ComboBoxRenderer Classe

Definizione

Spazio dei nomi:

System.Windows.Forms

Assembly:

System.Windows.Forms.dll

Origine:

ComboBoxRenderer.cs

Fornisce metodi utilizzati per eseguire il rendering di un controllo casella combinata con stili di visualizzazione. Questa classe non può essere ereditata.

public ref class ComboBoxRenderer abstract sealed

public static class ComboBoxRenderer

type ComboBoxRenderer = class

Public Class ComboBoxRenderer

Ereditarietà

Object

ComboBoxRenderer

Esempio

Nell'esempio di codice seguente viene illustrato come creare un controllo personalizzato che utilizza i DrawTextBox metodi e DrawDropDownButton per disegnare una casella combinata che risponde ai clic del mouse.

#using <System.dll>
#using <System.Drawing.dll>
#using <System.Windows.Forms.dll>

using namespace System;
using namespace System::Drawing;
using namespace System::Windows::Forms;
using namespace System::Windows::Forms::VisualStyles;

namespace ComboBoxRendererSample
{
    ref class CustomComboBox: public Control
    {
    private:
        System::Drawing::Size arrowSize;
        Rectangle arrowRectangle;
        Rectangle topTextBoxRectangle;
        Rectangle bottomTextBoxRectangle;
        ComboBoxState textBoxState;
        ComboBoxState arrowState;
        String^ bottomText;
        bool isActivated;
        int minHeight;
        int minWidth;

    public:
        CustomComboBox() : Control()

          {
              minHeight = 38;
              minWidth = 40; 
              this->Location = Point(10, 10);
              this->Size = System::Drawing::Size(140, 38);
              this->Font = SystemFonts::IconTitleFont;
              this->Text = "Click the button";
              textBoxState = ComboBoxState::Normal;
              bottomText = "Using ComboBoxRenderer";
              arrowState = ComboBoxState::Normal;

              // Initialize the rectangles to look like the standard combo
              // box control.
              arrowSize = System::Drawing::Size(18, 20);
              arrowRectangle = Rectangle(ClientRectangle.X +
                  ClientRectangle.Width - arrowSize.Width - 1,
                  ClientRectangle.Y + 1,
                  arrowSize.Width,
                  arrowSize.Height);
              topTextBoxRectangle = Rectangle(ClientRectangle.X,
                  ClientRectangle.Y,
                  ClientRectangle.Width,
                  arrowSize.Height + 2);
              bottomTextBoxRectangle = Rectangle(ClientRectangle.X,
                  ClientRectangle.Y + topTextBoxRectangle.Height,
                  ClientRectangle.Width,
                  topTextBoxRectangle.Height - 6);
          }

          // 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();
            }
        }

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

            if (arrowRectangle.Contains(e->Location) &&
                ComboBoxRenderer::IsSupported)
            {
                arrowState = ComboBoxState::Normal;
                Invalidate();
            }
        }
    };

    ref class Form1 : public Form
    {
    public:
        Form1() : Form()
        {
            this->Size = System::Drawing::Size(300, 300);
            CustomComboBox^ ComboBox1 = gcnew CustomComboBox();
            Controls->Add(ComboBox1);
        }

    };

}

[STAThread]
int main()
{
    // The call to EnableVisualStyles below does not affect
    // whether ComboBoxRenderer.IsSupported is true; as long as visual
    // styles are enabled by the operating system, IsSupported is true.
    Application::EnableVisualStyles();
    Application::Run(gcnew ComboBoxRendererSample::Form1());

}

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

namespace ComboBoxRendererSample
{
    class Form1 : Form
    {
        public Form1()
            : base()
        {
            this.Size = new Size(300, 300);
            CustomComboBox ComboBox1 = new CustomComboBox();
            Controls.Add(ComboBox1);
        }

        [STAThread]
        static void Main()
        {
            // The call to EnableVisualStyles below does not affect
            // whether ComboBoxRenderer.IsSupported is true; as long as visual
            // styles are enabled by the operating system, IsSupported is true.
            Application.EnableVisualStyles();
            Application.Run(new Form1());
        }
    }

    public class CustomComboBox : Control
    {
        private Size arrowSize;
        private Rectangle arrowRectangle;
        private Rectangle topTextBoxRectangle;
        private Rectangle bottomTextBoxRectangle;
        private ComboBoxState textBoxState = ComboBoxState.Normal;
        private ComboBoxState arrowState = ComboBoxState.Normal;
        private String bottomText = "Using ComboBoxRenderer";
        private bool isActivated = false;
        private const int minHeight = 38;
        private const int minWidth = 40;

        public CustomComboBox()
            : base()
        {
            this.Location = new Point(10, 10);
            this.Size = new Size(140, 38);
            this.Font = SystemFonts.IconTitleFont;
            this.Text = "Click the button";

            // Initialize the rectangles to look like the standard combo 
            // box control.
            arrowSize = new Size(18, 20);
            arrowRectangle = new Rectangle(ClientRectangle.X +
                ClientRectangle.Width - arrowSize.Width - 1,
                ClientRectangle.Y + 1,
                arrowSize.Width,
                arrowSize.Height);
            topTextBoxRectangle = new Rectangle(ClientRectangle.X,
                ClientRectangle.Y,
                ClientRectangle.Width,
                arrowSize.Height + 2);
            bottomTextBoxRectangle = new Rectangle(ClientRectangle.X,
                ClientRectangle.Y + topTextBoxRectangle.Height,
                ClientRectangle.Width,
                topTextBoxRectangle.Height - 6);
        }

        // 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();
            }
        }

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

            if (arrowRectangle.Contains(e.Location) &&
                ComboBoxRenderer.IsSupported)
            {
                arrowState = ComboBoxState.Normal;
                Invalidate();
            }
        }
    }
}

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

Namespace ComboBoxRendererSample
    Class Form1
        Inherits Form

        Public Sub New()
            Me.Size = New Size(300, 300)
            Dim ComboBox1 As New CustomComboBox()
            Controls.Add(ComboBox1)
        End Sub

        <STAThread()> _
        Shared Sub Main()
            ' The call to EnableVisualStyles below does not affect
            ' whether ComboBoxRenderer.IsSupported is true; as long as visual
            ' styles are enabled by the operating system, IsSupported is true.
            Application.EnableVisualStyles()
            Application.Run(New Form1())
        End Sub
    End Class

    Public Class CustomComboBox
        Inherits Control

        Private arrowSize As Size
        Private arrowRectangle As Rectangle
        Private topTextBoxRectangle As Rectangle
        Private bottomTextBoxRectangle As Rectangle
        Private textBoxState As ComboBoxState = ComboBoxState.Normal
        Private arrowState As ComboBoxState = ComboBoxState.Normal
        Private bottomText As String = "Using ComboBoxRenderer"
        Private isActivated As Boolean = False
        Private minHeight As Integer = 38
        Private minWidth As Integer = 40

        Public Sub New()
            Me.Location = New Point(10, 10)
            Me.Size = New Size(140, 38)
            Me.Font = SystemFonts.IconTitleFont
            Me.Text = "Click the button"

            ' Initialize the rectangles to look like the standard combo 
            ' box control.
            arrowSize = New Size(18, 20)
            arrowRectangle = New Rectangle(Me.ClientRectangle.X + _
                Me.ClientRectangle.Width - arrowSize.Width - 1, _
                Me.ClientRectangle.Y + 1, arrowSize.Width, _
                arrowSize.Height)
            topTextBoxRectangle = New Rectangle(Me.ClientRectangle.X, _
                Me.ClientRectangle.Y, Me.ClientRectangle.Width, _
                arrowSize.Height + 2)
            bottomTextBoxRectangle = New Rectangle(Me.ClientRectangle.X, _
                Me.ClientRectangle.Y + topTextBoxRectangle.Height, _
                Me.ClientRectangle.Width, topTextBoxRectangle.Height - 6)
        End Sub

        ' 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

        Protected Overrides Sub OnMouseUp(ByVal e As MouseEventArgs)
            MyBase.OnMouseUp(e)
            If arrowRectangle.Contains(e.Location) And _
                ComboBoxRenderer.IsSupported Then
                arrowState = ComboBoxState.Normal
                Invalidate()
            End If
        End Sub

    End Class
End Namespace

Commenti

La ComboBoxRenderer classe fornisce un set di static metodi che possono essere utilizzati per eseguire il rendering di un controllo casella combinata con lo stile di visualizzazione corrente del sistema operativo. Il rendering di un controllo fa riferimento al disegno dell'interfaccia utente di un controllo. Ciò è utile se si disegna un controllo personalizzato che deve avere l'aspetto dello stile di visualizzazione corrente. Per disegnare una casella combinata, utilizzare il DrawTextBox metodo per disegnare la casella di testo e il DrawDropDownButton metodo per disegnare la freccia a discesa.

Se gli stili di visualizzazione sono abilitati nel sistema operativo e gli stili di visualizzazione vengono applicati all'area client delle finestre DrawTextBox dell'applicazione e DrawDropDownButton disegnare la casella combinata con lo stile di visualizzazione corrente. In caso contrario, questi metodi generano un'eccezione InvalidOperationException. Per determinare se è possibile utilizzare i membri di questa classe, è possibile controllare il valore della IsSupported proprietà .

Questa classe esegue il wrapping della funzionalità di un oggetto System.Windows.Forms.VisualStyles.VisualStyleRenderer impostato su uno degli elementi esposti dalle System.Windows.Forms.VisualStyles.VisualStyleElement.ComboBox.DropDownButton classi e System.Windows.Forms.VisualStyles.VisualStyleElement.TextBox.TextEdit . Per altre informazioni, vedere Rendering dei controlli con stili di visualizzazione.

Proprietà

Nome	Descrizione
IsSupported	Ottiene un valore che indica se la ComboBoxRenderer classe può essere utilizzata per disegnare una casella combinata con stili di visualizzazione.

Metodi

Nome	Descrizione
DrawDropDownButton(Graphics, Rectangle, ComboBoxState)	Disegna una freccia a discesa con lo stile di visualizzazione corrente del sistema operativo.
DrawTextBox(Graphics, Rectangle, ComboBoxState)	Disegna una casella di testo nello stato e nei limiti specificati.
DrawTextBox(Graphics, Rectangle, String, Font, ComboBoxState)	Disegna una casella di testo nello stato e nei limiti specificati, con il testo specificato.
DrawTextBox(Graphics, Rectangle, String, Font, Rectangle, ComboBoxState)	Disegna una casella di testo nello stato e nei limiti specificati, con il testo e i limiti di testo specificati.
DrawTextBox(Graphics, Rectangle, String, Font, Rectangle, TextFormatFlags, ComboBoxState)	Disegna una casella di testo nello stato e nei limiti specificati, con il testo, la formattazione del testo e i limiti di testo specificati.
DrawTextBox(Graphics, Rectangle, String, Font, TextFormatFlags, ComboBoxState)	Disegna una casella di testo nello stato e nei limiti specificati, con il testo e la formattazione del testo specificati.

Vedi anche

• VisualStyleRenderer
• VisualStyleElement