Select first Item in CollectionView Swift4

Question

I'm trying to select the first Item in CollectionView when the Collectionview loads. I found many solutions for Swift 3 but nothing of that worked for me in Swift4. What I tried(viewDidAppear):

import UIKit
import SDWebImage

class PostsTab_Details: UIViewController, UICollectionViewDelegate, UICollectionViewDataSource, UICollectionViewDelegateFlowLayout {

@IBOutlet weak var PostsSelectRarityCollectionView: UICollectionView!
@IBOutlet weak var RarityTypeLbl: UILabel!

//Center my Collectionview Horizontal
func collectionView(_ collectionView: UICollectionView, layout collectionViewLayout: UICollectionViewLayout, insetForSectionAt section: Int) -> UIEdgeInsets {

        let totalCellWidth = 100 * (selectedPosts?.rarity.count)!
        let totalSpacingWidth = 10 * (3 - 1)

        let leftInset = (PostsSelectRarityCollectionView.frame.width - CGFloat(totalCellWidth + totalSpacingWidth)) / 2
        let rightInset = leftInset

        return UIEdgeInsetsMake(0, leftInset, 0, rightInset)

}

func collectionView(_ collectionView: UICollectionView, numberOfItemsInSection section: Int) -> Int {

    return (selectedPosts?.rarity.count)!
}

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

    cell.PostssTab_DetailCollectionImage.sd_setImage(with: URL(string: (selectedPosts?.PostsImageURL)!))



    return cell
}

func collectionView(_ collectionView: UICollectionView, didSelectItemAt indexPath: IndexPath) {
    RarityTypeLbl.text = selectedPosts?.rarity[indexPath.row].rarity

}

 //Tried this also with IndexPath(item: 0, section: 0)
override func viewDidAppear(_ animated: Bool) {
    let selectedIndexPath = IndexPath(row: 0, section: 0)
    PostsSelectRarityCollectionView.selectItem(at: selectedIndexPath, animated: true, scrollPosition: .right)
}



var selectedPosts: Posts?

override func viewDidLoad() {
    PostsSelectRarityCollectionView.delegate = self
    PostsSelectRarityCollectionView.dataSource = self
}
}

But this is not working... I hope someone knows what I'm doing wrong..

Thanks in advance

Update: This worked for me now, thanks to Razib's answer:

override func viewWillAppear(_ animated: Bool) {
    self.collectionView(PostsSelectRarityCollectionView, didSelectItemAt: IndexPath(row: 0, section: 0))
}

Possible duplicate of [Select items programmatically in UICollectionView](https://stackoverflow.com/questions/13177201/select-items-programmatically-in-uicollectionview) — Gereon, Apr 02 '18 at 15:50

Razib Mollick · Accepted Answer · 2018-04-03T11:17:59.113

4

Your code seems okay to me. If you like to trigger the didSelectItemAt method, use the following code.

 override func viewDidAppear(_ animated: Bool) {
    self.PostsSelectRarityCollectionView(self.PostsSelectRarityCollectionView, didSelectItemAt: IndexPath(row: 0, section: 0))
}

edited Apr 03 '18 at 11:17

answered Apr 03 '18 at 11:07

Razib Mollick

4,617
2
22
20

Ahh thank you... I will give it a try it later this day or tomorrow, not sure if I come home today. But I will give you some feedback then – Nxt97 Apr 03 '18 at 12:30
Great stuff! Works like a charm – sugarakis Jan 18 '21 at 21:54

score 4 · Answer 2 · answered May 08 '20 at 20:04

To programmatically select the first Item in CollectionViewCell when the Collectionview loads you should code in viewDidAppear:

override func viewDidAppear(_ animated: Bool) {
    let indexPath:IndexPath = IndexPath(row: 0, section: 0)
    collectionView?.selectItem(at: indexPath, animated: false, scrollPosition: .top)
}

score 0 · Answer 3 · answered Jul 25 '19 at 11:11

0

Try this (Swift 5):

    let indexPath:IndexPath = IndexPath(row: 0, section: 0)
    collectionView?.selectItem(at: indexPath, animated: false, scrollPosition: .top)

answered Jul 25 '19 at 11:11

Claytog

618
8
8

Select first Item in CollectionView Swift4

3 Answers3