【发布时间】：2012-02-16 06:26:25
【问题描述】：
我有一个显示的表单，不是通过 ShowDialog，而是通过将其 visible 属性设置为 true。这样它的行为就像一个下拉菜单。
表单安装鼠标钩子，使用SetWindowsHookEx(WH_MOUSE, ...)。
我检测鼠标是否在下拉列表之外被点击，如果是，则在我的HookProc 方法中返回 1 并关闭下拉列表。
奇怪的是，如果我在下拉菜单之外点击文本框，在我的下拉菜单关闭后，文本框仍然会收到鼠标点击，即使它是由我的 HookProc 方法处理的。
它变得陌生...如果我点击一个标签或按钮，他们不会像预期的那样在下拉关闭后收到鼠标点击！
知道发生了什么吗？
预计到达时间 2：
您可以忽略我下面的所有代码，因为经过进一步调查，我发现这种行为至少在一个实现下拉类型表单的框架控件中表现出来。
要复制，创建一个表单并添加一个属性网格、按钮、文本框和标签。将属性网格的选定对象设置为字体。
运行表单并选择字体名称。出现一个下拉列表。现在单击表单的文本框。触发文本框单击事件。但是，按钮或标签不会发生同样的情况。
发生了什么事？
预计到达时间 1：
这里有一些来自 How to set a Windows hook in Visual C# .NET 的基本代码来演示发生了什么。我使用转换器将代码转换回 C#，但希望没问题。我不确定，但您可能需要将 Console.WriteLine 替换为 Debug.WriteLine。
创建两个表单，Form1 和 DropDown。
(1) VB.NET
在Form1中，添加Button、Label和TextBox，代码如下。
Imports System.Runtime.InteropServices
Public Class Form1
Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
Console.WriteLine("Button1_Click")
Dim dd As New DropDown
dd.Visible = True
Do While dd.Visible
Application.DoEvents()
MsgWaitForMultipleObjectsEx(0, IntPtr.Zero, 250, &HFF, 4)
Loop
End Sub
<DllImport("user32.dll", CharSet:=CharSet.Auto, ExactSpelling:=True)> _
Public Shared Function MsgWaitForMultipleObjectsEx(ByVal nCount As Integer, ByVal pHandles As IntPtr, ByVal dwMilliseconds As Integer, ByVal dwWakeMask As Integer, ByVal dwFlags As Integer) As Integer
End Function
Private Sub Label1_Click(ByVal sender As Object, ByVal e As System.EventArgs) Handles Label1.Click
Console.WriteLine("Label1_Click")
End Sub
Private Sub TextBox1_Click(ByVal sender As Object, ByVal e As System.EventArgs) Handles TextBox1.Click
Console.WriteLine("TextBox1_Click")
End Sub
End Class
在 DropDown 中，放置以下代码。
Imports System.Runtime.InteropServices
Public Class DropDown
Public Delegate Function HookProc(ByVal nCode As Integer, ByVal wParam As IntPtr, ByVal lParam As IntPtr) As Integer
Private hHook As Integer = 0
Public Const WH_MOUSE As Integer = 7
Private MouseHookProcedure As HookProc
<StructLayout(LayoutKind.Sequential)> _
Public Class POINT
Public x As Integer
Public y As Integer
End Class
<StructLayout(LayoutKind.Sequential)> _
Public Class MouseHookStruct
Public pt As POINT
Public hwnd As Integer
Public wHitTestCode As Integer
Public dwExtraInfo As Integer
End Class
<DllImport("user32.dll", CharSet:=CharSet.Auto, CallingConvention:=CallingConvention.StdCall)> _
Public Shared Function SetWindowsHookEx(ByVal idHook As Integer, ByVal lpfn As HookProc, ByVal hInstance As IntPtr, ByVal threadId As Integer) As Integer
End Function
<DllImport("user32.dll", CharSet:=CharSet.Auto, CallingConvention:=CallingConvention.StdCall)> _
Public Shared Function UnhookWindowsHookEx(ByVal idHook As Integer) As Boolean
End Function
<DllImport("user32.dll", CharSet:=CharSet.Auto, CallingConvention:=CallingConvention.StdCall)> _
Public Shared Function CallNextHookEx(ByVal idHook As Integer, ByVal nCode As Integer, ByVal wParam As IntPtr, ByVal lParam As IntPtr) As Integer
End Function
Protected Overrides Sub OnDeactivate(ByVal e As System.EventArgs)
MyBase.OnDeactivate(e)
UnhookWindowsHookEx(hHook)
hHook = 0
End Sub
Public Sub New()
InitializeComponent()
MouseHookProcedure = New HookProc(AddressOf MouseHookProc)
hHook = SetWindowsHookEx(WH_MOUSE, MouseHookProcedure, New IntPtr(0), AppDomain.GetCurrentThreadId())
End Sub
Public Function MouseHookProc(ByVal nCode As Integer, ByVal wParam As IntPtr, ByVal lParam As IntPtr) As Integer
Dim MyMouseHookStruct As MouseHookStruct = DirectCast(Marshal.PtrToStructure(lParam, GetType(MouseHookStruct)), MouseHookStruct)
If nCode < 0 Then
Return CallNextHookEx(hHook, nCode, wParam, lParam)
Else
Select Case CInt(wParam)
Case &H21, &HA1, &HA4, &H204, &H207, &HA7, &H201
Me.Visible = False
Return 1
End Select
Return CallNextHookEx(hHook, nCode, wParam, lParam)
End If
End Function
End Class
(2) C#
在Form1中添加一个Button、Label和TextBox，代码如下：
using System.Runtime.InteropServices;
public class Form1
{
public Form1()
{
InitializeComponent();
Button1.Click += Button1_Click;
Label1.Click += Label1_Click;
TextBox1.Click += TextBox1_Click;
}
private void Button1_Click(System.Object sender, System.EventArgs e)
{
Console.WriteLine("Button1_Click");
DropDown dd = new DropDown();
dd.Visible = true;
while (dd.Visible) {
Application.DoEvents();
MsgWaitForMultipleObjectsEx(0, IntPtr.Zero, 250, 0xff, 4);
}
}
[DllImport("user32.dll", CharSet = CharSet.Auto, ExactSpelling = true)]
public static extern int MsgWaitForMultipleObjectsEx(int nCount, IntPtr pHandles, int dwMilliseconds, int dwWakeMask, int dwFlags);
private void Label1_Click(object sender, System.EventArgs e)
{
Console.WriteLine("Label1_Click");
}
private void TextBox1_Click(object sender, System.EventArgs e)
{
Console.WriteLine("TextBox1_Click");
}
}
在 DropDown 中，放置以下代码：
using System.Runtime.InteropServices;
public class DropDown
{
public delegate int HookProc(int nCode, IntPtr wParam, IntPtr lParam);
private int hHook = 0;
public const int WH_MOUSE = 7;
private HookProc MouseHookProcedure;
[StructLayout(LayoutKind.Sequential)]
public class POINT
{
public int x;
public int y;
}
[StructLayout(LayoutKind.Sequential)]
public class MouseHookStruct
{
public POINT pt;
public int hwnd;
public int wHitTestCode;
public int dwExtraInfo;
}
[DllImport("user32.dll", CharSet = CharSet.Auto, CallingConvention = CallingConvention.StdCall)]
public static extern int SetWindowsHookEx(int idHook, HookProc lpfn, IntPtr hInstance, int threadId);
[DllImport("user32.dll", CharSet = CharSet.Auto, CallingConvention = CallingConvention.StdCall)]
public static extern bool UnhookWindowsHookEx(int idHook);
[DllImport("user32.dll", CharSet = CharSet.Auto, CallingConvention = CallingConvention.StdCall)]
public static extern int CallNextHookEx(int idHook, int nCode, IntPtr wParam, IntPtr lParam);
protected override void OnDeactivate(System.EventArgs e)
{
base.OnDeactivate(e);
UnhookWindowsHookEx(hHook);
hHook = 0;
}
public DropDown()
{
InitializeComponent();
MouseHookProcedure = new HookProc(MouseHookProc);
hHook = SetWindowsHookEx(WH_MOUSE, MouseHookProcedure, new IntPtr(0), AppDomain.GetCurrentThreadId());
}
public int MouseHookProc(int nCode, IntPtr wParam, IntPtr lParam)
{
MouseHookStruct MyMouseHookStruct = (MouseHookStruct)Marshal.PtrToStructure(lParam, typeof(MouseHookStruct));
if (nCode < 0) {
return CallNextHookEx(hHook, nCode, wParam, lParam);
}
else {
switch ((int)wParam) {
case 0x21:
case 0xa1:
case 0xa4:
case 0x204:
case 0x207:
case 0xa7:
case 0x201:
this.Visible = false;
return 1;
}
return CallNextHookEx(hHook, nCode, wParam, lParam);
}
}
}
【问题讨论】：
标签： .net vb.net winforms mouse-hook