vb.net 中实现画图

项目中要用图形来显示一个阀门的开度，以及控制阀的开度。本来是要用什么公司买的控件中的饼图之类的实现，不过我觉得也是麻烦，就想，还是自己画吧。

首先添加一个TrackBar，名字是“TrackBar1”，一个label，名字是“L_A_SHANG”，一个GroupBox，名字是“GB_RIGHT”,，然后添加拉动滚动条时的处理函数

'上位机控制
  Dim m_start As Integer
  Dim RcDraw As System.Drawing.Rectangle

Private Sub TrackBar1_Scroll(ByVal sender As Object, ByVal e As System.EventArgs) Handles TrackBar1.Scroll
   m_start = (100 - TrackBar1.Value)
   Me.L_A_SHANG.Text = Me.TrackBar1.Value.ToString
   GB_RIGHT.Invalidate() '重画GB_RIGHT
  End Sub

添加GB_RIGHT重画时的处理函数

Private Sub GB_RIGHT_Paint(ByVal sender As Object, ByVal e As System.Windows.Forms.PaintEventArgs) Handles GB_RIGHT.Paint
   RcDraw.X = TrackBar1.Location.X - 40
   RcDraw.Y = 20
   RcDraw.Height = 100
   RcDraw.Width = 20
   e.Graphics.DrawRectangle(New Pen(Color.Blue, 5), RcDraw)
   Dim i = TrackBar1.Location.X - 40
   For i = TrackBar1.Location.X - 40 To TrackBar1.Location.X - 20
e.Graphics.DrawLine(New Pen(Color.Blue, 5), i, m_start + 20, i, 120)
   Next

Me.L_A_SHANG.Text = Me.TrackBar1.Value.ToString + "%"
  End Sub

到此以及可以实现拉动条的时候，图像跟着变化，并显示百分比。