捕获文本框的WPF滚动条上的鼠标点击
本文关键字:鼠标 滚动条 WPF 文本 | 更新日期: 2023-09-27 18:18:40
我有一个WPF ScrollingTextBox
定义如下。这个文本框是只读的,当ViewModel中的事件被触发时,它的内容会被更新。
<Grid>
<StackPanel>
<local:ScrollingTextBox x:Name="textBox1"
Width="480"
Height="100"
Margin="12,12,0,0"
HorizontalAlignment="Left"
VerticalAlignment="Top"
IsReadOnly="True"
Background="Black"
Foreground="White"
Text="{Binding Path=UpdatedText, UpdateSourceTrigger=PropertyChanged, Mode=OneWay}"/>
</StackPanel>
</Grid>
我必须定义以下类,以便在向文本框中添加新文本时启用自动向下滚动。此外,我需要重写OnPreviewMouseLeftButtonDown
和OnPreviewMouseLeftButtonUp
方法,以便在用户单击滚动条时禁用自动向下滚动:这些方法和FindVisualParent
方法中包含的说明来自本页。
public class ScrollingTextBox : TextBox
{
private volatile bool _AutomaticScrollingEnabled = true;
protected override void OnInitialized(EventArgs e)
{
base.OnInitialized(e);
VerticalScrollBarVisibility = ScrollBarVisibility.Visible;
HorizontalScrollBarVisibility = ScrollBarVisibility.Visible;
}
protected override void OnTextChanged(TextChangedEventArgs e)
{
base.OnTextChanged(e);
if (_AutomaticScrollingEnabled)
{
Focus();
CaretIndex = Text.Length;
ScrollToEnd();
}
}
protected override void OnPreviewMouseLeftButtonDown(MouseButtonEventArgs e)
{
base.OnPreviewMouseLeftButtonDown(e);
object original = e.OriginalSource;
if (!original.GetType().Equals(typeof(ScrollViewer)))
{
if (FindVisualParent<ScrollBar>(original as DependencyObject) != null)
{
_AutomaticScrollingEnabled = false;
Trace.WriteLine("scroll bar is clicked down");
}
}
}
protected override void OnPreviewMouseLeftButtonUp(MouseButtonEventArgs e)
{
base.OnPreviewMouseLeftButtonUp(e);
object original = e.OriginalSource;
if (!original.GetType().Equals(typeof(ScrollViewer)))
{
if (FindVisualParent<ScrollBar>(original as DependencyObject) != null)
{
_AutomaticScrollingEnabled = true;
Trace.WriteLine("scroll bar is clicked up");
}
}
}
private parentItem FindVisualParent<parentItem>(DependencyObject obj) where parentItem : DependencyObject
{
DependencyObject parent = VisualTreeHelper.GetParent(obj);
while (parent != null && !parent.GetType().Equals(typeof(parentItem)))
{
parent = VisualTreeHelper.GetParent(parent);
}
return parent as parentItem;
}
}
- 为什么我需要验证事件原始源是否不等于
typeof(ScrollViewer)
? -
FindVisualParent
方法是如何工作的?
为什么我需要验证事件原始源是否不等于typeof(ScrollViewer)?
我认为关键是要确定用户在ScrollViewer
中单击的确切位置。因此,如果ScrollViewer本身正在发送事件,那是没有用的,您希望等到事件传递到您感兴趣的特定子节点之一。(请注意,PreviewMouseLeftButtonUp
和PreviewMouseLeftButtonDown
是隧道事件,这意味着事件从根向下通过可视化树,直到它们被处理。)
FindVisualParent方法是如何工作的?
它只是沿着可视化树往上爬,直到找到指定类型的元素("parentItem"),或者到达顶部。
private parentItem FindVisualParent<parentItem>(DependencyObject obj)
where parentItem : DependencyObject
{
// start by getting the parent of the input element
DependencyObject parent = VisualTreeHelper.GetParent(obj);
// repeat until there is no parent, or the current element matches the target type
while (parent != null && !parent.GetType().Equals(typeof(parentItem)))
{
// get the next element up
parent = VisualTreeHelper.GetParent(parent);
}
// return the found element of type "parentItem", or null if not found
return parent as parentItem;
}