问题
Is it possible to let a WPF-TextBox autoscroll but stop that behavior when the ScrollBar is moved. When the user scrolls to end the TextBox should scroll again automatically to end on text change.
textBox1.ScrollToEnd();
This would work as long as the user does not move the ScrollBar.
回答1:
I have recreated what I think you have in your setup:
<StackPanel>
<ScrollViewer Height="50" x:Name="_scroll">
<TextBox x:Name="_text" Width="50" Text="Lorem ipsum dolor sit amet, consectetur adipisicing elit, sed do eiusmod tempor incididunt ut labore et dolore magna aliqua." TextWrapping="Wrap"/>
</ScrollViewer>
<Button Click="Button_Click" Content="Add Text"/>
</StackPanel>
I assume that you have some event that edits this textbox in my setup it is a button. And its click handler:
private void Button_Click(object sender, RoutedEventArgs e)
{
var shouldScroll = _scroll.VerticalOffset == _scroll.ScrollableHeight;
_text.Text += "AAA ";
if (shouldScroll)
{
_scroll.ScrollToEnd();
}
}
This will auto scroll to end after text edit only if scrollbar is on the bottom.
Edit
For cleaner solution you can use behavior:
public class AutoScrollingBehavior : Behavior<ScrollViewer>
{
public object UpdateTrigger
{
get { return (object)GetValue(UpdateTriggerProperty); }
set { SetValue(UpdateTriggerProperty, value); }
}
public static readonly DependencyProperty UpdateTriggerProperty =
DependencyProperty.Register("UpdateTrigger", typeof(object), typeof(AutoScrollingBehavior), new UIPropertyMetadata(Update));
private bool IsScrolledDown
{
get { return (bool)GetValue(IsScrolledDownProperty); }
set { SetValue(IsScrolledDownProperty, value); }
}
public static readonly DependencyProperty IsScrolledDownProperty =
DependencyProperty.Register("IsScrolledDown", typeof(bool), typeof(AutoScrollingBehavior), new UIPropertyMetadata(false));
private static void Update(DependencyObject d, DependencyPropertyChangedEventArgs e)
{
if ((bool)d.GetValue(IsScrolledDownProperty))
{
var scroll = ((AutoScrollingBehavior)d).AssociatedObject;
scroll.ScrollToEnd();
}
}
protected override void OnAttached()
{
AssociatedObject.Loaded += new RoutedEventHandler(AssociatedObject_Loaded);
AssociatedObject.ScrollChanged += new ScrollChangedEventHandler(AssociatedObject_ScrollChanged);
}
private void AssociatedObject_ScrollChanged(object sender, ScrollChangedEventArgs e)
{
IsScrolledDown = AssociatedObject.VerticalOffset == AssociatedObject.ScrollableHeight;
}
private void AssociatedObject_Loaded(object sender, RoutedEventArgs e)
{
IsScrolledDown = AssociatedObject.VerticalOffset == AssociatedObject.ScrollableHeight;
}
}
and xaml:
<StackPanel>
<ScrollViewer Height="50" >
<e:Interaction.Behaviors>
<local:AutoScrollingBehavior UpdateTrigger="{Binding ElementName=_text,Path=Text}" />
</e:Interaction.Behaviors>
<TextBox x:Name="_text" Width="50" Text="Lorem ipsum dolor sit amet, consectetur adipisicing elit, sed do eiusmod tempor incididunt ut labore et dolore magna aliqua." TextWrapping="Wrap"/>
</ScrollViewer>
<Button Click="Button_Click" Content="Add Text"/>
</StackPanel>
回答2:
I found a somehow hacky way to do this:
public class AutoScrollTextBox : TextBox
{
ScrollViewer sv;
public override void OnApplyTemplate()
{
base.OnApplyTemplate();
if (Template != null)
{
sv = (ScrollViewer)Template.FindName("PART_ContentHost", this);
}
}
protected override void OnTextChanged(TextChangedEventArgs e)
{
base.OnTextChanged(e);
if (sv != null && sv.ScrollableHeight == sv.VerticalOffset)
{
this.ScrollToEnd();
}
}
}
But this would stop working if the name of the ScrollViewer in the TextBox-Template changes.
来源:https://stackoverflow.com/questions/11897937/autoscroll-textbox-if-user-has-not-moved-the-scrollbar