Procedura: Visualizzare i pulsanti di opzione in un MenuStrip (Windows Forms)

Articolo
12/19/2024

I pulsanti di opzione, noti anche come pulsanti di scelta, sono simili alle caselle di controllo, ma gli utenti possono selezionare solo uno alla volta. Anche se per impostazione predefinita la classe ToolStripMenuItem non fornisce il comportamento del pulsante di opzione, la classe fornisce un comportamento della casella di controllo che è possibile personalizzare per implementare il comportamento del pulsante di opzione per le voci di menu in un controllo MenuStrip.

Quando la proprietà CheckOnClick di una voce di menu è true, gli utenti possono fare clic sull'elemento per attivare o disattivare la visualizzazione di un segno di spunta. La proprietà Checked indica lo stato corrente dell'elemento. Per implementare il comportamento di base del pulsante opzione, bisogna assicurarsi che quando si seleziona un elemento, la proprietà Checked dell'elemento precedentemente selezionato venga impostata su false.

Le procedure seguenti descrivono come implementare questa e funzionalità aggiuntive in una classe che eredita la classe ToolStripMenuItem. La classe ToolStripRadioButtonMenuItem esegue l'override di membri quali OnCheckedChanged e OnPaint per fornire il comportamento di selezione e l'aspetto dei pulsanti di opzione. Inoltre, questa classe esegue l'override della proprietà Enabled in modo che le opzioni di un sottomenu siano disabilitate a meno che l'elemento padre non sia selezionato.

Per implementare il comportamento di selezione del pulsante di opzione

Inizializza la proprietà CheckOnClick a true per abilitare la selezione degli elementi.

// Called by all constructors to initialize CheckOnClick.
private void Initialize()
{
    CheckOnClick = true;
}

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

Eseguire l'override del metodo OnCheckedChanged per cancellare la selezione dell'elemento selezionato in precedenza quando viene selezionato un nuovo elemento.

protected override void OnCheckedChanged(EventArgs e)
{
    base.OnCheckedChanged(e);

    // If this item is no longer in the checked state or if its
    // parent has not yet been initialized, do nothing.
    if (!Checked || this.Parent == null) return;

    // Clear the checked state for all siblings.
    foreach (ToolStripItem item in Parent.Items)
    {
        ToolStripRadioButtonMenuItem radioItem =
            item as ToolStripRadioButtonMenuItem;
        if (radioItem != null && radioItem != this && radioItem.Checked)
        {
            radioItem.Checked = false;

            // Only one item can be selected at a time,
            // so there is no need to continue.
            return;
        }
    }
}

Protected Overrides Sub OnCheckedChanged(ByVal e As EventArgs)

    MyBase.OnCheckedChanged(e)

    ' If this item is no longer in the checked state or if its 
    ' parent has not yet been initialized, do nothing.
    If Not Checked OrElse Me.Parent Is Nothing 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

Eseguire l'override del metodo OnClick per assicurarsi che facendo clic su un elemento già selezionato non venga cancellata la selezione.

protected override void OnClick(EventArgs e)
{
    // If the item is already in the checked state, do not call
    // the base method, which would toggle the value.
    if (Checked) return;

    base.OnClick(e);
}

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

Per modificare l'aspetto degli elementi del pulsante di opzione

Eseguire l'override del metodo OnPaint per sostituire il segno di spunta predefinito con un pulsante di opzione usando la classe RadioButtonRenderer.

// Let the item paint itself, and then paint the RadioButton
// where the check mark is normally displayed.
protected override void OnPaint(PaintEventArgs e)
{
    if (Image != null)
    {
        // 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.
        base.OnPaint(e);
        return;
    }
    else
    {
        // If the Image property is not set, call the base OnPaint method
        // with the CheckState property temporarily cleared to prevent
        // the check mark from being painted.
        CheckState currentState = this.CheckState;
        this.CheckState = CheckState.Unchecked;
        base.OnPaint(e);
        this.CheckState = currentState;
    }

    // Determine the correct state of the RadioButton.
    RadioButtonState buttonState = RadioButtonState.UncheckedNormal;
    if (Enabled)
    {
        if (mouseDownState)
        {
            if (Checked) buttonState = RadioButtonState.CheckedPressed;
            else buttonState = RadioButtonState.UncheckedPressed;
        }
        else if (mouseHoverState)
        {
            if (Checked) buttonState = RadioButtonState.CheckedHot;
            else buttonState = RadioButtonState.UncheckedHot;
        }
        else
        {
            if (Checked) buttonState = RadioButtonState.CheckedNormal;
        }
    }
    else
    {
        if (Checked) buttonState = RadioButtonState.CheckedDisabled;
        else buttonState = RadioButtonState.UncheckedDisabled;
    }

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

    // Paint the RadioButton.
    RadioButtonRenderer.DrawRadioButton(
        e.Graphics, imageLocation, buttonState);
}

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

    If Image IsNot Nothing Then
        ' 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. 
        MyBase.OnPaint(e)
        Return
    Else
        ' If the Image property is not set, call the base OnPaint method 
        ' with the CheckState property temporarily cleared to prevent
        ' the check mark from being painted.
        Dim currentState As CheckState = Me.CheckState
        Me.CheckState = CheckState.Unchecked
        MyBase.OnPaint(e)
        Me.CheckState = currentState
    End If

    ' 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)

    ' Paint the RadioButton. 
    RadioButtonRenderer.DrawRadioButton( _
        e.Graphics, imageLocation, buttonState)

End Sub

Eseguire l'override dei metodi OnMouseEnter, OnMouseLeave, OnMouseDowne OnMouseUp per tenere traccia dello stato del mouse e assicurarsi che il metodo OnPaint disegni lo stato corretto del pulsante di opzione.

private bool mouseHoverState = false;

protected override void OnMouseEnter(EventArgs e)
{
    mouseHoverState = true;

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

    base.OnMouseEnter(e);
}

protected override void OnMouseLeave(EventArgs e)
{
    mouseHoverState = false;
    base.OnMouseLeave(e);
}

private bool mouseDownState = false;

protected override void OnMouseDown(MouseEventArgs e)
{
    mouseDownState = true;

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

    base.OnMouseDown(e);
}

protected override void OnMouseUp(MouseEventArgs e)
{
    mouseDownState = false;
    base.OnMouseUp(e);
}

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

Per disabilitare le opzioni in un sottomenu quando l'elemento padre non è selezionato

Eseguire l'override della proprietà Enabled in modo che l'elemento sia disabilitato se ha un elemento padre, con un valore CheckOnClick uguale a true e un valore Checked uguale a false.

// 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 override bool Enabled
{
    get
    {
        ToolStripMenuItem ownerMenuItem =
            OwnerItem as ToolStripMenuItem;

        // Use the base value in design mode to prevent the designer
        // from setting the base value to the calculated value.
        if (!DesignMode &&
            ownerMenuItem != null && ownerMenuItem.CheckOnClick)
        {
            return base.Enabled && ownerMenuItem.Checked;
        }
        else
        {
            return base.Enabled;
        }
    }
    set
    {
        base.Enabled = value;
    }
}

' 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

Sovrascrivere il metodo OnOwnerChanged per iscriversi all'evento CheckedChanged dell'elemento padre.

// When OwnerItem becomes available, if it is a ToolStripMenuItem
// with a CheckOnClick property value of true, subscribe to its
// CheckedChanged event.
protected override void OnOwnerChanged(EventArgs e)
{
    ToolStripMenuItem ownerMenuItem =
        OwnerItem as ToolStripMenuItem;
    if (ownerMenuItem != null && ownerMenuItem.CheckOnClick)
    {
        ownerMenuItem.CheckedChanged +=
            new EventHandler(OwnerMenuItem_CheckedChanged);
    }
    base.OnOwnerChanged(e);
}

' 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

Nel gestore dell'evento dell'elemento padre CheckedChanged, invalida l'elemento per aggiornare la visualizzazione con il nuovo stato abilitato.

// When the checked state of the parent item changes,
// repaint the item so that the new Enabled state is displayed.
private void OwnerMenuItem_CheckedChanged(
    object sender, EventArgs e)
{
    Invalidate();
}

' 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

Esempio

L'esempio di codice seguente fornisce la classe ToolStripRadioButtonMenuItem completa e una classe Form e Program per illustrare il comportamento del pulsante di opzione.

using System;
using System.Drawing;
using System.Windows.Forms;
using System.Windows.Forms.VisualStyles;

public class ToolStripRadioButtonMenuItem : ToolStripMenuItem
{
    public ToolStripRadioButtonMenuItem()
        : base()
    {
        Initialize();
    }

    public ToolStripRadioButtonMenuItem(string text)
        : base(text, null, (EventHandler)null)
    {
        Initialize();
    }

    public ToolStripRadioButtonMenuItem(Image image)
        : base(null, image, (EventHandler)null)
    {
        Initialize();
    }

    public ToolStripRadioButtonMenuItem(string text, Image image)
        : base(text, image, (EventHandler)null)
    {
        Initialize();
    }

    public ToolStripRadioButtonMenuItem(string text, Image image,
        EventHandler onClick)
        : base(text, image, onClick)
    {
        Initialize();
    }

    public ToolStripRadioButtonMenuItem(string text, Image image,
        EventHandler onClick, string name)
        : base(text, image, onClick, name)
    {
        Initialize();
    }

    public ToolStripRadioButtonMenuItem(string text, Image image,
        params ToolStripItem[] dropDownItems)
        : base(text, image, dropDownItems)
    {
        Initialize();
    }

    public ToolStripRadioButtonMenuItem(string text, Image image,
        EventHandler onClick, Keys shortcutKeys)
        : base(text, image, onClick)
    {
        Initialize();
        this.ShortcutKeys = shortcutKeys;
    }

    // Called by all constructors to initialize CheckOnClick.
    private void Initialize()
    {
        CheckOnClick = true;
    }

    protected override void OnCheckedChanged(EventArgs e)
    {
        base.OnCheckedChanged(e);

        // If this item is no longer in the checked state or if its
        // parent has not yet been initialized, do nothing.
        if (!Checked || this.Parent == null) return;

        // Clear the checked state for all siblings.
        foreach (ToolStripItem item in Parent.Items)
        {
            ToolStripRadioButtonMenuItem radioItem =
                item as ToolStripRadioButtonMenuItem;
            if (radioItem != null && radioItem != this && radioItem.Checked)
            {
                radioItem.Checked = false;

                // Only one item can be selected at a time,
                // so there is no need to continue.
                return;
            }
        }
    }

    protected override void OnClick(EventArgs e)
    {
        // If the item is already in the checked state, do not call
        // the base method, which would toggle the value.
        if (Checked) return;

        base.OnClick(e);
    }

    // Let the item paint itself, and then paint the RadioButton
    // where the check mark is normally displayed.
    protected override void OnPaint(PaintEventArgs e)
    {
        if (Image != null)
        {
            // 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.
            base.OnPaint(e);
            return;
        }
        else
        {
            // If the Image property is not set, call the base OnPaint method
            // with the CheckState property temporarily cleared to prevent
            // the check mark from being painted.
            CheckState currentState = this.CheckState;
            this.CheckState = CheckState.Unchecked;
            base.OnPaint(e);
            this.CheckState = currentState;
        }

        // Determine the correct state of the RadioButton.
        RadioButtonState buttonState = RadioButtonState.UncheckedNormal;
        if (Enabled)
        {
            if (mouseDownState)
            {
                if (Checked) buttonState = RadioButtonState.CheckedPressed;
                else buttonState = RadioButtonState.UncheckedPressed;
            }
            else if (mouseHoverState)
            {
                if (Checked) buttonState = RadioButtonState.CheckedHot;
                else buttonState = RadioButtonState.UncheckedHot;
            }
            else
            {
                if (Checked) buttonState = RadioButtonState.CheckedNormal;
            }
        }
        else
        {
            if (Checked) buttonState = RadioButtonState.CheckedDisabled;
            else buttonState = RadioButtonState.UncheckedDisabled;
        }

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

        // Paint the RadioButton.
        RadioButtonRenderer.DrawRadioButton(
            e.Graphics, imageLocation, buttonState);
    }

    private bool mouseHoverState = false;

    protected override void OnMouseEnter(EventArgs e)
    {
        mouseHoverState = true;

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

        base.OnMouseEnter(e);
    }

    protected override void OnMouseLeave(EventArgs e)
    {
        mouseHoverState = false;
        base.OnMouseLeave(e);
    }

    private bool mouseDownState = false;

    protected override void OnMouseDown(MouseEventArgs e)
    {
        mouseDownState = true;

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

        base.OnMouseDown(e);
    }

    protected override void OnMouseUp(MouseEventArgs e)
    {
        mouseDownState = false;
        base.OnMouseUp(e);
    }

    // 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 override bool Enabled
    {
        get
        {
            ToolStripMenuItem ownerMenuItem =
                OwnerItem as ToolStripMenuItem;

            // Use the base value in design mode to prevent the designer
            // from setting the base value to the calculated value.
            if (!DesignMode &&
                ownerMenuItem != null && ownerMenuItem.CheckOnClick)
            {
                return base.Enabled && ownerMenuItem.Checked;
            }
            else
            {
                return base.Enabled;
            }
        }
        set
        {
            base.Enabled = value;
        }
    }

    // When OwnerItem becomes available, if it is a ToolStripMenuItem
    // with a CheckOnClick property value of true, subscribe to its
    // CheckedChanged event.
    protected override void OnOwnerChanged(EventArgs e)
    {
        ToolStripMenuItem ownerMenuItem =
            OwnerItem as ToolStripMenuItem;
        if (ownerMenuItem != null && ownerMenuItem.CheckOnClick)
        {
            ownerMenuItem.CheckedChanged +=
                new EventHandler(OwnerMenuItem_CheckedChanged);
        }
        base.OnOwnerChanged(e);
    }

    // When the checked state of the parent item changes,
    // repaint the item so that the new Enabled state is displayed.
    private void OwnerMenuItem_CheckedChanged(
        object sender, EventArgs e)
    {
        Invalidate();
    }
}

public class Form1 : Form
{
    private MenuStrip menuStrip1 = new MenuStrip();
    private ToolStripMenuItem mainToolStripMenuItem = new ToolStripMenuItem();
    private ToolStripMenuItem toolStripMenuItem1 = new ToolStripMenuItem();
    private ToolStripRadioButtonMenuItem toolStripRadioButtonMenuItem1 =
        new ToolStripRadioButtonMenuItem();
    private ToolStripRadioButtonMenuItem toolStripRadioButtonMenuItem2 =
        new ToolStripRadioButtonMenuItem();
    private ToolStripRadioButtonMenuItem toolStripRadioButtonMenuItem3 =
        new ToolStripRadioButtonMenuItem();
    private ToolStripRadioButtonMenuItem toolStripRadioButtonMenuItem4 =
        new ToolStripRadioButtonMenuItem();
    private ToolStripRadioButtonMenuItem toolStripRadioButtonMenuItem5 =
        new ToolStripRadioButtonMenuItem();
    private ToolStripRadioButtonMenuItem toolStripRadioButtonMenuItem6 =
        new ToolStripRadioButtonMenuItem();

    public Form1()
    {
        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});

        menuStrip1.Items.AddRange(new ToolStripItem[] {mainToolStripMenuItem});
        Controls.Add(menuStrip1);
        MainMenuStrip = menuStrip1;
        Text = "ToolStripRadioButtonMenuItem demo";
    }
}

static class Program
{
    [STAThread]
    static void Main()
    {
        Application.EnableVisualStyles();
        Application.SetCompatibleTextRenderingDefault(false);
        Application.Run(new Form1());
    }
}

Imports System.Drawing
Imports System.Windows.Forms
Imports System.Windows.Forms.VisualStyles

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 or if its 
        ' parent has not yet been initialized, do nothing.
        If Not Checked OrElse Me.Parent Is Nothing 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 normally displayed.
    Protected Overrides Sub OnPaint(ByVal e As PaintEventArgs)

        If Image IsNot Nothing Then
            ' 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. 
            MyBase.OnPaint(e)
            Return
        Else
            ' If the Image property is not set, call the base OnPaint method 
            ' with the CheckState property temporarily cleared to prevent
            ' the check mark from being painted.
            Dim currentState As CheckState = Me.CheckState
            Me.CheckState = CheckState.Unchecked
            MyBase.OnPaint(e)
            Me.CheckState = currentState
        End If

        ' 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)

        ' Paint the RadioButton. 
        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

Public Class Form1
    Inherits Form

    Private menuStrip1 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})

        menuStrip1.Items.AddRange(New ToolStripItem() {mainToolStripMenuItem})
        Controls.Add(menuStrip1)
        MainMenuStrip = menuStrip1
        Text = "ToolStripRadioButtonMenuItem demo"
    End Sub
End Class

Public Class Program

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

End Class

Compilazione del codice

Questo esempio richiede:

Riferimenti agli assembly System, System.Drawing e System.Windows.Forms.

Vedere anche

MenuStrip
ToolStripMenuItem
ToolStripMenuItem.CheckOnClick
ToolStripMenuItem.Checked
ToolStripMenuItem.OnCheckedChanged
ToolStripMenuItem.OnPaint
ToolStripMenuItem.Enabled
RadioButtonRenderer
Barra dei menu Controllo
Procedura: Implementare un ToolStripRenderer personalizzato

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