Control.OnPaint(PaintEventArgs) Metódus
Definíció
Fontos
Egyes információk olyan, kiadás előtti termékekre vonatkoznak, amelyek a kiadásig még jelentősen módosulhatnak. A Microsoft nem vállal kifejezett vagy törvényi garanciát az itt megjelenő információért.
Az eseményt emeli Paint ki.
protected:
virtual void OnPaint(System::Windows::Forms::PaintEventArgs ^ e);protected virtual void OnPaint(System.Windows.Forms.PaintEventArgs e);abstract member OnPaint : System.Windows.Forms.PaintEventArgs -> unit
override this.OnPaint : System.Windows.Forms.PaintEventArgs -> unitProtected Overridable Sub OnPaint (e As PaintEventArgs)Paraméterek
Az PaintEventArgs eseményadatokat tartalmazó A.
Példák
Az alábbi példakód lehetővé teszi, hogy a felhasználó egy képet vagy képfájlt húzzon az űrlapra, és megjelenítse azt azon a ponton, ahol az el lett vetve. A OnPaint metódus felül van bírálva a kép újrafestéséhez minden alkalommal, amikor az űrlap meg van festve; ellenkező esetben a kép csak a következő újrafestésig maradna fenn. Az DragEnter eseménykezelési módszer meghatározza az űrlapra húzott adatok típusát, és megadja a megfelelő visszajelzést. Az DragDrop eseménykezelési módszer megjeleníti a képet az űrlapon, ha az adatokból létre lehet hozni egy Image képet. Mivel az és DragEventArgs.X az DragEventArgs.Y értékek képernyőkoordináták, a példa a PointToClient metódus használatával konvertálja őket ügyfélkoordinátává.
private:
Image^ picture;
Point pictureLocation;
public:
Form1()
{
// Enable drag-and-drop operations and
// add handlers for DragEnter and DragDrop.
this->AllowDrop = true;
this->DragDrop += gcnew DragEventHandler( this, &Form1::Form1_DragDrop );
this->DragEnter += gcnew DragEventHandler( this, &Form1::Form1_DragEnter );
}
protected:
virtual void OnPaint( PaintEventArgs^ e ) override
{
// If there is an image and it has a location,
// paint it when the Form is repainted.
Form::OnPaint( e );
if ( this->picture != nullptr && this->pictureLocation != Point::Empty )
{
e->Graphics->DrawImage( this->picture, this->pictureLocation );
}
}
private:
void Form1_DragDrop( Object^ /*sender*/, DragEventArgs^ e )
{
// Handle FileDrop data.
if ( e->Data->GetDataPresent( DataFormats::FileDrop ) )
{
// Assign the file names to a String* array, in
// case the user has selected multiple files.
array<String^>^files = (array<String^>^)e->Data->GetData( DataFormats::FileDrop );
try
{
// Assign the first image to the picture variable.
this->picture = Image::FromFile( files[ 0 ] );
// Set the picture location equal to the drop point.
this->pictureLocation = this->PointToClient( Point(e->X,e->Y) );
}
catch ( Exception^ ex )
{
MessageBox::Show( ex->Message );
return;
}
}
// Handle Bitmap data.
if ( e->Data->GetDataPresent( DataFormats::Bitmap ) )
{
try
{
// Create an Image and assign it to the picture variable.
this->picture = dynamic_cast<Image^>(e->Data->GetData( DataFormats::Bitmap ));
// Set the picture location equal to the drop point.
this->pictureLocation = this->PointToClient( Point(e->X,e->Y) );
}
catch ( Exception^ ex )
{
MessageBox::Show( ex->Message );
return;
}
}
// Force the form to be redrawn with the image.
this->Invalidate();
}
void Form1_DragEnter( Object^ /*sender*/, DragEventArgs^ e )
{
// If the data is a file or a bitmap, display the copy cursor.
if ( e->Data->GetDataPresent( DataFormats::Bitmap ) || e->Data->GetDataPresent( DataFormats::FileDrop ) )
{
e->Effect = DragDropEffects::Copy;
}
else
{
e->Effect = DragDropEffects::None;
}
}
private Image picture;
private Point pictureLocation;
public Form1()
{
// Enable drag-and-drop operations and
// add handlers for DragEnter and DragDrop.
this.AllowDrop = true;
this.DragDrop += new DragEventHandler(this.Form1_DragDrop);
this.DragEnter += new DragEventHandler(this.Form1_DragEnter);
}
protected override void OnPaint(PaintEventArgs e)
{
// If there is an image and it has a location,
// paint it when the Form is repainted.
base.OnPaint(e);
if(this.picture != null && this.pictureLocation != Point.Empty)
{
e.Graphics.DrawImage(this.picture, this.pictureLocation);
}
}
private void Form1_DragDrop(object sender, DragEventArgs e)
{
// Handle FileDrop data.
if(e.Data.GetDataPresent(DataFormats.FileDrop) )
{
// Assign the file names to a string array, in
// case the user has selected multiple files.
string[] files = (string[])e.Data.GetData(DataFormats.FileDrop);
try
{
// Assign the first image to the picture variable.
this.picture = Image.FromFile(files[0]);
// Set the picture location equal to the drop point.
this.pictureLocation = this.PointToClient(new Point(e.X, e.Y) );
}
catch(Exception ex)
{
MessageBox.Show(ex.Message);
return;
}
}
// Handle Bitmap data.
if(e.Data.GetDataPresent(DataFormats.Bitmap) )
{
try
{
// Create an Image and assign it to the picture variable.
this.picture = (Image)e.Data.GetData(DataFormats.Bitmap);
// Set the picture location equal to the drop point.
this.pictureLocation = this.PointToClient(new Point(e.X, e.Y) );
}
catch(Exception ex)
{
MessageBox.Show(ex.Message);
return;
}
}
// Force the form to be redrawn with the image.
this.Invalidate();
}
private void Form1_DragEnter(object sender, DragEventArgs e)
{
// If the data is a file or a bitmap, display the copy cursor.
if (e.Data.GetDataPresent(DataFormats.Bitmap) ||
e.Data.GetDataPresent(DataFormats.FileDrop) )
{
e.Effect = DragDropEffects.Copy;
}
else
{
e.Effect = DragDropEffects.None;
}
}
Private picture As Image
Private pictureLocation As Point
Public Sub New()
' Enable drag-and-drop operations.
Me.AllowDrop = True
End Sub
Protected Overrides Sub OnPaint(ByVal e As PaintEventArgs)
MyBase.OnPaint(e)
' If there is an image and it has a location,
' paint it when the Form is repainted.
If (Me.picture IsNot Nothing) And _
Not (Me.pictureLocation.Equals(Point.Empty)) Then
e.Graphics.DrawImage(Me.picture, Me.pictureLocation)
End If
End Sub
Private Sub Form1_DragDrop(ByVal sender As Object, _
ByVal e As DragEventArgs) Handles MyBase.DragDrop
' Handle FileDrop data.
If e.Data.GetDataPresent(DataFormats.FileDrop) Then
' Assign the file names to a string array, in
' case the user has selected multiple files.
Dim files As String() = CType(e.Data.GetData(DataFormats.FileDrop), String())
Try
' Assign the first image to the 'picture' variable.
Me.picture = Image.FromFile(files(0))
' Set the picture location equal to the drop point.
Me.pictureLocation = Me.PointToClient(New Point(e.X, e.Y))
Catch ex As Exception
MessageBox.Show(ex.Message)
Return
End Try
End If
' Handle Bitmap data.
If e.Data.GetDataPresent(DataFormats.Bitmap) Then
Try
' Create an Image and assign it to the picture variable.
Me.picture = CType(e.Data.GetData(DataFormats.Bitmap), Image)
' Set the picture location equal to the drop point.
Me.pictureLocation = Me.PointToClient(New Point(e.X, e.Y))
Catch ex As Exception
MessageBox.Show(ex.Message)
Return
End Try
End If
' Force the form to be redrawn with the image.
Me.Invalidate()
End Sub
Private Sub Form1_DragEnter(ByVal sender As Object, _
ByVal e As DragEventArgs) Handles MyBase.DragEnter
' If the data is a file or a bitmap, display the copy cursor.
If e.Data.GetDataPresent(DataFormats.Bitmap) _
Or e.Data.GetDataPresent(DataFormats.FileDrop) Then
e.Effect = DragDropEffects.Copy
Else
e.Effect = DragDropEffects.None
End If
End Sub
// This example creates a PictureBox control on the form and draws to it.
// This example assumes that the Form_Load event handler method is
// connected to the Load event of the form.
private:
PictureBox^ pictureBox1;
void Form1_Load( Object^ /*sender*/, System::EventArgs^ /*e*/ )
{
pictureBox1 = gcnew PictureBox;
// Dock the PictureBox to the form and set its background to white.
pictureBox1->Dock = DockStyle::Fill;
pictureBox1->BackColor = Color::White;
// Connect the Paint event of the PictureBox to the event handler method.
pictureBox1->Paint += gcnew System::Windows::Forms::PaintEventHandler( this, &Form1::pictureBox1_Paint );
// Add the PictureBox control to the Form.
this->Controls->Add( pictureBox1 );
}
void pictureBox1_Paint( Object^ /*sender*/, System::Windows::Forms::PaintEventArgs^ e )
{
// Create a local version of the graphics object for the PictureBox.
Graphics^ g = e->Graphics;
// Draw a string on the PictureBox.
g->DrawString( "This is a diagonal line drawn on the control",
gcnew System::Drawing::Font( "Arial",10 ), System::Drawing::Brushes::Blue, Point(30,30) );
// Draw a line in the PictureBox.
g->DrawLine( System::Drawing::Pens::Red, pictureBox1->Left, pictureBox1->Top,
pictureBox1->Right, pictureBox1->Bottom );
}
// This example creates a PictureBox control on the form and draws to it.
// This example assumes that the Form_Load event handler method is
// connected to the Load event of the form.
private PictureBox pictureBox1 = new PictureBox();
// Cache font instead of recreating font objects each time we paint.
private Font fnt = new Font("Arial",10);
private void Form1_Load(object sender, System.EventArgs e)
{
// Dock the PictureBox to the form and set its background to white.
pictureBox1.Dock = DockStyle.Fill;
pictureBox1.BackColor = Color.White;
// Connect the Paint event of the PictureBox to the event handler method.
pictureBox1.Paint += new System.Windows.Forms.PaintEventHandler(this.pictureBox1_Paint);
// Add the PictureBox control to the Form.
this.Controls.Add(pictureBox1);
}
private void pictureBox1_Paint(object sender, System.Windows.Forms.PaintEventArgs e)
{
// Create a local version of the graphics object for the PictureBox.
Graphics g = e.Graphics;
// Draw a string on the PictureBox.
g.DrawString("This is a diagonal line drawn on the control",
fnt, System.Drawing.Brushes.Blue, new Point(30,30));
// Draw a line in the PictureBox.
g.DrawLine(System.Drawing.Pens.Red, pictureBox1.Left, pictureBox1.Top,
pictureBox1.Right, pictureBox1.Bottom);
}
' This example creates a PictureBox control on the form and draws to it.
' This example assumes that the Form_Load event handler method is connected
' to the Load event of the form.
Private pictureBox1 As New PictureBox()
Private fnt as New Font("Arial", 10)
Private Sub Form1_Load(ByVal sender As Object, ByVal e As System.EventArgs) Handles MyBase.Load
' Dock the PictureBox to the form and set its background to white.
pictureBox1.Dock = DockStyle.Fill
pictureBox1.BackColor = Color.White
' Connect the Paint event of the PictureBox to the event handler method.
AddHandler pictureBox1.Paint, AddressOf Me.pictureBox1_Paint
' Add the PictureBox control to the Form.
Me.Controls.Add(pictureBox1)
End Sub
Private Sub pictureBox1_Paint(ByVal sender As Object, ByVal e As System.Windows.Forms.PaintEventArgs)
' Create a local version of the graphics object for the PictureBox.
Dim g As Graphics = e.Graphics
' Draw a string on the PictureBox.
g.DrawString("This is a diagonal line drawn on the control", _
fnt, Brushes.Red, New PointF(30.0F, 30.0F))
' Draw a line in the PictureBox.
g.DrawLine(System.Drawing.Pens.Red, pictureBox1.Left, _
pictureBox1.Top, pictureBox1.Right, pictureBox1.Bottom)
End Sub
Megjegyzések
Az esemény létrehozása meghívja az eseménykezelőt egy meghatalmazotton keresztül. További információ: Események kezelése és emelése.
A OnPaint metódus lehetővé teszi a származtatott osztályok számára, hogy meghatalmazott csatolása nélkül kezeljék az eseményt. Ez az előnyben részesített módszer az esemény származtatott osztályban való kezelésére.
Megjegyzések az öröklőkhöz
Származtatott osztályban történő felülbíráláskor OnPaint(PaintEventArgs) mindenképpen hívja meg az alaposztály metódusát OnPaint(PaintEventArgs) , hogy a regisztrált meghatalmazottak megkapják az eseményt.
