UICollectionView 单元格选择的奇怪行为

Question

I currently have this (pseudo)code:

var selectedCell: UICollectionViewCell?

override func viewDidLoad() {
    super.viewDidLoad()
    ...
    #initialize all objects and pull data from the server to fill the cells

    UIView.animate(withDuration: 0, animations: {
        self.dataCollectionView.reloadData()
    }, completion: {(finished) in

        let indexPath = IndexPath(row: 0, section: 0)
        self.dataCollectionView.selectItem(at: indexPath, animated: true, scrollPosition: .top)
        self.collectionView(self.dataCollectionView, didSelectItemAt: indexPath)
    })
}

func collectionView(_ collectionView: UICollectionView, cellForItemAt indexPath: IndexPath) -> UICollectionViewCell {
    let cell = collectionView.dequeueReusableCell(withReuseIdentifier: "Cell", for: indexPath) as! DataCollectionViewCell
    if !selectedCell {
        cell.layer.borderWidth = 1
    }
    else {
       cell.layer.borderWidth = 2            
    }
}

func collectionView(_ collectionView: UICollectionView, didSelectItemAtindexPath: IndexPath) {

    let cell = collectionView.cellForItem(at: indexPath)
    selectedCell = cell
    cell.image = SomeImageFromServer
    cell.layer.borderWidth = 2
}

func collectionView(_ collectionView: UICollectionView, didDeselectItemAt indexPath: IndexPath) {

    let cell = collectionView.cellForItem(at: indexPath)
    cell.layer.borderWidth = 1
}

My thinking is that this code will select the first cell right after the collection view has been loaded, and it does. The problem is it selects the last cell as well, but didSelectItemAtindexPath is never called for the last cell, and only the first cell.

I've tried selecting the second cell by using let indexPath = IndexPath(row: 1, section: 0) and it does select the second cell once the collectionview has been loaded, and the last cell is not selected as you would think.

And once any cell is selected, the last cell is unselected.

So my hypothesis is that this isn't the code thinking the cell is "selected" but that it's for some reason giving the selected cell a "selected cell border" but only when the first selected cell is the first one. Any thoughts?

Answer 1

Try moving the border setting into cell, UICollectionView will automatically manage the border width:

//Swift3
class TestCollectionViewCell: UICollectionViewCell {

    override func awakeFromNib() {
        super.awakeFromNib()

        self.layer.borderWidth = 1 //Default border width
    }

    override var isSelected: Bool {
        didSet{
            if self.isSelected {
                self.layer.borderWidth = 2
            }
            else{
                self.layer.borderWidth = 1
            }
        }
    }
}