Question

您可以从下面的代码中看到ViewDidLoad()中已经设置了布局参数，但这给了我一个错误：

由于未捕获的异常而终止应用程序 “ NSInvalidArgumentException”，原因：“ UICollectionView必须为使用非nil布局参数初始化

var layer: UICollectionViewFlowLayout = {

        var item = UICollectionViewFlowLayout()

        item.itemSize = CGSize(width: 100, height: 100)

        return item

    }()

UICollectionView对象已在属性初始化程序中设置，因为显然我希望此UICollectionView对象可全局访问：

var dataCollectionViews = UICollectionView()

viewDidLoad(){

dataCollectionViews = UICollectionView(frame: CGRect(x: 0, y: 0, width: 0, height: 0) , collectionViewLayout: self.layer)

        view.addSubview(dataCollectionViews)

        self.dataCollectionViews.delegate = self
        self.dataCollectionViews.dataSource = self
        self.dataCollectionViews.register(UICollectionViewCell.self, forCellWithReuseIdentifier: collectionViewReuse)
        self.dataCollectionViews.layer.cornerRadius = 10
        self.dataCollectionViews.translatesAutoresizingMaskIntoConstraints = false
        self.dataCollectionViews.isHidden = true

  changed()
}

当我将changed()内的内容移动到viewDidLoad()内并在viewDidLoad()内初始化dataCollectionViews时，一切都按预期工作，选择分段的第一个按钮时显示UICollectionView对象控制。

@objc func changed() {

    if segmentTime.selectedSegmentIndex == 0 {

        self.dataCollectionViews.isHidden = false

        let dataCollectionTop = NSLayoutConstraint(item: self.dataCollectionViews, attribute: .top, relatedBy: .equal, toItem: sortLabel, attribute: .bottom, multiplier: 1.0, constant: 10)

        let dataCollectionLeft = NSLayoutConstraint(item: self.dataCollectionViews, attribute: .leading, relatedBy: .equal, toItem: self.view, attribute: .leading, multiplier: 1.0, constant: 10)

        let dataCollectionRight = NSLayoutConstraint(item: self.dataCollectionViews, attribute: .trailing, relatedBy: .equal, toItem: self.view, attribute: .trailing, multiplier: 1.0, constant: -10)

        let dataCollectionHeight = NSLayoutConstraint(item: self.dataCollectionViews, attribute: .height, relatedBy: .equal, toItem: self.view, attribute: .height, multiplier: 520/812, constant: 0)

        let dataCollectionWidth = NSLayoutConstraint(item: self.dataCollectionViews, attribute: .width, relatedBy: .equal, toItem: self.view, attribute: .width, multiplier: 355/375, constant: 0)

        NSLayoutConstraint.activate([dataCollectionLeft, dataCollectionRight, dataCollectionHeight, dataCollectionWidth, dataCollectionTop])

    }

    if segmentTime.selectedSegmentIndex == 1 {



    }

    if segmentTime.selectedSegmentIndex == 2 {



    }

}

我很想尝试在属性初始值设定项中设置dataCollectionViews对象，但我知道这是不可能的，但是似乎dataCollectionViews首次尝试时需要用UICollectionViewFlowLayout()进行初始化。还有什么其他选择？

Answer 1

这样的事情怎么样？

private lazy var collectionView: UICollectionView = {
    let layout: UICollectionViewFlowLayout = UICollectionViewFlowLayout()
    layout.itemSize = CGSize(width: 188.0, height: 268.0)

    let result: UICollectionView = UICollectionView(frame: .zero, collectionViewLayout: layout)
    result.register(CellClass.self, forCellWithReuseIdentifier: "cell")
    result.dataSource = self
    result.delegate = self
    return result
}()

即使设置了布局参数，也会出现“ UICollectionView必须使用非空布局参数初始化”的问题

1 个答案: