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如何控制MVVM WPF应用程序中列表框的滚动位置

scrollviewer listbox mvvm wpf c#

Jobi Joy · 技术社区 · 15 年前

我有一个大的列表框,启用了垂直滚动,我的MVVM有新的和编辑的图标命令。我正在将新项添加到集合的末尾,但我希望当调用MVVM AddCommand时,滚动条也自动定位到末尾。我还将从应用程序的其他部分使项目可编辑(通过使用特定行项目调用editcommand),以便我的ListBoxItem使用DataTrigger进入编辑模式,但是如何通过调整滚动位置将特定行(ListBoxItem)带到视图中。

如果在视图侧执行此操作,则可以调用ListBox.ScrollInToView(lstBoxItem)。但从MVVM的角度来看,解决这个常见滚动问题的最佳方法是什么?

4 回复 | 直到 8 年前

Noctis 10 年前

我通常设定 IsSynchronizedWithCurrentItem="True" 上 ListBox . 然后我添加了一个 SelectionChanged 处理程序,并始终将所选项目带到视图中,代码如下:

    private void BringSelectionIntoView(object sender, SelectionChangedEventArgs e)
    {
        Selector selector = sender as Selector;
        if (selector is ListBox)
        {
            (selector as ListBox).ScrollIntoView(selector.SelectedItem);
        }
    }

从我的虚拟机中,我可以获取默认的集合视图,并使用 MoveCurrent*() 方法以确保正在编辑的项是当前项。

CollectionViewSource.GetDefaultView(_myCollection).MoveCurrentTo(thisItem);

注:编辑后使用 ListBox.ScrollIntoView() 适应虚拟化

LightBulb 8 年前

在MVVM中使用它可以通过如下附加行为轻松完成:

using System.Windows.Controls;
using System.Windows.Interactivity;

namespace Jarloo.Sojurn.Behaviors
{
    public sealed class ScrollIntoViewBehavior : Behavior<ListBox>
    {
        protected override void OnAttached()
        {
            base.OnAttached();
            AssociatedObject.SelectionChanged += ScrollIntoView;
        }

        protected override void OnDetaching()
        {
            AssociatedObject.SelectionChanged -= ScrollIntoView;
            base.OnDetaching();
        }

        private void ScrollIntoView(object o, SelectionChangedEventArgs e)
        {
            ListBox b = (ListBox) o;
            if (b == null)
                return;
            if (b.SelectedItem == null)
                return;

            ListBoxItem item = (ListBoxItem) ((ListBox) o).ItemContainerGenerator.ContainerFromItem(((ListBox) o).SelectedItem);
            if (item != null) item.BringIntoView();
        }
    }
}

然后在视图中,在顶部添加此引用:

xmlns:i="clr-namespace:System.Windows.Interactivity;assembly=System.Windows.Interactivity"

然后这样做:

<ListBox ItemsSource="{Binding MyData}" SelectedItem="{Binding MySelectedItem}">
         <i:Interaction.Behaviors>
             <behaviors:ScrollIntoViewBehavior />
         </i:Interaction.Behaviors>
</ListBox>

现在,当selectedItem更改时,行为将为您执行bringintoView()调用。

VahidN 10 年前

这是已接受答案的随附属性表:

using System.Windows;
using System.Windows.Controls;

namespace CommonBehaviors
{
    public static class ScrollCurrentItemIntoViewBehavior
    {
        public static readonly DependencyProperty AutoScrollToCurrentItemProperty =
            DependencyProperty.RegisterAttached("AutoScrollToCurrentItem",
                typeof(bool), typeof(ScrollCurrentItemIntoViewBehavior),
                new UIPropertyMetadata(default(bool), OnAutoScrollToCurrentItemChanged));

        public static bool GetAutoScrollToCurrentItem(DependencyObject obj)
        {
            return (bool)obj.GetValue(AutoScrollToCurrentItemProperty);
        }

        public static void OnAutoScrollToCurrentItemChanged(DependencyObject obj, DependencyPropertyChangedEventArgs e)
        {
            var listBox = obj as ListBox;
            if (listBox == null) return;

            var newValue = (bool)e.NewValue;
            if (newValue)
                listBox.SelectionChanged += listBoxSelectionChanged;
            else
                listBox.SelectionChanged -= listBoxSelectionChanged;
        }

        static void listBoxSelectionChanged(object sender, SelectionChangedEventArgs e)
        {
            var listBox = sender as ListBox;
            if (listBox == null || listBox.SelectedItem == null || listBox.Items == null) return;

            listBox.Items.MoveCurrentTo(listBox.SelectedItem);
            listBox.ScrollIntoView(listBox.SelectedItem);
        }

        public static void SetAutoScrollToCurrentItem(DependencyObject obj, bool value)
        {
            obj.SetValue(AutoScrollToCurrentItemProperty, value);
        }
    }
}

用途:

<ListBox ItemsSource="{Binding}"
          IsSynchronizedWithCurrentItem="True"
          behaviors:ScrollCurrentItemIntoViewBehavior.AutoScrollToCurrentItem="True">

D.Kempkes 11 年前

如果上面的代码对您不起作用,请尝试一下

public class ListBoxExtenders : DependencyObject
{
    public static readonly DependencyProperty AutoScrollToCurrentItemProperty = DependencyProperty.RegisterAttached("AutoScrollToCurrentItem", typeof(bool), typeof(ListBoxExtenders), new UIPropertyMetadata(default(bool), OnAutoScrollToCurrentItemChanged));

    public static bool GetAutoScrollToCurrentItem(DependencyObject obj)
    {
        return (bool)obj.GetValue(AutoScrollToSelectedItemProperty);
    }

    public static void SetAutoScrollToCurrentItem(DependencyObject obj, bool value)
    {
        obj.SetValue(AutoScrollToSelectedItemProperty, value);
    }

    public static void OnAutoScrollToCurrentItemChanged(DependencyObject s, DependencyPropertyChangedEventArgs e)
    {
        var listBox = s as ListBox;
        if (listBox != null)
        {
            var listBoxItems = listBox.Items;
            if (listBoxItems != null)
            {
                var newValue = (bool)e.NewValue;

                var autoScrollToCurrentItemWorker = new EventHandler((s1, e2) => OnAutoScrollToCurrentItem(listBox, listBox.Items.CurrentPosition));

                if (newValue)
                    listBoxItems.CurrentChanged += autoScrollToCurrentItemWorker;
                else
                    listBoxItems.CurrentChanged -= autoScrollToCurrentItemWorker;
            }
        }
    }

    public static void OnAutoScrollToCurrentItem(ListBox listBox, int index)
    {
        if (listBox != null && listBox.Items != null && listBox.Items.Count > index && index >= 0)
            listBox.ScrollIntoView(listBox.Items[index]);
    }

}

XAML中的用法

<ListBox IsSynchronizedWithCurrentItem="True" extenders:ListBoxExtenders.AutoScrollToCurrentItem="True" ..../>