UICollectionView so much slow to load

Question

The instance I've successfully called the images from array JSON returned object the UICollection is very slow to load especially if it has main images.

func collectionView(_ collectionView: UICollectionView, cellForItemAt indexPath: IndexPath) -> UICollectionViewCell {


    let childDict: NSDictionary = subCategoryData .object(at: indexPath.row) as! NSDictionary

    let cell = collectionView.dequeueReusableCell(withReuseIdentifier: "listcollectionview", for: indexPath) as! subCategoryCollectionViewCell

    subCategoryTable.register(UINib(nibName: "subCategoryCollectionViewCell", bundle: nil), forCellWithReuseIdentifier: "listcollectionview")

    let subimages = childDict.object(forKey: "image") as! String!
    let data = NSData(contentsOf: NSURL(string: subimages!)! as URL)
    cell.backgroundImageView.image = UIImage(data: data! as Data)

    cell.categoryName.text = (subCategoryMenuData [indexPath.row] as? String)
    cell.categoryName?.textColor = UIColor.white
    cell.categoryName?.backgroundColor = UIColor().HexToColor(hexString: GREYBLACK)

    return cell;
}

I tried as well the dispatch.queue in didselectitemat when calling the segue but this didn't solve the problem

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

    let childDict: NSDictionary = subCategoryData .object(at: indexPath.row) as! NSDictionary

    if (childDict.object(forKey: "children") as! NSArray).count > 0{
        let sb = UIStoryboard(name: "Main", bundle: nil)
        let initViewController: subCategory? = (sb.instantiateViewController(withIdentifier: "subCategory") as? subCategory)
        initViewController?.subCategoryData = (childDict.object(forKey: "children") as! NSArray)
        initViewController?.subName = childDict.object(forKey: "name") as! String!
        initViewController?.subId = childDict.object(forKey: "path") as! String!
        initViewController?.modalTransitionStyle = .flipHorizontal
        self.navigationController?.pushViewController(initViewController!, animated: true)
    }else{

        categoryName = childDict .object(forKey: "name") as! String
        categoryId = childDict .object(forKey: "path") as! String
        DispatchQueue.main.async {
            self.performSegue(withIdentifier: "productCategorySegue",sender: self)
        }
    }


}

It some times take 30 seconds to load

`let data = NSData(contentsOf: NSURL(string: subimages!)! as URL)`, can you explain why you do that synchronously on the main thread, please? also it would be great to understand the idea behind registering nib _every time_ when you create a cell for the collection-view...? — holex, Aug 13 '18 at 07:57
Using it to load the placeholder while all the images and page are loaded. — David Buik, Aug 15 '18 at 00:43
where is the code what loads the image / page then? would you intend to share that with us too? — holex, Aug 15 '18 at 07:14

score 3 · Answer 1 · edited Aug 27 '18 at 18:53

3

You load your image in cell for index you can use sdwebimage library install theough pods for lazy loading. It will definitely resolved your issue.

edited Aug 27 '18 at 18:53

marc_s

732,580
175
1,330
1,459

answered Aug 12 '18 at 01:31

Anil Kumar

1,830
15
24

or AlamofireImage – Jeff Bootsholz Aug 12 '18 at 01:34
I have AlamorfireImage installed in my libs. Examples are highly appreciated. – David Buik Aug 12 '18 at 01:36
Folle this https://medium.com/ios-os-x-development/best-image-download-extension-library-for-swift-3-cf64ec1f84a0 – Anil Kumar Aug 12 '18 at 01:39

score 2 · Answer 2 · answered Aug 12 '18 at 01:04

Oh I just found the solutions thanks to @abhishekkharwar post here

I converted the ObjC to Swift 3 to resolve the issue.

DispatchQueue.global(qos: .default).async(execute: {() -> Void in
    var image = UIImage(contentsOfFile: frontPath)
    DispatchQueue.main.async(execute: {() -> Void in
        frontButton.setBackgroundImage(image, for: .normal)
    })
})

score 0 · Answer 3 · answered Aug 13 '18 at 07:25

0

Using AlamofireImage library:

let subimages = childDict.object(forKey: "image") as! String!
if let imageUrl = URL(string: subimages){
     cell.backgroundImageView.af_setImage(withURL: imageUrl, placeholderImage: nil)
}

answered Aug 13 '18 at 07:25

Moayad Al kouz

1,342
1
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score 0 · Answer 4 · answered Aug 17 '18 at 18:25

-----Swift 4-----

Step 1: Add this Extension : if you dont know about extension , check this : Swift extension example

 extension UIImageView {
        func downloadImage(from url:String){

            if url != ""{
            let urlRequest = URLRequest(url: URL(string:url)!)

            let task = URLSession.shared.dataTask(with: urlRequest){(data,response,error) in

                if error != nil{
                    return
                }
                DispatchQueue.main.async {
                    self.image = UIImage(data: data!)
                }
            }
            task.resume()
            }
        }
    }

Step 2 : Using UIImageViewExtension for Downloading Image : In your 'cellForItemAt indexPath' method use this code :

cell.backgroundImageView.downloadImage(from: data)

Additional: check your image file size. if it is big in size thats obiously takes time to load . You can add this smooth image appearing animation before your image load for making it cool.

UIView.transition(with: cell.backgroundImageView,
                              duration: 0.5,
                              options: .transitionCrossDissolve,
                              animations: { cell.backgroundImageView.downloadImage(from: data) },
                              completion: nil)

UICollectionView so much slow to load

4 Answers4