Swift:如何在设备旋转后刷新 UICollectionView 布局 [英] Swift: How to refresh UICollectionView layout after rotation of the device

问题描述

我使用 UICollectionView (flowlayout) 构建了一个简单的布局.每个单元格的宽度使用 self.view.frame.width

I used UICollectionView (flowlayout) to build a simple layout. the width for each cell is set to the width of screen using self.view.frame.width

但是当我旋转设备时，单元格没有得到更新.

but when I rotate the device, the cells don't get updated.

我找到了一个函数，它会在方向改变时调用:

I have found a function, which is called upon orientation change :

override func willRotateToInterfaceOrientation(toInterfaceOrientation: 
  UIInterfaceOrientation, duration: NSTimeInterval) {
    //code
}

但我无法找到更新 UICollectionView 布局的方法

but I am unable to find a way to update the UICollectionView layout

主要代码在这里:

class ViewController: UIViewController , UICollectionViewDelegate , UICollectionViewDataSource , UICollectionViewDelegateFlowLayout{

    @IBOutlet weak var myCollection: UICollectionView!

    var numOfItemsInSecOne: Int!
    override func viewDidLoad() {
        super.viewDidLoad()

        numOfItemsInSecOne = 8
        // Do any additional setup after loading the view, typically from a nib.
    }

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

    override func willRotateToInterfaceOrientation(toInterfaceOrientation: UIInterfaceOrientation, duration: NSTimeInterval) {

        //print("orientation Changed")
    }

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

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

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

        return cell
    }

    func collectionView(collectionView: UICollectionView, layout collectionViewLayout: UICollectionViewLayout, sizeForItemAtIndexPath indexPath: NSIndexPath) -> CGSize{
    let itemSize = CGSize(width: self.view.frame.width, height: 100)
    return itemSize
    }}

推荐答案

添加这个功能:

override func viewDidLayoutSubviews() {
    super.viewDidLayoutSubviews() 
    myCollection.collectionViewLayout.invalidateLayout()
}

当你改变方向时，这个函数会被调用.

When you change the orientation, this function would be called.

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