利用BitBlt画的图，如何重画？
用BitBlt在PictureBox上画图成功，但如果把PictureBox前面挡住的窗口移走后，PictureBox被挡住部分没有更新，请问应该如何刷新呢？用OnPaint事件也不行。
Public Class Form1
Declare Auto Function BitBlt Lib "GDI32.DLL" ( _
ByVal hdcDest As IntPtr, _
ByVal nXDest As Integer, _
ByVal nYDest As Integer, _
ByVal nWidth As Integer, _
ByVal nHeight As Integer, _
ByVal hdcSrc As IntPtr, _
ByVal nXSrc As Integer, _
ByVal nYSrc As Integer, _
ByVal dwRop As Int32) As Boolean
Private Const ROP_SrcCopy As Integer = &HCC0020
Private Declare Function SelectObject Lib "GDI32" (ByVal hDC As Integer, ByVal hObject As Integer) As Integer
Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
TestBitBlt()
End Sub
Private Sub PictureBox1_Paint(ByVal sender As System.Object, ByVal e As System.Windows.Forms.PaintEventArgs) Handles PictureBox1.Paint
End Sub
Private Sub TestBitBlt()
Dim bmp As Bitmap = Image.FromFile("C:\Documents and Settings\All Users\Documents\My Pictures\Sample Pictures\Sunset.jpg")
Dim g1 As Graphics = Graphics.FromImage(bmp)
Dim g2 As Graphics = Me.PictureBox1.CreateGraphics
Dim hdc1 As IntPtr = g1.GetHdc
Dim hdc2 As IntPtr = g2.GetHdc
SelectObject(hdc1, bmp.GetHbitmap()) '
BitBlt(hdc2, 0, 0, bmp.Width, bmp.Height, hdc1, 0, 0, ROP_SrcCopy)
g1.ReleaseHdc()
g2.ReleaseHdc()
g1.Dispose()
g2.Dispose()
End Sub
End Class
[解决办法]
直接用GDI好了
Private Sub PictureBox1_Paint(ByVal sender As System.Object, ByVal e As System.Windows.Forms.PaintEventArgs) Handles PictureBox1.Paint
Dim bmp As Bitmap = Image.FromFile("C:\Documents and Settings\All Users\Documents\My Pictures\Sample Pictures\Sunset.jpg")
Dim g As Graphics = e.Graphics
g.DrawImage(bmp, 0, 0)
End Sub
然后其他地方用PictureBox.Invalidate()就可以清除了 也能达到你想要的效果
[解决办法]
OnPaint里面g2不要用CreateGraphics，用e.Graphics
后面也不能Dispose g2,Hdc要释放掉。
