ComboBoxRenderer.DrawDropDownButton Methode

Definition

Namespace:

System.Windows.Forms

Assembly:

System.Windows.Forms.dll

Zeichnet einen Dropdownpfeil mit dem aktuellen visuellen Stil des Betriebssystems.

public:
 static void DrawDropDownButton(System::Drawing::Graphics ^ g, System::Drawing::Rectangle bounds, System::Windows::Forms::VisualStyles::ComboBoxState state);

public static void DrawDropDownButton (System.Drawing.Graphics g, System.Drawing.Rectangle bounds, System.Windows.Forms.VisualStyles.ComboBoxState state);

static member DrawDropDownButton : System.Drawing.Graphics * System.Drawing.Rectangle * System.Windows.Forms.VisualStyles.ComboBoxState -> unit

Public Shared Sub DrawDropDownButton (g As Graphics, bounds As Rectangle, state As ComboBoxState)

Parameter

g

Graphics

Die zum Zeichnen des Dropdownpfeils verwendete Graphics.

bounds

Rectangle

Das Rectangle, das die Begrenzungen des Dropdownpfeils angibt.

state

ComboBoxState

Einer der ComboBoxState-Werte, die den visuellen Zustand des Dropdownpfeils angeben.

Ausnahmen

InvalidOperationException

Das Betriebssystem unterstützt keine visuellen Stile.

- oder -

Visuelle Stile wurden durch den Benutzer im Betriebssystem deaktiviert.

- oder -

Visuelle Stile werden nicht auf den Clientbereich der Anwendungsfenster angewendet.

Beispiele

Im folgenden Codebeispiel wird die -Methode in der DrawDropDownButton -Methode eines benutzerdefinierten Steuerelements OnPaint verwendet, um einen Dropdownpfeil in dem Zustand zu zeichnen, der durch die Position des Mauszeigers bestimmt wird. Dieses Codebeispiel ist Teil eines größeren Beispiels, das für die ComboBoxRenderer-Klasse bereitgestellt wird.

      // Draw the combo box in the current state.
protected:
    virtual void OnPaint(PaintEventArgs^ e) override 
    {
        Control::OnPaint(e);

        if (!ComboBoxRenderer::IsSupported)
        {
            this->Parent->Text = "Visual Styles Disabled";
            return;
        }

        this->Parent->Text = "CustomComboBox Enabled";

        // Always draw the main text box and drop down arrow in their
        // current states
        ComboBoxRenderer::DrawTextBox(e->Graphics, topTextBoxRectangle,
            this->Text, this->Font, textBoxState);
        ComboBoxRenderer::DrawDropDownButton(e->Graphics, arrowRectangle,
            arrowState);

        // Only draw the bottom text box if the arrow has been clicked
        if (isActivated)
        {
            ComboBoxRenderer::DrawTextBox(e->Graphics,
                bottomTextBoxRectangle, bottomText, this->Font,
                textBoxState);
        }
    }

protected:
    virtual void OnMouseDown(MouseEventArgs^ e) override 
    {
        Control::OnMouseDown(e);

        // Check whether the user clicked the arrow.
        if (arrowRectangle.Contains(e->Location) &&
            ComboBoxRenderer::IsSupported)
        {
            // Draw the arrow in the pressed state.
            arrowState = ComboBoxState::Pressed;

            // The user has activated the combo box.
            if (!isActivated)
            {
                this->Text = "Clicked!";
                textBoxState = ComboBoxState::Pressed;
                isActivated = true;
            }

            // The user has deactivated the combo box.
            else
            {
                this->Text = "Click here";
                textBoxState = ComboBoxState::Normal;
                isActivated = false;
            }

            // Redraw the control.
            Invalidate();
        }
    }

// Draw the combo box in the current state.
protected override void OnPaint(PaintEventArgs e)
{
    base.OnPaint(e);

    if (!ComboBoxRenderer.IsSupported)
    {
        this.Parent.Text = "Visual Styles Disabled";
        return;
    }

    this.Parent.Text = "CustomComboBox Enabled";

    // Always draw the main text box and drop down arrow in their 
    // current states
    ComboBoxRenderer.DrawTextBox(e.Graphics, topTextBoxRectangle,
        this.Text, this.Font, textBoxState);
    ComboBoxRenderer.DrawDropDownButton(e.Graphics, arrowRectangle,
        arrowState);

    // Only draw the bottom text box if the arrow has been clicked
    if (isActivated)
    {
        ComboBoxRenderer.DrawTextBox(e.Graphics,
            bottomTextBoxRectangle, bottomText, this.Font,
            textBoxState);
    }
}

protected override void OnMouseDown(MouseEventArgs e)
{
    base.OnMouseDown(e);

    // Check whether the user clicked the arrow.
    if (arrowRectangle.Contains(e.Location) &&
        ComboBoxRenderer.IsSupported)
    {
        // Draw the arrow in the pressed state.
        arrowState = ComboBoxState.Pressed;

        // The user has activated the combo box.
        if (!isActivated)
        {
            this.Text = "Clicked!";
            textBoxState = ComboBoxState.Pressed;
            isActivated = true;
        }

        // The user has deactivated the combo box.
        else
        {
            this.Text = "Click here";
            textBoxState = ComboBoxState.Normal;
            isActivated = false;
        }

        // Redraw the control.
        Invalidate();
    }
}

' Draw the combo box in the current state.
Protected Overrides Sub OnPaint(ByVal e As PaintEventArgs)
    MyBase.OnPaint(e)

    If Not ComboBoxRenderer.IsSupported Then
        Me.Parent.Text = "Visual Styles	Disabled"
        Return
    End If

    Me.Parent.Text = "CustomComboBox Enabled"

    ' Always draw the main text box and drop down arrow in their 
    ' current states.
    ComboBoxRenderer.DrawTextBox(e.Graphics, topTextBoxRectangle, _
        Me.Text, Me.Font, textBoxState)
    ComboBoxRenderer.DrawDropDownButton(e.Graphics, arrowRectangle, _
        arrowState)

    ' Only draw the bottom text box if the arrow has been clicked.
    If isActivated Then
        ComboBoxRenderer.DrawTextBox(e.Graphics, _
            bottomTextBoxRectangle, bottomText, Me.Font, textBoxState)
    End If
End Sub

Protected Overrides Sub OnMouseDown(ByVal e As MouseEventArgs)
    MyBase.OnMouseDown(e)

    ' Check whether the user clicked the arrow.
    If arrowRectangle.Contains(e.Location) And _
        ComboBoxRenderer.IsSupported Then

        ' Draw the arrow in the pressed state.
        arrowState = ComboBoxState.Pressed

        ' The user has activated the combo box.
        If Not isActivated Then
            Me.Text = "Clicked!"
            textBoxState = ComboBoxState.Pressed
            isActivated = True

        ' The user has deactivated the combo box.
        Else
            Me.Text = "Click here"
            textBoxState = ComboBoxState.Normal
            isActivated = False
        End If

        ' Redraw the control.
        Invalidate()
    End If
End Sub

Hinweise

Bevor Sie diese Methode aufrufen, sollten Sie überprüfen, ob die IsSupported -Eigenschaft zurückgibt true.