隐藏显示窗口

Posted 2021-12-06 VB.Net

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使用系统的API函数ShowWindow可以隐藏和显示其它程序的窗口。
vb.net中的声明如下：

Declare Function ShowWindow Lib "user32" Alias "ShowWindow" (ByVal hwnd As IntPtr, ByVal nCmdShow As Integer) As Integer

参数hwnd是窗口的句柄；

参数nCmdShow是指定窗口如何显示，用来隐藏和显示的常数：

SW_HIDE= 0

SW_SHOW= 5
隐藏窗口代码：

    Private Sub Button1_Click(sender As Object, e As EventArgs) Handles Button1.Click
        Dim result As Integer
        For Each pro As Process In Process.GetProcesses
            Try
                If pro.ProcessName = "notepad" Then
                    Dim mainWin As IntPtr = pro.MainWindowHandle
                    result = ShowWindow(mainWin, SW_HIDE)
                End If
            Catch ex As Exception

            End Try
        Next
    End Sub

显示窗口代码：

    Private Sub Button2_Click(sender As Object, e As EventArgs) Handles Button2.Click
        Dim result As Integer
        For Each pro As Process In Process.GetProcesses
            Try
                If pro.ProcessName = "notepad" Then
                    Dim mainWin As IntPtr = pro.MainWindowHandle
                    result = ShowWindow(mainWin, SW_SHOW)
                End If
            Catch ex As Exception

            End Try
        Next
    End Sub

如果用了以上代码，会发现，隐藏窗口没问题，但是却不能显示窗口。

添加监视，可以发现显示窗口代码中，mainWin为0，这是因为窗口隐藏后不会有窗口句柄。

只需要在隐藏时把窗口的句柄保存下来就可以隐藏后又显示出来。

修改后的代码如下：

    Declare Function ShowWindow Lib "user32" Alias "ShowWindow" (ByVal hwnd As IntPtr, ByVal nCmdShow As Integer) As Integer
    Public Const SW_HIDE As Integer = 0
    Public Const SW_SHOW As Integer = 5

    Dim hwnd As IntPtr = IntPtr.Zero

    Private Sub Button1_Click(sender As Object, e As EventArgs) Handles Button1.Click
        Dim result As Integer
        For Each pro As Process In Process.GetProcesses
            Try
                If pro.ProcessName = "notepad" Then
                    hwnd = pro.MainWindowHandle
                    result = ShowWindow(hwnd, SW_HIDE)
                    Exit For
                End If
            Catch ex As Exception

            End Try
        Next
    End Sub


    Private Sub Button3_Click(sender As Object, e As EventArgs) Handles Button3.Click
        Dim result As Integer
        Try
            result = ShowWindow(hwnd, SW_SHOW)
        Catch ex As Exception

        End Try
    End Sub

在网上找到的很多代码，只会告诉使用ShowWindow可以隐藏显示窗口，但是并没有告诉需要保存原窗口的句柄。

由于.net平台下C#和vb.NET很相似，本文也可以为C#爱好者提供参考。

学习更多vb.net知识，请参看 vb.net 教程 目录