从作为子项的datatemplete访问scrollviewer作为父级 [英] Access scrollviewer as a parent from datatemplete as child

问题描述

如果MessageListItemControl ex中有新项目，我需要附加属性触发器自动滚动到底部：

I need an attached property trigger auto scroll to bottom if there is a new item in MessageListItemControl ex:

<Grid VerticalAlignment="Bottom" d:DataContext="{x:Static core:MessageListDesignModel.Instance}">
	<ScrollViewer
		local:ScrollToBottomOnLoadProperty.Value="True"
		<ItemsControl ItemsSource="{Binding Items}">
			<ItemsControl.ItemTemplate>
				<DataTemplate>
					<local:MessageListItemControl
					
		From There controll scrollviewer			
						local:SlideInOnLoadProperty.Value="{Binding NewItem}" />
				</DataTemplate>
			</ItemsControl.ItemTemplate>
		</ItemsControl>
	</ScrollViewer>
</Grid>

推荐答案

您好    Shereif Awad，



>>从datatemplete作为子级访问scrollviewer作为父级



>>如果MessageListItemControl ex中有新项目，我需要一个附加属性触发器自动滚动到底部：
$


当你在MessageListItemControl中添加一个新项，它将触发一个事件，该事件将找到ScrollViewer和Scroll To End。



所以，我建议你尝试以下建议。



1：为ItemsControl ItemsSource定义一个ObservableCollection，并将一个监听器注册到集合的CollectionChanged-event：

Hi    Shereif Awad,

>>Access scrollviewer as a parent from datatemplete as child

>>I need an attached property trigger auto scroll to bottom if there is a new item in MessageListItemControl ex:

When you add a new item in MessageListItemControl, it will trigger an event, the event will find the ScrollViewer and Scroll To End.

So, I suggest you try the following suggestion.

1: Define a ObservableCollection for your ItemsControl ItemsSource and Register a listener to collection's CollectionChanged-event:

Collectionsitems.CollectionChanged += (s, args) => ScrollToBottom();

2：您可以使用VisualTreeHelper查找控件。下面是一个方法，它使用VisualTreeHelper查找指定类型的父控件（ScrollViewer）。

    public static class UIHelper
    {
        public static T FindVisualParent<T>(DependencyObject child)
          where T : DependencyObject
        {
            // get parent item
            DependencyObject parentObject = VisualTreeHelper.GetParent(child);

            // we’ve reached the end of the tree
            if (parentObject == null) return null;

            // check if the parent matches the type we’re looking for
            T parent = parentObject as T;
            if (parent != null)
            {
                return parent;
            }
            else
            {
                // use recursion to proceed with next level
                return FindVisualParent<T>(parentObject);
            }
        }
    }

3：在ScrollToBottom方法中，找到ScrollIntoView并滚动到结尾。

3: In the ScrollToBottom-method, find the ScrollIntoView and scroll to the end.

        private void ScrollToBottom()
        {
            ScrollViewer scrollviewer = UIHelper.FindVisualParent<ScrollViewer>(tetecontrol);
            if (scrollviewer!=null)
            {
                scrollviewer.ScrollToEnd();
            }
        }

$

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