将按钮添加到 TreeNode

Question

美好的一天。 有一个自定义控件，为每个Node添加一个按钮

Imports System.Windows.Forms.VisualStyles

Public Class CustomTreeView
    Inherits TreeView

    Private buttonRect As New Rectangle(80, 2, 50, 26)
    Private ReadOnly stringFormat As StringFormat

    Public Sub New()
        SetStyle(ControlStyles.OptimizedDoubleBuffer, True)

        DrawMode = TreeViewDrawMode.OwnerDrawText
        ShowLines = False
        FullRowSelect = True
        ItemHeight = 30

        stringFormat = New StringFormat With {
            .Alignment = StringAlignment.Near,
            .LineAlignment = StringAlignment.Center
        }
    End Sub

    Protected Overrides Sub OnDrawNode(ByVal e As DrawTreeNodeEventArgs)
        e.Graphics.DrawString(e.Node.Text, Me.Font, New SolidBrush(Me.ForeColor), e.Bounds, stringFormat)
        ButtonRenderer.DrawButton(e.Graphics, New Rectangle(e.Node.Bounds.Location + New Size(buttonRect.Location), buttonRect.Size), "btn", Me.Font, True, If(e.Node.Tag IsNot Nothing, CType(e.Node.Tag, PushButtonState), PushButtonState.Normal))
    End Sub

    Protected Overrides Sub OnNodeMouseClick(ByVal e As TreeNodeMouseClickEventArgs)
        Select Case e.Node.Tag
            Case Nothing, Is <> PushButtonState.Pressed
                Return
        End Select
        e.Node.Tag = PushButtonState.Normal
        MessageBox.Show(e.Node.Text & " clicked")
        ' force redraw
        e.Node.Text = e.Node.Text
    End Sub

    Protected Overrides Sub OnMouseDown(ByVal e As MouseEventArgs)
        Dim tnode As TreeNode = GetNodeAt(e.Location)
        If tnode Is Nothing Then
            Return
        End If

        Dim btnRectAbsolute As New Rectangle(tnode.Bounds.Location + New Size(buttonRect.Location), buttonRect.Size)
        If btnRectAbsolute.Contains(e.Location) Then
            tnode.Tag = PushButtonState.Pressed
            tnode.Text = tnode.Text
        End If
    End Sub
End Class

告诉我如何只在第一个（主要）点头时显示按钮？ 以及，当您单击此按钮时，如何不显示消息，而是调用某个过程？

Answer 1

没有内置的按钮树节点。但是您可以自己创建一个具有按钮的自定义树节点。此自定义树节点继承自 TreeNode。为了提高可扩展性，我们为具有DrawNode 方法的树节点声明了一个接口：

Imports System.Windows.Forms.VisualStyles

Public Interface ICustomDrawTreeNode
    Sub DrawNode(ByVal e As DrawTreeNodeEventArgs, buttonState As PushButtonState)
End Interface

我们还创建了一个模块，其中包含一些在自定义树视图和自定义树节点中使用的设置

Module Settings
    Public ReadOnly ButtonRect As New Rectangle(80, 2, 50, 26)

    Public ReadOnly TextStringFormat = New StringFormat() With {
        .Alignment = StringAlignment.Near,
        .LineAlignment = StringAlignment.Center,
        .FormatFlags = StringFormatFlags.NoClip Or StringFormatFlags.FitBlackBox Or StringFormatFlags.LineLimit
    }

End Module

然后我们可以像这样实现一个按钮节点

Imports System.Windows.Forms.VisualStyles

Public Class ButtonTreeNode
    Inherits TreeNode
    Implements ICustomDrawTreeNode

    Private ReadOnly buttonText As String

    Public Sub New(text As String, buttonText As String)
        MyBase.New(text)

        Me.buttonText = buttonText
    End Sub

    Public Sub DrawNode(e As DrawTreeNodeEventArgs, buttonState As PushButtonState) _
        Implements ICustomDrawTreeNode.DrawNode

        Dim font As Font = e.Node.TreeView.Font

        ' Draw Text to the left of the button
        Dim rect As Rectangle = New Rectangle(
            e.Node.Bounds.Location,
            New Size(Settings.ButtonRect.Left, e.Bounds.Height))
        e.Graphics.DrawString(e.Node.Text, font, Brushes.Black, rect, Settings.TextStringFormat)

        ' Draw the button
        rect = New Rectangle(
            e.Node.Bounds.Location + Settings.ButtonRect.Location,
            Settings.ButtonRect.Size)
        ButtonRenderer.DrawButton(e.Graphics, rect, buttonText, font, True, buttonState)
    End Sub
End Class

它有一个Private ReadOnly buttonText As String 来存储按钮的文本。普通节点文本和按钮文本在ButtonTreeNode的构造函数中传递：

Public Sub New(text As String, buttonText As String)

DrawNode 方法将被称为OnDrawNode 中的CustomTreeView。

---

在CustomTreeView 中，我声明了一个NodeButtonClick 事件，该事件将在单击节点按钮时引发。然后，您可以在表单中处理此事件。当您在设计器中选择CustomTreeView 时，此新事件将出现在事件的“操作”部分。

Imports System.ComponentModel
Imports System.Windows.Forms.VisualStyles

Public Class CustomTreeView
    Inherits TreeView

    <Category("Action")>
    Public Event NodeButtonClick(e As TreeNodeMouseClickEventArgs)

    Private _isButtonPressed As Boolean

    Public Sub New()
        SetStyle(ControlStyles.OptimizedDoubleBuffer, True)
        DrawMode = TreeViewDrawMode.OwnerDrawText
        ShowLines = False
        FullRowSelect = True
        ItemHeight = 30
    End Sub

    Protected Overrides Sub OnDrawNode(e As DrawTreeNodeEventArgs)
        Dim customDrawNode As ICustomDrawTreeNode = TryCast(e.Node, ICustomDrawTreeNode)
        If customDrawNode Is Nothing Then ' Normal text node.
            e.Graphics.DrawString(e.Node.Text, Font, Brushes.Black, e.Node.Bounds, Settings.TextStringFormat)
        Else
            customDrawNode.DrawNode(e, If(_isButtonPressed, PushButtonState.Pressed, PushButtonState.Normal))
        End If
    End Sub

    Protected Overrides Sub OnNodeMouseClick(e As TreeNodeMouseClickEventArgs)
        If _isButtonPressed Then
            _isButtonPressed = False
            Refresh()
            Dim buttonNode = TryCast(e.Node, ButtonTreeNode)
            If buttonNode IsNot Nothing Then
                RaiseEvent NodeButtonClick(e)
            End If
        End If
    End Sub

    Protected Overrides Sub OnMouseDown(e As MouseEventArgs)
        Dim buttonNode = TryCast(GetNodeAt(e.Location), ButtonTreeNode)
        If buttonNode IsNot Nothing Then
            Dim btnRectAbsolute As New Rectangle(
                buttonNode.Bounds.Location + Settings.ButtonRect.Location,
                Settings.ButtonRect.Size)
            _isButtonPressed = btnRectAbsolute.Contains(e.Location)
            If _isButtonPressed Then
                Refresh()
            End If
        End If
    End Sub
End Class

你可以写的形式

Public Class Form1
    Private Sub Form1_Load(sender As Object, e As EventArgs) Handles MyBase.Load
        TreeView1.Nodes.Add("Text")
        TreeView1.Nodes.Add(New ButtonTreeNode("Caption", "Button"))
    End Sub

    Private Sub TreeView1_NodeButtonClick(e As TreeNodeMouseClickEventArgs) _
        Handles TreeView1.NodeButtonClick

        MessageBox.Show(e.Node.Text & " clicked")
    End Sub
End Class

这会向 TreeView 添加一个普通文本节点和一个自定义按钮节点。它还处理自定义 TreeView 的NodeButtonClick。