单击按钮时如何打开弹出菜单? [英] How to open a popup menu when a button is clicked?

问题描述

我在工具栏中有一个带有图像作为其内容的按钮.我希望此按钮在单击时在其下方打开一个菜单.怎么样?

I have a button with an Image as its content in a toolbar. I would like this button to open a menu beneath it when clicked. How?

<Toolbar>
            <Button>
                <Button.Content>
                    <Image  Source="../Resources/help.png"></Image>
                </Button.Content>
            </Button>
</Toolbar>

谢谢！！

推荐答案

您可以使用附加属性或行为来实现下拉按钮功能，而不是使用子类的 Button类似 WPF 的方法，因此您不会影响按钮样式:

Instead of using a subclassed Button, you can use Attached Properties or a Behavior to implement the drop down button functionality, for a more WPF-like approach and so you don't impact the button style:

using System.Windows.Interactivity;

public class DropDownButtonBehavior : Behavior<Button>
{
    private bool isContextMenuOpen;

    protected override void OnAttached()
    {
        base.OnAttached();
        AssociatedObject.AddHandler(Button.ClickEvent, new RoutedEventHandler(AssociatedObject_Click), true);
    }

    void AssociatedObject_Click(object sender, System.Windows.RoutedEventArgs e)
    {
        Button source = sender as Button;
        if (source != null && source.ContextMenu != null)
        {
            if (!isContextMenuOpen)
            {
                // Add handler to detect when the ContextMenu closes
                source.ContextMenu.AddHandler(ContextMenu.ClosedEvent, new RoutedEventHandler(ContextMenu_Closed), true);
                // If there is a drop-down assigned to this button, then position and display it 
                source.ContextMenu.PlacementTarget = source;
                source.ContextMenu.Placement = PlacementMode.Bottom;
                source.ContextMenu.IsOpen = true;
                isContextMenuOpen = true;
            }
        }            
    }

    protected override void OnDetaching()
    {
        base.OnDetaching();
        AssociatedObject.RemoveHandler(Button.ClickEvent, new RoutedEventHandler(AssociatedObject_Click));
    }

    void ContextMenu_Closed(object sender, RoutedEventArgs e)
    {
        isContextMenuOpen = false;
        var contextMenu = sender as ContextMenu;
        if (contextMenu != null)
        {
            contextMenu.RemoveHandler(ContextMenu.ClosedEvent, new RoutedEventHandler(ContextMenu_Closed));
        }
    }
}

用法:

<!-- NOTE: xmlns:i="schemas.microsoft.com/expression/2010/interactivity‌​" -->
<Button>
    <i:Interaction.Behaviors>
        <local:DropDownButtonBehavior/>
    </i:Interaction.Behaviors>
    <Button.Content>
        <StackPanel Orientation="Horizontal">
            <Image Source="/DropDownButtonExample;component/Assets/add.png" SnapsToDevicePixels="True" Height="16" Width="16" />
            <TextBlock Text="Add"/>
            <Separator Margin="2,0">
                <Separator.LayoutTransform>
                    <TransformGroup>
                        <TransformGroup.Children>
                            <TransformCollection>
                                <RotateTransform Angle="90"/>
                            </TransformCollection>
                        </TransformGroup.Children>
                    </TransformGroup>
                </Separator.LayoutTransform>
            </Separator>
            <Path Margin="2" VerticalAlignment="Center" Width="6" Fill="#FF527DB5" Stretch="Uniform" HorizontalAlignment="Right" Data="F1 M 301.14,-189.041L 311.57,-189.041L 306.355,-182.942L 301.14,-189.041 Z "/>
        </StackPanel>
    </Button.Content>
    <Button.ContextMenu>
        <ContextMenu>
            <MenuItem Header="Attribute"/>
            <MenuItem Header="Setting"/>
            <Separator/>
            <MenuItem Header="Property"/>
        </ContextMenu>
    </Button.ContextMenu>
</Button>

当前要点源和示例此处.

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