Message-Struktur
Implementiert eine Windows-Meldung.
Namespace: System.Windows.Forms
Assembly: System.Windows.Forms (in system.windows.forms.dll)
Syntax
'Declaration
Public Structure Message
'Usage
Dim instance As Message
public struct Message
public value class Message
public final class Message extends ValueType
JScript unterstützt die Verwendung von Strukturen, aber nicht die Deklaration von neuen Strukturen.
Hinweise
Die Message-Struktur bindet von Windows gesendete Meldungen ein. Mit dieser Struktur können Sie eine Meldung einbinden und der Fensterprozedur zum Verteilen zuweisen. Sie können mit dieser Struktur auch Informationen über eine vom System an die Anwendung oder an Steuerelemente gesendete Meldung abrufen.
Die Message kann nicht direkt erstellt werden. Verwenden Sie stattdessen die Create-Methode. Aus Effizienzgründen verwendet die Message den Pool vorhandener Message, anstatt, sofern möglich, eine neue zu instanziieren. Wenn im Pool jedoch keine Message verfügbar ist, wird eine neue instanziiert.
Beispiel
Im folgenden Codebeispiel wird das Überschreiben der WndProc-Methode zum Behandeln von in der Message angegebenen Betriebssystemmeldungen veranschaulicht. In diesem Beispiel wird die Betriebssystemmeldung WM_ACTIVATEAPP behandelt, um zu ermitteln, wann eine andere Anwendung aktiviert wird. In der Platform SDK-Dokumentation der MSDN Library finden Sie Informationen zu den verfügbaren Werten Message.Msg, Message.LParam und Message.WParam. Die tatsächlichen konstanten Werte finden Sie in der Headerdatei Windows.h, die Sie im Download des Platform SDK (Abschnitt Core SDK) und im MSDN finden.
Imports System
Imports System.Drawing
Imports System.Windows.Forms
Namespace csTempWindowsApplication1
Public Class Form1
Inherits System.Windows.Forms.Form
' Constant value was found in the "windows.h" header file.
Private Const WM_ACTIVATEAPP As Integer = &H1C
Private appActive As Boolean = True
<STAThread()> _
Shared Sub Main()
Application.Run(New Form1())
End Sub 'Main
Public Sub New()
MyBase.New()
Me.Size = New System.Drawing.Size(300, 300)
Me.Text = "Form1"
Me.Font = New System.Drawing.Font("Microsoft Sans Serif", 18.0!, System.Drawing.FontStyle.Bold, System.Drawing.GraphicsUnit.Point, CType(0, Byte))
End Sub
Protected Overrides Sub OnPaint(ByVal e As PaintEventArgs)
' Paint a string in different styles depending on whether the
' application is active.
If (appActive) Then
e.Graphics.FillRectangle(SystemBrushes.ActiveCaption, 20, 20, 260, 50)
e.Graphics.DrawString("Application is active", Me.Font, SystemBrushes.ActiveCaptionText, 20, 20)
Else
e.Graphics.FillRectangle(SystemBrushes.InactiveCaption, 20, 20, 260, 50)
e.Graphics.DrawString("Application is Inactive", Me.Font, SystemBrushes.ActiveCaptionText, 20, 20)
End If
End Sub
<System.Security.Permissions.PermissionSetAttribute(System.Security.Permissions.SecurityAction.Demand, Name:="FullTrust")> _
Protected Overrides Sub WndProc(ByRef m As Message)
' Listen for operating system messages
Select Case (m.Msg)
' The WM_ACTIVATEAPP message occurs when the application
' becomes the active application or becomes inactive.
Case WM_ACTIVATEAPP
' The WParam value identifies what is occurring.
appActive = (m.WParam.ToInt32() <> 0)
' Invalidate to get new text painted.
Me.Invalidate()
End Select
MyBase.WndProc(m)
End Sub
End Class
End Namespace
using System;
using System.Drawing;
using System.Windows.Forms;
namespace csTempWindowsApplication1
{
public class Form1 : System.Windows.Forms.Form
{
// Constant value was found in the "windows.h" header file.
private const int WM_ACTIVATEAPP = 0x001C;
private bool appActive = true;
[STAThread]
static void Main()
{
Application.Run(new Form1());
}
public Form1()
{
this.Size = new System.Drawing.Size(300,300);
this.Text = "Form1";
this.Font = new System.Drawing.Font("Microsoft Sans Serif", 18F, System.Drawing.FontStyle.Bold, System.Drawing.GraphicsUnit.Point, ((System.Byte)(0)));
}
protected override void OnPaint(PaintEventArgs e)
{
// Paint a string in different styles depending on whether the
// application is active.
if (appActive)
{
e.Graphics.FillRectangle(SystemBrushes.ActiveCaption,20,20,260,50);
e.Graphics.DrawString("Application is active", this.Font, SystemBrushes.ActiveCaptionText, 20,20);
}
else
{
e.Graphics.FillRectangle(SystemBrushes.InactiveCaption,20,20,260,50);
e.Graphics.DrawString("Application is Inactive", this.Font, SystemBrushes.ActiveCaptionText, 20,20);
}
}
[System.Security.Permissions.PermissionSet(System.Security.Permissions.SecurityAction.Demand, Name="FullTrust")]
protected override void WndProc(ref Message m)
{
// Listen for operating system messages.
switch (m.Msg)
{
// The WM_ACTIVATEAPP message occurs when the application
// becomes the active application or becomes inactive.
case WM_ACTIVATEAPP:
// The WParam value identifies what is occurring.
appActive = (((int)m.WParam != 0));
// Invalidate to get new text painted.
this.Invalidate();
break;
}
base.WndProc(ref m);
}
}
}
using namespace System;
using namespace System::Drawing;
using namespace System::Windows::Forms;
using namespace System::Security::Permissions;
namespace csTempWindowsApplication1
{
public ref class Form1: public System::Windows::Forms::Form
{
private:
// Constant value was found in the "windows.h" header file.
static const Int32 WM_ACTIVATEAPP = 0x001C;
Boolean appActive;
public:
Form1()
{
appActive = true;
this->Size = System::Drawing::Size( 300, 300 );
this->Text = "Form1";
this->Font = gcnew System::Drawing::Font( "Microsoft Sans Serif",18.0F,System::Drawing::FontStyle::Bold,System::Drawing::GraphicsUnit::Point,((System::Byte)(0)) );
}
protected:
virtual void OnPaint( PaintEventArgs^ e ) override
{
// Paint a string in different styles depending on whether the
// application is active.
if ( appActive )
{
e->Graphics->FillRectangle( SystemBrushes::ActiveCaption, 20, 20, 260, 50 );
e->Graphics->DrawString( "Application is active", this->Font, SystemBrushes::ActiveCaptionText, 20, 20 );
}
else
{
e->Graphics->FillRectangle( SystemBrushes::InactiveCaption, 20, 20, 260, 50 );
e->Graphics->DrawString( "Application is Inactive", this->Font, SystemBrushes::ActiveCaptionText, 20, 20 );
}
}
[SecurityPermission(SecurityAction::Demand, Flags=SecurityPermissionFlag::UnmanagedCode)]
virtual void WndProc( Message% m ) override
{
// Listen for operating system messages.
switch ( m.Msg )
{
case WM_ACTIVATEAPP:
// The WParam value identifies what is occurring.
appActive = (int)m.WParam != 0;
// Invalidate to get new text painted.
this->Invalidate();
break;
}
Form::WndProc( m );
}
};
}
[STAThread]
int main()
{
Application::Run( gcnew csTempWindowsApplication1::Form1 );
}
package JSLTempWindowsApplication1;
import System.*;
import System.Drawing.*;
import System.Windows.Forms.*;
import System.Security.Permissions.*;
public class Form1 extends System.Windows.Forms.Form
{
// Constant value was found in the "windows.h" header file.
private final int WM_ACTIVATEAPP = 0x1C;
private boolean appActive = true;
/** @attribute STAThread()
*/
public static void main(String[] args)
{
Application.Run(new Form1());
} //main
public Form1()
{
this.set_Size(new System.Drawing.Size(300, 300));
this.set_Text("Form1");
this.set_Font(new System.Drawing.Font("Microsoft Sans Serif", 18,
System.Drawing.FontStyle.Bold, System.Drawing.GraphicsUnit.Point,
(ubyte)0));
} //Form1
protected void OnPaint(PaintEventArgs e)
{
// Paint a string in different styles depending on whether the
// application is active.
if (appActive) {
e.get_Graphics().FillRectangle(SystemBrushes.get_ActiveCaption(),
20, 20, 260, 50);
e.get_Graphics().DrawString("Application is active",
this.get_Font(), SystemBrushes.get_ActiveCaptionText(),
20, 20);
}
else {
e.get_Graphics().FillRectangle(SystemBrushes.get_InactiveCaption(),
20, 20, 260, 50);
e.get_Graphics().DrawString("Application is Inactive",
this.get_Font(), SystemBrushes.get_ActiveCaptionText(),
20, 20);
}
} //OnPaint
/** @attribute SecurityPermissionAttribute(SecurityAction.Demand, Flags=SecurityPermissionFlag.UnmanagedCode)
*/
protected void WndProc(/** @ref */Message m)
{
// Listen for operating system messages.
switch (m.get_Msg()) {
// The WM_ACTIVATEAPP message occurs when the application
// becomes the active application or becomes inactive.
case WM_ACTIVATEAPP:
// The WParam value identifies what is occurring.
appActive = m.get_WParam().ToInt32() != 0;
// Invalidate to get new text painted.
this.Invalidate();
break;
}
super.WndProc(m);
} //WndProc
} //Form1
Threadsicherheit
Alle öffentlichen statischen (Shared in Visual Basic) Member dieses Typs sind threadsicher. Bei Instanzmembern ist die Threadsicherheit nicht gewährleistet.
Plattformen
Windows 98, Windows 2000 SP4, Windows CE, Windows Millennium Edition, Windows Mobile für Pocket PC, Windows Mobile für Smartphone, Windows Server 2003, Windows XP Media Center Edition, Windows XP Professional x64 Edition, Windows XP SP2, Windows XP Starter Edition
.NET Framework unterstützt nicht alle Versionen sämtlicher Plattformen. Eine Liste der unterstützten Versionen finden Sie unter Systemanforderungen.
Versionsinformationen
.NET Framework
Unterstützt in: 2.0, 1.1, 1.0