ContextMenu 或 ContextMenuStrip [winforms] 上的单选按钮

Question

我正在寻找实现具有如下单选按钮外观的上下文菜单项的方法：Windows 7's ContextMenu with RadioButton menu item

我通过 Google 和 SO 进行了搜索，这篇文章 Adding RadioButtons to ContextMenu 很接近，但它与 Java 相关，我正在寻找 .NET 中用于 winforms 的控件或渲染器。

任何解决方案或建议都会有很大帮助。谢谢。

Answer 1

选项按钮，也称为单选按钮，类似于复选框，只是用户一次只能选择一个。尽管默认情况下 ToolStripMenuItem 类不提供选项按钮行为，但该类确实提供了复选框行为，您可以自定义该行为以实现 MenuStrip 中菜单项的选项按钮行为强>控制。

当菜单项的 CheckOnClick 属性为 true 时，用户可以单击该菜单项来切换复选标记的显示。 Checked 属性表示项目的当前状态。要实现基本的选项按钮行为，您必须确保在选择项目时，将先前选择的项目的 Checked 属性设置为 false。

以下过程描述了如何在继承 ToolStripMenuItem 类的类中实现此功能和其他功能。 ToolStripRadioButtonMenuItem 类覆盖了诸如 OnCheckedChanged 和 OnPaint 等成员，以提供选项按钮的选择行为和外观。此外，此类会覆盖 Enabled 属性，因此除非选择父项，否则会禁用 子菜单 上的选项。

首先为RadioButton 创建一个类

---

这是RadioButton 和ToggleButton 的组合。

Public Class ToolStripRadioButtonMenuItem
Inherits ToolStripMenuItem

Public Sub New()
    MyBase.New()
    Initialize()
End Sub

Public Sub New(ByVal text As String)
    MyBase.New(text, Nothing, CType(Nothing, EventHandler))
    Initialize()
End Sub

Public Sub New(ByVal image As Image)
    MyBase.New(Nothing, image, CType(Nothing, EventHandler))
    Initialize()
End Sub

Public Sub New(ByVal text As String, ByVal image As Image)
    MyBase.New(text, image, CType(Nothing, EventHandler))
    Initialize()
End Sub

Public Sub New(ByVal text As String, _
    ByVal image As Image, ByVal onClick As EventHandler)
    MyBase.New(text, image, onClick)
    Initialize()
End Sub

Public Sub New(ByVal text As String, ByVal image As Image, _
    ByVal onClick As EventHandler, ByVal name As String)
    MyBase.New(text, image, onClick, name)
    Initialize()
End Sub

Public Sub New(ByVal text As String, ByVal image As Image, _
    ByVal ParamArray dropDownItems() As ToolStripItem)
    MyBase.New(text, image, dropDownItems)
    Initialize()
End Sub

Public Sub New(ByVal text As String, ByVal image As Image, _
    ByVal onClick As EventHandler, ByVal shortcutKeys As Keys)
    MyBase.New(text, image, onClick)
    Initialize()
    Me.ShortcutKeys = shortcutKeys
End Sub

' Called by all constructors to initialize CheckOnClick.
Private Sub Initialize()
    CheckOnClick = True
End Sub

Protected Overrides Sub OnCheckedChanged(ByVal e As EventArgs)

    MyBase.OnCheckedChanged(e)

    ' If this item is no longer in the checked state, do nothing.
    If Not Checked Then Return

    ' Clear the checked state for all siblings. 
    For Each item As ToolStripItem In Parent.Items

        Dim radioItem As ToolStripRadioButtonMenuItem = _
            TryCast(item, ToolStripRadioButtonMenuItem)
        If radioItem IsNot Nothing AndAlso _
            radioItem IsNot Me AndAlso _
            radioItem.Checked Then

            radioItem.Checked = False

            ' Only one item can be selected at a time, 
            ' so there is no need to continue.
            Return

        End If
    Next

End Sub

Protected Overrides Sub OnClick(ByVal e As EventArgs)

    ' If the item is already in the checked state, do not call 
    ' the base method, which would toggle the value. 
    If Checked Then Return

    MyBase.OnClick(e)
End Sub

' Let the item paint itself, and then paint the RadioButton
' where the check mark is displayed, covering the check mark
' if it is present.
Protected Overrides Sub OnPaint(ByVal e As PaintEventArgs)

    MyBase.OnPaint(e)

    ' If the client sets the Image property, the selection behavior
    ' remains unchanged, but the RadioButton is not displayed and the
    ' selection is indicated only by the selection rectangle. 
    If Image IsNot Nothing Then Return

    ' Determine the correct state of the RadioButton.
    Dim buttonState As RadioButtonState = RadioButtonState.UncheckedNormal
    If Enabled Then
        If mouseDownState Then
            If Checked Then
                buttonState = RadioButtonState.CheckedPressed
            Else
                buttonState = RadioButtonState.UncheckedPressed
            End If
        ElseIf mouseHoverState Then
            If Checked Then
                buttonState = RadioButtonState.CheckedHot
            Else
                buttonState = RadioButtonState.UncheckedHot
            End If
        Else
            If Checked Then buttonState = RadioButtonState.CheckedNormal
        End If
    Else
        If Checked Then
            buttonState = RadioButtonState.CheckedDisabled
        Else
            buttonState = RadioButtonState.UncheckedDisabled
        End If
    End If

    ' Calculate the position at which to display the RadioButton.
    Dim offset As Int32 = CInt((ContentRectangle.Height - _
        RadioButtonRenderer.GetGlyphSize( _
        e.Graphics, buttonState).Height) / 2)
    Dim imageLocation As Point = New Point( _
        ContentRectangle.Location.X + 4, _
        ContentRectangle.Location.Y + offset)

    ' If the item is selected and the RadioButton paints with partial
    ' transparency, such as when theming is enabled, the check mark
    ' shows through the RadioButton image. In this case, paint a 
    ' non-transparent background first to cover the check mark.
    If Checked AndAlso RadioButtonRenderer _
        .IsBackgroundPartiallyTransparent(buttonState) Then

        Dim glyphSize As Size = RadioButtonRenderer _
            .GetGlyphSize(e.Graphics, buttonState)
        glyphSize.Height -= 1
        glyphSize.Width -= 1
        Dim backgroundRectangle As _
            New Rectangle(imageLocation, glyphSize)
        e.Graphics.FillEllipse( _
            SystemBrushes.Control, backgroundRectangle)
    End If

    RadioButtonRenderer.DrawRadioButton( _
        e.Graphics, imageLocation, buttonState)

End Sub

Private mouseHoverState As Boolean = False

Protected Overrides Sub OnMouseEnter(ByVal e As EventArgs)
    mouseHoverState = True

    ' Force the item to repaint with the new RadioButton state.
    Invalidate()

    MyBase.OnMouseEnter(e)
End Sub

Protected Overrides Sub OnMouseLeave(ByVal e As EventArgs)
    mouseHoverState = False
    MyBase.OnMouseLeave(e)
End Sub

Private mouseDownState As Boolean = False

Protected Overrides Sub OnMouseDown(ByVal e As MouseEventArgs)
    mouseDownState = True

    ' Force the item to repaint with the new RadioButton state.
    Invalidate()

    MyBase.OnMouseDown(e)
End Sub

Protected Overrides Sub OnMouseUp(ByVal e As MouseEventArgs)
    mouseDownState = False
    MyBase.OnMouseUp(e)
End Sub

' Enable the item only if its parent item is in the checked state 
' and its Enabled property has not been explicitly set to false. 
Public Overrides Property Enabled() As Boolean
    Get
        Dim ownerMenuItem As ToolStripMenuItem = _
            TryCast(OwnerItem, ToolStripMenuItem)

        ' Use the base value in design mode to prevent the designer
        ' from setting the base value to the calculated value.
        If Not DesignMode AndAlso _
            ownerMenuItem IsNot Nothing AndAlso _
            ownerMenuItem.CheckOnClick Then
            Return MyBase.Enabled AndAlso ownerMenuItem.Checked
        Else
            Return MyBase.Enabled
        End If
    End Get

    Set(ByVal value As Boolean)
        MyBase.Enabled = value
    End Set
End Property

' When OwnerItem becomes available, if it is a ToolStripMenuItem 
' with a CheckOnClick property value of true, subscribe to its 
' CheckedChanged event. 
Protected Overrides Sub OnOwnerChanged(ByVal e As EventArgs)

    Dim ownerMenuItem As ToolStripMenuItem = _
        TryCast(OwnerItem, ToolStripMenuItem)

    If ownerMenuItem IsNot Nothing AndAlso _
        ownerMenuItem.CheckOnClick Then
        AddHandler ownerMenuItem.CheckedChanged, New  _
            EventHandler(AddressOf OwnerMenuItem_CheckedChanged)
    End If

    MyBase.OnOwnerChanged(e)

End Sub

' When the checked state of the parent item changes, 
' repaint the item so that the new Enabled state is displayed. 
Private Sub OwnerMenuItem_CheckedChanged( _
    ByVal sender As Object, ByVal e As EventArgs)
    Invalidate()
End Sub

End Class

第二次创建Form1的类

---

Public Class Form1

Inherits Form

Private sample As New MenuStrip()
Private mainToolStripMenuItem As New ToolStripMenuItem()
Private toolStripMenuItem1 As New ToolStripMenuItem()
Private toolStripRadioButtonMenuItem1 As New ToolStripRadioButtonMenuItem()
Private toolStripRadioButtonMenuItem2 As New ToolStripRadioButtonMenuItem()
Private toolStripRadioButtonMenuItem3 As New ToolStripRadioButtonMenuItem()
Private toolStripRadioButtonMenuItem4 As New ToolStripRadioButtonMenuItem()
Private toolStripRadioButtonMenuItem5 As New ToolStripRadioButtonMenuItem()
Private toolStripRadioButtonMenuItem6 As New ToolStripRadioButtonMenuItem()

Public Sub New()

    Me.mainToolStripMenuItem.Text = "main"
    toolStripRadioButtonMenuItem1.Text = "option 1"
    toolStripRadioButtonMenuItem2.Text = "option 2"
    toolStripRadioButtonMenuItem3.Text = "option 2-1"
    toolStripRadioButtonMenuItem4.Text = "option 2-2"
    toolStripRadioButtonMenuItem5.Text = "option 3-1"
    toolStripRadioButtonMenuItem6.Text = "option 3-2"
    toolStripMenuItem1.Text = "toggle"
    toolStripMenuItem1.CheckOnClick = True

    mainToolStripMenuItem.DropDownItems.AddRange(New ToolStripItem() { _
        toolStripRadioButtonMenuItem1, toolStripRadioButtonMenuItem2, _
        toolStripMenuItem1})
    toolStripRadioButtonMenuItem2.DropDownItems.AddRange( _
        New ToolStripItem() {toolStripRadioButtonMenuItem3, _
        toolStripRadioButtonMenuItem4})
    toolStripMenuItem1.DropDownItems.AddRange(New ToolStripItem() { _
        toolStripRadioButtonMenuItem5, toolStripRadioButtonMenuItem6})

    sample.Items.AddRange(New ToolStripItem() {mainToolStripMenuItem})
    Controls.Add(sample)
    MainMenuStrip = sample
    Text = "ToolStripRadioButtonMenuItem demo"
End Sub
End Class

最后是为Program 创建一个类

---

Public Class Program

<STAThread()> Public Shared Sub Main()
    Application.EnableVisualStyles()
    Application.SetCompatibleTextRenderingDefault(False)
    Application.Run(New Form1())
End Sub

End Class

截图

---

.

感谢Karl Erickson 和他关于RadioButton 和Menustrip 的博客。

查看他的博客here。