Ios 为什么invalidateLayout没有在UICollectionView中触发sizeForItemAtIndexPath？（附代码）

问题是collectionView中的列数在旋转时没有保持在7（所需的数量）。修复此问题需要进行哪些代码更改

自定义UICollectionViewFlowLayout中的invalidateLayout似乎没有触发collectionView中的sizeForItemAtIndexPath方法？有什么想法吗？我真的只希望在旋转时通过sizeForItemAtIndexPath来调整列的大小

注意：这里我没有使用故事板，而是有一个自定义视图，我在其中插入collectionView并引用我自己的collectionView类

下面的代码工作正常，但是在旋转时，它不会像应该的那样将列数保持在7。最初运行代码时，控制台输出显示：

GCCalendar - init coder
GCCalendar - commonInit
GCCalendarLayout:invalidateLayout
GCCalendarLayout:invalidateLayout
ViewController:viewWillLayoutSubviews
GCCalendarLayout:invalidateLayout
GCCalendarLayout:prepareLayout
sizeForItemAtIndexPath
.
.
sizeForItemAtIndexPath
minimumInteritemSpacingForSectionAtIndex
minimumLineSpacingForSectionAtIndex
GCCalendarLayout:collectionViewContentSize
GCCalendarLayout:layoutAttributesForElementsInRect
GCCalendarLayout:collectionViewContentSize
ViewController:viewWillLayoutSubviews
GCCalendarCell:drawRect
.
.
GCCalendarCell:drawRect

但是，旋转屏幕后，我看到以下内容：

ViewController:viewWillLayoutSubviews
GCCalendarLayout:shouldInvalidateLayoutForBoundsChange
GCCalendarLayout:invalidateLayout
GCCalendarLayout:prepareLayout
GCCalendarLayout:collectionViewContentSize
GCCalendarLayout:layoutAttributesForElementsInRect
GCCalendarLayout:collectionViewContentSize

所以问题是“SizeFormiteIndeXPath”从未被调用过？？？

旋转时输出代码

注意：“SizeFormiteIndeXPath”不会被触发，即使“invalidateLayout”是

ViewController:ViewWillLayoutSubView GCCalendarLayout:应为边界设置验证布局 GCCalendarLayout:invalidateLayout

**包含集合视图的自定义视图**

import UIKit

@IBDesignable class GCCalendarView: UIView {

    required init?(coder aDecoder: NSCoder) {
        super.init(coder: aDecoder)
        commonInit()
    }

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



    // Private

    private func commonInit() {
        if self.subviews.count == 0 {
            let bundle = NSBundle(forClass: self.dynamicType)
            let nib = UINib(nibName: "GCCalendarView", bundle: bundle)
            let view = nib.instantiateWithOwner(self, options: nil)[0] as! UIView
            view.frame = bounds
            view.autoresizingMask = [.FlexibleWidth, .FlexibleHeight]
            addSubview(view)
        }
    }

}

自定义收藏视图

import UIKit

class GCCalendar : UICollectionView, UICollectionViewDataSource, UICollectionViewDelegate {

    // Init ---------------

    func commonInit(coder aDecoder: NSCoder) {
        print("GCCalendar - commonInit")
        self.registerClass(GCCalendarCell.self, forCellWithReuseIdentifier: "GCCalendarCell")
        self.dataSource = self
        self.delegate = self

        let layout : GCCalendarLayout = GCCalendarLayout(coder: aDecoder)!
        self.setCollectionViewLayout(layout, animated: false)

        self.backgroundColor = UIColor.whiteColor()
    }

    required init?(coder aDecoder: NSCoder) {
        print("GCCalendar - init coder")
        super.init(coder: aDecoder)
        commonInit(coder: aDecoder)
    }


    // UICollectionViewDelegateFlowLayout ------------

    func collectionView(collectionView: UICollectionView, layout collectionViewLayout: UICollectionViewLayout, sizeForItemAtIndexPath indexPath: NSIndexPath) -> CGSize {
        print("sizeForItemAtIndexPath")
        let w : CGFloat = floor(self.frame.size.width/7)
        return CGSize(width: w, height: w)
    }

    func collectionView(collectionView: UICollectionView, layout collectionViewLayout: UICollectionViewLayout, minimumInteritemSpacingForSectionAtIndex section: Int) ->
        CGFloat {
        print("minimumInteritemSpacingForSectionAtIndex")
        return 0.0
    }

    func collectionView(collectionView: UICollectionView, layout collectionViewLayout: UICollectionViewLayout, minimumLineSpacingForSectionAtIndex section: Int) -> CGFloat {
        print("minimumLineSpacingForSectionAtIndex")
        return 0.0
    }


    // UICollectionViewDataSource -------------------

    func collectionView(collectionView: UICollectionView, numberOfItemsInSection section: Int) -> Int {
        return 21
    }

    func collectionView(collectionView: UICollectionView, cellForItemAtIndexPath indexPath: NSIndexPath) -> UICollectionViewCell {
        let cell = collectionView.dequeueReusableCellWithReuseIdentifier("GCCalendarCell", forIndexPath: indexPath) as? GCCalendarCell


        return cell!
    }
}

**自定义集合视图单元格**

import UIKit

class GCCalendarCell: UICollectionViewCell {

    @IBOutlet weak var title : UITextField!
    @IBOutlet weak var date: UILabel!

    required init?(coder aDecoder: NSCoder) {
        print("GCCalendarCell - init:coder")
        super.init(coder: aDecoder)
        commonInit()
    }

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

    override func drawRect(rect: CGRect) {
        print("GCCalendarCell:drawRect")
        self.layer.borderWidth = 1
        self.layer.borderColor = UIColor.grayColor().CGColor
    }

    // Private

    private func commonInit() {
        let bundle = NSBundle(forClass: self.dynamicType)
        let nib = UINib(nibName: "GCCalendarCell", bundle: bundle)
        let view = nib.instantiateWithOwner(self, options: nil)[0] as! UIView
        view.frame = bounds
        view.autoresizingMask = [.FlexibleWidth, .FlexibleHeight]
        addSubview(view)
    }

}

自定义布局

import UIKit

class GCCalendarLayout : UICollectionViewFlowLayout {
    required init?(coder aDecoder: NSCoder) {
        super.init(coder: aDecoder)
    }

    override func shouldInvalidateLayoutForBoundsChange(newBounds: CGRect) -> Bool {
        print("GCCalendarLayout:shouldInvalidateLayoutForBoundsChange")
        return true
    }

    override func invalidateLayout() {
        print("GCCalendarLayout:invalidateLayout")
        super.invalidateLayout()

    }

    override func prepareForCollectionViewUpdates(updateItems: [UICollectionViewUpdateItem]) {
        print("GCCalendarLayout:prepareForCollectionViewUpdates")
        super.prepareForCollectionViewUpdates(updateItems)
    }

    override func finalizeCollectionViewUpdates() {
        print("GCCalendarLayout:finalizeCollectionViewUpdates")
        super.finalizeCollectionViewUpdates()
    }


}

---

如果您使用的是故事板，请在下面所附的故事板I中设置CollectionviewFlowLayout类

---

编辑：在viewController中尝试以下操作：

override func viewWillTransitionToSize(size: CGSize, withTransitionCoordinator coordinator: UIViewControllerTransitionCoordinator) 
{
    (self.collectionview.collectionViewLayout).setItemSize(CGSizeMake(floor(size.width / 7), floor(size.width / 7)))
    self.collectionview.collectionViewLayout.invalidateLayout()
}

---

@Kujey的解决方案可以应用于

UIView

，而无需访问

UIViewController

：

func traitCollectionDidChange(previousTraitCollection : UITraitCollection) {
    super.traitCollectionDidChange(previousTraitCollection)
    self.collectionView.collectionViewLayout.invalidateLayout()
}

---

现有答案对我没有任何帮助（iPhone X模拟器iOS 11.2）。
我发现，更改的有助于解决此问题：

<...>
//***new line
flowLayout.estimatedItemSize = [self getIconSize];//get a new size for items

[flowLayout invalidateLayout];
<...>

//***新线
flowLayout.estimatedItemSize=[self-getIconSize]//获取项目的新尺寸
[flowLayout invalidateLayout]；

您是否在使用故事板否。不使用故事板我可以帮你，但我不知道斯威夫特。你能读懂obj-c吗？是的，这应该是好的，我必须有这个权利，因为它在运行时确实设置了正确的尺寸，它只是在旋转时改变问题可能是的。但是，您是否可以在自定义flowlayout的itemSize函数中添加一个日志，看看它是否在旋转时被调用。sizeForItemAtIndexPath（如果这是您的意思）在旋转时没有被调用……这就是issue@EricAya我认为编程语言对于这个问题并不重要。