VB.NET Form.OnPaint方法代碼示例

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

public class MainClass

   Shared Sub Main()
      Dim form1 As Form = New Form1
      Application.Run(form1)
   End Sub

End Class



Public Class Form1
    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
    Friend WithEvents cmdDrawStuff As System.Windows.Forms.Button
    Friend WithEvents cmdInvalidate As System.Windows.Forms.Button
    Friend WithEvents cmdOtherForm As System.Windows.Forms.Button

    '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.
    <System.Diagnostics.DebuggerStepThrough()> Private Sub InitializeComponent()
        Me.cmdOtherForm = New System.Windows.Forms.Button()
        Me.cmdDrawStuff = New System.Windows.Forms.Button()
        Me.cmdInvalidate = New System.Windows.Forms.Button()
        Me.SuspendLayout()
        '
        'cmdOtherForm
        '
        Me.cmdOtherForm.Location = New System.Drawing.Point(184, 136)
        Me.cmdOtherForm.Name = "cmdOtherForm"
        Me.cmdOtherForm.Size = New System.Drawing.Size(96, 32)
        Me.cmdOtherForm.TabIndex = 2
        Me.cmdOtherForm.Text = "Other Form"
        '
        'cmdDrawStuff
        '
        Me.cmdDrawStuff.Location = New System.Drawing.Point(184, 80)
        Me.cmdDrawStuff.Name = "cmdDrawStuff"
        Me.cmdDrawStuff.Size = New System.Drawing.Size(96, 32)
        Me.cmdDrawStuff.TabIndex = 1
        Me.cmdDrawStuff.Text = "Draw Stuff"
        '
        'cmdInvalidate
        '
        Me.cmdInvalidate.Location = New System.Drawing.Point(184, 24)
        Me.cmdInvalidate.Name = "cmdInvalidate"
        Me.cmdInvalidate.Size = New System.Drawing.Size(96, 32)
        Me.cmdInvalidate.TabIndex = 0
        Me.cmdInvalidate.Text = "Invalidate"
        '
        'Form1
        '
        Me.AutoScaleBaseSize = New System.Drawing.Size(5, 13)
        Me.ClientSize = New System.Drawing.Size(292, 273)
        Me.Controls.AddRange(New System.Windows.Forms.Control() {Me.cmdOtherForm, Me.cmdDrawStuff, Me.cmdInvalidate})
        Me.Name = "Form1"
        Me.Text = "Form1"
        Me.ResumeLayout(False)

    End Sub

#End Region

    Dim backgroundbitmap As Bitmap

    Protected Overrides Sub OnResize(ByVal e As System.EventArgs)
        If Not Me.ClientRectangle.IsEmpty Then            
            If Not Me.ClientSize.Equals(New Size(backgroundbitmap.Width, backgroundbitmap.Height)) Then
                Dim newbitmap As Bitmap
                newbitmap = New Bitmap(Me.ClientSize.Width, Me.ClientSize.Height)
                If Not backgroundbitmap Is Nothing Then
                    Dim g As Graphics = graphics.FromImage(newbitmap)
                    g.DrawImage(backgroundbitmap, 0, 0)
                End If
                backgroundbitmap = newbitmap
            End If
        End If
    End Sub

    Protected Overrides Sub OnPaint(ByVal e As System.Windows.Forms.PaintEventArgs)
'        MyBase.OnPaint(e)
        e.Graphics.DrawLine(pens.Black, 0, 0, 200, 200)
        e.Graphics.DrawLine(pens.Red, 0, 200, 200, 0)
        'RaiseEvent Paint(Me, e)
    End Sub

End Class