DrawTreeNodeEventArgs.DrawDefault Proprietà

Definizione

Spazio dei nomi:

System.Windows.Forms

Assembly:

System.Windows.Forms.dll

Origine:

DrawTreeNodeEventArgs.cs

Ottiene o imposta un valore che indica se l'oggetto TreeNode deve essere creato automaticamente invece che dal proprietario.

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

public bool DrawDefault { get; set; }

member this.DrawDefault : bool with get, set

Public Property DrawDefault As Boolean

Valore della proprietà

Boolean

true se il nodo deve essere creato automaticamente; false se il nodo deve essere creato nel gestore eventi. Il valore predefinito è false.

Esempio

Nell'esempio di codice seguente viene illustrato l'uso di questa proprietà. Nell'esempio un gestore per l'evento TreeView.DrawNode disegna manualmente il tag del nodo e un colore di evidenziazione personalizzato per il nodo selezionato. I nodi non selezionati non richiedono la personalizzazione. Per i nodi non selezionati, la DrawDefault proprietà è impostata su true in modo che vengano disegnate dal sistema operativo e non avrà un aspetto personalizzato.

Nota

Se si disegna un nodo manualmente e si imposta anche la DrawDefault proprietà su true, alcuni o tutti gli elementi di disegno potrebbero essere sovrascritti dal sistema operativo.

Per l'esempio completo, vedere l'argomento di DrawTreeNodeEventArgs riferimento di panoramica.

   // Draws a node.
private:
   void myTreeView_DrawNode( Object^ sender, DrawTreeNodeEventArgs^ e )
   {
      // Draw the background and node text for a selected node.
      if ( (e->State & TreeNodeStates::Selected) != (TreeNodeStates)0 )
      {
         // Draw the background of the selected node. The NodeBounds
         // method makes the highlight rectangle large enough to
         // include the text of a node tag, if one is present.
         e->Graphics->FillRectangle( Brushes::Green, NodeBounds( e->Node ) );

         // Retrieve the node font. If the node font has not been set,
         // use the TreeView font.
         System::Drawing::Font^ nodeFont = e->Node->NodeFont;
         if ( nodeFont == nullptr )
                  nodeFont = (dynamic_cast<TreeView^>(sender))->Font;

         // Draw the node text.
         e->Graphics->DrawString( e->Node->Text, nodeFont, Brushes::White, Rectangle::Inflate( e->Bounds, 2, 0 ) );
      }
      // Use the default background and node text.
      else
      {
         e->DrawDefault = true;
      }

      // If a node tag is present, draw its string representation 
      // to the right of the label text.
      if ( e->Node->Tag != nullptr )
      {
         e->Graphics->DrawString( e->Node->Tag->ToString(), tagFont, Brushes::Yellow, (float)e->Bounds.Right + 2, (float)e->Bounds.Top );
      }

      
      // If the node has focus, draw the focus rectangle large, making
      // it large enough to include the text of the node tag, if present.
      if ( (e->State & TreeNodeStates::Focused) != (TreeNodeStates)0 )
      {
         Pen^ focusPen = gcnew Pen( Color::Black );
         try
         {
            focusPen->DashStyle = System::Drawing::Drawing2D::DashStyle::Dot;
            Rectangle focusBounds = NodeBounds( e->Node );
            focusBounds.Size = System::Drawing::Size( focusBounds.Width - 1, focusBounds.Height - 1 );
            e->Graphics->DrawRectangle( focusPen, focusBounds );
         }
         finally
         {
            if ( focusPen )
               delete safe_cast<IDisposable^>(focusPen);
         }

      }
   }

// Draws a node.
private void myTreeView_DrawNode(
    object sender, DrawTreeNodeEventArgs e)
{
    // Draw the background and node text for a selected node.
    if ((e.State & TreeNodeStates.Selected) != 0)
    {
        // Draw the background of the selected node. The NodeBounds
        // method makes the highlight rectangle large enough to
        // include the text of a node tag, if one is present.
        e.Graphics.FillRectangle(Brushes.Green, NodeBounds(e.Node));

        // Retrieve the node font. If the node font has not been set,
        // use the TreeView font.
        Font nodeFont = e.Node.NodeFont;
        if (nodeFont == null) nodeFont = ((TreeView)sender).Font;

        // Draw the node text.
        e.Graphics.DrawString(e.Node.Text, nodeFont, Brushes.White,
            Rectangle.Inflate(e.Bounds, 2, 0));
    }

    // Use the default background and node text.
    else 
    {
        e.DrawDefault = true;
    }

    // If a node tag is present, draw its string representation 
    // to the right of the label text.
    if (e.Node.Tag != null)
    {
        e.Graphics.DrawString(e.Node.Tag.ToString(), tagFont,
            Brushes.Yellow, e.Bounds.Right + 2, e.Bounds.Top);
    }

    // If the node has focus, draw the focus rectangle large, making
    // it large enough to include the text of the node tag, if present.
    if ((e.State & TreeNodeStates.Focused) != 0)
    {
        using (Pen focusPen = new Pen(Color.Black))
        {
            focusPen.DashStyle = System.Drawing.Drawing2D.DashStyle.Dot;
            Rectangle focusBounds = NodeBounds(e.Node);
            focusBounds.Size = new Size(focusBounds.Width - 1, 
            focusBounds.Height - 1);
            e.Graphics.DrawRectangle(focusPen, focusBounds);
        }
    }
}

' Draws a node.
Private Sub myTreeView_DrawNode(ByVal sender As Object, _
    ByVal e As DrawTreeNodeEventArgs) Handles myTreeView.DrawNode

    ' Draw the background and node text for a selected node.
    If (e.State And TreeNodeStates.Selected) <> 0 Then

        ' Draw the background of the selected node. The NodeBounds
        ' method makes the highlight rectangle large enough to
        ' include the text of a node tag, if one is present.
        e.Graphics.FillRectangle(Brushes.Green, NodeBounds(e.Node))

        ' Retrieve the node font. If the node font has not been set,
        ' use the TreeView font.
        Dim nodeFont As Font = e.Node.NodeFont
        If nodeFont Is Nothing Then
            nodeFont = CType(sender, TreeView).Font
        End If

        ' Draw the node text.
        e.Graphics.DrawString(e.Node.Text, nodeFont, Brushes.White, _
            e.Bounds.Left - 2, e.Bounds.Top)

    ' Use the default background and node text.
    Else
        e.DrawDefault = True
    End If

    ' If a node tag is present, draw its string representation 
    ' to the right of the label text.
    If (e.Node.Tag IsNot Nothing) Then
        e.Graphics.DrawString(e.Node.Tag.ToString(), tagFont, _
            Brushes.Yellow, e.Bounds.Right + 2, e.Bounds.Top)
    End If

    ' If the node has focus, draw the focus rectangle large, making
    ' it large enough to include the text of the node tag, if present.
    If (e.State And TreeNodeStates.Focused) <> 0 Then
        Dim focusPen As New Pen(Color.Black)
        Try
            focusPen.DashStyle = System.Drawing.Drawing2D.DashStyle.Dot
            Dim focusBounds As Rectangle = NodeBounds(e.Node)
            focusBounds.Size = New Size(focusBounds.Width - 1, _
                focusBounds.Height - 1)
            e.Graphics.DrawRectangle(focusPen, focusBounds)
        Finally
            focusPen.Dispose()
        End Try
    End If

End Sub

Commenti

Impostare questa proprietà su true per i nodi che non si desidera personalizzare quando si gestisce l'evento DrawNode . Ad esempio, ciò è utile quando si desidera personalizzare solo i nodi che si trovano in uno stato specifico.