GetWindowText 什么也不返回

Question

在我的一个项目中，我必须获得前景窗口的标题，所以我调用 GetForegroundWindow() 入口点表单 User32.dll 来获取窗口句柄，然后我调用 GetWindowText() 来获取标题，但输出的错误更少什么都没有，这是我在 VB.NET 程序中使用的代码。

Imports System.Runtime.InteropServices

Public Class Form1

<DllImport("user32.dll")> _
Private Shared Function GetForegroundWindow() As IntPtr

End Function

<DllImport("user32.dll")> _
Private Shared Function GetWindowText(ByVal hwnd As Long, ByVal lpString As System.Text.StringBuilder, ByVal cch As Long) As Integer

End Function


Private Sub Form1_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
End Sub

Private Sub Timer1_Tick(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Timer1.Tick
    Dim hWnd As IntPtr
    hWnd = GetForegroundWindow()
    Dim title As New System.Text.StringBuilder(256)
    GetWindowText(hWnd, title, title.Capacity)
    Me.Text = title.ToString
End Sub
End Class

Answer 1

我自己找到了解决方案，这是hWnd 参数中的错误Long 值，程序正常运行它必须是IntPtr。新的正确代码如下所示。

Imports System.Runtime.InteropServices

Public Class Form1

<DllImport("user32.dll")> _
Private Shared Function GetForegroundWindow() As IntPtr

End Function

<DllImport("user32.dll")> _
Private Shared Function GetWindowText(ByVal hwnd As IntPtr, ByVal lpString As System.Text.StringBuilder, ByVal cch As Long) As Integer

End Function


Private Sub Form1_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
End Sub

Private Sub Timer1_Tick(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Timer1.Tick
    Dim hWnd As IntPtr
    hWnd = GetForegroundWindow()
    Dim title As New System.Text.StringBuilder(256)
    GetWindowText(hWnd, title, title.Capacity)
    Me.Text = title.ToString


End Sub
End Class