HOOK（钩子，挂钩）是一种实现Windows平台下类似于中断的机制。HOOK机制允许应用程序拦截并处理Windows消息或指定事件，当指定的消息发出后，HOOK程序就可以在消息到达目标窗口之前将其捕获，从而得到对消息的控制权，进而可以对该消息进行处理或修改，加入我们所需的功能。钩子按使用范围分，可分为线程钩子和系统钩子，其中，系统钩子具有相当大的功能，几乎可以实现对所有Windows消息的拦截、处理和监控。这项技术涉及到两个重要的API，一个是SetWindowsHookEx，安装钩子；另一个是UnHookWindowsHookEx，卸载钩子。
本文使用的HOOK API技术，是指截获系统或进程对某个API函数的调用，使得API的执行流程转向我们指定的代码段，从而实现我们所需的功能。Windows下的每个进程均拥有自己的地址空间，并且进程只能调用其地址空间内的函数，因此HOOK API尤为关键的一步是，设法将自己的代码段注入到目标进程中，才能进一步实现对该进程调用的API进行拦截。然而微软并没有提供HOOK API的调用接口，这就需要开发者自己编程实现。
一般来说，HOOK API由两个组成部分，即实现HOOK API的DLL文件，和启动注入的主调程序。本文采用HOOK API 技术对剪切板相关的API 函数进行拦截，从而实现对剪切板内容的监控功能，同样使用该技术实现进程防终止功能。其中DLL文件支持HOOK API的实现，而主调客户端程序将在初始化时把带有HOOK API功能的DLL随着鼠标钩子的加载注入到目标进程中，这里的鼠标钩子属于系统钩子。
下面介绍在Revit中，如何应用Hook对鼠标双击元素事件进行拦截。
第一步，先封装HookBase抽象类，因所有Hook的都具有注册、卸载逻辑，且注册、卸载大同小易。如下
public abstract class HookBase : IHook
{
private static Dictionary<int, IHook> m_Hooks;
private IntPtr m_ProcessId;
private int m_ThreadId;
private HookType m_HookType;
private HookProc m_HookProc;
protected internal int m_HookId;
static HookBase(){
m_Hooks = new Dictionary<int, IHook>();
}
private HookBase(HookType hookType){
m_HookType = hookType;
m_HookProc = HookProc;
}
protected HookBase(IntPtr processId, HookType hookType):this(hookType){
m_ProcessId = processId;
if (m_ProcessId == IntPtr.Zero)
{
m_ProcessId = HookHelper.GetCurrentProcessId();
}
}
protected HookBase(int threadId, HookType hookType):this(hookType){
m_ThreadId = threadId;
if (m_ThreadId == 0)
{
m_ThreadId = HookHelper.GetCurrentThreadId();
}
}
public void Install(){
if (m_ThreadId != 0)
{
m_HookId = HookHelper.SetWindowsHookEx(m_HookType, m_HookProc, IntPtr.Zero, m_ThreadId);
}
else
{
if (m_ProcessId == IntPtr.Zero)
{
return;
}
m_HookId = HookHelper.SetWindowsHookEx(m_HookType, m_HookProc, m_ProcessId,0);
}
if (m_HookId == 0)
{
return;
}
if (!m_Hooks.ContainsKey(m_HookId))
{
m_Hooks.Add(m_HookId, this);
}
}
public void Uninstall()
{
if (m_HookId == 0)
{
return;
}
var flag = HookHelper.UnhookWindowsHookEx(m_HookId);
if (flag)
{
if (m_Hooks.Remove(m_HookId))
{
m_HookId = 0;
}
}
}
protected abstract int HookProc(int nCode, IntPtr wParam, IntPtr lParam);
第二步 ，因鼠标Hook分为线程鼠标Hook以及全局鼠标Hook两种，仅注册方式有点区别。为使用方便，将其封装为事件注册方式。如下
public abstract class MouseHookBase : HookBase
{
protected MouseHookBase(IntPtr processId)
: base(processId, HookType.WH_MOUSE_LL)
{
}
protected MouseHookBase(int threadId)
: base(threadId, HookType.WH_MOUSE)
{
}
public event HookHandler<MouseEventArgs> MouseDoubleClick;
public event HookHandler<MouseEventArgs> MouseMove;
public event HookHandler<MouseEventArgs> MouseDown;
public event HookHandler<MouseEventArgs> MouseUp;
protected override int HookProc(int nCode, IntPtr wParam, IntPtr lParam)
{
if (nCode < 0)
{
return HookHelper.CallNextHookEx(m_HookId, nCode, wParam, lParam);
}
var mouseMsg = (MouseMessage)wParam.ToInt32();
var mouseHookStruct = lParam.ToStruct<MOUSEHOOKSTRUCT>();
var button = this.GetMouseButtons(mouseMsg);
switch (mouseMsg)
{
case MouseMessage.WM_LBUTTONDOWN:
case MouseMessage.WM_RBUTTONDOWN:
case MouseMessage.WM_MBUTTONDOWN:
return this.OnRaiseMouseDown(button, 1, mouseHookStruct.pt.X, mouseHookStruct.pt.Y, mouseHookStruct.mouseData);
case MouseMessage.WM_LBUTTONUP:
case MouseMessage.WM_MBUTTONUP:
case MouseMessage.WM_RBUTTONUP:
return this.OnRaiseMouseUp(button, 1, mouseHookStruct.pt.X, mouseHookStruct.pt.Y, mouseHookStruct.mouseData);
case MouseMessage.WM_LBUTTONDBLCLK:
case MouseMessage.WM_RBUTTONDBLCLK:
case MouseMessage.WM_MBUTTONDBLCLK:
return this.OnRaiseMouseDoubleClick(button, 2, mouseHookStruct.pt.X, mouseHookStruct.pt.Y, mouseHookStruct.mouseData);
case MouseMessage.WM_MOUSEMOVE:
return this.OnRaiseMouseMove(MouseButtons.None, 0, mouseHookStruct.pt.X, mouseHookStruct.pt.Y, mouseHookStruct.mouseData);
default:
return HookHelper.CallNextHookEx(m_HookId, nCode, wParam, lParam);
}
}
private MouseButtons GetMouseButtons(MouseMessage mouseMsg)
{
MouseButtons result = MouseButtons.None;
switch (mouseMsg)
{
case MouseMessage.WM_LBUTTONDBLCLK:
case MouseMessage.WM_LBUTTONDOWN:
case MouseMessage.WM_LBUTTONUP:
result = MouseButtons.Left;
break;
case MouseMessage.WM_MBUTTONDBLCLK:
case MouseMessage.WM_MBUTTONDOWN:
case MouseMessage.WM_MBUTTONUP:
result = MouseButtons.Middle;
break;
case MouseMessage.WM_RBUTTONDBLCLK:
case MouseMessage.WM_RBUTTONDOWN:
case MouseMessage.WM_RBUTTONUP:
result = MouseButtons.Right;
break;
}
return result;
}
private int OnRaiseMouseDoubleClick(MouseButtons button, int clicks, int x, int y, intdelta)
{
if (this.MouseDoubleClick != null)
{
return this.MouseDoubleClick(this, new MouseEventArgs(button, clicks, x, y, delta));
}
return 0;
}
private int OnRaiseMouseDown(MouseButtons button, int clicks, int x, int y, int delta)
{
if (this.MouseDown != null)
{
return this.MouseDown(this, new MouseEventArgs(button, clicks, x, y, delta));
}
return 0;
}
private int OnRaiseMouseUp(MouseButtons button, int clicks, int x, int y, int delta)
{
if (this.MouseUp != null)
{
return this.MouseUp(this, new MouseEventArgs(button, clicks, x, y, delta));
}
return 0;
}
private int OnRaiseMouseMove(MouseButtons button, int clicks, int x, int y, int delta)
{
if (this.MouseMove != null)
{
return this.MouseMove(this, new MouseEventArgs(button, clicks, x, y, delta));
}
return 0;
}
}
第三步，依次实现线程鼠标Hook以及全局鼠标Hook.
public class MouseHook : MouseHookBase{
public MouseHook(int threadId = 0)
: base(threadId)
{
}
}
public class GlobalMouseHook : MouseHookBase
{
public GlobalMouseHook(IntPtr processId)
: base(processId)
{
}
}
第四步，有了鼠标Hook，我们如果在Revit内使用并且拦截鼠标双击元素事件呢？我们继续封装一个元素监控类 ，如下：
public class ElementMonitor
{
private static ElementMonitor m_Instance;
private MouseHook m_MouseHook;
private bool m_IsMonitor;
private UIApplication m_UIApplication;
private ElementMonitor(UIApplication uiApp)
{
m_Instance = this;
m_UIApplication = uiApp;
m_MouseHook = new MouseHook();
m_MouseHook.Install();
m_MouseHook.MouseDoubleClick += OnRaiseMouseDoubleClick;
}
/// <summary>
/// 静态实例，可在入口类判断此实例是否为null，防止重复注册.
/// </summary>
public static ElementMonitor Instance
{
get
{
return m_Instance;
}
}
/// <summary>
/// 当鼠标双击元素时触发此事件.
/// </summary>
public event HookHandler<DoubleClickElementEventArgs> DoubleClickElement;
/// <summary>
/// 注册元素监控，并指定是否立即监控.
/// </summary>
public static void Register(UIApplication uiApp, bool immediatelyMonitor = true)
{
if (uiApp == null)
{
throw new ArgumentNullException(nameof(uiApp));
}
new ElementMonitor(uiApp)
{
m_IsMonitor = immediatelyMonitor
};
}
/// <summary>
/// 注册元素监控，并指定是否立即监控.
/// </summary>
public static void Register(UIControlledApplication uiControllApp, bool immediatelyMonitor = true)
{
if (uiControllApp == null)
{
throw new ArgumentNullException(nameof(uiControllApp));
}
var flag = System.Reflection.BindingFlags.NonPublic | System.Reflection.BindingFlags.Instance | System.Reflection.BindingFlags.InvokeMethod;
var uiApp = (UIApplication)uiControllApp.GetType().InvokeMember("getUIApplication", flag, Type.DefaultBinder, uiControllApp, null);
Register(uiApp, immediatelyMonitor);
}
/// <summary>
/// 返回1，则拦截鼠标消息，返回0则传递给真正消息接收者.
/// </summary>
private int OnRaiseMouseDoubleClick(object sender, System.Windows.Forms.MouseEventArgs e)
{
if (!m_IsMonitor || e.Button != MouseButtons.Left || e.Clicks != 2)
{
return 0;
}
var uiDoc = m_UIApplication.ActiveUIDocument;
if (uiDoc == null)
{
return 0;
}
var elemIds = uiDoc.Selection.GetElementIds();
if (elemIds.Count == 1)
{
var elem = uiDoc.Document.GetElement(elemIds.First());
if (elem == null)
{
return 0;
}
if (this.DoubleClickElement == null)
{
return 0;
}
return this.DoubleClickElement(this, new DoubleClickElementEventArgs(elem));
}
return 0;
}
}
第五步，调用测试，如下
[Transaction(TransactionMode.Manual)]
public class MouseHookTest : IExternalCommand
{
Result IExternalCommand.Execute(ExternalCommandData commandData, ref string message, ElementSet elements)
{
if (ElementMonitor.Instance == null)
{
ElementMonitor.Register(commandData.Application);
}
ElementMonitor.Instance.DoubleClickElement += OnRaiseDoubleClickElement;
return Result.Succeeded;
}
private int OnRaiseDoubleClickElement(object sender, DoubleClickElementEventArgs e)
{
if (e.Element == null)
{
return 0;
}
System.Windows.Forms.MessageBox.Show(string.Format("双击击元素Id： {0}", e.Element.Id));
return 1;
}
}
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