch_get_main_queue()) {  // if you are setting in different thread
            collectionView.reloadData()
        }
    }

如果不检查它是否正在调用'numberOfItemsInSection'方法。如果不是，你可能没有设置dataSource和委托。

无法设置UICollectionView

1 个答案: