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我正在使用语义缩放控件在我的 WinRT 应用程序中显示联系人列表。当我手动滚动列表时，我想获取当前视图中的项目（视图中将有多个项目，但我想获取最近的项目）。这样我就可以保存滚动位置以在用户导航回此联系人列表时将其设置为原样。有什么建议吗？我尝试获取当前的选定索引，但在滚动列表时它从未更新：

int lastViewedItem = ((ListViewBase)this.semanticZoom.ZoomedInView).SelectedIndex;

在导航返回

(ListViewBase)this.semanticZoom.ZoomedInView).SelectedIndex = lastViewedItem;

 ((ListViewBase)this.semanticZoom.ZoomedInView).ScrollIntoView(((ListViewBase)this.semanticZoom.ZoomedInView).SelectedItem);
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1 回答 1

1

我创建了一个扩展，只为我在这里ItemsControl知道的任何人做。

using System;
using System.Collections;
using Windows.Foundation;
using Windows.UI.Xaml;
using Windows.UI.Xaml.Controls;

/// <summary>
/// Gets the first visible element.
/// </summary>
/// <param name="itemsControl">The ItemsControl.</param>
/// <returns>The first visible item or null if not found.</returns>
public static object GetFirstVisibleItem(this ItemsControl itemsControl)
{
    var index = GetFirstVisibleIndex(itemsControl);

    if (index == -1)
    {
        return null;
    }

    var list = itemsControl.ItemsSource as IList;

    if (itemsControl.ItemsSource != null &&
        list != null &&
        list.Count > index)
    {
        return list[index];
    }

    if (itemsControl.Items != null &&
        itemsControl.Items.Count > index)
    {
        return itemsControl.Items[index];
    }

    throw new InvalidOperationException();
}

/// <summary>
/// Gets the index of the first visible element.
/// </summary>
/// <param name="itemsControl">The ItemsControl.</param>
/// <returns>The index of the first visible item or -1 if not found.</returns>
public static int GetFirstVisibleIndex(this ItemsControl itemsControl)
{
    // First checking if no items source or an empty one is used
    if (itemsControl.ItemsSource == null)
    {
        return -1;
    }

    var enumItemsSource = itemsControl.ItemsSource as IEnumerable;

    if (enumItemsSource != null && !enumItemsSource.GetEnumerator().MoveNext())
    {
        return -1;
    }

    // Check if a modern panel is used as an items panel
    var sourcePanel = itemsControl.ItemsPanelRoot;

    if (sourcePanel == null)
    {
        throw new InvalidOperationException("Can't get first visible index from an ItemsControl with no ItemsPanel.");
    }

    var isp = sourcePanel as ItemsStackPanel;

    if (isp != null)
    {
        return isp.FirstVisibleIndex;
    }

    var iwg = sourcePanel as ItemsWrapGrid;

    if (iwg != null)
    {
        return iwg.FirstVisibleIndex;
    }

    // Check containers for first one in view
    if (sourcePanel.Children.Count == 0)
    {
        return -1;
    }

    if (itemsControl.ActualWidth == 0)
    {
        throw new InvalidOperationException("Can't get first visible index from an ItemsControl that is not loaded or has zero size.");
    }

    for (int i = 0; i < sourcePanel.Children.Count; i++)
    {
        var container = (FrameworkElement)sourcePanel.Children[i];
        var bounds = container.TransformToVisual(itemsControl).TransformBounds(new Rect(0, 0, container.ActualWidth, container.ActualHeight));

        if (bounds.Left < itemsControl.ActualWidth &&
            bounds.Top < itemsControl.ActualHeight &&
            bounds.Right > 0 &&
            bounds.Bottom > 0)
        {
            return itemsControl.IndexFromContainer(container);
        }
    }

    throw new InvalidOperationException();
}
于 2015-02-26T20:41:25.793 回答