Проблема с распределением памяти с помощью LazyVGrid SwiftUI при отображении медиафайлов ⇐ IOS

[Anonymous]

Сейчас я работаю над приложением SwiftUI, которое отображает медиафайлы в сетке с включенным LazyVGrid.

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GalleryView

where there will be 3 media files per row. The media files are loaded from the app's cache and not from the user's

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Photos

app. When user scrolls down to see more media data, media files are lazily loaded into memory and the ones hidden from view are not deallocated from memory because LazyVGrid does not have a built-in memory deallocation mechanism. Проблемы с памятью становятся более очевидными (

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n>10

where

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n

is the number of media files) when there exists a large number of images or videos to show on appear of

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GalleryView

:

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struct GalleryView: View {
@Binding var mediaFiles: [Media]
var body: some View {
GeometryReader { geometry in
ScrollView {
let width = geometry.size.width / 3 - 10
let gridItemLayout = [GridItem(.fixed(width)), GridItem(.fixed(width)), GridItem(.fixed(width))]
LazyVGrid(columns: gridItemLayout, spacing: 10) {
ForEach(mediaFiles, id: \.id) { media in
if let image = media.image {
Image(uiImage: image)
.resizable()
.scaledToFit()
.frame(width: width)
} else if let videoURL = media.videoURL {
// Display video thumbnail here
}
}
}
}
}
}
}

struct Media: Identifiable {
let id = UUID()
let creationTime: Date
var image: UIImage?
var videoURL: URL?
}

I have tried a custom UIKit approach to handle the memory deallocation issue:

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struct CollectionView: UIViewControllerRepresentable {
typealias UIViewControllerType = UICollectionViewController

@Binding var mediaFiles: [Media]
var width: CGFloat

func makeUIViewController(context: Context) -> UICollectionViewController {
let layout = UICollectionViewFlowLayout()
layout.itemSize = CGSize(width: width / 3, height: width / 3)
layout.minimumLineSpacing = 10
layout.minimumInteritemSpacing = 10
let collectionViewController = UICollectionViewController(collectionViewLayout: layout)
collectionViewController.collectionView?.register(MediaCell.self, forCellWithReuseIdentifier: "cell")
collectionViewController.collectionView?.backgroundColor = .white
return collectionViewController
}

func updateUIViewController(_ uiViewController: UICollectionViewController, context: Context) {
uiViewController.collectionView?.dataSource = context.coordinator
uiViewController.collectionView?.delegate = context.coordinator
uiViewController.collectionView?.reloadData()
}

func makeCoordinator() -> Coordinator {
Coordinator(self)
}

class Coordinator: NSObject, UICollectionViewDataSource, UICollectionViewDelegate {
var parent: CollectionView

init(_ parent: CollectionView) {
self.parent = parent
}

func collectionView(_ collectionView: UICollectionView, numberOfItemsInSection section: Int) -> Int {
return parent.mediaFiles.count
}

func collectionView(_ collectionView: UICollectionView, cellForItemAt indexPath: IndexPath) -> UICollectionViewCell {
let cell = collectionView.dequeueReusableCell(withReuseIdentifier: "cell", for: indexPath) as! MediaCell
let media = parent.mediaFiles[indexPath.row]
if let image = media.image {
cell.imageView.image = image
}
return cell
}

func collectionView(_ collectionView: UICollectionView, didSelectItemAt indexPath: IndexPath) {
// Handle selection here
}
}
}

so that I can use

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CollectionView

in place of LazyVGrid in

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GalleryView

like this:

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CollectionView(mediaFiles: $mediaFiles, width: width)
.frame(width: geometry.size.width, height: geometry.size.height)
.onAppear {
model.loadMediaFiles()
if let lastMediaIndex = mediaFiles.indices.last {
scrollView.scrollTo(lastMediaIndex, anchor: .bottom)
}
}

But the custom UIKit code didn't work as expected because

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GalleryView

now shows a blank white screen (on either light/dark mode) instead of showing 3 media items per row. I have also tried using List in place of LazyVGrid, or trying Chris C's code to try optimizing the memory complexity of the problem to

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O(1)

but neither approach worked. Я также попытался разбить данные на части и создать строки с более чем одним изображением, как было предложено @baronfac в другой теме. Однако предложение @baronfac оптимизирует проблему с памятью только за счет

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n

to

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n/3

, which this linear reduction doesn't really change the memory complexity of the problem since it's still

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O(n)

.
Is there a simple and intuitive way to deal with this absence of memory deallocation issue with LazyVGrid? If a UIKit implementation is the best approach, could someone help identify what’s wrong with my current UIKit code that’s causing the GalleryView to display a blank screen?


Источник: https://stackoverflow.com/questions/781 ... edia-files