如何在集合视图中更改视图的颜色

Question

How to change the color of view in collection view when it select and when the select the other view before view came to original color How to set it?

Answer 1

You can use the didSelectItemAtIndexPath method and the didDeselectItemAtIndexPath method from the UICollectionViewDelegate protocol. UICollectionViewDelegate is an Objective-C protocol, indicated by @objc , that allows you to have optional methods like didSelectItemAtIndexPath and didDeselectItemAtIndexPath that you can choose to implement optionally in your delegate.

When UICollectionView gets instantiated initially, it goes through all the available methods you've implemented in the instance of UICollectionViewDelegate with responds(to:) , which takes a selector parameter and returns a bool, to see which methods from the UICollectionViewDelegate protocol you've implemented without actually sending a message to them. As it detects the following methods, it remembers them and calls those methods whenever you select or deselect a cell from the collection view:

func collectionView(_ collectionView: UICollectionView, cellForItemAt indexPath: IndexPath) -> UICollectionViewCell {
    let cell = collectionView.dequeueReusableCell(withReuseIdentifier: "cell", for: indexPath)
    if let indexPaths = collectionView.indexPathsForSelectedItems, let firstIndex = indexPaths.first {
        cell.backgroundColor = firstIndex == indexPath ? .white : .gray
    }
    return cell
}

func collectionView(_ collectionView: UICollectionView, didSelectItemAt indexPath: IndexPath) {
    if let cell = collectionView.cellForItem(at: indexPath) {
        cell.backgroundColor = .white
    }
}

func collectionView(_ collectionView: UICollectionView, didDeselectItemAt indexPath: IndexPath) {
    guard let cell = collectionView.cellForItem(at: indexPath) else {
        return
    }
    cell.backgroundColor = .gray
}

Alternatively, you can use the collectionView(_:didHighlightItemAt:) method and the collectionView(_:didUnhighlightItemAt:) method. The following sample code is from here :

func collectionView(_ collectionView: UICollectionView, didHighlightItemAt indexPath: IndexPath) {
    if let cell = collectionView.cellForItem(at: indexPath) {
        cell.contentView.backgroundColor = #colorLiteral(red: 1, green: 0.4932718873, blue: 0.4739984274, alpha: 1)
    }
}

func collectionView(_ collectionView: UICollectionView, didUnhighlightItemAt indexPath: IndexPath) {
    if let cell = collectionView.cellForItem(at: indexPath) {
        cell.contentView.backgroundColor = nil
    }
}

Answer 2

You can simply add two methods for changing colour of the view or cell in the collectionView:-

//When cell got selected

func collectionView(_ collectionView: UICollectionView, didSelectItemAt indexPath: IndexPath) {
    if let cell = collectionView.cellForItem(at: indexPath){
        cell.backgroundColor = .green
    }
}

//When cell deselected

    func collectionView(_ collectionView: UICollectionView, didDeselectItemAt indexPath: IndexPath) {
    if let cell = collectionView.cellForItem(at: indexPath){
        cell.backgroundColor = .clear
    }
} 

If you have view inside your cell as backgroundView then you can use same functions and just need to replace cell.backgroundView.backgroundColor in place of the cell.backgroundColor. Just remember "backgroundView" is the name of the view you have inside cell.

If you want more information about this then you can follow below attached links:-

1). https://www.tutorialfor.com/questions-296884.html

2). https://en.it1352.com/article/fccf358a040b4ddba872d7324602754c.html