使用分页在 gridview 中显示图像

Question

我有一个带有增量加载的 gridview，它显示本地文件夹中的书籍封面。

XAML：

<GridView  
    x:Name="komikGridView" 
        DataFetchSize="18" 
        IncrementalLoadingTrigger="Edge" 
        IncrementalLoadingThreshold="1" 
        HorizontalAlignment="Stretch"
        VerticalAlignment="Stretch">
        <GridView.Resources>
            <DataTemplate x:Key="DataTemplatekomikGridView">
                    <Grid
                            x:Name="komikGrid1"
                                Margin="5,5,0,0"
                                Width="145"
                                Height="255"
                                Background="White">
                                <Image
                                    x:Name="cover"
                                        Width="145"
                                        Height="210"
                                        VerticalAlignment="Top"
                                        Source="{Binding Image}"
                                        Stretch="Fill" />
            </Grid>
        </DataTemplate>
    </GridView.Resources>
    <GridView.ItemTemplate>
        <StaticResource ResourceKey="DataTemplatekomikGridView"/>
    </GridView.ItemTemplate>
</GridView>

代码：

    var booksource = new BookSource();
            var collection = new IncrementalLoadingCollection<BookSource, Book>(booksource, 18);
            try
            {
                await collection.LoadMoreItemsAsync(0);
            }
 komikGridView.ItemsSource = collection;

书籍.cs：

public class Book
    {
        public string Name { get; set; }

        public string Judul { get; set; }

        public string Image { get; set; }
    }

    public class BookSource : IIncrementalSource<Book>
    {
        public List<Book> _books;

        public BookSource()
        {
            _books = new List<Book>();
        }

        IReadOnlyList<StorageFile> files;
        IReadOnlyList<StorageFile> thumbfiles;
        StorageFolder kategorithumb;
        StorageFolder kategori;
        StorageFolder localfolder = ApplicationData.Current.LocalFolder;

        public async Task<List<Book>> CopyResource()
        {
            await Task.Run(async () =>
            {
                StorageFolder _pdffolder = Windows.ApplicationModel.Package.Current.InstalledLocation;
                _pdffolder = await _pdffolder.GetFolderAsync("files");
                _pdffolder = await _pdffolder.GetFolderAsync("pdf");
                _pdffolder = await _pdffolder.GetFolderAsync("komik");
                IReadOnlyList<StorageFile> _pdffiles = await _pdffolder.GetFilesAsync();
                StorageFolder library = await localfolder.CreateFolderAsync("library", CreationCollisionOption.OpenIfExists);
                kategori = await library.CreateFolderAsync("komik", CreationCollisionOption.OpenIfExists);
                files = await kategori.GetFilesAsync();
                if (((App)(App.Current)).FolderName == "komik" && files.Count == 0)
                {
                    foreach (var item in _pdffiles)
                    {
                        await item.CopyAsync(kategori, item.Name, NameCollisionOption.ReplaceExisting);
                    }
                    files = await kategori.GetFilesAsync();
                }
                StorageFolder _thumbfolder = Windows.ApplicationModel.Package.Current.InstalledLocation;
                _thumbfolder = await _thumbfolder.GetFolderAsync("files");
                _thumbfolder = await _thumbfolder.GetFolderAsync("cover");
                _thumbfolder = await _thumbfolder.GetFolderAsync("komik");
                IReadOnlyList<StorageFile> _coverfiles = await _thumbfolder.GetFilesAsync(); //which returns List<StorageFile>
                StorageFolder thumbfolder = await localfolder.CreateFolderAsync("thumb", CreationCollisionOption.OpenIfExists);
                kategorithumb = await thumbfolder.CreateFolderAsync("komik", CreationCollisionOption.OpenIfExists);
                thumbfiles = await kategorithumb.GetFilesAsync();
                if (((App)(App.Current)).FolderName == "komik" && thumbfiles.Count == 0)
                {
                    foreach (var item in _coverfiles)
                    {
                        await item.CopyAsync(kategorithumb, item.Name, NameCollisionOption.ReplaceExisting);
                    }
                }
            });
            IEnumerable<Temp> sortingFiles = files.Select(x => new Temp { File = x }).ToList();
            IEnumerable<StorageFile> sortedfiles = sortingFiles.OrderByDescending(x => x.LastModified).Select(x => x.File).ToList();
            var books = new List<Book>();
            string filePath = "";
            foreach (StorageFile file in sortedfiles)
            {
                Book book = new Book();
                StorageFile thumbFile = await kategorithumb.GetFileAsync(file.Name.ToString() + ".png");
                string path = kategorithumb.Path;
                filePath = Path.Combine(path, file.Name.ToString() + ".png");
                book.Name = file.DisplayName.ToString();
                book.Image = thumbFile.Path;
                await Window.Current.CoreWindow.Dispatcher.RunAsync(Windows.UI.Core.CoreDispatcherPriority.Normal, () =>
                {
                    books.Add(book);
                });
            }
            return books;
        }

        private ProgressRing progressRing = ((Window.Current.Content as Frame).Content as LibraryPage).loading;
        public async Task<IEnumerable<Book>> GetPagedItemsAsync(int pageIndex, int pageSize, CancellationToken cancellationToken = default(CancellationToken))
        {
            progressRing.Visibility = Visibility.Visible;
            progressRing.IsActive = true;
            if (_books.Count == 0)
            {
                foreach (var item in await CopyResource())
                {
                    _books.Add(item);
                }
            }
            var result = (from p in _books
                          select p).Skip(pageIndex * pageSize).Take(pageSize);
            await Task.Delay(1000);
            progressRing.Visibility = Visibility.Collapsed;
            progressRing.IsActive = false;
            return result;
        }
        public class Temp
        {
            public StorageFile File { get; set; }
            public string Name { get; set; }
        }

我想首先在 gridview 中显示 18 本书的封面。 然后如果用户滚动，它将显示接下来的 18 本书封面，以此类推，直到所有的书籍封面都显示在 gridview 中。 如何应用它？

Answer 1

如果您需要控制每次加载的源的大小。 您只需在创建IncrementalLoadingCollection时将itemsPerPage参数设置为 18。

像这样：

  collection = new IncrementalLoadingCollection<NamedColorSource, NamedColor>(18);

然后您可以在GetPagedItemsAsync方法中放置一个断点并检查pageSize参数。 你会看到它是你想要的 18。