vb.net如何在屏幕上画图，就像手写板那样

[wangearn]

vb.net如何在屏幕上画图，就像手写板那样

[北京的雾霾天]

那首先要用GetDesktopWindow来得到桌面的画图句柄.
然后由桌面的窗口句柄建立一个Graphics,这样就可以画图了.

[wangearn]

能不能给出具体代码，小弟很菜的

[北京的雾霾天]

这个好说,参考下下面的代码:
[DllImport("user32.dll", CharSet = CharSet.Auto, ExactSpelling = true)]
public static extern IntPtr GetDesktopWindow();
[DllImport("user32.dll", EntryPoint = "GetDCEx", CharSet = CharSet.Auto, ExactSpelling = true)]
private static extern IntPtr GetDCEx(IntPtr hWnd, IntPtr hrgnClip, int flags);

private void button1_Click(object sender, EventArgs e)
{
IntPtr desk = GetDesktopWindow();
IntPtr deskDC = GetDCEx(desk, IntPtr.Zero, 0x403);
Graphics g = Graphics.FromHdc(deskDC);
g.FillEllipse(SystemBrushes.ControlText, 0, 0, 100, 100);
}

[wangearn]

还是没弄出来，麻烦你翻译成vb的语言嘛

[snowfox007]

VB.Net版本

Public Declare Function GetDesktopWindow Lib "user32" Alias "GetDesktopWindow" () As Integer

Public Declare Function GetDCEx Lib "user32" Alias "GetDCEx" (ByVal hwnd As Integer, ByVal hrgnclip As Integer, ByVal fdwOptions As Integer) As Integer

Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click

Dim desk As Integer = GetDesktopWindow()

Dim deskDC As Integer = GetDCEx(desk, IntPtr.Zero, 1027)

Dim g As Graphics = Graphics.FromHdc(deskDC)

g.FillEllipse(SystemBrushes.ControlText, 0, 0, 100, 100)

g.Dispose()

End Sub

[北京的雾霾天]

对应的VB的代码如下:

Public Declare Function GetDesktopWindow Lib "user32" Alias "GetDesktopWindow" () As IntPtr
Public Declare Function GetDCEx Lib "user32" Alias "GetDCEx" (ByVal hwnd As IntPtr, ByVal hrgnclip As IntPtr, ByVal fdwOptions As Integer) As IntPtr

Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
Dim desk As Integer = GetDesktopWindow()
Dim deskDC As Integer = GetDCEx(desk, IntPtr.Zero, &H403)
Dim g As Graphics = Graphics.FromHdc(deskDC)
g.FillEllipse(SystemBrushes.ControlText, 0, 0, 100, 100)
g.Dispose()
End Sub

[wangearn]

Dim deskDC As Integer = GetDCEx(desk, IntPtr.Zero, &H403)
这句提示错误：
对 PInvoke 函数“桌面留言板!桌面留言板.Form1::GetDCEx”的调用导致堆栈不对称。原因可能是托管的 PInvoke 签名与非托管的目标签名不匹配。请检查 PInvoke 签名的调用约定和参数与非托管的目标签名是否匹配。

[wangearn]

是我的问题，已经成功了 ，谢谢

[北京的雾霾天]

我是在XP下的VS2005中运行通过的.

[uteflyaway]

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