How do I got Multiple Selections in UICollection View using Swift 4

问题

I'm new to swift and building iOS Application from the scratch (using swift 4) and want to do something like below. 1. Implement Multiple cell selections in UICollectionView, 2. Pass selected cells data to Server. Please anyone can help me, how to do that? Tell me the process and supporting articles to do that.

Below is reference Image. Thanks in Advance.

回答1:

This basic example. You can change as per your data.

When you select any cell then you need to check that selected cell is already selected before or not.

If not then add selected cell indexPath in indexArray and selected cell value in valueArray.

If current selected cell is previously selected then remove indexPath from indexArray and also remove selected cell value from valueArray

on continue button press pass arrSelectedData to server or next screen.

Define below 3 array.

var arrData = [String]() // This is your data array
var arrSelectedIndex = [IndexPath]() // This is selected cell Index array
var arrSelectedData = [String]() // This is selected cell data array

//UICollectionView Delegate & DataSource

extension ViewController: UICollectionViewDelegate, UICollectionViewDataSource, UICollectionViewDelegateFlowLayout 
{
    func collectionView(_ collectionView: UICollectionView, numberOfItemsInSection section: Int) -> Int {
        return self.arrData.count
    }

    func collectionView(_ collectionView: UICollectionView, cellForItemAt indexPath: IndexPath) -> UICollectionViewCell {
        let cell : CollectionViewCell = collectionView.dequeueReusableCell(withReuseIdentifier: "CollectionViewCell", for: indexPath) as! CollectionViewCell

        if arrSelectedIndex.contains(indexPath) { // You need to check wether selected index array contain current index if yes then change the color
            cell.vw.backgroundColor = UIColor.red
        }
        else {
            cell.vw.backgroundColor = UIColor.lightGray
        }

        cell.layoutSubviews()
        return cell
    }

    func collectionView(_ collectionView: UICollectionView, layout collectionViewLayout: UICollectionViewLayout, sizeForItemAt indexPath: IndexPath) -> CGSize {
        return CGSize(width: 100, height: 100)
    }

    func collectionView(_ collectionView: UICollectionView, didSelectItemAt indexPath: IndexPath) {
        print("You selected cell #\(indexPath.item)!")

        let strData = arrData[indexPath.item]

        if arrSelectedIndex.contains(indexPath) {
            arrSelectedIndex = arrSelectedIndex.filter { $0 != indexPath}
            arrSelectedData = arrSelectedData.filter { $0 != strData}
        }
        else {
            arrSelectedIndex.append(indexPath)
            arrSelectedData.append(strData)
        }

        collectionView.reloadData()
    }
}

回答2:

You can write the code like this to Enable Multiple Selection :-

yourCollectionViewName.allowsMultipleSelection = true   

then you can Do it like this to see the cell Selected -

func collectionView(collectionView: UICollectionView, didSelectItemAtIndexPath indexPath: NSIndexPath) {
    var cell = collectionView.cellForItemAtIndexPath(indexPath)
    if cell?.selected == true {
        cell?.backgroundColor = UIColor.orangeColor()
    }
}

To Deselect You can do something Like this -

func collectionView(collectionView: UICollectionView, didDeselectItemAtIndexPath indexPath: NSIndexPath) {        
   var cell = collectionView.cellForItemAtIndexPath(indexPath)
   cell?.backgroundColor = UIColor.clearColor()
}

回答3:

Well, to achieve a thing like that, you need to mainly perform the following tasks

1. Whenever user clicks on a particular cell, you need to change the background colour for that item in the didSelectItemAt delegate method of UICollectionView

2. Now to send that data to server, you need an array to store all the selected cells and then send that array to server . You can perform the same in didSelectItemAt method as well

I can show you a prototype of what the function will look like:

Let's assume you have an array named arrayForPopulating for populating data inside Collection View and we have array named finalSelections which consist of names of all the selections that user made

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

   let cell = collectionView.cellForItem(at: indexPath)

   // Change the background colour of the cell here
   cell.contentView.backgroundColor = UIColor.red

   // Add the selected cell's data to the array
   finalSelections.append(arrayForPopulating[indexPath.row])

}

Now you can send you finalSelections array to the server !

回答4:

Well, the best way to handle multiple selections in UICollectionView

1) Enable Multiple Selection

myCollectionView.allowsMultipleSelection = true

2) override isSelected var in your custom cell class

override var isSelected: Bool {
        didSet {
            if self.isSelected {
                backgroundColor = UIColor.red
            }
            else {
                backgroundColor = UIColor.purple
            }
        }
    }

3) and you can get the selected indexPath items

let items = myCollectionView.indexPathsForSelectedItems

来源：https://stackoverflow.com/questions/52757524/how-do-i-got-multiple-selections-in-uicollection-view-using-swift-4