Question

我正在研究在Canvas周围拖动对象，这些对象封装在ListBoxItems中 - 效果是创建一个简单的伪桌面。

我有一个带有Canvas的ListBox作为ItemsPanelTempalte，因此ListBoxItems可以出现在屏幕上的任何位置：

<ListBox ItemsSource="{Binding Windows}">
    <ListBox.ItemsPanel>
        <ItemsPanelTemplate>
            <Canvas />
        </ItemsPanelTemplate>
    </ListBox.ItemsPanel>
</ListBox>

我有一个Style来定义ListBoxItems应该如何显示：

<Style TargetType="{x:Type ListBoxItem}">
    <Setter Property="IsSelected" Value="{Binding IsSelected, Mode=TwoWay}" />
    <Setter Property="Canvas.Left" Value="{Binding Left, Mode=TwoWay}" />
    <Setter Property="Canvas.Top" Value="{Binding Top, Mode=TwoWay}" />
    <Setter Property="OverridesDefaultStyle" Value="True" />
    <Setter Property="Template">
        <Setter.Value>
            <ControlTemplate TargetType="{x:Type ListBoxItem}">
                <local:PseudoWindowContainer Content="{TemplateBinding Content}" />
            </ControlTemplate>
        </Setter.Value>
    </Setter>
</Style>

“PseudoWindowContainer”从ContentControl扩展并应用了自己的Style，使其看起来像一个对话框（标题栏，关闭按钮等......）。这是它的一大块：

  <Style TargetType="{x:Type local:PseudoWindowContainer}">
<Setter Property="IsSelected" Value="{Binding IsSelected, Mode=TwoWay}" />
<Setter Property="Width" Value="{Binding Width, Mode=TwoWay}" />
<Setter Property="Height" Value="{Binding Height, Mode=TwoWay}" />
<Setter Property="OverridesDefaultStyle" Value="True" />
<Setter Property="Template">
  <Setter.Value>
    <ControlTemplate TargetType="{x:Type local:PseudoWindowContainer}">
      <Grid Name="LayoutRoot" Background="White">
        <!-- ... snip ... -->
            <Border Name="PART_TitleBar" Grid.Row="0" Background="LightGray" CornerRadius="2,2,0,0" VerticalAlignment="Stretch" Cursor="Hand" />
            <TextBlock Name="TitleBar_Caption" Text="{Binding DisplayName}" Grid.Row="0" Background="Transparent" Padding="5,0,0,0" HorizontalAlignment="Left" VerticalAlignment="Center" />
            <Button Name="TitleBar_CloseButton" Command="{Binding CloseCommand}" Grid.Row="0" VerticalAlignment="Top" HorizontalAlignment="Right" Margin="0,5,5,0" Width="20" Height="20" Cursor="Hand" Background="#FFFF0000" Foreground="#FF212121" />
            <!-- ContentPresenter -->
            <ContentPresenter Grid.Row="1" />
        <!-- ... snip ... -->
      </Grid>
      <ControlTemplate.Triggers>
        <Trigger Property="IsSelected" Value="True">
          <Setter TargetName="WindowBorder" Property="Background" Value="Blue" />
        </Trigger>
        <Trigger Property="IsSelected" Value="False">
          <Setter TargetName="WindowBorder" Property="Background" Value="#22000000" />
        </Trigger>
      </ControlTemplate.Triggers>
    </ControlTemplate>
  </Setter.Value>
</Setter>

在PseudoWindowContainer.cs类中，我创建了一些事件处理程序来监听MouseDown / MouseUp / MoveMove事件：

public override void OnApplyTemplate()
{
  _titleBar = (Border)Template.FindName("PART_TitleBar", this);
  if (_titleBar != null)
  {
    _titleBar.MouseDown += TitleBar_MouseDown;
    _titleBar.MouseUp += TitleBar_MouseUp;
  }

  _grip = (ResizeGrip)Template.FindName("PART_ResizeGrip", this);
  if (_grip != null)
  {
    _grip.MouseLeftButtonDown += ResizeGrip_MouseLeftButtonDown;
    _grip.MouseLeftButtonUp += ResizeGrip_MouseLeftButtonUp;
  }

  base.OnApplyTemplate();
}

private void TitleBar_MouseDown(object sender, MouseButtonEventArgs e)
{
  _titleBar.MouseMove += TitleBar_MouseMove;
  ((Border)sender).CaptureMouse();

  _windowLocation.X = Left;
  _windowLocation.Y = Top;

  _clickLocation = this.PointToScreen(Mouse.GetPosition(this));
}

private void TitleBar_MouseUp(object sender, MouseButtonEventArgs e)
{
  _titleBar.MouseMove -= TitleBar_MouseMove;
  ((Border)sender).ReleaseMouseCapture();
}

private void TitleBar_MouseMove(object sender, MouseEventArgs e)
{
  Point currentLocation = this.PointToScreen(Mouse.GetPosition(this));

  Left = _windowLocation.X + currentLocation.X - _clickLocation.X;
  Top = _windowLocation.Y + currentLocation.Y - _clickLocation.Y;
}

我遇到的麻烦是“Left”和“Top”都没有定义属性，并且将它们更新为Canvas.SetLeft / SetTop（或相应的GetLeft / GetTop）不会更新Canvas上的位置。

我在中将放入 ListBoxItems的控件的ViewModel中定义了“Left”和“Top”，因此随后由于模板而被PseudoWindowContainer包装。这些值得到兑现，当应用程序最初出现时，对象确实出现在正确的位置。

我相信我需要以某种方式在我的PseudoWindowContainer（又名：ContentControl）中定义“Left”和“Top”，并让它们传播回我的ViewModel。这可能吗？

再次感谢您的帮助！

Answer 1

我找到了问题的解决方案。而不是再次输入，我将指向描述我所做的MSDN论坛帖子： http://social.msdn.microsoft.com/Forums/en-US/wpf/thread/d9036b30-bc6e-490e-8f1e-763028a50153

Answer 2

你读过Bea Stollnitz的文章：The power of Styles and Templates in WPF吗？这是Listbox的一个示例，其中项目是在Converter中计算的特定坐标处绘制的。

在Canvas周围移动ListBoxItems？

2 个答案: