c# - 如何阻止滚动更改事件触发数据绑定(bind)(WPF)

Question

                </ItemsControl.ItemTemplate>
                <ItemsControl.GroupStyle>
                    <GroupStyle>
                        <GroupStyle.ContainerStyle>
                            <Style TargetType="GroupItem">
                                <Setter Property="Template">
                                    <Setter.Value>
                                        <ControlTemplate TargetType="GroupItem">
                                            <Grid>
                                                <Grid.RowDefinitions>
                                                    <RowDefinition/>
                                                    <RowDefinition/>
                                                </Grid.RowDefinitions>
                                                <TextBlock Grid.Row="0" HorizontalAlignment="Center"  FontWeight="Bold"  Foreground="{StaticResource Accent}" Text="{Binding Path=Name , StringFormat={}{0:D}}"  />
                                                <ItemsPresenter Grid.Row="1"/>
                                            </Grid>
                                        </ControlTemplate>
                                    </Setter.Value>
                                </Setter>
                            </Style>
                        </GroupStyle.ContainerStyle>
                    </GroupStyle>
                </ItemsControl.GroupStyle>
            </ItemsControl>
            <Interactivity:Interaction.Triggers>
                <Interactivity:EventTrigger EventName="ScrollChanged" >
                    <Presentation:InvokeDelegateCommandAction  Command="{Binding ChatScrollViewer_OnViewChange}" CommandParameter="{Binding RelativeSource={RelativeSource Self}, Path=InvokeParameter}" />
                </Interactivity:EventTrigger>
            </Interactivity:Interaction.Triggers>
        </ScrollViewer>



private void ChatScrollViewer_OnViewChangeEvent(ScrollChangedEventArgs Event)
    {
        ScrollViewer scrollViewer = Event.OriginalSource as ScrollViewer;
        if (scrollViewer.VerticalOffset == 0)
        {

        }
    }

When data binding take place scroll changed event is triggered . How check that this is a trigger from data binding and do nothing and when triggered manually do something

Answer 1

绑定(bind)更新时，是滚动查看器的ItemsSource吗？

绑定(bind)可能会添加或删除某些内容，从而导致滚动查看器更改其内容的大小。看看the scroll changed event args , 触发此事件的条件很多。

您可能只想检查事件属性，例如:

VerticalChange - 获取一个值，该值指示 ScrollViewer 的垂直偏移量的变化。

因此，尝试仅在 VerticalChange != 0 时执行您的操作。或者在其中放置一个调试器，看看是否有任何您想要忽略的特定事件类型，这些事件类型仅在绑定(bind)更改时发生，例如:

ExtentHeightChange - 获取指示 ScrollViewerextent 高度变化的值。

当绑定(bind)更新时可能只有非零值，使滚动条变大(但不改变滚动位置)。

所以像这样:

private void ChatScrollViewer_OnViewChangeEvent(ScrollChangedEventArgs Event)
{
    if (Event.VerticalChange != 0)
    {
        ScrollViewer scrollViewer = Event.OriginalSource as ScrollViewer;
        if (scrollViewer.VerticalOffset == 0)
        {

        }
    }
}

希望对您有所帮助。