TreeView.CheckBoxes Propiedad
Definición
Importante
Parte de la información hace referencia a la versión preliminar del producto, que puede haberse modificado sustancialmente antes de lanzar la versión definitiva. Microsoft no otorga ninguna garantía, explícita o implícita, con respecto a la información proporcionada aquí.
Obtiene o establece un valor que indica si se muestran casillas al lado de los nodos de árbol del control de vista de árbol.
public:
property bool CheckBoxes { bool get(); void set(bool value); };public bool CheckBoxes { get; set; }member this.CheckBoxes : bool with get, setPublic Property CheckBoxes As BooleanValor de propiedad
Es true si se muestra una casilla al lado de cada nodo de árbol del control de vista de árbol; en caso contrario, es false. De manera predeterminada, es false.
Ejemplos
En el ejemplo de código siguiente se muestra cómo cambiar el estado de contracción de para TreeView que todos los nodos comprobados estén visibles. En primer lugar, se contraen todos los nodos y se agrega un controlador para el BeforeExpand evento. A continuación, se expanden todos los nodos. El BeforeExpand controlador de eventos determina si un nodo determinado tiene nodos secundarios que se comprueban. Si un nodo no tiene elementos secundarios comprobados, la expansión se cancela para ese nodo. Para permitir la expansión de nodos estándar cuando se hace clic en el signo más junto a un nodo, se quita el BeforeExpand controlador de eventos.
Este comportamiento también se puede implementar controlando el BeforeCollapse evento, como se muestra en el ejemplo de ese tema.
#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 Form1: public Form
{
private:
TreeView^ treeView1;
Button^ showCheckedNodesButton;
TreeViewCancelEventHandler^ checkForCheckedChildren;
public:
Form1()
{
treeView1 = gcnew TreeView;
showCheckedNodesButton = gcnew Button;
checkForCheckedChildren = gcnew TreeViewCancelEventHandler( this, &Form1::CheckForCheckedChildrenHandler );
this->SuspendLayout();
// Initialize treeView1.
treeView1->Location = Point(0,25);
treeView1->Size = System::Drawing::Size( 292, 248 );
treeView1->Anchor = static_cast<AnchorStyles>(AnchorStyles::Top | AnchorStyles::Left | AnchorStyles::Bottom | AnchorStyles::Right);
treeView1->CheckBoxes = true;
// Add nodes to treeView1.
TreeNode^ node;
for ( int x = 0; x < 3; ++x )
{
// Add a root node.
node = treeView1->Nodes->Add( String::Format( "Node{0}", x * 4 ) );
for ( int y = 1; y < 4; ++y )
{
// Add a node as a child of the previously added node.
node = node->Nodes->Add( String::Format( "Node{0}", x * 4 + y ) );
}
}
// Set the checked state of one of the nodes to
// demonstrate the showCheckedNodesButton button behavior.
treeView1->Nodes[ 1 ]->Nodes[ 0 ]->Nodes[ 0 ]->Checked = true;
// Initialize showCheckedNodesButton.
showCheckedNodesButton->Size = System::Drawing::Size( 144, 24 );
showCheckedNodesButton->Text = "Show Checked Nodes";
showCheckedNodesButton->Click += gcnew EventHandler( this, &Form1::showCheckedNodesButton_Click );
// Initialize the form.
this->ClientSize = System::Drawing::Size( 292, 273 );
array<Control^>^temp0 = {showCheckedNodesButton,treeView1};
this->Controls->AddRange( temp0 );
this->ResumeLayout( false );
}
private:
void showCheckedNodesButton_Click( Object^ /*sender*/, EventArgs^ /*e*/ )
{
// Disable redrawing of treeView1 to prevent flickering
// while changes are made.
treeView1->BeginUpdate();
// Collapse all nodes of treeView1.
treeView1->CollapseAll();
// Add the checkForCheckedChildren event handler to the BeforeExpand event.
treeView1->BeforeExpand += checkForCheckedChildren;
// Expand all nodes of treeView1. Nodes without checked children are
// prevented from expanding by the checkForCheckedChildren event handler.
treeView1->ExpandAll();
// Remove the checkForCheckedChildren event handler from the BeforeExpand
// event so manual node expansion will work correctly.
treeView1->BeforeExpand -= checkForCheckedChildren;
// Enable redrawing of treeView1.
treeView1->EndUpdate();
}
// Prevent expansion of a node that does not have any checked child nodes.
void CheckForCheckedChildrenHandler( Object^ /*sender*/, TreeViewCancelEventArgs^ e )
{
if ( !HasCheckedChildNodes( e->Node ) )
e->Cancel = true;
}
// Returns a value indicating whether the specified
// TreeNode has checked child nodes.
bool HasCheckedChildNodes( TreeNode^ node )
{
if ( node->Nodes->Count == 0 )
return false;
System::Collections::IEnumerator^ myEnum = node->Nodes->GetEnumerator();
while ( myEnum->MoveNext() )
{
TreeNode^ childNode = safe_cast<TreeNode^>(myEnum->Current);
if ( childNode->Checked )
return true;
// Recursively check the children of the current child node.
if ( HasCheckedChildNodes( childNode ) )
return true;
}
return false;
}
};
int main()
{
Application::Run( gcnew Form1 );
}
using System;
using System.Drawing;
using System.Windows.Forms;
public class Form1 : Form
{
private TreeView treeView1;
private Button showCheckedNodesButton;
private TreeViewCancelEventHandler checkForCheckedChildren;
public Form1()
{
treeView1 = new TreeView();
showCheckedNodesButton = new Button();
checkForCheckedChildren =
new TreeViewCancelEventHandler(CheckForCheckedChildrenHandler);
this.SuspendLayout();
// Initialize treeView1.
treeView1.Location = new Point(0, 25);
treeView1.Size = new Size(292, 248);
treeView1.Anchor = AnchorStyles.Top | AnchorStyles.Left |
AnchorStyles.Bottom | AnchorStyles.Right;
treeView1.CheckBoxes = true;
// Add nodes to treeView1.
TreeNode node;
for (int x = 0; x < 3; ++x)
{
// Add a root node.
node = treeView1.Nodes.Add(String.Format("Node{0}", x*4));
for (int y = 1; y < 4; ++y)
{
// Add a node as a child of the previously added node.
node = node.Nodes.Add(String.Format("Node{0}", x*4 + y));
}
}
// Set the checked state of one of the nodes to
// demonstrate the showCheckedNodesButton button behavior.
treeView1.Nodes[1].Nodes[0].Nodes[0].Checked = true;
// Initialize showCheckedNodesButton.
showCheckedNodesButton.Size = new Size(144, 24);
showCheckedNodesButton.Text = "Show Checked Nodes";
showCheckedNodesButton.Click +=
new EventHandler(showCheckedNodesButton_Click);
// Initialize the form.
this.ClientSize = new Size(292, 273);
this.Controls.AddRange(new Control[]
{ showCheckedNodesButton, treeView1 } );
this.ResumeLayout(false);
}
[STAThreadAttribute()]
static void Main()
{
Application.Run(new Form1());
}
private void showCheckedNodesButton_Click(object sender, EventArgs e)
{
// Disable redrawing of treeView1 to prevent flickering
// while changes are made.
treeView1.BeginUpdate();
// Collapse all nodes of treeView1.
treeView1.CollapseAll();
// Add the checkForCheckedChildren event handler to the BeforeExpand event.
treeView1.BeforeExpand += checkForCheckedChildren;
// Expand all nodes of treeView1. Nodes without checked children are
// prevented from expanding by the checkForCheckedChildren event handler.
treeView1.ExpandAll();
// Remove the checkForCheckedChildren event handler from the BeforeExpand
// event so manual node expansion will work correctly.
treeView1.BeforeExpand -= checkForCheckedChildren;
// Enable redrawing of treeView1.
treeView1.EndUpdate();
}
// Prevent expansion of a node that does not have any checked child nodes.
private void CheckForCheckedChildrenHandler(object sender,
TreeViewCancelEventArgs e)
{
if (!HasCheckedChildNodes(e.Node)) e.Cancel = true;
}
// Returns a value indicating whether the specified
// TreeNode has checked child nodes.
private bool HasCheckedChildNodes(TreeNode node)
{
if (node.Nodes.Count == 0) return false;
foreach (TreeNode childNode in node.Nodes)
{
if (childNode.Checked) return true;
// Recursively check the children of the current child node.
if (HasCheckedChildNodes(childNode)) return true;
}
return false;
}
}
Imports System.Drawing
Imports System.Windows.Forms
Public Class Form1
Inherits Form
Private treeView1 As TreeView
Private showCheckedNodesButton As Button
Public Sub New()
treeView1 = New TreeView
showCheckedNodesButton = New Button
Me.SuspendLayout()
' Initialize treeView1.
treeView1.Location = New Point(0, 25)
treeView1.Size = New Size(292, 248)
treeView1.Anchor = AnchorStyles.Top Or AnchorStyles.Left Or AnchorStyles.Bottom Or AnchorStyles.Right
treeView1.CheckBoxes = True
' Add nodes to treeView1.
Dim node As TreeNode
Dim x As Integer
For x = 0 To 3
' Add a root node.
node = treeView1.Nodes.Add(String.Format("Node{0}", x * 4))
Dim y As Integer
For y = 1 To 4
' Add a node as a child of the previously added node.
node = node.Nodes.Add(String.Format("Node{0}", x * 4 + y))
Next y
Next x
' Set the checked state of one of the nodes to
' demonstrate the showCheckedNodesButton button behavior.
treeView1.Nodes(1).Nodes(0).Nodes(0).Checked = True
' Initialize showCheckedNodesButton.
showCheckedNodesButton.Size = New Size(144, 24)
showCheckedNodesButton.Text = "Show Checked Nodes"
AddHandler showCheckedNodesButton.Click, AddressOf showCheckedNodesButton_Click
' Initialize the form.
Me.ClientSize = New Size(292, 273)
Me.Controls.AddRange(New Control() {showCheckedNodesButton, treeView1})
Me.ResumeLayout(False)
End Sub
<STAThreadAttribute()> _
Shared Sub Main()
Application.Run(New Form1)
End Sub
Private Sub showCheckedNodesButton_Click(ByVal sender As Object, ByVal e As EventArgs)
' Disable redrawing of treeView1 to prevent flickering
' while changes are made.
treeView1.BeginUpdate()
' Collapse all nodes of treeView1.
treeView1.CollapseAll()
' Add the CheckForCheckedChildren event handler to the BeforeExpand event.
AddHandler treeView1.BeforeExpand, AddressOf CheckForCheckedChildren
' Expand all nodes of treeView1. Nodes without checked children are
' prevented from expanding by the checkForCheckedChildren event handler.
treeView1.ExpandAll()
' Remove the checkForCheckedChildren event handler from the BeforeExpand
' event so manual node expansion will work correctly.
RemoveHandler treeView1.BeforeExpand, AddressOf CheckForCheckedChildren
' Enable redrawing of treeView1.
treeView1.EndUpdate()
End Sub
' Prevent expansion of a node that does not have any checked child nodes.
Private Sub CheckForCheckedChildren(ByVal sender As Object, ByVal e As TreeViewCancelEventArgs)
If Not HasCheckedChildNodes(e.Node) Then
e.Cancel = True
End If
End Sub
' Returns a value indicating whether the specified
' TreeNode has checked child nodes.
Private Function HasCheckedChildNodes(ByVal node As TreeNode) As Boolean
If node.Nodes.Count = 0 Then
Return False
End If
Dim childNode As TreeNode
For Each childNode In node.Nodes
If childNode.Checked Then
Return True
End If
' Recursively check the children of the current child node.
If HasCheckedChildNodes(childNode) Then
Return True
End If
Next childNode
Return False
End Function 'HasCheckedChildNodes
End Class
Comentarios
Se muestra una casilla a la izquierda de la etiqueta del nodo de árbol y del nodo Imagede árbol , si existe. Las casillas permiten al usuario seleccionar más de un nodo de árbol a la vez.
Cuando la CheckBoxes propiedad de se TreeView establece trueen y la StateImageList propiedad se establece, cada TreeNode una de las cuales se encuentra en muestra TreeView la primera y la segunda imagen de StateImageList para indicar un estado no comprobado o comprobado, respectivamente. Sin embargo, las imágenes mostradas pueden ser diferentes si se produce la siguiente situación: si el SelectedImageIndex del nodo está establecido en un valor distinto de 0 o 1, y la CheckBoxes propiedad del elemento primario TreeView se establece falseen , no SelectedImageIndex se restablecerá automáticamente a -1 para indicar que no está establecida. En este caso, se muestra la imagen de estado en la posición de índice indicada. Si CheckBoxes se establece true en otra vez, se muestran las primeras y segundas imágenes de StateImageList para indicar un estado activado o desactivado, respectivamente.
Nota
Al establecer la CheckBoxes propiedad en tiempo de ejecución, se vuelve a crear el TreeView identificador (vea Control.RecreateHandle) para actualizar la apariencia del control. Esto hace que todos los nodos de árbol se contraigan, con la excepción del seleccionado TreeNode.
