VB.NET Application.DoEvents方法代码示例

Private Sub InitializePictureBox()
    Me.PictureBox1 = New System.Windows.Forms.PictureBox
    Me.PictureBox1.BorderStyle = _
        System.Windows.Forms.BorderStyle.FixedSingle
    Me.PictureBox1.SizeMode = PictureBoxSizeMode.StretchImage
    Me.PictureBox1.Location = New System.Drawing.Point(72, 112)
    Me.PictureBox1.Name = "PictureBox1"
    Me.PictureBox1.Size = New System.Drawing.Size(160, 136)
    Me.PictureBox1.TabStop = False
End Sub

Private Sub InitializeOpenFileDialog()
    Me.OpenFileDialog1 = New System.Windows.Forms.OpenFileDialog

    ' Set the file dialog to filter for graphics files.
    Me.OpenFileDialog1.Filter = _
    "Images (*.BMP;*.JPG;*.GIF)|*.BMP;*.JPG;*.GIF|All files (*.*)|*.*"

    ' Allow the user to select multiple images.
    Me.OpenFileDialog1.Multiselect = True
    Me.OpenFileDialog1.Title = "My Image Browser"
End Sub

Private Sub fileButton_Click(ByVal sender As System.Object, _
    ByVal e As System.EventArgs) Handles FileButton.Click
    OpenFileDialog1.ShowDialog()
End Sub


' This method handles the FileOK event.  It opens each file 
' selected and loads the image from a stream into PictureBox1.
Private Sub OpenFileDialog1_FileOk(ByVal sender As Object, _
ByVal e As System.ComponentModel.CancelEventArgs) _
 Handles OpenFileDialog1.FileOk

    Me.Activate()
    Dim file, files() As String
    files = OpenFileDialog1.FileNames

    ' Open each file and display the image in PictureBox1.
    ' Call Application.DoEvents to force a repaint after each
    ' file is read.        
    For Each file In files
        Dim fileInfo As System.IO.FileInfo = New System.IO.FileInfo(file)
        Dim fileStream As System.IO.FileStream = fileInfo.OpenRead()
        PictureBox1.Image = System.Drawing.Image.FromStream(fileStream)
        Application.DoEvents()
        fileStream.Close()

        ' Call Sleep so the picture is briefly displayed, 
        'which will create a slide-show effect.
        System.Threading.Thread.Sleep(2000)
    Next
    PictureBox1.Image = Nothing
End Sub

Option Strict On
imports System
imports System.Drawing
imports System.Windows.Forms

public class ProgressBars : inherits Form

  dim pb as ProgressBar
  dim lbl as Label

  public sub New()
    Size = new Size(300,200)

    dim btn as new Button()
    btn.Parent = me
    btn.Text = "&Start"
    btn.Location = new Point(0,0)
    AddHandler btn.Click, AddressOf btn_OnClick

    lbl = new Label()
    lbl.Parent = me
    lbl.Size = new Size(100,23)
    lbl.Location = new Point(0,25)
    lbl.BorderStyle = BorderStyle.FixedSingle
    lbl.TextAlign = ContentAlignment.MiddleCenter
    lbl.Text = ""

    pb = new ProgressBar()
    pb.Parent = me
    pb.Location = new Point(0, 70)
    pb.Size = new Size(400, 20) 
    pb.Minimum = 0      '  the default value
    pb.Maximum = 100    '  the default value
  end sub  '  close for constructor

  private sub btn_OnClick(ByVal sender as object,ByVal e as EventArgs)
    dim cntr as integer = 0
    pb.Value = 0
    pb.Step = 1
    for i as integer = 0 to 100000
      cntr  = cntr + 1
      if cntr mod 100 = 0 then
        lbl.Text = cntr.ToString()
        pb.PerformStep()
        Application.DoEvents()
        System.Threading.Thread.Sleep(40)
      end if
    next
  end sub

  public shared sub Main() 
    Application.Run(new ProgressBars())
  end sub

end class