Question

vb.net GDI绘图刷新问题

用GDI函数在窗体上绘图，窗体最小化或者被覆盖等的时候图像就会被抹掉，怎么Paint事件的时候保留窗体上的图像

Answer 1

绘图代码写在Paint事件中，如
Private Sub Form1_Paint(ByVal sender As Object, ByVal e As System.Windows.Forms.PaintEventArgs) Handles Me.Paint
Dim g As Graphics = Me.CreateGraphics
g.DrawLine(Pens.Red, 100, 100, 200, 100)
End Sub
'方法二：在 PictureBox1上显示图像----图画在Bitmap
PictureBox1.Image = Nothing
Dim wid As Integer = PictureBox1.ClientSize.Width
Dim hgt As Integer = PictureBox1.ClientSize.Height
Dim bm As New Bitmap(wid, hgt)
Dim g As Graphics = Graphics.FromImage(bm)
'画图代码
'画图代码

PictureBox1.Image = bm
PictureBox1.Refresh()
g.Dispose()

Answer 2

你可以把绘图的代码放在Paint事件里