为什么CreateWindowEx返回0

Question

VB.NET 2008 Express

Private Declare Function CreateWindowEx Lib "user32" Alias "CreateWindowExA" (ByVal dwExStyle As Integer, ByVal lpClassName As String, ByVal lpWindowName As String, ByVal dwStyle As Integer, ByVal x As Integer, ByVal y As Integer, ByVal nWidth As Integer, ByVal nHeight As Integer, ByVal hwndParent As Integer, ByVal hMenu As Integer, ByVal hInstance As Integer, ByRef lpParam As Object) As Integer

Private Const WS_EX_APPWINDOW = &H40000
Private Const WS_EX_WINDOWEDGE = &H100&
Private Const WS_SYSMENU = &H80000
Private Const WS_CAPTION = &HC00000
Private Const WS_MINIMIZEBOX = &H20000
Private Const WS_THICKFRAME = &H40000
Private Const WS_MAXIMIZEBOX = &H10000
Private Const WS_OVERLAPPEDWINDOW = (WS_OVERLAPPED Or WS_CAPTION Or WS_SYSMENU Or WS_THICKFRAME Or WS_MINIMIZEBOX Or WS_MAXIMIZEBOX)

Dim AppHandle As Int32 = System.Runtime.InteropServices.Marshal.GetHINSTANCE(System.Reflection.Assembly.GetExecutingAssembly.GetModules()(0)).ToInt32()

Dim WindowHandle as integer = CreateWindowEx(WS_EX_APPWINDOW Or WS_EX_WINDOWEDGE, "MyWindow", "MyTitle", WS_OVERLAPPEDWINDOW, 0, 0, 640, 480, 0, 0, AppHandle, Nothing)

CreateWindowEx 返回 0？

Answer 1

调用 CreateWindowEx 后需要检查是否为 NULL，如果是，则可以立即调用 Marshal.GetLastWin32Error 了解原因。

Answer 2

可能的原因是您忘记使用RegisterClass/Ex()注册“MyWindow”窗口类，没有正确设置窗口过程或没有正确处理WM_CREATE消息。另外，您的 P/Invoke 声明是错误的，它无法在 64 位操作系统上运行。

不要自己编写此类代码，Windows 窗体是 CreateWindowEx() 的一个非常好的包装器。