CreateParams Classe

Definizione

public ref class CreateParams

public class CreateParams

type CreateParams = class

Public Class CreateParams

Ereditarietà

Object

CreateParams

Esempio

Nell'esempio di codice seguente viene creata una Button classe derivata denominata MyIconButton e viene fornita l'implementazione necessaria per visualizzare un'icona anziché un'immagine. La CreateParams proprietà è estesa e un valore aggiunto alla Style proprietà che causa la visualizzazione di un Icon pulsante anziché di un Imageoggetto .

#include <windows.h>

#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::Runtime::InteropServices;
using namespace System::Diagnostics;
using namespace System::IO;

public ref class MyIconButton: public Button
{
private:
   Icon^ icon;

public:
   MyIconButton()
   {
      
      // Set the button's FlatStyle property.
      FlatStyle = ::FlatStyle::System;
   }

   MyIconButton( Icon^ ButtonIcon )
   {
      
      // Set the button's FlatStyle property.
      FlatStyle = ::FlatStyle::System;
      
      // Assign the icon to the private field.
      this->icon = ButtonIcon;
      
      // Size the button to 4 pixels larger than the icon.
      this->Height = icon->Height + 4;
      this->Width = icon->Width + 4;
   }


protected:

   property System::Windows::Forms::CreateParams^ CreateParams 
   {

      virtual System::Windows::Forms::CreateParams^ get() override
      {
         
         // Extend the CreateParams property of the Button class.
         System::Windows::Forms::CreateParams^ cp = __super::CreateParams;

         // Update the button Style.
         cp->Style |= 0x00000040; // BS_ICON value
         return cp;
      }
   }

public:
   property System::Drawing::Icon^ Icon
   {
      System::Drawing::Icon^ get()
      {
         return icon;
      }
      void set(System::Drawing::Icon^ value)
      {
         icon = value;
         UpdateIcon();
         this->Height = icon->Height + 4;
         this->Width = icon->Width + 4;
      }
   }

protected:
   virtual void OnHandleCreated( EventArgs^ e ) override
   {
      Button::OnHandleCreated( e );
      
      // Update the icon on the button if there is currently an icon assigned to the icon field.
      if ( icon != nullptr )
      {
         UpdateIcon();
      }
   }


private:
   void UpdateIcon()
   {
      IntPtr iconHandle = IntPtr::Zero;
      
      // Get the icon's handle.
      if ( icon != nullptr )
      {
         iconHandle = icon->Handle;
      }

      
      // Send Windows the message to update the button.
      SendMessage( (HWND)Handle.ToPointer(), 0x00F7, 1, (int)iconHandle );
      
      /*BM_SETIMAGE value*/
      /*IMAGE_ICON value*/
   }

   public:
    [DllImport("user32.dll")]
    static LRESULT SendMessage(HWND hWnd, int msg, int wParam, int lParam);

};

using System;
using System.Drawing;
using System.Windows.Forms;
using System.Runtime.InteropServices;
using System.Diagnostics;
using System.IO;

public class MyIconButton : Button
{
    private Icon icon;

    public MyIconButton()
    {
        // Set the button's FlatStyle property.
        FlatStyle = FlatStyle.System;
    }

    public MyIconButton(Icon ButtonIcon)
        : this()
    {
        // Assign the icon to the private field.   
        this.icon = ButtonIcon;

        // Size the button to 4 pixels larger than the icon.
        this.Height = icon.Height + 4;
        this.Width = icon.Width + 4;
    }

    protected override CreateParams CreateParams
    {
        get
        {
            // Extend the CreateParams property of the Button class.
            CreateParams cp = base.CreateParams;
            // Update the button Style.
            cp.Style |= 0x00000040; // BS_ICON value

            return cp;
        }
    }

    public Icon Icon
    {
        get
        {
            return icon;
        }

        set
        {
            icon = value;
            UpdateIcon();
            // Size the button to 4 pixels larger than the icon.
            this.Height = icon.Height + 4;
            this.Width = icon.Width + 4;
        }
    }

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

        // Update the icon on the button if there is currently an icon assigned to the icon field.
        if (icon != null)
        {
            UpdateIcon();
        }
    }

    private void UpdateIcon()
    {
        IntPtr iconHandle = IntPtr.Zero;

        // Get the icon's handle.
        if (icon != null)
        {
            iconHandle = icon.Handle;
        }

        // Send Windows the message to update the button. 
        SendMessage(Handle, 0x00F7 /*BM_SETIMAGE value*/, 1 /*IMAGE_ICON value*/, (int)iconHandle);
    }

    // Import the SendMessage method of the User32 DLL.   
    [DllImport("user32.dll", CharSet = CharSet.Auto)]
    public static extern IntPtr SendMessage(IntPtr hWnd, int msg, int wParam, int lParam);
}

Imports System.Windows.Forms
Imports System.Drawing
Imports System.IO
Imports System.Security.Permissions

Public Class MyIconButton
    Inherits Button

    Private ButtonIcon As Icon

    Public Sub New()
        MyBase.New()

        ' Set the button's FlatStyle property.
        Me.FlatStyle = System.Windows.Forms.FlatStyle.System
    End Sub

    Public Sub New(ByVal Icon As Icon)
        MyBase.New()

        ' Assign the icon to the private field.   
        Me.ButtonIcon = Icon

        ' Size the button to 4 pixels larger than the icon.
        Me.Height = ButtonIcon.Height + 4
        Me.Width = ButtonIcon.Width + 4
    End Sub


    Protected Overrides ReadOnly Property CreateParams() As System.Windows.Forms.CreateParams
        Get
            Dim SecPerm As New SecurityPermission(SecurityPermissionFlag.UnmanagedCode)
            SecPerm.Demand()

            ' Extend the CreateParams property of the Button class.
            Dim cp As System.Windows.Forms.CreateParams = MyBase.CreateParams
            ' Update the button Style.
            cp.Style = cp.Style Or &H40 ' BS_ICON value

            Return cp
        End Get
    End Property

    Public Property Icon() As Icon
        Get
            Return ButtonIcon
        End Get

        Set(ByVal Value As Icon)
            ButtonIcon = Value
            UpdateIcon()
            ' Size the button to 4 pixels larger than the icon.
            Me.Height = ButtonIcon.Height + 4
            Me.Width = ButtonIcon.Width + 4
        End Set
    End Property

    <SecurityPermission(SecurityAction.Demand, UnmanagedCode := True)> _
    Protected Overrides Sub OnHandleCreated(ByVal e As EventArgs)
        MyBase.OnHandleCreated(e)

        ' Update the icon on the button if there is currently an icon assigned to the icon field.
        If Me.ButtonIcon IsNot Nothing Then
            UpdateIcon()
        End If
    End Sub

    Private Sub UpdateIcon()
        Dim IconHandle As IntPtr = IntPtr.Zero

        ' Get the icon's handle.
        If Me.Icon IsNot Nothing Then
            IconHandle = Icon.Handle
        End If

        ' Send Windows the message to update the button. 
        ' BM_SETIMAGE (second parameter) and IMAGE_ICON (third parameter).
        SendMessage(Handle, &HF7, &H1, IconHandle.ToInt32())
    End Sub

    ' Declare the SendMessage function.
    Declare Auto Function SendMessage Lib "user32" (ByVal hWnd As IntPtr, _
            ByVal msg As Integer, ByVal wParam As Integer, ByVal lParam As Integer) As IntPtr
End Class

Nell'esempio di codice seguente viene creata un'istanza di un controllo standard Button e un'istanza del controllo derivato, , MyIconButtoncreata nell'esempio precedente. In questo esempio è necessario che sia presente un Icon file denominato Default.ico nella stessa posizione dell'applicazione. All'avvio dell'applicazione, l'icona Default viene visualizzata sul MyIconButton pulsante. Se l'icona non è presente, la Default faccia del pulsante è vuota. Quando viene fatto clic sullo standard Button , OpenFileDialog verrà visualizzata una casella in modo che sia possibile selezionare una nuova icona da visualizzare nell'oggetto MyIconButton.

public ref class MyApplication: public Form
{
private:
   MyIconButton^ myIconButton;
   Button^ stdButton;
   OpenFileDialog^ openDlg;

public:
   MyApplication()
   {
      try
      {
         
         // Create the button with the default icon.
         myIconButton = gcnew MyIconButton( gcnew System::Drawing::Icon( String::Concat( Application::StartupPath, "\\Default.ico" ) ) );
      }
      catch ( Exception^ ex ) 
      {
         
         // If the default icon does not exist, create the button without an icon.
         myIconButton = gcnew MyIconButton;
         #if defined(DEBUG)
         Debug::WriteLine( ex );
         #endif
      }
      finally
      {
         stdButton = gcnew Button;
         
         // Add the Click event handlers.
         myIconButton->Click += gcnew EventHandler( this, &MyApplication::myIconButton_Click );
         stdButton->Click += gcnew EventHandler( this, &MyApplication::stdButton_Click );
         
         // Set the location, text and width of the standard button.
         stdButton->Location = Point(myIconButton->Location.X,myIconButton->Location.Y + myIconButton->Height + 20);
         stdButton->Text = "Change Icon";
         stdButton->Width = 100;
         
         // Add the buttons to the Form.
         this->Controls->Add( stdButton );
         this->Controls->Add( myIconButton );
      }

   }


private:
   void myIconButton_Click( Object^ /*Sender*/, EventArgs^ /*e*/ )
   {
      
#undef MessageBox 
      
      // Make sure MyIconButton works.
      MessageBox::Show( "MyIconButton was clicked!" );
   }

   void stdButton_Click( Object^ /*Sender*/, EventArgs^ /*e*/ )
   {
      
      // Use an OpenFileDialog to allow the user to assign a new image to the derived button.
      openDlg = gcnew OpenFileDialog;
      openDlg->InitialDirectory = Application::StartupPath;
      openDlg->Filter = "Icon files (*.ico)|*.ico";
      openDlg->Multiselect = false;
      openDlg->ShowDialog();
      if (  !openDlg->FileName->Equals( "" ) )
      {
         myIconButton->Icon = gcnew System::Drawing::Icon( openDlg->FileName );
      }
   }

};

int main()
{
   Application::Run( gcnew MyApplication );
}

public class MyApplication : Form
{
    private MyIconButton myIconButton;
    private Button stdButton;
    private OpenFileDialog openDlg;

    static void Main()
    {
        Application.Run(new MyApplication());
    }

    public MyApplication()
    {
        try
        {
            // Create the button with the default icon.
            myIconButton = new MyIconButton(new Icon(Application.StartupPath + "\\Default.ico"));
        }
        catch (Exception ex)
        {
            // If the default icon does not exist, create the button without an icon.
            myIconButton = new MyIconButton();
            Debug.WriteLine(ex.ToString());
        }
        finally
        {
            stdButton = new Button();

            // Add the Click event handlers.
            myIconButton.Click += new EventHandler(this.myIconButton_Click);
            stdButton.Click += new EventHandler(this.stdButton_Click);

            // Set the location, text and width of the standard button.
            stdButton.Location = new Point(myIconButton.Location.X, myIconButton.Location.Y + myIconButton.Height + 20);
            stdButton.Text = "Change Icon";
            stdButton.Width = 100;

            // Add the buttons to the Form.
            this.Controls.Add(stdButton);
            this.Controls.Add(myIconButton);
        }
    }

    private void myIconButton_Click(object Sender, EventArgs e)
    {
        // Make sure MyIconButton works.
        MessageBox.Show("MyIconButton was clicked!");
    }

    private void stdButton_Click(object Sender, EventArgs e)
    {
        // Use an OpenFileDialog to allow the user to assign a new image to the derived button.
        openDlg = new OpenFileDialog();
        openDlg.InitialDirectory = Application.StartupPath;
        openDlg.Filter = "Icon files (*.ico)|*.ico";
        openDlg.Multiselect = false;
        openDlg.ShowDialog();

        if (openDlg.FileName != "")
        {
            myIconButton.Icon = new Icon(openDlg.FileName);
        }
    }
}

Public Class Form1
    Inherits System.Windows.Forms.Form

    Friend WithEvents MyStdButton As System.Windows.Forms.Button
    Friend WithEvents MyIconButton As MyIconButton
    Friend WithEvents OpenDlg As OpenFileDialog

    Public Sub New()
        MyBase.New()
        Try
            ' Create the button with the default icon.
            MyIconButton = New MyIconButton(New Icon(Application.StartupPath + "\Default.ico"))

        Catch ex As Exception
            ' If the default icon does not exist, create the button without an icon.
            MyIconButton = New MyIconButton()
            System.Diagnostics.Debug.WriteLine(ex.ToString())
        Finally
            MyStdButton = New Button()

            'Set the location, text and width of the standard button.
            MyStdButton.Location = New Point(MyIconButton.Location.X, _
                        MyIconButton.Location.Y + MyIconButton.Height + 20)
            MyStdButton.Text = "Change Icon"
            MyStdButton.Width = 100

            ' Add the buttons to the Form.
            Me.Controls.Add(MyStdButton)
            Me.Controls.Add(MyIconButton)
        End Try

    End Sub

    Public Shared Sub Main()
        Application.Run(New Form1())
    End Sub

    Private Sub MyStdButton_Click(ByVal sender As System.Object, _
                ByVal e As System.EventArgs) Handles MyStdButton.Click
        ' Use an OpenFileDialog to allow the user to assign a new image to the derived button.
        OpenDlg = New OpenFileDialog()
        OpenDlg.InitialDirectory = Application.StartupPath
        OpenDlg.Filter = "Icon files (*.ico)|*.ico"
        OpenDlg.Multiselect = False
        OpenDlg.ShowDialog()

        If OpenDlg.FileName <> "" Then
            MyIconButton.Icon = New Icon(OpenDlg.FileName)
        End If
    End Sub

    Private Sub MyIconButton_Click(ByVal sender As System.Object, _
                ByVal e As System.EventArgs) Handles MyIconButton.Click
        ' Make sure MyIconButton works.
        MessageBox.Show("MyIconButton was clicked!")
    End Sub
End Class

Commenti

Le informazioni in un CreateParams possono essere usate per passare informazioni sullo stato iniziale e sull'aspetto di un controllo. La maggior parte Control dei controlli derivati esegue l'override della CreateParams proprietà per passare i valori appropriati o includere informazioni aggiuntive nell'oggetto CreateParams.

Per altre informazioni sulla creazione di parametri di controllo, vedere La macro CreateWindow, la funzione CreateWindowEx e la struttura CREATESTRUCT.

Costruttori

Proprietà

Metodi

Si applica a

Vedi anche

• CreateParams