vb.net 教程 3-4 窗体编程 公共控件10 TreeView 3

上一节学习了从vs中利用编辑器手动编辑节点，本节主要谈谈使用代码来编辑节点，实际也就是对TreeNode的操作。

先看看窗体中控件的布局：

为了区别根节点和子节点，特地做了点区分。

窗体载入的时候，把ImageList中的图片载入4个ListView中，

ListView的SmallImageList属性设置为ImageList1;View属性设置为SmallIcon：

    Private Sub Form7_Load(sender As Object, e As EventArgs) Handles MyBase.Load        For i As Integer = 0 To ImageList1.Images.Count - 1            ListView1.Items.Add(New ListViewItem("", i))            ListView2.Items.Add(New ListViewItem("", i))            ListView3.Items.Add(New ListViewItem("", i))            ListView4.Items.Add(New ListViewItem("", i))        Next    End Sub

添加根节点：

    '添加根节点    Private Sub Button1_Click(sender As Object, e As EventArgs) Handles Button1.Click        Dim strNodeName As String = TextBox1.Text        If ListView1.SelectedIndices.Count = 0 OrElse ListView2.SelectedIndices.Count = 0 Then            MessageBox.Show("未选择根节点图标")            Exit Sub        End If        Dim tnRoot As New TreeNode(strNodeName)        tnRoot.ImageIndex = ListView1.SelectedIndices(0)        tnRoot.SelectedImageIndex = ListView2.SelectedIndices(0)        TreeView1.Nodes.Add(tnRoot)    End Sub

其中TreeNode的构造函数之一：

然后再增加显示的图标（tnRoot.ImageIndex =……）和选中时候的图标（tnRoot.SelectedImageIndex =……）

同时请注意，判断是否已经在ListView1和ListView2中选择图标的代码：

If ListView2.SelectedIndices.Count = 0 OrElse ListView2.SelectedIndices.Count = 0 Then

删除根节点：

    '删除根节点    Private Sub Button2_Click(sender As Object, e As EventArgs) Handles Button2.Click        If IsNothing(TreeView1.SelectedNode) Then Exit Sub        Dim tnSelectedNode As TreeNode = TreeView1.SelectedNode        If tnSelectedNode.Level = 0 Then            TreeView1.Nodes.Remove(tnSelectedNode)        Else            MessageBox.Show("此按钮只用于删除根节点")        End If    End Sub

判断是否选中有节点的代码：

IsNothing(TreeView1.SelectedNode)

判断节点等级的代码：

tnSelectedNode.Level

如果是根节点，那么Level=0。

清除根节点，也就是清空TreeView：

    '清除根节点    Private Sub Button3_Click(sender As Object, e As EventArgs) Handles Button3.Click        TreeView1.Nodes.Clear()    End Sub

同样，子节点的操作：

添加子节点：

    '添加子节点    Private Sub Button6_Click(sender As Object, e As EventArgs) Handles Button6.Click        If IsNothing(TreeView1.SelectedNode) Then Exit Sub        Dim tnSelectedNode As TreeNode = TreeView1.SelectedNode        If ListView3.SelectedIndices.Count = 0 OrElse ListView4.SelectedIndices.Count = 0 Then            MessageBox.Show("未选择节点图标")            Exit Sub        End If        Dim strNodeName As String = TextBox2.Text        Dim tnAddNode As New TreeNode(strNodeName, ListView3.SelectedIndices(0), ListView4.SelectedIndices(0))        tnSelectedNode.Nodes.Add(tnAddNode)    End Sub

首先判断是否已经选择了一个节点，如果选择了再添加：

 If IsNothing(TreeView1.SelectedNode) Then Exit Sub

这里用了TreeNode的另外一个构造函数

Dim tnAddNode As New TreeNode(strNodeName, ListView3.SelectedIndices(0), ListView4.SelectedIndices(0))

删除节点：

    '删除普通节点    Private Sub Button5_Click(sender As Object, e As EventArgs) Handles Button5.Click        If IsNothing(TreeView1.SelectedNode) Then Exit Sub        Dim tnSelectedNode As TreeNode = TreeView1.SelectedNode        If tnSelectedNode.Level <> 0 Then            TreeView1.Nodes.Remove(tnSelectedNode)        Else            MessageBox.Show("此按钮只用于删除普通节点")        End If    End Sub

清除子节点：

    '清除当前节点下的所有子节点    Private Sub Button4_Click(sender As Object, e As EventArgs) Handles Button4.Click        If IsNothing(TreeView1.SelectedNode) Then Exit Sub        Dim tnSelectedNode As TreeNode = TreeView1.SelectedNode        If tnSelectedNode.Nodes.Count > 0 Then            tnSelectedNode.Nodes.Clear()        Else            MessageBox.Show("此节点下没有子节点")        End If    End Sub

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