Application.DoEvents Application.DoEvents Application.DoEvents Application.DoEvents Method

Definition

Verarbeitet alle Windows-Meldungen, die sich derzeit in der Meldungswarteschlange befinden.Processes all Windows messages currently in the message queue.

public:
 static void DoEvents();
public static void DoEvents ();
static member DoEvents : unit -> unit
Public Shared Sub DoEvents ()

Beispiele

Das folgende Codebeispiel veranschaulicht die Verwendung der DoEvents Methode.The following code example demonstrates using the DoEvents method. Wenn das Beispiel ausgeführt wird, kann ein Benutzer auswählen Graphics-Dateien aus einem OpenFileDialog.When the example runs, a user can select graphics files from an OpenFileDialog. Die ausgewählten Dateien werden in der Form angezeigt.The selected files are displayed in the form. Die DoEvents Methode erzwingt das Neuzeichnen des Formulars für jede geöffnete Grafikdatei.The DoEvents method forces a repaint of the form for each graphics file opened. Um dieses Beispiel auszuführen, fügen Sie in den folgenden Code in ein Formular mit einem PictureBox mit dem Namen PictureBox1, OpenFileDialog mit dem Namen OpenFileDialog1, und eine Schaltfläche mit dem Namen fileButton.To run this example, paste the following code in a form containing a PictureBox named PictureBox1, an OpenFileDialog named OpenFileDialog1, and a button named fileButton. Rufen Sie die InitializePictureBox und InitializeOpenFileDialog Methoden aus den Konstruktor des Formulars oder Load Methode.Call the InitializePictureBox and InitializeOpenFileDialog methods from the form's constructor or Load method.

Hinweis

In Visual Studio, wenn Sie beim Hinzufügen einer OpenFileDialog zu Ihrem Formular mithilfe eines Ziehvorgangs, müssen Sie Folgendes ändern InitializeOpenFileDialog Methode durch das Entfernen der Zeile, die erstellt eine neue Instanz der OpenFileDialog.In Visual Studio, if you add an OpenFileDialog to your form by using a drag operation, you will have to modify the following InitializeOpenFileDialog method by removing the line that creates a new instance of OpenFileDialog.

Im Beispiel erfordert außerdem, dass die Control.Click Ereignis die Button Steuerelement und die FileOk Ereignis die OpenFileDialog verbunden sind, an die Ereignishandler, die im Beispiel definiert.The example also requires that the Control.Click event of the Button control and the FileOk event of the OpenFileDialog are connected to the event handlers defined in the example. Wenn das Beispiel ausgeführt wird, wird anzuzeigen Sie das Dialogfeld durch Klicken auf die Schaltfläche.When the example is running, display the dialog box by clicking the button.

void InitializePictureBox()
{
   this->PictureBox1 = gcnew System::Windows::Forms::PictureBox;
   this->PictureBox1->BorderStyle =
      System::Windows::Forms::BorderStyle::FixedSingle;
   this->PictureBox1->SizeMode = PictureBoxSizeMode::StretchImage;
   this->PictureBox1->Location = System::Drawing::Point( 72, 112 );
   this->PictureBox1->Name = "PictureBox1";
   this->PictureBox1->Size = System::Drawing::Size( 160, 136 );
   this->PictureBox1->TabIndex = 6;
   this->PictureBox1->TabStop = false;
}

void InitializeOpenFileDialog()
{
   this->OpenFileDialog1 = gcnew System::Windows::Forms::OpenFileDialog;
   
   // Set the file dialog to filter for graphics files.
   this->OpenFileDialog1->Filter =
      "Images (*.BMP;*.JPG;*.GIF)|*.BMP;*.JPG;*.GIF|" +
      "All files (*.*)|*.*";
   
   // Allow the user to select multiple images.
   this->OpenFileDialog1->Multiselect = true;
   this->OpenFileDialog1->Title = "My Image Browser";
}

void fileButton_Click( System::Object^ sender, System::EventArgs^ e )
{
   OpenFileDialog1->ShowDialog();
}

// This method handles the FileOK event.  It opens each file 
// selected and loads the image from a stream into PictureBox1.
void OpenFileDialog1_FileOk( Object^ sender,
   System::ComponentModel::CancelEventArgs^ e )
{
   this->Activate();
   array<String^>^ files = OpenFileDialog1->FileNames;
   
   // Open each file and display the image in PictureBox1.
   // Call Application.DoEvents to force a repaint after each
   // file is read.        
   for each ( String^ file in files )
   {
      System::IO::FileInfo^ fileInfo = gcnew System::IO::FileInfo( file );
      System::IO::FileStream^ fileStream = fileInfo->OpenRead();
      PictureBox1->Image = System::Drawing::Image::FromStream( fileStream );
      Application::DoEvents();
      fileStream->Close();
      
      // Call Sleep so the picture is briefly displayed, 
      //which will create a slide-show effect.
      System::Threading::Thread::Sleep( 2000 );
   }
   PictureBox1->Image = nullptr;
}
private void InitializePictureBox()
{
	this.pictureBox1 = new System.Windows.Forms.PictureBox();
	this.pictureBox1.BorderStyle = 
		System.Windows.Forms.BorderStyle.FixedSingle;
	this.pictureBox1.SizeMode = PictureBoxSizeMode.StretchImage;
	this.pictureBox1.Location = new System.Drawing.Point(72, 112);
	this.pictureBox1.Name = "pictureBox1";
	this.pictureBox1.Size = new System.Drawing.Size(160, 136);
	this.pictureBox1.TabIndex = 6;
	this.pictureBox1.TabStop = false;
}

private void InitializeOpenFileDialog()
{
	this.openFileDialog1 = new System.Windows.Forms.OpenFileDialog();

	// Set the file dialog to filter for graphics files.
	this.openFileDialog1.Filter = 
		"Images (*.BMP;*.JPG;*.GIF)|*.BMP;*.JPG;*.GIF|" + 
		"All files (*.*)|*.*";

	// Allow the user to select multiple images.
	this.openFileDialog1.Multiselect = true;
	this.openFileDialog1.Title = "My Image Browser";
	
}

private void fileButton_Click(System.Object sender, System.EventArgs e)
{
	openFileDialog1.ShowDialog();
}


// This method handles the FileOK event.  It opens each file 
// selected and loads the image from a stream into pictureBox1.
private void openFileDialog1_FileOk(object sender, 
	System.ComponentModel.CancelEventArgs e)
{

	this.Activate();
	 string[] files = openFileDialog1.FileNames;

	// Open each file and display the image in pictureBox1.
	// Call Application.DoEvents to force a repaint after each
	// file is read.        
	foreach (string file in files )
	{
		System.IO.FileInfo fileInfo = new System.IO.FileInfo(file);
		System.IO.FileStream fileStream = fileInfo.OpenRead();
		pictureBox1.Image = System.Drawing.Image.FromStream(fileStream);
		Application.DoEvents();
		fileStream.Close();

		// Call Sleep so the picture is briefly displayed, 
		//which will create a slide-show effect.
		System.Threading.Thread.Sleep(2000);
	}
	pictureBox1.Image = null;
}
Private Sub InitializePictureBox()
    Me.PictureBox1 = New System.Windows.Forms.PictureBox
    Me.PictureBox1.BorderStyle = _
        System.Windows.Forms.BorderStyle.FixedSingle
    Me.PictureBox1.SizeMode = PictureBoxSizeMode.StretchImage
    Me.PictureBox1.Location = New System.Drawing.Point(72, 112)
    Me.PictureBox1.Name = "PictureBox1"
    Me.PictureBox1.Size = New System.Drawing.Size(160, 136)
    Me.PictureBox1.TabStop = False
End Sub

Private Sub InitializeOpenFileDialog()
    Me.OpenFileDialog1 = New System.Windows.Forms.OpenFileDialog

    ' Set the file dialog to filter for graphics files.
    Me.OpenFileDialog1.Filter = _
    "Images (*.BMP;*.JPG;*.GIF)|*.BMP;*.JPG;*.GIF|All files (*.*)|*.*"

    ' Allow the user to select multiple images.
    Me.OpenFileDialog1.Multiselect = True
    Me.OpenFileDialog1.Title = "My Image Browser"
End Sub

Private Sub fileButton_Click(ByVal sender As System.Object, _
    ByVal e As System.EventArgs) Handles FileButton.Click
    OpenFileDialog1.ShowDialog()
End Sub


' This method handles the FileOK event.  It opens each file 
' selected and loads the image from a stream into PictureBox1.
Private Sub OpenFileDialog1_FileOk(ByVal sender As Object, _
ByVal e As System.ComponentModel.CancelEventArgs) _
 Handles OpenFileDialog1.FileOk

    Me.Activate()
    Dim file, files() As String
    files = OpenFileDialog1.FileNames

    ' Open each file and display the image in PictureBox1.
    ' Call Application.DoEvents to force a repaint after each
    ' file is read.        
    For Each file In files
        Dim fileInfo As System.IO.FileInfo = New System.IO.FileInfo(file)
        Dim fileStream As System.IO.FileStream = fileInfo.OpenRead()
        PictureBox1.Image = System.Drawing.Image.FromStream(fileStream)
        Application.DoEvents()
        fileStream.Close()

        ' Call Sleep so the picture is briefly displayed, 
        'which will create a slide-show effect.
        System.Threading.Thread.Sleep(2000)
    Next
    PictureBox1.Image = Nothing
End Sub

Hinweise

Wenn Sie ein Windows-Formular ausführen, wird das neue Formular, das dann zu behandelnden Ereignisse wartet.When you run a Windows Form, it creates the new form, which then waits for events to handle. Jedes Mal das Formular ein Ereignis behandelt wird, wird alle diesem Ereignis zugeordneten Code verarbeitet.Each time the form handles an event, it processes all the code associated with that event. Alle anderen Ereignisse werden in der Warteschlange warten.All other events wait in the queue. Während der Code das Ereignis behandelt, reagiert die Anwendung nicht.While your code handles the event, your application does not respond. Das Fenster ist z. B. nicht neu aufgebaut, wenn ein anderes Fenster im Vordergrund gezogen wird.For example, the window does not repaint if another window is dragged on top.

Wenn Sie aufrufen DoEvents in Ihrem Code Ihrer Anwendung kann die anderen Ereignisse behandelt.If you call DoEvents in your code, your application can handle the other events. Angenommen, Sie haben ein Formular, mit dem Hinzufügen von Daten in einem ListBox und fügen DoEvents an Ihrem Code, das Formular neu aufgebaut, wenn ein anderes Fenster darüber gezogen wird.For example, if you have a form that adds data to a ListBox and add DoEvents to your code, your form repaints when another window is dragged over it. Wenn Sie entfernen DoEvents aus Ihrem Code das Formular nicht neu aufgebaut, bis zum Abschluss der Click-Ereignishandler der Schaltfläche ausführen.If you remove DoEvents from your code, your form will not repaint until the click event handler of the button is finished executing. Weitere Informationen zu messaging, finden Sie unter Benutzereingaben in Windows Forms.For more information on messaging, see User Input in Windows Forms.

Im Gegensatz zu Visual Basic 6.0 die DoEvents Methode ruft nicht die Thread.Sleep Methode.Unlike Visual Basic 6.0, the DoEvents method does not call the Thread.Sleep method.

In der Regel verwenden Sie diese Methode in einer Schleife zum Verarbeiten von Nachrichten an.Typically, you use this method in a loop to process messages.

Achtung

Das Aufrufen dieser Methode wird der aktuelle Thread angehalten werden soll, während alle wartenden fenstermeldungen verarbeitet werden.Calling this method causes the current thread to be suspended while all waiting window messages are processed. Wenn eine Nachricht bewirkt, ein Ereignis dass ausgelöst wird, können andere Bereiche des Anwendungscodes führen.If a message causes an event to be triggered, then other areas of your application code may execute. Dadurch kann Ihre Anwendung zu unerwarteten Verhaltensweisen, die schwer zu debuggen sind.This can cause your application to exhibit unexpected behaviors that are difficult to debug. Wenn Sie ausführen, Vorgänge oder Berechnungen, die eine lange Zeit in Anspruch nehmen, ist es oft besser, diese Vorgänge in einem neuen Thread ausführen.If you perform operations or computations that take a long time, it is often preferable to perform those operations on a new thread. Weitere Informationen zur asynchronen Programmierung finden Sie unter Asynchronous Programming Model (APM).For more information about asynchronous programming, see Asynchronous Programming Model (APM).

Gilt für:

Siehe auch