【wxWidgets】【響應Windows消息】【監聽WM_DEVICECHANGE消息、解決監聽不到DBT_DEVICEARRIVAL的問題、監測USB設備拔插】

緣由：在修改一份舊代碼，是基於wxWidgets開發的，使用VS2017編譯。修改過程中，發現wxWidgets需要響應WM_DEVICECHANGE消息，用來監測USB設備的拔插，但是，進一步發現，如果只是依靠wxWidgets本身提供的功能是不能知道USB設備插入（DBT_DEVICEARRIVAL）事件的。這其實涉及到幾方面問題了。

1，wxWidgets怎麼攔截/監聽/響應Windows的消息？

只要在wxFrame的繼承類重寫下面MSWWindowProc函數即可，比如

//如果有必要就 #include <Windows.h>

WXLRESULT ProjectWindow::MSWWindowProc(WXUINT message, WXWPARAM wParam, WXLPARAM lParam)
{
	wxLogDebug(wxT("MSWWindowProc nMsg=%x,%x %x"), nMsg, wParam, lParam);
	if (WM_PAINT == message) {
		//...這裏就可以額外響應WM_PAINT消息了。
	}
	return wxFrame::MSWWindowProc(message, wParam, lParam);
}

2，攔截/監聽 WM_DEVICECHANGE消息

記住要包含頭文件

#include <Dbt.h>
#include <usb.h>
#include <usbuser.h>
#include <usbiodef.h>

實踐表明，單單就照着下面這麼寫，可以監聽到WM_DEVICECHANGE，能知道DBT_DEVNODES_CHANGED，但是不能獲取到DBT_DEVICEARRIVAL和DBT_DEVICEREMOVECOMPLETE 事件。

WXLRESULT ProjectWindow::MSWWindowProc(WXUINT message, WXWPARAM wParam, WXLPARAM lParam)
{
	//wxLogDebug(wxT("MSWWindowProc %08x %08x %08x"), nMsg, wParam, lParam);
	if ( WM_DEVICECHANGE == message) 
	{    
		//注意，此時，只能獲取到DBT_DEVNODES_CHANGED事件
		if ( DBT_DEVICEARRIVAL == wParam) {
			wxLogDebug(wxT("system detected a new device"));
		}
		else if( DBT_DEVICEREMOVECOMPLETE == wParam ) {
			wxLogDebug(wxT("device is gone"));
		}
		else if( DBT_DEVNODES_CHANGED == wParam ) {
			wxLogDebug(wxT("device nodes changed"));
		}
	}
	return wxFrame::MSWWindowProc(message, wParam, lParam);
}

3，怎麼知道USB設備拔插事件？

基於WM_DEVICECHANGE 要區分DBT_DEVICEARRIVAL和DBT_DEVICEREMOVECOMPLETE事件，怎麼實現？

關鍵之處就是，要額外註冊USB設備事件，完整版如下

//Howard 2020-04-01
WXLRESULT ProjectWindow::MSWWindowProc(WXUINT message, WXWPARAM wParam, WXLPARAM lParam)
{
	//wxLogDebug(wxT("MSWWindowProc nMsg=%x,%x %x"), nMsg, wParam, lParam);
	if (WM_PAINT == message) {
		//僅僅方便測試，關鍵就是要註冊！！
		static bool isNeedRegister = true;
		if (isNeedRegister) {
			isNeedRegister = false;

			DEV_BROADCAST_DEVICEINTERFACE NotificationFilter;
			ZeroMemory(&NotificationFilter, sizeof(NotificationFilter));
			NotificationFilter.dbcc_size = sizeof(DEV_BROADCAST_DEVICEINTERFACE);
			NotificationFilter.dbcc_devicetype = DBT_DEVTYP_DEVICEINTERFACE;
			NotificationFilter.dbcc_classguid = GUID_DEVINTERFACE_USB_DEVICE;
			HWND hWnd = (HWND)this->GetHWND();
			RegisterDeviceNotification(hWnd, &NotificationFilter, DEVICE_NOTIFY_WINDOW_HANDLE);
		}
	}

	else if ( WM_DEVICECHANGE == message)
	{
		wxLogDebug(wxT("WM_DEVICECHANGE %x %x"), wParam, lParam);
		if ( DBT_DEVICEARRIVAL == wParam) {
			wxLogDebug(wxT("system detected a new device"));//USB設備插入
		}
		else if( DBT_DEVICEREMOVECOMPLETE == wParam ) {
			wxLogDebug(wxT("device is gone"));//USB設備拔出
		}
		else if( DBT_DEVNODES_CHANGED == wParam ) {
			wxLogDebug(wxT("device nodes changed"));
		}
	}
	return wxFrame::MSWWindowProc(message, wParam, lParam);
}

 

4，特別說明，設備類型與GUID

特別強調，對於監聽HID設備，使用的GUID是不同的。不同類型設備，對應的GUID是有明確規定的。

Common Device Class GUIDs
Class	GUID	Device Description
CDROM	4D36E965-E325-11CE-BFC1-08002BE10318	CD/DVD/Blu-ray drives
DiskDrive	4D36E967-E325-11CE-BFC1-08002BE10318	Hard drives
Display	4D36E968-E325-11CE-BFC1-08002BE10318	Video adapters
FDC	4D36E969-E325-11CE-BFC1-08002BE10318	Floppy controllers
FloppyDisk	4D36E980-E325-11CE-BFC1-08002BE10318	Floppy drives
HDC	4D36E96A-E325-11CE-BFC1-08002BE10318	Hard drive controllers
HIDClass	745A17A0-74D3-11D0-B6FE-00A0C90F57DA	Some USB devices
1394	6BDD1FC1-810F-11D0-BEC7-08002BE2092F	IEEE 1394 host controller
Image	6BDD1FC6-810F-11D0-BEC7-08002BE2092F	Cameras and scanners
Keyboard	4D36E96B-E325-11CE-BFC1-08002BE10318	Keyboards
Modem	4D36E96D-E325-11CE-BFC1-08002BE10318	Modems
Mouse	4D36E96F-E325-11CE-BFC1-08002BE10318	Mice and pointing devices
Media	4D36E96C-E325-11CE-BFC1-08002BE10318	Audio and video devices
Net	4D36E972-E325-11CE-BFC1-08002BE10318	Network adapters
Ports	4D36E978-E325-11CE-BFC1-08002BE10318	Serial and parallel ports
SCSIAdapter	4D36E97B-E325-11CE-BFC1-08002BE10318	SCSI and RAID controllers
System	4D36E97D-E325-11CE-BFC1-08002BE10318	System buses, bridges, etc.
USB	36FC9E60-C465-11CF-8056-444553540000	USB host controllers and hubs

參考資料：

https://docs.microsoft.com/en-us/windows/win32/devio/detecting-media-insertion-or-removal

https://stackoverflow.com/questions/30399992/wm-devicechange-received-but-not-dbt-devicearrival-in-my-qt-app