Control.AllowDrop プロパティとは何？わかりやすく解説 Weblio辞書

.NET Framework クラスライブラリリファレンス

索引トップ用語の索引ランキング

Control.AllowDrop プロパティ

ユーザーがコントロールにドラッグしたデータを、そのコントロールが受け入れることができるかどうかを示す値を取得または設定します。

名前空間: System.Windows.Forms
アセンブリ: System.Windows.Forms (system.windows.forms.dll 内)
構文

Visual Basic (宣言)

Public Overridable Property
 AllowDrop As Boolean

Visual Basic (使用法)

Dim instance As Control
Dim value As Boolean

value = instance.AllowDrop

instance.AllowDrop = value

public virtual bool AllowDrop { get;
 set; }

C++

public:
virtual property bool AllowDrop {
    bool get ();
    void set (bool value);
}

/** @property */
public boolean get_AllowDrop ()

/** @property */
public void set_AllowDrop (boolean value)

JScript

public function get AllowDrop
 () : boolean

public function set AllowDrop
 (value : boolean)

プロパティ値
コントロールでドラッグアンドドロップ操作を実行できる場合は true。それ以外の場合は false。既定値は false です。

解説

継承時の注意 派生クラスで AllowDrop プロパティをオーバーライドする場合は、基本クラスの AllowDrop プロパティを使用して、基本の実装を拡張します。それ以外の場合は、すべての実装を提供する必要があります。AllowDrop プロパティの get アクセサと set アクセサの両方をオーバーライドする必要はありません。必要に応じて 1 つのアクセサだけをオーバーライドできます。

使用例

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コード例を次に示します。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。

Visual Basic

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

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 += 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.set_AllowDrop(true);
    this.add_DragDrop(new DragEventHandler(this.Form1_DragDrop));
    this.add_DragEnter(new DragEventHandler(this.Form1_DragEnter));
} //Form1

protected void OnPaint(PaintEventArgs e)
{
    // If there is an image and it has a location, 
    // paint it when the Form is repainted.
    super.OnPaint(e);
    if (this.picture != null
 && !this.pictureLocation.Equals(Point.Empty)) {
        e.get_Graphics().DrawImage(this.picture, this.pictureLocation);
    }
} //OnPaint

private void Form1_DragDrop(Object sender,
 DragEventArgs e)
{
    // Handle FileDrop data.
    if (e.get_Data().GetDataPresent(DataFormats.FileDrop)) {
        // Assign the file names to a string array, in 
        // case the user has selected multiple files.
        String files[] = (String[])(e.get_Data().GetData(
            DataFormats.FileDrop));
        try {
            // Assign the first image to the picture variable.
            this.picture = Image.FromFile(files.toString());
            // Set the picture location equal to the drop point.
            this.pictureLocation = this.PointToClient(new
 Point(e.get_X(), 
                e.get_Y()));
        }
        catch (System.Exception ex) {
            MessageBox.Show(ex.get_Message());
            return;
        }
    }
    // Handle Bitmap data.
    if (e.get_Data().GetDataPresent(DataFormats.Bitmap)) {
        try {
            // Create an Image and assign it to the picture variable.
            this.picture = (Image)e.get_Data().GetData(DataFormats.Bitmap);
            // Set the picture location equal to the drop point.
            this.pictureLocation = this.PointToClient(new
 Point(e.get_X(), 
                e.get_Y()));
        }
        catch (System.Exception ex) {
            MessageBox.Show(ex.get_Message());
            return;
        }
    }
    // Force the form to be redrawn with the image.
    this.Invalidate();
} //Form1_DragDrop

private void Form1_DragEnter(Object sender,
 DragEventArgs e)
{
    // If the data is a file or a bitmap, display the copy cursor.
    if (e.get_Data().GetDataPresent(DataFormats.Bitmap) || e.get_Data().
        GetDataPresent(DataFormats.FileDrop)) {
        e.set_Effect(DragDropEffects.Copy);
    }
    else {
        e.set_Effect(DragDropEffects.None);
    }
} //Form1_DragEnter