VB.NET ListBox.MeasureItem事件代碼示例

Friend WithEvents ListBox1 As System.Windows.Forms.ListBox

Private Sub InitializeOwnerDrawnListBox()
    Me.ListBox1 = New System.Windows.Forms.ListBox

    ' Set the location and size.
    ListBox1.Location = New Point(20, 20)
    ListBox1.Size = New Size(240, 240)

    ' Populate the ListBox.ObjectCollection property 
    ' with several strings, using the AddRange method.
    Me.ListBox1.Items.AddRange(New Object() _
        {"System.Windows.Forms", "System.Drawing", "System.Xml", _
        "System.Net", "System.Runtime.Remoting", "System.Web"})

    ' Turn off the scrollbar.
    ListBox1.ScrollAlwaysVisible = False

    ' Set the border style to a single, flat border.
    ListBox1.BorderStyle = BorderStyle.FixedSingle

    ' Set the DrawMode property to the OwnerDrawVariable value. 
    ' This means the MeasureItem and DrawItem events must be 
    ' handled.
    ListBox1.DrawMode = DrawMode.OwnerDrawVariable
    Me.Controls.Add(Me.ListBox1)
End Sub


' Handle the DrawItem event for an owner-drawn ListBox.
Private Sub ListBox1_DrawItem(ByVal sender As Object, _
    ByVal e As DrawItemEventArgs) Handles ListBox1.DrawItem

    ' If the item is the selected item, then draw the rectangle filled in
    ' blue. The item is selected when a bitwise And of the State property
    ' and the DrawItemState.Selected property is true. 
    If (e.State And DrawItemState.Selected = DrawItemState.Selected) Then
        e.Graphics.FillRectangle(Brushes.CornflowerBlue, e.Bounds)
    Else
        ' Otherwise, draw the rectangle filled in beige.
        e.Graphics.FillRectangle(Brushes.Beige, e.Bounds)
    End If

    ' Draw a rectangle in blue around each item.
    e.Graphics.DrawRectangle(Pens.Blue, e.Bounds)

    ' Draw the text in the item.
    e.Graphics.DrawString(Me.ListBox1.Items(e.Index), Me.Font, _
        Brushes.Black, e.Bounds.X, e.Bounds.Y)

    ' Draw the focus rectangle around the selected item.
    e.DrawFocusRectangle()
End Sub

' Handle the MeasureItem event for an owner-drawn ListBox.
Private Sub ListBox1_MeasureItem(ByVal sender As Object, _
    ByVal e As MeasureItemEventArgs) Handles ListBox1.MeasureItem

    ' Cast the sender object back to ListBox type.
    Dim theListBox As ListBox = CType(sender, ListBox)

    ' Get the string contained in each item.
    Dim itemString As String = CType(theListBox.Items(e.Index), String)

    ' Split the string at the " . "  character.
    Dim resultStrings() As String = itemString.Split(".")

    ' If the string contains more than one period, increase the 
    ' height by ten pixels; otherwise, increase the height by 
    ' five pixels.
    If (resultStrings.Length > 2) Then
        e.ItemHeight += 10
    Else
        e.ItemHeight += 5
    End If

End Sub

' 導入命名空間
Imports System
Imports System.Drawing
Imports System.Windows.Forms


Public Class MainClass


   Public Shared Sub Main()
         Application.Run(New OwnerDrawnVariableListBox())
   End Sub
   
   
End Class

Public Class OwnerDrawnVariableListBox
    Inherits System.Windows.Forms.Form

#Region " Windows Form Designer generated code "

    Public Sub New()
        MyBase.New()

        'This call is required by the Windows Form Designer.
        InitializeComponent()

        'Add any initialization after the InitializeComponent() call

    End Sub

    'Form overrides dispose to clean up the component list.
    Protected Overloads Overrides Sub Dispose(ByVal disposing As Boolean)
        If disposing Then
            If Not (components Is Nothing) Then
                components.Dispose()
            End If
        End If
        MyBase.Dispose(disposing)
    End Sub

    'Required by the Windows Form Designer
    Private components As System.ComponentModel.IContainer

    'NOTE: The following procedure is required by the Windows Form Designer
    'It can be modified using the Windows Form Designer.  
    'Do not modify it using the code editor.
    Friend WithEvents listBox2 As System.Windows.Forms.ListBox
    <System.Diagnostics.DebuggerStepThrough()> Private Sub InitializeComponent()
        Me.listBox2 = New System.Windows.Forms.ListBox()
        Me.SuspendLayout()
        '
        'listBox2
        '
        Me.listBox2.DrawMode = System.Windows.Forms.DrawMode.OwnerDrawVariable
        Me.listBox2.Items.AddRange(New Object() {"A", "a", "B"})
        Me.listBox2.Location = New System.Drawing.Point(6, 15)
        Me.listBox2.Name = "listBox2"
        Me.listBox2.Size = New System.Drawing.Size(280, 192)
        Me.listBox2.TabIndex = 5
        '
        'OwnerDrawnVariableListBox
        '
        Me.AutoScaleBaseSize = New System.Drawing.Size(5, 13)
        Me.ClientSize = New System.Drawing.Size(292, 222)
        Me.Controls.AddRange(New System.Windows.Forms.Control() {Me.listBox2})
        Me.Name = "OwnerDrawnVariableListBox"
        Me.Text = "OwnerDrawnVariableListBox"
        Me.ResumeLayout(False)

    End Sub

#End Region

    Private Sub listBox2_DrawItem(ByVal sender As Object, ByVal e As System.Windows.Forms.DrawItemEventArgs) Handles listBox2.DrawItem
        e.DrawBackground()

        Dim textFont As Font
        textFont = New Font(e.Font.FontFamily, e.Font.Size * 2)

        e.Graphics.DrawString(listBox2.Items(e.Index).ToString(), _
                                textFont, _
                                New SolidBrush(e.ForeColor), _
                                e.Bounds.X, e.Bounds.Y)

        e.DrawFocusRectangle()
    End Sub

    Private Sub listBox2_MeasureItem(ByVal sender As Object, ByVal e As System.Windows.Forms.MeasureItemEventArgs) Handles listBox2.MeasureItem
        If e.Index Mod 2 = 0 Then e.ItemHeight *= 2
    End Sub
End Class