DrawTreeNodeEventArgs.Graphics 属性
定义
重要
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public:
property System::Drawing::Graphics ^ Graphics { System::Drawing::Graphics ^ get(); };public System.Drawing.Graphics Graphics { get; }member this.Graphics : System.Drawing.GraphicsPublic ReadOnly Property Graphics As Graphics属性值
示例
下面的代码示例演示如何使用所有者绘图自定义 TreeView 控件。 TreeView示例中的 控件在标准节点标签旁边显示可选节点标记。 使用 TreeNode.Tag 属性指定节点标记。 控件 TreeView 还使用自定义颜色，包括自定义突出显示颜色。
可以通过设置颜色属性来自定义大多数 TreeView 颜色，但选择突出显示颜色不能作为属性使用。 此外，默认选择突出显示矩形仅围绕节点标签扩展。 必须使用所有者绘图来绘制节点标记，并绘制足够大以包含节点标记的自定义突出显示矩形。
在示例中，事件的处理程序 TreeView.DrawNode 手动绘制节点标记和自定义选择突出显示。 未选择的节点不需要自定义。 对于这些， DrawDefault 属性设置为 true ，以便由操作系统绘制它们。
有关完整示例，请参阅 DrawTreeNodeEventArgs 概述参考主题。
// 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
注解
类 Graphics 提供可用于在显示设备上绘图的属性和方法。
