ComboBoxRenderer.DrawDropDownButton(Graphics, Rectangle, ComboBoxState) Метод

Определение

Рисует стрелку раскрывающегося списка с учетом текущего визуального стиля операционной системы.Draws a drop-down arrow with the current visual style of the operating system.

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)

Параметры

g
Graphics

Graphics используется для отрисовки стрелки раскрывающегося списка.The Graphics used to draw the drop-down arrow.

bounds
Rectangle

Rectangle указывает границы стрелки раскрывающегося списка.The Rectangle that specifies the bounds of the drop-down arrow.

state
ComboBoxState

Одно из значений ComboBoxState, с помощью которого задается видимое состояние стрелки раскрывающегося списка.One of the ComboBoxState values that specifies the visual state of the drop-down arrow.

Исключения

Эта операционная система не поддерживает стили оформления.The operating system does not support visual styles.

-или--or-

Стили оформления отключены пользователем этой операционной системы.Visual styles are disabled by the user in the operating system.

-или--or-

Визуальные стили не применяются к клиентской области окон приложений.Visual styles are not applied to the client area of application windows.

Примеры

В следующем примере кода DrawDropDownButton метод в методе пользовательского элемента управления используется OnPaint для отрисовки стрелки раскрывающегося списка в состоянии, определенного расположением указателя мыши.The following code example uses the DrawDropDownButton method in a custom control's OnPaint method to draw a drop-down arrow in the state determined by the location of the mouse pointer. Этот пример кода является частью большого примера, приведенного для ComboBoxRenderer класса.This code example is part of a larger example provided for the ComboBoxRenderer class.

      // 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

Комментарии

Перед вызовом этого метода следует убедиться, что IsSupported свойство возвращает true .Before calling this method, you should verify that the IsSupported property returns true.

Применяется к