我正在制作一个使用列表框的触摸屏界面 我在列表框的上方和下方有一个按钮，用于向上/向下翻页。
我正试图将它向上滚动，一直向上滚动页面按钮被禁用 当向下滚动时，向下翻页按钮也会被禁用。
以下是我的Styles.xaml中列表框的代码
<Style x:Key="{x:Type ListBox}" TargetType="{x:Type ListBox}">
<Setter Property="Template">
<Setter.Value>
<ControlTemplate x:Key="{x:Type ListBox}" TargetType="{x:Type ListBox}">
<DockPanel>
<RepeatButton x:Name="LineUpButton" DockPanel.Dock="Top"
HorizontalAlignment="Stretch"
Height="50"
Content="/\"
Command="{x:Static ScrollBar.PageUpCommand}"
CommandTarget="{Binding ElementName=scrollviewer}" />
<RepeatButton x:Name="LineDownButton" DockPanel.Dock="Bottom"
HorizontalAlignment="Stretch"
Height="50"
Content="\/"
Command="{x:Static ScrollBar.PageDownCommand}"
CommandTarget="{Binding ElementName=scrollviewer}" />
<Border BorderThickness="1" BorderBrush="Gray" Background="White">
<ScrollViewer x:Name="scrollviewer">
<ItemsPresenter/>
</ScrollViewer>
</Border>
</DockPanel>
</ControlTemplate>
</Setter.Value>
</Setter>
<Setter Property="ScrollViewer.HorizontalScrollBarVisibility" Value="Hidden"/>
<Setter Property="ScrollViewer.VerticalScrollBarVisibility" Value="Hidden"/>
<Setter Property="FocusVisualStyle" Value="{x:Null}" />
</Style>
这是我实例化列表框的地方
<ListBox SelectedItem="{Binding SelectedCan}" ItemsSource="{Binding Path=SelectedKioskCashCans}">
<ListBox.ItemTemplate>
<DataTemplate>
<ContentPresenter Content="{Binding image}" MaxWidth="75" />
</DataTemplate>
</ListBox.ItemTemplate>
<ListBox.ItemsPanel>
<ItemsPanelTemplate>
<VirtualizingStackPanel Orientation="Vertical"/>
</ItemsPanelTemplate>
</ListBox.ItemsPanel>
</ListBox>
我昨天四处搜寻，没有运气 我希望能够在xaml中完成所有工作。
我正在使用按钮的图像，但为了上述可读性而将它们拿出来，
他们真的很像......
<RepeatButton x:Name="LineUpButton" DockPanel.Dock="Top" HorizontalAlignment="Stretch"
Height="50"
Command="{x:Static ScrollBar.PageUpCommand}"
CommandTarget="{Binding ElementName=scrollviewer}">
<RepeatButton.Template>
<ControlTemplate TargetType="{x:Type RepeatButton}">
<Grid>
<Image Name="Normal" Source="/Images/up.png"/>
<Image Name="Pressed" Source="/Images/up.png" Visibility="Hidden"/>
</Grid>
<ControlTemplate.Triggers>
<Trigger Property="IsPressed" Value="True">
<Setter TargetName="Normal" Property="Visibility" Value="Hidden"/>
<Setter TargetName="Pressed" Property="Visibility" Value="Visible"/>
</Trigger>
</ControlTemplate.Triggers>
</ControlTemplate>
</RepeatButton.Template>
</RepeatButton>
答案 0 :(得分：2)
只需使用CanExecute的{{1}}方法即可。如果没有页面，则返回PageUpCommand，该按钮将自动禁用。
修改
我创建了一个简单的attached behavior，可以用来解决这个问题。只需在false上设置以下附加属性：
ScrollViewer以下是行为的源代码：
<ScrollViewer x:Name="scrollviewer"
z:ScrollBarCommandsCanExecuteFixBehavior.IsEnabled="True">
<ItemsPresenter/>
</ScrollViewer>
基本思想是我们为每个命令的public static class ScrollBarCommandsCanExecuteFixBehavior
{
#region Nested Types
public class CommandCanExecuteMonitor<T> where T : UIElement
{
protected T Target { get; private set; }
protected CommandCanExecuteMonitor(T target, RoutedCommand command)
{
Target = target;
var binding = new CommandBinding(command);
binding.CanExecute += OnCanExecute;
target.CommandBindings.Add(binding);
}
protected virtual void OnCanExecute(object sender, CanExecuteRoutedEventArgs e)
{
}
}
public class PageUpCanExecuteMonitor : CommandCanExecuteMonitor<ScrollViewer>
{
public PageUpCanExecuteMonitor(ScrollViewer scrollViewer)
: base(scrollViewer, ScrollBar.PageUpCommand)
{
}
protected override void OnCanExecute(object sender, CanExecuteRoutedEventArgs e)
{
if (e.Handled)
{
return;
}
if (Equals(Target.VerticalOffset, 0.0))
{
e.CanExecute = false;
e.Handled = true;
}
}
}
public class PageDownCanExecuteMonitor : CommandCanExecuteMonitor<ScrollViewer>
{
public PageDownCanExecuteMonitor(ScrollViewer scrollViewer)
: base(scrollViewer, ScrollBar.PageDownCommand)
{
}
protected override void OnCanExecute(object sender, CanExecuteRoutedEventArgs e)
{
if (e.Handled)
{
return;
}
if (Equals(Target.VerticalOffset, Target.ScrollableHeight))
{
e.CanExecute = false;
e.Handled = true;
}
}
}
#endregion
#region IsEnabled Attached Property
public static bool GetIsEnabled(DependencyObject obj)
{
return (bool) obj.GetValue(IsEnabledProperty);
}
public static void SetIsEnabled(DependencyObject obj, bool value)
{
obj.SetValue(IsEnabledProperty, value);
}
public static readonly DependencyProperty IsEnabledProperty =
DependencyProperty.RegisterAttached("IsEnabled", typeof (bool), typeof (ScrollBarCommandsCanExecuteFixBehavior), new PropertyMetadata(false, OnIsEnabledChanged));
private static void OnIsEnabledChanged(DependencyObject d, DependencyPropertyChangedEventArgs e)
{
if ((bool) e.NewValue)
{
var scrollViewer = d as ScrollViewer;
if (scrollViewer != null)
{
OnAttached(scrollViewer);
}
else
{
throw new NotSupportedException("This behavior only supports ScrollViewer instances.");
}
}
}
private static void OnAttached(ScrollViewer target)
{
SetPageUpCanExecuteMonitor(target, new PageUpCanExecuteMonitor(target));
SetPageDownCanExecuteMonitor(target, new PageDownCanExecuteMonitor(target));
}
#endregion
#region PageUpCanExecuteMonitor Attached Property
private static void SetPageUpCanExecuteMonitor(DependencyObject obj, PageUpCanExecuteMonitor value)
{
obj.SetValue(PageUpCanExecuteMonitorProperty, value);
}
private static readonly DependencyProperty PageUpCanExecuteMonitorProperty =
DependencyProperty.RegisterAttached("PageUpCanExecuteMonitor", typeof (PageUpCanExecuteMonitor), typeof (ScrollBarCommandsCanExecuteFixBehavior), new PropertyMetadata(null));
#endregion
#region PageDownCanExecuteMonitor Attached Property
private static void SetPageDownCanExecuteMonitor(DependencyObject obj, PageDownCanExecuteMonitor value)
{
obj.SetValue(PageDownCanExecuteMonitorProperty, value);
}
private static readonly DependencyProperty PageDownCanExecuteMonitorProperty =
DependencyProperty.RegisterAttached("PageDownCanExecuteMonitor", typeof (PageDownCanExecuteMonitor), typeof (ScrollBarCommandsCanExecuteFixBehavior), new PropertyMetadata(null));
#endregion
}
添加CommandBinding，并在这些绑定上订阅CanExecute事件。在事件处理程序中，我们检查滚动的当前位置并相应地设置ScrollViewer属性。