如何在viewWillTransitionToSize後獲取子視圖的大小

Question

我有一個UICollectionView，它由彈出窗口顯示。 UICollectionView包含16行，每行10個單元格，我希望單元格填充UICollectionView的寬度。我試圖調整viewWillTransitionToSize中每個單元格的大小，但我無法獲得正確的值。

如何獲得UICollectionView的寬度，因爲它將在之後轉換？在iPad上航2

從70/30到50/50 50/50改變至70/30分屏之間切換時

的問題顯示出來給我太小細胞：

從50/50到70/30改變給了我太大細胞：

當前代碼：

class ColorPickerCollectionViewController: UICollectionViewController { 


var cellsize:CGSize?; 


override func viewDidLoad() { 
    super.viewDidLoad() 

    // Register cell classes 
    self.collectionView!.registerClass(UICollectionViewCell.self, forCellWithReuseIdentifier: reuseIdentifier) 

    // Do any additional setup after loading the view. 
    if let flowLayout = self.collectionViewLayout as? UICollectionViewFlowLayout { 

     flowLayout.minimumInteritemSpacing = 0; 
     flowLayout.minimumLineSpacing = 0; 
     flowLayout.sectionInset = UIEdgeInsetsMake(0,0,0,0); 

    } 

} 

// MARK: UICollectionViewDataSource 

override func numberOfSectionsInCollectionView(collectionView: UICollectionView) -> Int { 
    return 16; 
} 


override func collectionView(collectionView: UICollectionView, numberOfItemsInSection section: Int) -> Int { 
    return 10; 
} 

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

    // Configure the cell 

    let colorView = getColorViewForCell(indexPath, cell: cell); 
    cell.contentView.addSubview(colorView); 

    cell.selectedBackgroundView = UIView(); 
    cell.selectedBackgroundView!.backgroundColor = UIColor.whiteColor(); 

    return cell 
} 

func getColorViewForCell(indexPath:NSIndexPath, cell:UICollectionViewCell) -> UIView { 
    let colorView = UIView(); 
    colorView.backgroundColor = UIColor.blueColor(); 
    colorView.frame = CGRectMake(cell.bounds.origin.x + 1, cell.bounds.origin.y + 1, cell.bounds.width - 2, cell.bounds.height - 2); 
    colorView.translatesAutoresizingMaskIntoConstraints = false; 
    return colorView; 
} 


func collectionView(collectionView: UICollectionView, 
    layout collectionViewLayout: UICollectionViewLayout, 
    sizeForItemAtIndexPath indexPath: NSIndexPath) -> CGSize { 

     if self.cellsize == nil { 
      let width = CGFloat(collectionView.frame.width/10); 
      cellsize = CGSize(width: width, height: width); 
     } 

     return self.cellsize!; 
} 

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

    NSLog("viewWillTransitionToSize") 
    super.viewWillTransitionToSize(size, withTransitionCoordinator: coordinator); 

    //What do I do here? 
    self.cellsize //= ???; 


    let cView:UICollectionView = self.collectionView!; 
    cView.performBatchUpdates(nil, completion: nil); 


} 

} 

Answer 1

新的解決方案，這要歸功於@ MikePollard的關於繼承的UICollectionViewFlowLayout評論。

我創建了一個子類ColorPickerFlowLayout，其全部內容如下。我將它設置爲Collection View的佈局，並讓func collectionView(collectionView: UICollectionView, layout collectionViewLayout: UICollectionViewLayout, sizeForItemAtIndexPath indexPath: NSIndexPath) -> CGSize返回佈局的單元大小。

我可以刪除UICollectionViewController中的viewWillTransitionToSize。

import UIKit 

class ColorPickerFlowLayout: UICollectionViewFlowLayout { 

    private var cellSize:CGSize? = nil 
    var previousBounds: CGRect? = nil 

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

    func getCellSize() -> CGSize? { 

    return cellSize 
    } 

    override func shouldInvalidateLayoutForBoundsChange(newBounds: CGRect) -> Bool { 

    if previousBounds == nil || previousBounds!.width != newBounds.width { 

     let width = CGFloat(newBounds.width/10) 
     cellSize = CGSize(width: width, height: width) 

     previousBounds = newBounds 

     self.collectionView?.performBatchUpdates(nil, completion: nil) 

     return true 
    } else { 

     return false 
    } 

    } 

}