.net - 处理 Windows USB 事件

Question

我创建了一个通用的 USB HID 通信驱动程序，能够监视 USB 事件并在设备之间发送/接收数据包。自从我的WinForms日子以来，我一直在成功使用它，因为大部分代码都是从 MSDN 中挑选出来的，并且与这里建议的方式非常相似。我的问题是：我看到的示例继续依赖似乎是旧的“Windows 消息”架构，即System.Runtime.InteropServicesWM_xxxxxxx 类型的消息，在纯C# WPF应用程序中注册/处理这些HwndHandler，覆盖WndProc等。我想知道没有一种使用更现代的、事件驱动的方法来处理 USB 事件的方法，比如使用delegates、订阅EventHandlers等？甚至这个SO帖子建议不要使用这种过时的方法，我想也必须有针对USB事件的解决方案。谢谢。

Answer 1

经过一番研究，似乎 Windows 消息传递是处理 USB 设备更改通知的必要部分。我有一个工作的 USB 通信驱动程序类，其中包括一个简单的实现。该解决方案由两部分组成，1)EventNotifier生成事件的类和 2) 订阅事件的“接收器”（即接收 USB 事件通知的客户端）。示例代码是 C++/CLI，虽然我不赞成将可执行代码放在头文件中的做法，但为了简洁起见，我在这里这样做。

#pragma once

#include <Windows.h>    // Declares required datatypes.
#include <Dbt.h>        // Required for WM_DEVICECHANGE messages.
#include <initguid.h>   // Required for DEFINE_GUID definition (see below).

namespace USBComms 
{
    using namespace System;
    using namespace System::Runtime::InteropServices;
    using namespace System::Windows;
    using namespace System::Windows::Forms;

    // This function is required for receieving WM_DEVICECHANGE messages.
    // Note: name is remapped "RegisterDeviceNotificationUM"
    [DllImport("user32.dll" , CharSet = CharSet::Unicode, EntryPoint="RegisterDeviceNotification")]                 
    extern "C" HDEVNOTIFY WINAPI RegisterDeviceNotificationUM(
        HANDLE hRecipient,
        LPVOID NotificationFilter,
        DWORD Flags);

    // Generic guid for usb devices (see e.g. http://msdn.microsoft.com/en-us/library/windows/hardware/ff545972%28v=vs.85%29.aspx).
    // Note: GUIDs are device and OS specific and may require modification. Using the wrong guid will cause notification to fail.
    // You may have to tinker with your device to find the appropriate GUID. "hid.dll" has a function `HidD_GetHidGuid' that returns
    // "the device interfaceGUID for HIDClass devices" (see http://msdn.microsoft.com/en-us/library/windows/hardware/ff538924%28v=vs.85%29.aspx).
    // However, testing revealed it does not always return a useful value. The GUID_DEVINTERFACE_USB_DEVICE value, defined as
    // {A5DCBF10-6530-11D2-901F-00C04FB951ED}, has worked with cell phones, thumb drives, etc. For more info, see e.g.
    // http://msdn.microsoft.com/en-us/library/windows/hardware/ff553426%28v=vs.85%29.aspx. 
    DEFINE_GUID(GUID_DEVINTERFACE_USB_DEVICE, 0xA5DCBF10L, 0x6530, 0x11D2, 0x90, 0x1F, 0x00, 0xC0, 0x4F, 0xB9, 0x51, 0xED);

    /// <summary>
    /// Declare a delegate for the notification event handler.
    /// </summary>
    /// <param name="sender">The object where the event handler is attached.</param>
    /// <param name="e">The event data.</param>
    public delegate void NotificationEventHandler(Object^ sender, EventArgs^ e);

    /// <summary>
    /// Class that generetaes USB Device Change notification events.
    /// </summary>
    /// <remarks>
    /// A Form is not necessary. Any type wherein you can override WndProc() can be used.
    /// </remarks>
    public ref class EventNotifier : public Control
    {
    private:
        /// <summary>
        /// Raises the NotificationEvent.
        /// </summary>
        /// <param name="e">The event data.</param>
        void RaiseNotificationEvent(EventArgs^ e) {
            NotificationEvent(this, e);
        }

    protected:
        /// <summary>
        /// Overrides the base class WndProc method.
        /// </summary>
        /// <param name="message">The Windows Message to process. </param>
        /// <remarks>
        /// This method receives Windows Messages (WM_xxxxxxxxxx) and
        /// raises our NotificationEvent as appropriate. Here you should
        /// add any message filtering (e.g. for the WM_DEVICECHANGE) and
        /// preprocessing before raising the event (or not).
        /// </remarks>
        virtual void WndProc(Message% message) override {
            if(message.Msg == WM_DEVICECHANGE)
            {
                RaiseNotificationEvent(EventArgs::Empty);
            }
            __super::WndProc(message);
        }

    public:
        /// <summary>
        /// Creates a new instance of the EventNotifier class.
        /// </summary>
        EventNotifier(void) {
            RequestNotifications(this->Handle); // Register ourselves as the Windows Message processor.
        }

        /// <summary>
        /// Registers an object, identified by the handle, for
        /// Windows WM_DEVICECHANGE messages.
        /// </summary>
        /// <param name="handle">The object's handle.</param>
        void RequestNotifications(IntPtr handle) {
            GUID InterfaceClassGuid = GUID_DEVINTERFACE_USB_DEVICE;
            DEV_BROADCAST_DEVICEINTERFACE MyDeviceBroadcastHeader;

            MyDeviceBroadcastHeader.dbcc_devicetype = DBT_DEVTYP_DEVICEINTERFACE;
            MyDeviceBroadcastHeader.dbcc_size = sizeof(DEV_BROADCAST_DEVICEINTERFACE);
            MyDeviceBroadcastHeader.dbcc_reserved = 0;
            MyDeviceBroadcastHeader.dbcc_classguid = InterfaceClassGuid;
            RegisterDeviceNotificationUM((HANDLE)handle, &MyDeviceBroadcastHeader, DEVICE_NOTIFY_WINDOW_HANDLE);
        }

        /// <summary>
        /// Defines the notification event.
        /// </summary>
        virtual event NotificationEventHandler^ NotificationEvent;
    };
}

然后，在“接收者”（订阅和消费我们的对象）中NotificationEvent，您所要做的就是：

void Receiver::SomeFunction(void)
{
    USBComms::EventNotifier usb = gcnew USBComms::EventNotifier();

    usb->NotificationEvent += gcnew USBComms::NotificationEventHandler(this, &Receiver::USBEvent);
}

void Receiver::USBEvent(Object^ sender, EventArgs^ e)
{
    // Handle the event notification as appropriate.
}