迅速收集缓慢查看

Question

I have a collection view that takes images I have stored and displays them. However, when I run it, I get a memory error and a really slow/laggy display. Here is my code:

var players = ["1", "2", "3", "4", "5", "10", "11", "12", "13", "15", "20", "22", "24", "25", "31", "31", "33", "34"]


@IBOutlet weak var collectionView: UICollectionView!
func numberOfSectionsInCollectionView(collectionView: UICollectionView) -> Int {
    return 1
}

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

    return 17


}
func collectionView(collectionView: UICollectionView, cellForItemAtIndexPath indexPath: NSIndexPath) -> UICollectionViewCell {
    var cell = collectionView.dequeueReusableCellWithReuseIdentifier("MyCell", forIndexPath: indexPath) as HomeCollectionViewCell
    cell.imageViewTwo.image = UIImage(named: "\(players[indexPath.row])")
    return cell
}

Is there an easier way to do this that I'm missing?

Answer 1

You should use Instruments to figure out what it is that is slow. That's what it's for!

However, I'm going to guess that this line is the problem:

cell.imageViewTwo.image = UIImage(named: "\(players[indexPath.row])")

If those images are big, two bad things will happen: it takes time to open each one, and you are wasting memory because the displayed image is much smaller than the loaded image. And this is happening while you scroll . Everything you do in cellForItemAtIndexPath: needs to be very, very fast for exactly this reason. Well, your implementation is clearly not fast.

You have two choices - actually you could use both:

• Prepare better images. Use png and use them at the actual size needed for display.

• Use lazy image loading so that you load the images in a background thread and don't slow down the scrolling.