Question

我在组合框中的自定义下拉列表或弹出模板中连接某些事件时遇到问题。

顺便说一句，这个自定义模板看起来就像IE 10中的那个。这是图片 enter image description here 我得到了部分外观（下面的是我的）。但我在删除历史列表中的项目时遇到问题。下面是我的PART_Popup模板

<Popup x:Name="PART_Popup" AllowsTransparency="true" Grid.ColumnSpan="2" IsOpen="{Binding IsDropDownOpen, RelativeSource={RelativeSource TemplatedParent}}" PopupAnimation="{DynamicResource {x:Static SystemParameters.ComboBoxPopupAnimationKey}}" Placement="Bottom">
    <Themes:SystemDropShadowChrome x:Name="Shdw" Color="Transparent" MinWidth="{Binding ActualWidth, ElementName=Placement}">
        <Border x:Name="DropDownBorder" BorderBrush="{DynamicResource {x:Static SystemColors.WindowFrameBrushKey}}" BorderThickness="1" Background="{DynamicResource {x:Static SystemColors.WindowBrushKey}}">
            <!--<ScrollViewer>-->
            <Grid>
                <Grid.RowDefinitions>
                    <RowDefinition Height="*" />
                    <RowDefinition Height="Auto" />
                </Grid.RowDefinitions>

                <StackPanel>
                    <ItemsPresenter KeyboardNavigation.DirectionalNavigation="Contained" SnapsToDevicePixels="{TemplateBinding SnapsToDevicePixels}"/>

                    <Border Padding="5">
                        <StackPanel>
                            <Grid>
                                <Grid.ColumnDefinitions>
                                    <ColumnDefinition Width="Auto" />
                                    <ColumnDefinition Width="*" />
                                </Grid.ColumnDefinitions>
                                <TextBlock Text="History" Foreground="{StaticResource SeparatorLine}" />
                                <Border Height="2" Grid.Column="1" Margin="5,0,0,0" BorderBrush="{StaticResource SeparatorLine}" BorderThickness="0.5" />
                            </Grid>
                            <ListBox x:Name="listHistory"  BorderThickness="0" Margin="0" Padding="0" HorizontalContentAlignment="Stretch">
                                <ListBox.ItemTemplate>
                                    <DataTemplate>
                                        <Grid>
                                            <TextBlock Text="{Binding }" />
                                            <Button Grid.Column="1" HorizontalAlignment="Right" x:Name="btnDeleteHistoryItem" Content="r" FontFamily="Marlett" Style="{DynamicResource ButtonStyle}" Visibility="Hidden" Opacity="0.75" />
                                        </Grid>

                                        <DataTemplate.Triggers>
                                            <Trigger Property="IsMouseOver" Value="True">
                                                <Setter Property="Visibility" TargetName="btnDeleteHistoryItem" Value="Visible" />
                                            </Trigger>
                                        </DataTemplate.Triggers>
                                    </DataTemplate>
                                </ListBox.ItemTemplate>
                            </ListBox>
                    </StackPanel>
                    </Border>
                </StackPanel>

                <Border Grid.Row="1" BorderBrush="{StaticResource SeparatorLine}" BorderThickness="0,1,0,0" Padding="5" Height="30">
                    <Border.Background>
                        <LinearGradientBrush EndPoint="0.5,1" StartPoint="0.5,0">
                            <GradientStop Color="#33000000" Offset="0"/>
                            <GradientStop Offset="1"/>
                            <GradientStop Offset="0.375"/>
                        </LinearGradientBrush>
                    </Border.Background>

                    <StackPanel Orientation="Horizontal" HorizontalAlignment="Right">
                        <Button x:Name="btnClearHistory" Content=" Clear History " Style="{DynamicResource ButtonStyle}" />
                    </StackPanel>
                </Border>
            </Grid>
            <!--</ScrollViewer>-->
        </Border>
    </Themes:SystemDropShadowChrome>
</Popup>

好吧，在列表框（listHistory）中，我有一个名为 btnDeleteHistoryItem 的按钮，我无法挂钩。它在我的代码中返回Null错误

protected override void OnSourceInitialized(EventArgs e)
{
    ListBox lb = (ListBox)cbSearch.Template.FindName("listHistory", cbSearch);
    lb.ItemsSource = this.SearchHistory;
    lb.SelectionChanged += cbResults_SelectionChanged;

    Button btnDeleteHistoryItem = (Button)lb.Template.FindName("btnDeleteHistoryItem", lb);
    // if (btnDeleteHistoryItem != null)
    {
        btnDeleteHistoryItem.Click += DeleteHistoryItem_Click;
    }

    // or --------------

    Button btnDeleteHistoryItem = (Button)cbSearch.Template.FindName("btnDeleteHistoryItem", cbSearch);
    // if (btnDeleteHistoryItem != null)
    {
        btnDeleteHistoryItem.Click += DeleteHistoryItem_Click;
    }
}

编码在这里有点经典，因此在与事件挂钩时没有实现MVVM。所以问题是这个 Button btnDeleteHistoryItem =（Button）lb.Template.FindName（“btnDeleteHistoryItem”，lb）; 或 Button btnDeleteHistoryItem =（Button）cbSearch.Template.FindName（“btnDeleteHistoryItem” ，cbSearch）; 它无法找到btnDeleteHistoryItem的行。

我该如何解决这个问题？

- 更新 -

lb.Loaded += (a, b) =>
{
    Button btnDeleteHistoryItem = (Button)lb.Template.FindName("btnDeleteHistoryItem", lb);
    //if (btnDeleteHistoryItem != null)
    {
        btnDeleteHistoryItem.Click += DeleteHistoryItem_Click;
    }
};

不起作用

Answer 1

使用命令可能是最简单的解决方案。您可以将命令挂钩到删除按钮，并将当前项目作为参数传递。这是一个简单的例子来说明。

public partial class MainWindow : Window {
    public MainWindow() {
        InitializeComponent();
        SomeCommand = new MySampleCommand();

        cbo.Items.Add("Hello");
        cbo.Items.Add("Item 1");
        cbo.Items.Add("Another Item");
        cbo.Items.Add("Something else");
        cbo.Items.Add("Yet another item");
    }

    public MySampleCommand SomeCommand { get; set; }
}

public class MySampleCommand : ICommand {
    public bool CanExecute(object parameter) {
        return true;
    }

    public event EventHandler CanExecuteChanged;

    public void Execute(object parameter) {
        MessageBox.Show(string.Format("You are trying to remove {0}", parameter.ToString()));
    }
}

你的组合框绑定看起来像：

<Window x:Class="SOComboWithEmbeddedButton2.MainWindow"
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
    x:Name="Window"
    Title="MainWindow" Height="350" Width="525">
<Window.Resources>
    <DataTemplate x:Key="ListBoxItemTemplate">
        <StackPanel Orientation="Horizontal">
            <TextBlock Text="{Binding}" />
            <Button Command="{Binding SomeCommand, ElementName=Window}" CommandParameter="{Binding}" Content="Remove" />
        </StackPanel>
    </DataTemplate>
</Window.Resources>
<StackPanel>
    <ComboBox ItemTemplate="{StaticResource ListBoxItemTemplate}" x:Name="cbo" />
</StackPanel>

只需调整DataTemplate上的Command绑定，指向具有命令对象实例的相应对象。希望有所帮助！

Combobox具有自定义下拉（弹出）模板等

1 个答案: