WM_DEVICECHANGE使用方式

WM_DEVICECHANGE的使用方式有二種，一種是透過WindowProc()的方式，一種是直接在程式裡加上OnDeviceChange()的函數，底下就先介紹第二種方式。

1. 新增消息 -- 在Dialog的.cpp裡加上藍色部份:
BEGIN_MESSAGE_MAP(CDeviceMonitorDlg, CDialog)
ON_WM_PAINT()
ON_WM_QUERYDRAGICON()
//}}AFX_MSG_MAP
ON_WM_DEVICECHANGE()
END_MESSAGE_MAP()

2.新增一個函數 -- 這是Microsoft所提供的函數型態
DECLARE_MESSAGE_MAP()
public:
afx_msg BOOL OnDeviceChange(UINT nEventType,DWORD_PTR dwData);

3.函数內容的实现
BOOL OnDeviceChange(UINT nEventType,DWORD_PTR dwData)
{

      switch(nEventType)

      {

      case DBT_DEVICEARRIVAL:

              return TRUE;

      }

}

4. 在MSDN上的說明

afx_msg BOOL OnDeviceChange(
   UINT nEventType,
   DWORD_PTR dwData 
);

Parameters

 nEventType

An event type. See the Remarks section for a description of the available values

dwData

The address of a structure that contains event-specific data. Its meaning depends on the given event.

For devices that offer software-controllable features, such as ejection and locking, the operating system typically sends aDBT_DEVICEREMOVEPENDING message to let applications and device drivers end their use of the device gracefully.

If the operating system forcefully removes of a device, it may not send a DBT_DEVICEQUERYREMOVE message before doing so.

The nEvent parameter can be one of these values:

• DBT_DEVICEARRIVAL   A device has been inserted and is now available.
• DBT_DEVICEQUERYREMOVE   Permission to remove a device is requested. Any application can deny this request and cancel the removal.
• DBT_DEVICEQUERYREMOVEFAILED   Request to remove a device has been canceled.
• DBT_DEVICEREMOVEPENDING   Device is about to be removed. Cannot be denied.
• DBT_DEVICEREMOVECOMPLETE   Device has been removed.
• DBT_DEVICETYPESPECIFIC   Device-specific event.
• DBT_CONFIGCHANGED   Current configuration has changed.
• DBT_DEVNODES_CHANGED   Device node has changed.

Note   This member function is called by the framework to allow your application to handle a Windows message. The parameters passed to your function reflect the parameters received by the framework when the message was received. If you call the base-class implementation of this function, that implementation will use the parameters originally passed with the message and not the parameters you supply to the function.

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WM_DEVICECHANGE使用方式

原文：http://www.cnblogs.com/poetblog/p/3608667.html