[英]Out of memory exception while using <ScrollViewer> with multiple ListViews in it
我有一个带有2个ListViews的用户控件。 一个用于保存预定义类别的列表,另一个用于包含所有类别的列表。 当我将ListViews放置在<Grid>
,一切都完美无缺。 有效的xaml代码(带有Grid):
<Grid Style="{StaticResource ResourceKey=ContentStyle}">
<Grid.RowDefinitions>
<RowDefinition Height="Auto"/>
<RowDefinition Height="*"/>
</Grid.RowDefinitions>
<ListView x:Name="lstPredefinedCategories" Grid.Row="0" ItemsSource="{Binding PredefinedCategories}" SelectionMode="Multiple" Margin="20">
<ListView.Header>
<StackPanel>
<TextBlock Text="Voorgestelde categorieën" Style="{StaticResource TextBlockStyle}" FontWeight="SemiBold" Foreground="Black" />
<Rectangle Style="{StaticResource DividerStyle}" Fill="Black"/>
</StackPanel>
</ListView.Header>
<ListView.ItemTemplate>
<DataTemplate>
<TextBlock Text="{Binding}" Style="{StaticResource TextBlockStyle}" HorizontalAlignment="Left" TextWrapping="Wrap" Width="300" />
</DataTemplate>
</ListView.ItemTemplate>
</ListView>
<Grid Grid.Row="1">
<Grid.RowDefinitions>
<RowDefinition Height="Auto" />
<RowDefinition Height="Auto" />
<RowDefinition Height="Auto" />
<RowDefinition Height="*" />
<RowDefinition Height="Auto" />
<RowDefinition Height="Auto" />
</Grid.RowDefinitions>
<StackPanel Grid.Row="0" Margin="20,0">
<TextBlock Text="Alle categorieën" Style="{StaticResource TextBlockStyle}" FontWeight="SemiBold" Foreground="Black" />
<Rectangle Style="{StaticResource DividerStyle}" Fill="Black"/>
</StackPanel>
<TextBox x:Name="txtSearch" PlaceholderText="Zoek categorie" Grid.Row="1" Style="{StaticResource SearchboxStyle}" Margin="20,0" TextChanged="txtSearch_TextChanged" />
<Rectangle Grid.Row="2" Style="{StaticResource DividerStyle}" Margin="20, 0" />
<ListView x:Name="lstCategories" Grid.Row="3" Margin="20,10,20,0" ItemsSource="{Binding Categories}" SelectionMode="Multiple" SelectionChanged="lstCategories_SelectionChanged">
<ListView.ItemTemplate>
<DataTemplate>
<TextBlock Text="{Binding Key}" Style="{StaticResource TextBlockStyle}" HorizontalAlignment="Left" TextWrapping="Wrap" Width="300" />
</DataTemplate>
</ListView.ItemTemplate>
</ListView>
<Rectangle Grid.Row="4" Style="{StaticResource DividerStyle}" Margin="20, 0" />
<Grid Grid.Row="5">
<Grid.ColumnDefinitions>
<ColumnDefinition Width="*" />
<ColumnDefinition Width="Auto" />
<ColumnDefinition Width="*" />
</Grid.ColumnDefinitions>
<Button x:Name="btnAnnuleren" Grid.Column="0" Content="Annuleren" Style="{StaticResource ButtonAnnulerenStyle}" Click="btnAnnuleren_Click"/>
<Rectangle Grid.Column="1" Fill="#A9A9A9" Width="0.5" Margin="10,0" />
<Button x:Name="btnSelecteren" Grid.Column="2" Content="Selecteren" Style="{StaticResource ButtonAnnulerenStyle}" Click="btnSelecteren_Click"/>
</Grid>
</Grid>
</Grid>
唯一的问题是我没有得到想要的UI行为。 如果我使用网格,则只有红色边框是可滚动的(由于ListView)。 但是我需要的是整个绿色边框都是可滚动的。
所以我想将所有内容放入<ScrollViewer><StackPanel></StackPanel></ScrollViewer>
。 但是,当我这样做时,有时会遇到内存不足的异常(有时应用程序会冻结并无例外关闭)。
这是我不使用<ScrollViewer>
xaml的方法:
<ScrollViewer>
<StackPanel>
<ListView x:Name="lstPredefinedCategories" ItemsSource="{Binding PredefinedCategories}" SelectionMode="Multiple" Margin="20">
<ListView.Header>
<StackPanel>
<TextBlock Text="Voorgestelde categorieën" Style="{StaticResource TextBlockStyle}" FontWeight="SemiBold" Foreground="Black" />
<Rectangle Style="{StaticResource DividerStyle}" Fill="Black"/>
</StackPanel>
</ListView.Header>
<ListView.ItemTemplate>
<DataTemplate>
<TextBlock Text="{Binding}" Style="{StaticResource TextBlockStyle}" HorizontalAlignment="Left" TextWrapping="Wrap" Width="300" />
</DataTemplate>
</ListView.ItemTemplate>
</ListView>
<Grid>
<Grid.RowDefinitions>
<RowDefinition Height="Auto" />
<RowDefinition Height="Auto" />
<RowDefinition Height="Auto" />
<RowDefinition Height="*" />
<RowDefinition Height="Auto" />
<RowDefinition Height="Auto" />
</Grid.RowDefinitions>
<StackPanel Grid.Row="0" Margin="20,0">
<TextBlock Text="Alle categorieën" Style="{StaticResource TextBlockStyle}" FontWeight="SemiBold" Foreground="Black" />
<Rectangle Style="{StaticResource DividerStyle}" Fill="Black"/>
</StackPanel>
<TextBox x:Name="txtSearch" PlaceholderText="Zoek categorie" Grid.Row="1" Style="{StaticResource SearchboxStyle}" Margin="20,0" TextChanged="txtSearch_TextChanged" />
<Rectangle Grid.Row="2" Style="{StaticResource DividerStyle}" Margin="20, 0" />
<ListView x:Name="lstCategories" Grid.Row="3" Margin="20,10,20,0" ItemsSource="{Binding Categories}" SelectionMode="Multiple" SelectionChanged="lstCategories_SelectionChanged">
<ListView.ItemTemplate>
<DataTemplate>
<TextBlock Text="{Binding Key}" Style="{StaticResource TextBlockStyle}" HorizontalAlignment="Left" TextWrapping="Wrap" Width="300" />
</DataTemplate>
</ListView.ItemTemplate>
</ListView>
<Rectangle Grid.Row="4" Style="{StaticResource DividerStyle}" Margin="20, 0" />
<Grid Grid.Row="5">
<Grid.ColumnDefinitions>
<ColumnDefinition Width="*" />
<ColumnDefinition Width="Auto" />
<ColumnDefinition Width="*" />
</Grid.ColumnDefinitions>
<Button x:Name="btnAnnuleren" Grid.Column="0" Content="Annuleren" Style="{StaticResource ButtonAnnulerenStyle}" Click="btnAnnuleren_Click"/>
<Rectangle Grid.Column="1" Fill="#A9A9A9" Width="0.5" Margin="10,0" />
<Button x:Name="btnSelecteren" Grid.Column="2" Content="Selecteren" Style="{StaticResource ButtonAnnulerenStyle}" Click="btnSelecteren_Click"/>
</Grid>
</Grid>
</StackPanel>
</ScrollViewer>
关于为什么我的应用程序冻结或获得OOM异常有任何想法吗?
这是因为在第二个ListView中,它们加载了太多对象。 因此,我将尝试使用ISupportIncrementalLoading对其进行修复。
还是有其他方法?
解决方案是使用虚拟化(ISupportIncrementalLoading),如注释中所建议。
在这里,您可以找到我的ISupportIncrementalLoading实现类:
public class StringKeyValueIncrementalCollection : ObservableCollection<StringKeyValue>, ISupportIncrementalLoading
{
private List<StringKeyValue> allCategories;
private int lastItem = 1;
public StringKeyValueIncrementalCollection(List<StringKeyValue> categories)
{
this.allCategories = categories;
}
public bool HasMoreItems
{
get
{
if (lastItem == allCategories.Count)
{
return false;
}
else
{
return true;
}
}
}
public IAsyncOperation<LoadMoreItemsResult> LoadMoreItemsAsync(uint count)
{
CoreDispatcher coreDispatcher = Window.Current.Dispatcher;
return Task.Run<LoadMoreItemsResult>(async () =>
{
List<StringKeyValue> items = new List<StringKeyValue>();
for (int i = 0; i < count; i++)
{
items.Add(allCategories[i]);
lastItem++;
Debug.WriteLine(lastItem);
if (lastItem == allCategories.Count)
{
break;
}
}
await coreDispatcher.RunAsync(CoreDispatcherPriority.Normal,
() =>
{
foreach (StringKeyValue item in items)
{
this.Add(item);
}
});
return new LoadMoreItemsResult() { Count = count };
}).AsAsyncOperation<LoadMoreItemsResult>();
}
}
然后我的代码在ViewModel中。 如您所见,我使用StringKeyValueIncrementalCollection
代替常规的List<object>
:
private StringKeyValueIncrementalCollection categories;
private StringKeyValueIncrementalCollection allCategories;
public StringKeyValueIncrementalCollection Categories
{
get { return categories; }
set
{
filteredCategories = value;
RaisePropertyChanged("Categories");
}
}
public async void LoadCategories()
{
List<StringKeyValue> temp = await this.openVlaanderenService.GetCategoriesData();
allCategories = new StringKeyValueIncrementalCollection(temp);
Categories = allCategories;
}
您唯一遇到的问题是ScollViewer将允许其内容填充所需的尽可能多的空间,因此数据将继续加载。 要解决此问题,我做了不支持ScrollViewer的ISupportIncrementalLoading中所建议的操作吗?
因此,我向SizeChanged="ScrollViewer_SizeChanged"
添加了SizeChanged="ScrollViewer_SizeChanged"
事件,并在后面的代码中根据ScrollViewer的视口大小属性设置了ListView的大小:
private void ScrollViewer_SizeChanged(object sender, SizeChangedEventArgs e)
{
lstCategories.Height = scrollViewer.ViewportHeight;
}
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