在列表视图中拖放加载可见项目 [英] Lazy-loading visible items in a Listview

问题描述

我有一个列表视图，使用以下代码：

I have a listview which uses the following code:

<ListView x:Name="Display" ItemsSource="{Binding}" Background="#373737" Margin="0,0,350,0" BorderThickness="0" >
        <ListView.ItemTemplate>
            <DataTemplate>
                <StackPanel Orientation="Horizontal" Width="767" Height="88">
                    <Border Height="64" Width="64" Margin="12,12,0,12">
                        <Image Source="{Binding Path=album.albumart}" Stretch="UniformToFill"/>
                    </Border>
                    <StackPanel Orientation="Vertical" VerticalAlignment="Top" Margin="0,10,0,0">
                        <TextBlock Text="{Binding Path=name}" 
                   Margin="10,0,0,0" Width="300" Height="40" 
                   TextTrimming="WordEllipsis" TextWrapping="Wrap" FontSize="16" HorizontalAlignment="Left"/>
                        <TextBlock Text="{Binding Path=album.name}" 
                   Margin="10,-15,0,0" Width="300" Height="20" 
                   TextTrimming="WordEllipsis" HorizontalAlignment="Left" 
                   FontSize="14" Opacity="0.49"/>
                        <TextBlock Text="{Binding Path=artistname}" 
                   Margin="10,2,0,0" Width="300"
                   TextTrimming="WordEllipsis" HorizontalAlignment="Left" 
                   FontSize="12" Opacity="0.49"/>
                    </StackPanel>
                </StackPanel>
            </DataTemplate>
        </ListView.ItemTemplate>
    </ListView>

我有大约400个对象与图像（这需要相当多的内存）

And I have about 400 objects with images (this takes quite a bit of memory)

然后在每个listviewit中显示。

Which are then displayed in each listviewitem.

列表视图有没有办法告诉项目从缓存我基于哪些对象在列表视图中可见，而不是一直加载所有的图像，如前所述，这些内容需要相当多的内存。

Is there any way for the listview to tell items to load their image from a cache I have based on which objects are visible in the listview instead of having all the images loaded all the time, which, as previously said takes quite a bit of memory.

希望你们明白我在说什么，谢谢。

Hope you guys understand what I'm on about, thank you.

推荐答案

我尝试这个解决方案，我的图片文件夹包含多于3500张高分辨率图片。内存使用达到120MB，激烈的滚动似乎触发垃圾收集，并将内存减少到大约50MB。我不知道这是否足够低的内存使用？

I tried this solution with my pictures folder containing more than 3500 pictures in high resolution. Memory usage peaked at 120MB with furious scrolling which seemed to trigger garbage collection and reduced memory to about 50MB. I don't know if that's sufficiently low memory usage?

 <ListBox ItemsSource="{Binding Images}" VirtualizingPanel.IsVirtualizing="True">
        <ListBox.ItemTemplate>
            <DataTemplate>
                <Image Height="64" Width="64">
                    <Image.Source>
                        <BitmapImage
                            DecodePixelHeight="64"
                            DecodePixelWidth="64"
                            UriSource="{Binding Path=., Mode=OneWay,UpdateSourceTrigger=Explicit}" 
                            CreateOptions="DelayCreation" 
                            CacheOption="None"  />
                    </Image.Source>
                </Image>
            </DataTemplate>
        </ListBox.ItemTemplate>
    </ListBox>

ViewModel：

ViewModel:

public class ViewModel : INotifyPropertyChanged
    {
        public ICollectionView Images { get; private set; }
        public ViewModel()
        {
        }
        public void LoadImages()
        {
            var folder = @"C:\Users\lrved_000\Pictures";
            var photos = System.IO.Directory.EnumerateFiles(folder, "*.jpg",SearchOption.AllDirectories);

            Images = CollectionViewSource.GetDefaultView(photos);
            RaisePropertyChanged("Images");
        }

        public event PropertyChangedEventHandler PropertyChanged;
        public void RaisePropertyChanged(string propName)
        {
            if (PropertyChanged != null)
            {
                PropertyChanged(this, new PropertyChangedEventArgs(propName));
            }
        }
    }

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