Question

我正在尝试在图片框上创建一个带有randome大小和位置的矩形。每次用户点击按钮时，该矩形将被删除，并且将显示新的矩形。

Private Sub btnDraw_Click(sender As Object, e As EventArgs) Handles btnDraw.Click
  RandomBox()
End Sub

Public Sub RandomBox()
  Dim r As New Rectangle(CInt(Rnd() * picGene.Width), CInt(Rnd() * picGene.Height), 20 + Rnd() * 50, 10 + Rnd() * 50)
  Dim g As System.Drawing.Graphics
  g = picGene.CreateGraphics()
  g.FillRectangle(Brushes.Blue, r)
End Sub

它始终保留先前绘制的矩形，因此我尝试在代码块之前或之后放置picGene.Invalide（）。它会删除旧的矩形，但不会绘制新的矩形。

Public Sub RandomBox()
  picGene.Invalidate()
  Dim r As New Rectangle(CInt(Rnd() * picGene.Width), CInt(Rnd() * picGene.Height), 20 + Rnd() * 50, 10 + Rnd() * 50)
  Dim g As System.Drawing.Graphics
  g = picGene.CreateGraphics()
  g.FillRectangle(Brushes.Blue, r)
  'picGene.Invalidate()
End Sub

有什么想法吗？

由于

Answer 1

将一个Rectangle存储在内存中，每次单击都要更改一个Rectangle，然后在paint事件中绘制它。对于随机生成的值，Random类是最好的选择。

Private rect As New Rectangle

Private Sub btnDraw_Click(sender As Object, e As EventArgs) Handles btnDraw.Click
  Static rnd As New Random 
  rect = New Rectangle(rnd.Next(picGene.Width), rnd.Next(picGene.Height), 20 + rnd.Next({somevalue}) * 50, 10 + rnd.Next({someValue}) * 50)
  pb.Refresh() 'redraw the rectangle
End Sub

Private Sub picGene_Paint(sender As Object, e As PaintEventArgs) Handles picGene.Paint
  e.Graphics.DrawRectangle(Pens.Black, rect)
End Sub

vb.net在picturebox上重绘矩形并使invalidate方法无效

1 个答案: