Swift：UICollectionViewCell didSelectItemAtIndexPath 更改 backgroundColor

Question

I'm easily able to change the background color of a cell in the CellForItemAtIndexPath method

func collectionView(collectionView: UICollectionView, cellForItemAtIndexPath     indexPath: NSIndexPath) -> UICollectionViewCell {
 cell.backgroundColor = UIColor.blackColor()
 }

However, when I attempt to change the color in the DidSelectItemAtIndexPath it does not work.

func collectionView(collectionView: UICollectionView, didSelectItemAtIndexPath     indexPath: NSIndexPath) {
        let cell: ButtonCollectionCell = collectionView.dequeueReusableCellWithReuseIdentifier("ButtonCell", forIndexPath: indexPath) as! ButtonCollectionCell {
cell.backgroundColor = UIColor.blackColor()

}

Also I read somewhere that using didSelectItemAtIndexPath won't work because once the collection view begins scrolling the color will change back

What is the fix in Swift?

Thank you so much for your help

Answer 1

You can use this method for that:

    func collectionView(collectionView: UICollectionView, didSelectItemAtIndexPath indexPath: NSIndexPath){

    var cell : UICollectionViewCell = collectionView.cellForItemAtIndexPath(indexPath)!
    cell.backgroundColor = UIColor.magentaColor()
}

Answer 2

Old question, but it can help someone:

You can't simply modify the cell, since your changes will be lost when you scroll your UICollectionView , or even worst, other cells could appear with a wrong background, because they'll be reused.

So, the best way to do that is create an array of NSIndexPath and append your selected indexPaths:

var selectedIndexes = [NSIndexPath]() {
    didSet {
        collectionView.reloadData()
    }
}

func collectionView(collectionView: UICollectionView, didSelectItemAtIndexPath indexPath: NSIndexPath){
    // ...
    if let indexSelecionado = selectedIndexes.indexOf(indexPath) {
        selectedIndexes.removeAtIndex(indexSelecionado)
    } else {
        selectedIndexes.append(indexPath)
    }
}

// ...

func collectionView(collectionView: UICollectionView, cellForItemAtIndexPath indexPath: NSIndexPath) -> UICollectionViewCell {
    // ...
    if self.selectedIndexes.indexOf(indexPath) == nil {
        cell.backgroundColor = UIColor.whiteColor() // Unselected
    } else {
        cell.backgroundColor = UIColor.redColor() // Selected
    }
    return cell
}

Answer 3

You can override UICollectionViewCell isSelected . It will apply changes in selected method.

class ButtonCollectionCell: UICollectionViewCell {

            override var isSelected: Bool{
                didSet{
                    if self.isSelected
                    {
                       self.layer.backgroundColor =  colorLiteral(red: 0.8058760762, green: 0.2736578584, blue: 0.1300437152, alpha: 1)

                    }  else
                    {
                       self.layer.backgroundColor =  colorLiteral(red: 0, green: 0, blue: 0, alpha: 0)

                    }
                }
            }

    }

Answer 4

cell.backgroundColor = UIColor.redColor()

let startTime = DateUtils.getDispatchTimeByDate(NSDate(timeIntervalSinceNow: 0.1))
dispatch_after(startTime, dispatch_get_main_queue()) {[weak self] in
    //there is the code redirect to other viewcontroller
    openOtherVC()
}