Control.OnPaint メソッド

[アーティクル]
03/28/2008

Paint イベントを発生させます。

Protected Overridable Sub OnPaint( _
   ByVal e As PaintEventArgs _)
[C#]
protected virtual void OnPaint(PaintEventArgse);
[C++]
protected: virtual void OnPaint(PaintEventArgs* e);
[JScript]
protected function OnPaint(
   e : PaintEventArgs);

パラメータ

e
イベントデータを格納している PaintEventArgs 。

解説

イベントが発生すると、デリゲートを使用してイベントハンドラが呼び出されます。詳細については、「イベントの発生」を参照してください。

OnPaint メソッドを使用すると、デリゲートを結び付けずに、派生クラスでイベントを処理することもできます。派生クラスでイベントを処理する場合は、この手法をお勧めします。

継承時の注意: 派生クラスで OnPaint をオーバーライドする場合は、登録されているデリゲートがイベントを受け取ることができるように、基本クラスの OnPaint メソッドを呼び出してください。

使用例

[Visual Basic, C#, C++] ユーザーがイメージまたはイメージファイルをフォームにドラッグできるようにし、ドロップされた場所にそのイメージを表示する例を次に示します。 OnPaint メソッドは、フォームが描画されるたびにイメージを再描画するためオーバーライドされます。されない場合、イメージは次回の再描画までそのままの状態で残ります。 DragEnter イベント処理メソッドでは、フォームにドラッグされているデータの種類を判別し、適切なフィードバックを提供します。 DragDrop イベント処理メソッドでは、 Image をデータから作成できる場合に、フォーム上にイメージを表示します。 DragEventArgs.X および DragEventArgs.Y の値は画面座標であるため、この例では PointToClient メソッドを使用して値をクライアント座標に変換しています。

 
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 Not (Me.picture Is 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

[C#] 
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;
   }
}

[C++] 
private:
   Image*  picture;
   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::Form1_DragDrop);
      this->DragEnter += new DragEventHandler(this, &Form1::Form1_DragEnter);
   }

protected:
   void OnPaint(PaintEventArgs* e) {
      // If there is an image and it has a location,
      // paint it when the Form is repainted.
      Form::OnPaint(e);
      if (this->picture != 0 && 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( 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;
         }
   }

[Visual Basic] 
' This example creates a PictureBox control on the form and draws to it. 
' This example assumes that the Form_Load event handling method is connected 
' to the Load event of the form.
Private pictureBox1 As New PictureBox()

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 handling method.
    AddHandler pictureBox1.Paint, AddressOf Me.pictureBox1_Paint

    ' Add the PictureBox control to the Form.
    Me.Controls.Add(pictureBox1)
End Sub 'Form1_Load


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", _
        New Font("Arial", 10), 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 'pictureBox1_Paint

[C#] 
// This example creates a PictureBox control on the form and draws to it.
// This example assumes that the Form_Load event handling method is
// connected to the Load event of the form.

private PictureBox pictureBox1 = new PictureBox();
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 handling 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",
        new Font("Arial",10), 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);
}

[C++] 
// This example creates a PictureBox control on the form and draws to it.
// This example assumes that the Form_Load event handling method is
// connected to the Load event of the form.

private:
PictureBox* pictureBox1;

void Form1_Load(Object* /*sender*/, System::EventArgs* /*e*/)
{
   pictureBox1 = new 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 handling method.
   pictureBox1->Paint += new 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(S"This is a diagonal line drawn on the control",
      new System::Drawing::Font(S"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);
}

[JScript] JScript のサンプルはありません。Visual Basic、C#、および C++ のサンプルを表示するには、このページの左上隅にある言語のフィルタボタンをクリックします。

必要条件

プラットフォーム: Windows 98, Windows NT 4.0, Windows Millennium Edition, Windows 2000, Windows XP Home Edition, Windows XP Professional, Windows Server 2003 ファミリ, .NET Compact Framework - Windows CE .NET

参照

Control クラス | Control メンバ | System.Windows.Forms 名前空間 | Paint

Control.OnPaint メソッド

パラメータ

解説

使用例

必要条件

参照

その他のリソース