如何从UICollectionView中获取所选单元格计数和所选单元格数组，我需要设置选择的限制。下面是我的代码，它不工作。请引导。谢谢
func collectionView(_ collectionView: UICollectionView, shouldSelectItemAt indexPath: IndexPath) -> Bool {
let indexPaths = collectionView.indexPathsForSelectedItems!
print(indexPaths)
if let selectedItems = collectionView.indexPathsForSelectedItems {
if selectedItems.count >= 3 {
collectionView.deselectItem(at: indexPath as IndexPath, animated: true)
return false
}
}
return true
}
上面的代码，当编写在didSelect方法中时，只返回选定的单元格索引，但这里只跳到最后一行
return true
您可以使用UICollectionViewDelegate中的ShouldSelectItemat委托方法来实现：
func collectionView(_ collectionView: UICollectionView, shouldSelectItemAt indexPath: IndexPath) -> Bool {
return collectionView.indexPathsForSelectedItems?.count ?? 0 <= selectionLimit
}
演示其工作方式的示例演示：
class ViewController : UIViewController {
private var myCollectionView:UICollectionView?
private var selectionLimit = 4
override func viewDidLoad() {
super.viewDidLoad()
let view = UIView()
view.backgroundColor = .white
let layout: UICollectionViewFlowLayout = UICollectionViewFlowLayout()
layout.sectionInset = UIEdgeInsets(top: 20, left: 10, bottom: 10, right: 10)
layout.itemSize = CGSize(width: UIScreen.main.bounds.width * 0.7, height: 60)
myCollectionView = UICollectionView(frame: self.view.frame, collectionViewLayout: layout)
myCollectionView?.register(UICollectionViewCell.self, forCellWithReuseIdentifier: "MyCell")
myCollectionView?.backgroundColor = UIColor.white
myCollectionView?.allowsMultipleSelection = true
myCollectionView?.dataSource = self
myCollectionView?.delegate = self
view.addSubview(myCollectionView ?? UICollectionView())
self.view = view
}
}
extension ViewController: UICollectionViewDataSource {
func collectionView(_ collectionView: UICollectionView, numberOfItemsInSection section: Int) -> Int {
return 20
}
func collectionView(_ collectionView: UICollectionView, cellForItemAt indexPath: IndexPath) -> UICollectionViewCell {
let myCell = collectionView.dequeueReusableCell(withReuseIdentifier: "MyCell", for: indexPath)
myCell.backgroundColor = UIColor.blue
return myCell
}
}
extension ViewController: UICollectionViewDelegate {
func collectionView(_ collectionView: UICollectionView, didSelectItemAt indexPath: IndexPath) {
print("Did select a cell at \(indexPath.row)")
let itemsLeftToSelect = selectionLimit - (collectionView.indexPathsForSelectedItems?.count ?? 0)
print("Have \(itemsLeftToSelect) items to select")
}
func collectionView(_ collectionView: UICollectionView, didDeselectItemAt indexPath: IndexPath) {
print("Did deselect a cell at \(indexPath.row)")
let itemsLeftToSelect = selectionLimit - (collectionView.indexPathsForSelectedItems?.count ?? 0)
print("Have \(itemsLeftToSelect) items to select")
}
func collectionView(_ collectionView: UICollectionView, shouldSelectItemAt indexPath: IndexPath) -> Bool {
return collectionView.indexPathsForSelectedItems?.count ?? 0 < selectionLimit
}
}
当您达到选择限制时，ShouldSelectItemat将返回false，DidSelectItemat函数将不再被调用。另一方面，如果您单击已选择的单元格，则DidDeselectItemat将被调用，您也将被调用，并且您能够再次选择+1个单元格，因为所选项的数量将随着1而减少。另请参阅示例中的调试日志。
