TreeView 构造函数
初始化 TreeView 类的新实例。
**命名空间:**System.Windows.Forms
**程序集:**System.Windows.Forms（在 system.windows.forms.dll 中）
语法
声明
Public Sub New
用法
Dim instance As New TreeView
public TreeView ()
public:
TreeView ()
public TreeView ()
public function TreeView ()
示例
下面的代码示例演示如何更改 TreeView 的折叠状态，以便所有选中的节点都可见。首先，展开所有节点，并为 BeforeCollapse 事件添加一个处理程序。然后，折叠所有节点。BeforeCollapse 事件处理程序确定给定节点是否有选中的子节点。如果某个节点有选中的子节点，则取消该节点的折叠操作。为了在单击节点旁边的减号时允许标准的节点折叠操作，BeforeCollapse 事件处理程序于是被移除。
此行为还可以通过处理 BeforeExpand 事件实现，该主题的示例中阐释了这一点。
Imports System
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 'New
<STAThreadAttribute()> _
Shared Sub Main()
Application.Run(New Form1())
End Sub 'Main
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.ExpandAll()
' Add the CheckForCheckedChildren event handler to the BeforeExpand event.
AddHandler treeView1.BeforeCollapse, AddressOf CheckForCheckedChildren
' Expand all nodes of treeView1. Nodes without checked children are
' prevented from expanding by the checkForCheckedChildren event handler.
treeView1.CollapseAll()
' Remove the checkForCheckedChildren event handler from the BeforeExpand
' event so manual node expansion will work correctly.
RemoveHandler treeView1.BeforeCollapse, AddressOf CheckForCheckedChildren
' Enable redrawing of treeView1.
treeView1.EndUpdate()
End Sub 'showCheckedNodesButton_Click
' Prevent collapse of a node that has checked child nodes.
Private Sub CheckForCheckedChildren(ByVal sender As Object, ByVal e As TreeViewCancelEventArgs)
If HasCheckedChildNodes(e.Node) Then
e.Cancel = True
End If
End Sub 'CheckForCheckedChildren
' 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 '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.ExpandAll();
// Add the checkForCheckedChildren event handler to the BeforeExpand event.
treeView1.BeforeCollapse += checkForCheckedChildren;
// Expand all nodes of treeView1. Nodes without checked children are
// prevented from expanding by the checkForCheckedChildren event handler.
treeView1.CollapseAll();
// Remove the checkForCheckedChildren event handler from the BeforeExpand
// event so manual node expansion will work correctly.
treeView1.BeforeCollapse -= checkForCheckedChildren;
// Enable redrawing of treeView1.
treeView1.EndUpdate();
}
// Prevent collapse of a node that has 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;
}
}
#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^>^temp1 = {showCheckedNodesButton,treeView1};
this->Controls->AddRange( temp1 );
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->ExpandAll();
// Add the checkForCheckedChildren event handler to the BeforeExpand event.
treeView1->BeforeCollapse += checkForCheckedChildren;
// Expand all nodes of treeView1. Nodes without checked children are
// prevented from expanding by the checkForCheckedChildren event handler.
treeView1->CollapseAll();
// Remove the checkForCheckedChildren event handler from the BeforeExpand
// event so manual node expansion will work correctly.
treeView1->BeforeCollapse -= checkForCheckedChildren;
// Enable redrawing of treeView1.
treeView1->EndUpdate();
}
// Prevent collapse of a node that has 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 );
}
import System.*;
import System.Drawing.*;
import System.Windows.Forms.*;
public class Form1 extends 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.set_Location(new Point(0, 25));
treeView1.set_Size(new Size(292, 248));
treeView1.set_Anchor(AnchorStyles.Top | AnchorStyles.Left
| AnchorStyles.Bottom | AnchorStyles.Right);
treeView1.set_CheckBoxes(true);
// Add nodes to treeView1.
TreeNode node;
for (int x = 0; x < 3; ++x) {
// Add a root node.
node = treeView1.get_Nodes().Add(String.Format
("Node{0}", (Int32)(x * 4)));
for (int y = 1; y < 4; ++y) {
// Add a node as a child of the previously added node.
node = node.get_Nodes().Add(String.Format
("Node{0}", (Int32)(x * 4 + y)));
}
}
// Set the checked state of one of the nodes to
// demonstrate the showCheckedNodesButton button behavior.
treeView1.get_Nodes().get_Item(1).get_Nodes().get_Item(0).
get_Nodes().get_Item(0).set_Checked(true);
// Initialize showCheckedNodesButton.
showCheckedNodesButton.set_Size(new Size(144, 24));
showCheckedNodesButton.set_Text("Show Checked Nodes");
showCheckedNodesButton.add_Click(new EventHandler
(showCheckedNodesButton_Click));
// Initialize the form.
this.set_ClientSize(new Size(292, 273));
this.get_Controls().AddRange(new Control[]
{ showCheckedNodesButton, treeView1 });
this.ResumeLayout(false);
} //Form1
public static void main(String[] args)
{
Application.Run(new Form1());
} //main
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.ExpandAll();
// Add the checkForCheckedChildren event handler to the
// BeforeExpand event.
treeView1.add_BeforeCollapse(checkForCheckedChildren);
// Expand all nodes of treeView1. Nodes without checked children are
// prevented from expanding by the checkForCheckedChildren event handler.
treeView1.CollapseAll();
// Remove the checkForCheckedChildren event handler from the
// BeforeExpand event so manual node expansion will work correctly.
treeView1.remove_BeforeCollapse(checkForCheckedChildren);
// Enable redrawing of treeView1.
treeView1.EndUpdate();
} //showCheckedNodesButton_Click
// Prevent collapse of a node that has checked child nodes.
private void CheckForCheckedChildrenHandler(Object sender,
TreeViewCancelEventArgs e)
{
if (HasCheckedChildNodes(e.get_Node())) {
e.set_Cancel(true);
}
} //CheckForCheckedChildrenHandler
// Returns a value indicating whether the specified
// TreeNode has checked child nodes.
private boolean HasCheckedChildNodes(TreeNode node)
{
if (node.get_Nodes().get_Count() == 0) {
return false;
}
for (int iCtr = 0; iCtr < node.get_Nodes().get_Count(); iCtr++) {
TreeNode childNode = node.get_Nodes().get_Item(iCtr);
if (childNode.get_Checked()) {
return true;
}
// Recursively check the children of the current child node.
if (HasCheckedChildNodes(childNode)) {
return true;
}
}
return false;
} //HasCheckedChildNodes
} //Form1
平台
Windows 98、Windows 2000 SP4、Windows CE、Windows Millennium Edition、Windows Mobile for Pocket PC、Windows Mobile for Smartphone、Windows Server 2003、Windows XP Media Center Edition、Windows XP Professional x64 Edition、Windows XP SP2、Windows XP Starter Edition
.NET Framework 并不是对每个平台的所有版本都提供支持。有关受支持版本的列表，请参见系统要求。
版本信息
.NET Framework
受以下版本支持：2.0、1.1、1.0
.NET Compact Framework
受以下版本支持：2.0、1.0