TreeView.DrawNode Kejadian
Definisi
Penting
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Terjadi ketika digambar TreeView dan DrawMode properti diatur ke TreeViewDrawMode nilai selain Normal.
public:
event System::Windows::Forms::DrawTreeNodeEventHandler ^ DrawNode;public event System.Windows.Forms.DrawTreeNodeEventHandler DrawNode;public event System.Windows.Forms.DrawTreeNodeEventHandler? DrawNode;member this.DrawNode : System.Windows.Forms.DrawTreeNodeEventHandler Public Custom Event DrawNode As DrawTreeNodeEventHandler Jenis Acara
Contoh
Contoh kode berikut menunjukkan cara mengkustomisasi TreeView kontrol menggunakan gambar pemilik. TreeView Kontrol dalam contoh menampilkan tag simpul opsional bersama label simpul standar. Tag simpul ditentukan dengan menggunakan TreeNode.Tag properti . Kontrol ini TreeView juga menggunakan warna kustom, yang mencakup warna sorotan kustom.
Anda dapat menyesuaikan sebagian TreeView besar warna dengan mengatur properti warna, tetapi warna sorotan pilihan tidak tersedia sebagai properti. Selain itu, persegi panjang sorotan pilihan default hanya meluas di sekitar label simpul. Gambar pemilik harus digunakan untuk menggambar tag simpul dan untuk menggambar persegi panjang sorotan yang disesuaikan cukup besar untuk menyertakan tag simpul.
Dalam contoh, handler untuk DrawNode peristiwa menggambar tag node dan sorotan pilihan kustom secara manual. Simpul yang tidak dipilih tidak memerlukan penyesuaian. Untuk ini, DrawTreeNodeEventArgs.DrawDefault properti diatur ke true sehingga mereka akan digambar oleh sistem operasi.
Selain itu, handler untuk peristiwa menyediakan MouseDown pengujian hit. Secara default, simpul hanya dapat dipilih dengan mengklik wilayah di sekitar labelnya. Penanganan MouseDown aktivitas memilih simpul yang diklik di mana saja dalam wilayah ini atau di dalam wilayah di sekitar tag simpul, jika ada.
#using <System.dll>
#using <System.Windows.Forms.dll>
#using <System.Drawing.dll>
using namespace System;
using namespace System::Drawing;
using namespace System::Windows::Forms;
public ref class TreeViewOwnerDraw: public Form
{
private:
TreeView^ myTreeView;
// Create a Font object for the node tags.
System::Drawing::Font^ tagFont;
public:
TreeViewOwnerDraw()
{
tagFont = gcnew System::Drawing::Font( "Helvetica",8,FontStyle::Bold );
// Create and initialize the TreeView control.
myTreeView = gcnew TreeView;
myTreeView->Dock = DockStyle::Fill;
myTreeView->BackColor = Color::Tan;
myTreeView->CheckBoxes = true;
// Add nodes to the TreeView control.
TreeNode^ node;
for ( int x = 1; x < 4; ++x )
{
// Add a root node to the TreeView control.
node = myTreeView->Nodes->Add( String::Format( "Task {0}", x ) );
for ( int y = 1; y < 4; ++y )
{
// Add a child node to the root node.
node->Nodes->Add( String::Format( "Subtask {0}", y ) );
}
}
myTreeView->ExpandAll();
// Add tags containing alert messages to a few nodes
// and set the node background color to highlight them.
myTreeView->Nodes[ 1 ]->Nodes[ 0 ]->Tag = "urgent!";
myTreeView->Nodes[ 1 ]->Nodes[ 0 ]->BackColor = Color::Yellow;
myTreeView->SelectedNode = myTreeView->Nodes[ 1 ]->Nodes[ 0 ];
myTreeView->Nodes[ 2 ]->Nodes[ 1 ]->Tag = "urgent!";
myTreeView->Nodes[ 2 ]->Nodes[ 1 ]->BackColor = Color::Yellow;
// Configure the TreeView control for owner-draw and add
// a handler for the DrawNode event.
myTreeView->DrawMode = TreeViewDrawMode::OwnerDrawText;
myTreeView->DrawNode += gcnew DrawTreeNodeEventHandler( this, &TreeViewOwnerDraw::myTreeView_DrawNode );
// Add a handler for the MouseDown event so that a node can be
// selected by clicking the tag text as well as the node text.
myTreeView->MouseDown += gcnew MouseEventHandler( this, &TreeViewOwnerDraw::myTreeView_MouseDown );
// Initialize the form and add the TreeView control to it.
this->ClientSize = System::Drawing::Size( 292, 273 );
this->Controls->Add( myTreeView );
}
protected:
// Clean up any resources being used.
~TreeViewOwnerDraw()
{
if ( tagFont != nullptr )
{
delete tagFont;
}
}
// 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);
}
}
}
// Selects a node that is clicked on its label or tag text.
void myTreeView_MouseDown( Object^ /*sender*/, MouseEventArgs^ e )
{
TreeNode^ clickedNode = myTreeView->GetNodeAt( e->X, e->Y );
if ( NodeBounds( clickedNode ).Contains( e->X, e->Y ) )
{
myTreeView->SelectedNode = clickedNode;
}
}
// Returns the bounds of the specified node, including the region
// occupied by the node label and any node tag displayed.
Rectangle NodeBounds( TreeNode^ node )
{
// Set the return value to the normal node bounds.
Rectangle bounds = node->Bounds;
if ( node->Tag != nullptr )
{
// Retrieve a Graphics object from the TreeView handle
// and use it to calculate the display width of the tag.
Graphics^ g = myTreeView->CreateGraphics();
int tagWidth = (int)g->MeasureString( node->Tag->ToString(), tagFont ).Width + 6;
// Adjust the node bounds using the calculated value.
bounds.Offset( tagWidth / 2, 0 );
bounds = Rectangle::Inflate( bounds, tagWidth / 2, 0 );
g->~Graphics();
}
return bounds;
}
};
[STAThreadAttribute]
int main()
{
Application::Run( gcnew TreeViewOwnerDraw );
}
using System;
using System.Drawing;
using System.Windows.Forms;
public class TreeViewOwnerDraw : Form
{
private TreeView myTreeView;
// Create a Font object for the node tags.
Font tagFont = new Font("Helvetica", 8, FontStyle.Bold);
public TreeViewOwnerDraw()
{
// Create and initialize the TreeView control.
myTreeView = new TreeView();
myTreeView.Dock = DockStyle.Fill;
myTreeView.BackColor = Color.Tan;
myTreeView.CheckBoxes = true;
// Add nodes to the TreeView control.
TreeNode node;
for (int x = 1; x < 4; ++x)
{
// Add a root node to the TreeView control.
node = myTreeView.Nodes.Add(String.Format("Task {0}", x));
for (int y = 1; y < 4; ++y)
{
// Add a child node to the root node.
node.Nodes.Add(String.Format("Subtask {0}", y));
}
}
myTreeView.ExpandAll();
// Add tags containing alert messages to a few nodes
// and set the node background color to highlight them.
myTreeView.Nodes[1].Nodes[0].Tag = "urgent!";
myTreeView.Nodes[1].Nodes[0].BackColor = Color.Yellow;
myTreeView.SelectedNode = myTreeView.Nodes[1].Nodes[0];
myTreeView.Nodes[2].Nodes[1].Tag = "urgent!";
myTreeView.Nodes[2].Nodes[1].BackColor = Color.Yellow;
// Configure the TreeView control for owner-draw and add
// a handler for the DrawNode event.
myTreeView.DrawMode = TreeViewDrawMode.OwnerDrawText;
myTreeView.DrawNode +=
new DrawTreeNodeEventHandler(myTreeView_DrawNode);
// Add a handler for the MouseDown event so that a node can be
// selected by clicking the tag text as well as the node text.
myTreeView.MouseDown += new MouseEventHandler(myTreeView_MouseDown);
// Initialize the form and add the TreeView control to it.
this.ClientSize = new Size(292, 273);
this.Controls.Add(myTreeView);
}
// Clean up any resources being used.
protected override void Dispose(bool disposing)
{
if (disposing)
{
tagFont.Dispose();
}
base.Dispose(disposing);
}
[STAThreadAttribute()]
static void Main()
{
Application.Run(new TreeViewOwnerDraw());
}
// 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);
}
}
}
// Selects a node that is clicked on its label or tag text.
private void myTreeView_MouseDown(object sender, MouseEventArgs e)
{
TreeNode clickedNode = myTreeView.GetNodeAt(e.X, e.Y);
if (NodeBounds(clickedNode).Contains(e.X, e.Y))
{
myTreeView.SelectedNode = clickedNode;
}
}
// Returns the bounds of the specified node, including the region
// occupied by the node label and any node tag displayed.
private Rectangle NodeBounds(TreeNode node)
{
// Set the return value to the normal node bounds.
Rectangle bounds = node.Bounds;
if (node.Tag != null)
{
// Retrieve a Graphics object from the TreeView handle
// and use it to calculate the display width of the tag.
Graphics g = myTreeView.CreateGraphics();
int tagWidth = (int)g.MeasureString
(node.Tag.ToString(), tagFont).Width + 6;
// Adjust the node bounds using the calculated value.
bounds.Offset(tagWidth/2, 0);
bounds = Rectangle.Inflate(bounds, tagWidth/2, 0);
g.Dispose();
}
return bounds;
}
}
Imports System.Drawing
Imports System.Windows.Forms
Public Class TreeViewOwnerDraw
Inherits Form
Private WithEvents myTreeView As TreeView
' Create a Font object for the node tags.
Private tagFont As New Font("Helvetica", 8, FontStyle.Bold)
Public Sub New()
' Create and initialize the TreeView control.
myTreeView = New TreeView()
myTreeView.Dock = DockStyle.Fill
myTreeView.BackColor = Color.Tan
myTreeView.CheckBoxes = True
' Add nodes to the TreeView control.
Dim node As TreeNode
Dim x As Integer
For x = 1 To 3
' Add a root node to the TreeView control.
node = myTreeView.Nodes.Add(String.Format("Task {0}", x))
Dim y As Integer
For y = 1 To 3
' Add a child node to the root node.
node.Nodes.Add(String.Format("Subtask {0}", y))
Next y
Next x
myTreeView.ExpandAll()
' Add tags containing alert messages to a few nodes
' and set the node background color to highlight them.
myTreeView.Nodes(1).Nodes(0).Tag = "urgent!"
myTreeView.Nodes(1).Nodes(0).BackColor = Color.Yellow
myTreeView.SelectedNode = myTreeView.Nodes(1).Nodes(0)
myTreeView.Nodes(2).Nodes(1).Tag = "urgent!"
myTreeView.Nodes(2).Nodes(1).BackColor = Color.Yellow
' Configure the TreeView control for owner-draw.
myTreeView.DrawMode = TreeViewDrawMode.OwnerDrawText
' Add a handler for the MouseDown event so that a node can be
' selected by clicking the tag text as well as the node text.
AddHandler myTreeView.MouseDown, AddressOf myTreeView_MouseDown
' Initialize the form and add the TreeView control to it.
Me.ClientSize = New Size(292, 273)
Me.Controls.Add(myTreeView)
End Sub
<STAThreadAttribute()> _
Shared Sub Main()
Application.Run(New TreeViewOwnerDraw())
End Sub
' 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
' Selects a node that is clicked on its label or tag text.
Private Sub myTreeView_MouseDown(ByVal sender As Object, ByVal e As MouseEventArgs)
Dim clickedNode As TreeNode = myTreeView.GetNodeAt(e.X, e.Y)
If NodeBounds(clickedNode).Contains(e.X, e.Y) Then
myTreeView.SelectedNode = clickedNode
End If
End Sub
' Returns the bounds of the specified node, including the region
' occupied by the node label and any node tag displayed.
Private Function NodeBounds(ByVal node As TreeNode) As Rectangle
' Set the return value to the normal node bounds.
Dim bounds As Rectangle = node.Bounds
If (node.Tag IsNot Nothing) Then
' Retrieve a Graphics object from the TreeView handle
' and use it to calculate the display width of the tag.
Dim g As Graphics = myTreeView.CreateGraphics()
Dim tagWidth As Integer = CInt(g.MeasureString( _
node.Tag.ToString(), tagFont).Width) + 6
' Adjust the node bounds using the calculated value.
bounds.Offset(tagWidth \ 2, 0)
bounds = Rectangle.Inflate(bounds, tagWidth \ 2, 0)
g.Dispose()
End If
Return bounds
End Function 'NodeBounds
End Class
Keterangan
Gunakan kejadian ini untuk menyesuaikan tampilan simpul dalam TreeView kontrol menggunakan gambar pemilik.
Kejadian ini dinaikkan hanya ketika DrawMode properti diatur ke TreeViewDrawMode nilai OwnerDrawAll atau OwnerDrawText. Tabel berikut menunjukkan bagaimana TreeNode bisa dikustomisasi saat DrawMode properti diatur ke nilai-nilai ini.
| Nilai properti DrawMode | Kustomisasi TreeNode |
|---|---|
| OwnerDrawText | Area TreeNode label dapat disesuaikan. Semua elemen lainnya TreeNode digambar secara otomatis. |
| OwnerDrawAll | Tampilan seluruhnya TreeNode dapat disesuaikan. Ikon, kotak centang, tanda plus dan minus, dan garis yang menghubungkan simpul harus digambar secara manual jika diinginkan. |
Wilayah yang TreeNode.Text akan ditempati nilai jika digambar menggunakan font yang ditentukan oleh TreeView properti kontrol Font adalah wilayah tempat simpul dapat diklik untuk memilihnya. Ini disebut wilayah uji hit. Jika Anda menggambar di luar wilayah ini, Anda harus memberikan kode Anda sendiri yang memilih simpul saat area yang terlihat diklik.
Wilayah pengujian hit sesuai dengan DrawTreeNodeEventArgs.Bounds properti saat menggunakan OwnerDrawText. Namun, saat menggunakan OwnerDrawAll, DrawTreeNodeEventArgs.Bounds properti mencakup seluruh lebar TreeView. Dalam hal ini, Anda dapat mengakses wilayah pengujian hit dengan mendapatkan DrawTreeNodeEventArgs.Node nilai dan mengakses propertinya TreeNode.Bounds . Anda kemudian dapat menggambar wilayah pengujian hit node dalam batas ini, atau Anda dapat memberikan kode uji hit Anda sendiri. Perhatikan bahwa mengatur TreeNode.NodeFont properti tidak mengubah ukuran wilayah pengujian hit, yang dihitung menggunakan font yang ditentukan untuk seluruh TreeView.
Untuk informasi selengkapnya tentang cara menangani peristiwa, lihat Menangani dan Menaikkan Peristiwa.
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