列表视图项目UWP的备用颜色 [英] Alternate color for listview item UWP

问题描述

我有一堂课，以替代项目的背景颜色，但如果我删除项目，则背景颜色不会更新. 删除项目后是否可以刷新背景颜色?

I have a class to color alternate the background of item, but if I delete a item, the background color does not update. Is there a way to refresh the background color after deleting an item?

备用颜色的代码. 类列表视图:

The code for alterante color. class listview:

public class AlternatingRowListView : ListView
{
    protected override void PrepareContainerForItemOverride(DependencyObject element, object item)
    {
        base.PrepareContainerForItemOverride(element, item);
        var listViewItem = element as ListViewItem;
        if (listViewItem != null)
        {
            var index = IndexFromContainer(element);

            if (index % 2 == 0)
            {
                listViewItem.Background = new SolidColorBrush(Colors.LightBlue);
            }
            else
            {
                listViewItem.Background = new SolidColorBrush(Colors.Transparent);
            }
        }

    }
}

代码xaml:

<local:AlternatingRowListView x:Name="listview">
        <ListViewItem>item 1</ListViewItem>
        <ListViewItem>item 2</ListViewItem>
        <ListViewItem>item 3</ListViewItem>
        <ListViewItem>item 4</ListViewItem>
        <local:AlternatingRowListView.ItemTemplate>
            <DataTemplate>

            </DataTemplate>
        </local:AlternatingRowListView.ItemTemplate>
</local:AlternatingRowListView>

提前谢谢.

推荐答案

您只需要稍微扩展一下已经扩展的AlternatingRowListView控件即可实现所需的功能.

You just need to extend your already extended AlternatingRowListView control a bit to achieve what you need.

您可以通过订阅Items的VectorChanged事件来监视何时从列表中删除某项，然后您只需遍历以下所有已实现项 (在视觉上)删除的项目并相应地更改其背景颜色.

You can monitor whenever an item gets removed from the list by subscribing to the VectorChanged event of the Items, and then you just loop through all the already realized items below(visually) the removed item and change their background colors accordingly.

类似的事情会发生-

public AlternatingRowListView()
{
    DefaultStyleKey = typeof(ListView);

    Items.VectorChanged += OnItemsVectorChanged;
}

private void OnItemsVectorChanged(IObservableVector<object> sender, IVectorChangedEventArgs args)
{
    // When an item is removed from the list...
    if (args.CollectionChange == CollectionChange.ItemRemoved)
    {
        var removedItemIndex = (int)args.Index;

        // We don't really care about the items that are above the deleted one, so the starting index
        // is the removed item's index.
        for (var i = removedItemIndex; i < Items.Count; i++)
        {
            if (ContainerFromIndex(i) is ListViewItem listViewItem)
            {
                listViewItem.Background = i % 2 == 0 ? 
                    new SolidColorBrush(Colors.LightBlue) : new SolidColorBrush(Colors.Transparent);
            }
            // If it's null, it means virtualization is on and starting from this index the container
            // is not yet realized, so we can safely break the loop.
            else
            {
                break;
            }
        }
    }
}

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