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如题，特别是它的各个返回参数是什么意思！
有人曾回答我说：
The WM_DEVICECHANGE device message notifies an application or device driver of a change to the hardware configuration of a device or the computer.
Event = (UINT) wParam;
dwData = (DWORD) lParam;
Parameters
Event
Event type. This parameter can be one of the following values:
Value Meaning
DBT_CONFIGCHANGECANCELED A request to change the current configuration (dock or undock) has been canceled.
DBT_CONFIGCHANGED The current configuration has changed, due to a dock or undock.
DBT_DEVICEARRIVAL A device has been inserted and is now available.
DBT_DEVICEQUERYREMOVE Permission is requested to remove a device. Any application can deny this request and cancel the removal.
DBT_DEVICEQUERYREMOVEFAILED A request to remove a device has been canceled.
DBT_DEVICEREMOVECOMPLETE A device has been removed.
DBT_DEVICEREMOVEPENDING A device is about to be removed. Cannot be denied.
DBT_DEVICETYPESPECIFIC A device-specific event has occurred.
DBT_QUERYCHANGECONFIG Permission is requested to change the current configuration (dock or undock).
DBT_USERDEFINED The meaning of this message is user-defined.
dwData
Address of a structure that contains event-specific data. Its meaning depends on the given event.
Return Values
Return TRUE to grant a requested action.
Return QUERY_BROADCAST_DENY to deny a requested action.
Remarks
For devices that offer software-controllable features, such as ejection and locking, the operating system typically sends a DBT_DEVICEREMOVEPENDING message to let applications and device drivers end their use of the device gracefully.
If the operating system forcibly removes a device, it may not send a DBT_DEVICEQUERYREMOVE message before doing so.
DBT_CONFIGCHANGECANCELED, DBT_CONFIGCHANGED, DBT_DEVICEARRIVAL, DBT_DEVICEQUERYREMOVE, DBT_DEVICEQUERYREMOVEFAILED, DBT_DEVICEREMOVECOMPLETE, DBT_DEVICEREMOVEPENDING, DBT_DEVICETYPESPECIFIC, DBT_QUERYCHANGECONFIG, DBT_USERDEFINED
不过我在使用这个函数时,已经使CDROM打开了,
这样使用:
procedure tform1.wmdevicechange(var msg:tmessage);
begin
if msg.wparam=DBT_DEVICEREMOVEPENDING then
msg.result:=true;
而delphi5系统却是报出错,DBT_DEVICEREMOVEPENDING 出现什么错误!
我已经在开头声明了这个函数了!
希望大家能给我一个解答,谢谢!
有人曾回答我说：
The WM_DEVICECHANGE device message notifies an application or device driver of a change to the hardware configuration of a device or the computer.
Event = (UINT) wParam;
dwData = (DWORD) lParam;
Parameters
Event
Event type. This parameter can be one of the following values:
Value Meaning
DBT_CONFIGCHANGECANCELED A request to change the current configuration (dock or undock) has been canceled.
DBT_CONFIGCHANGED The current configuration has changed, due to a dock or undock.
DBT_DEVICEARRIVAL A device has been inserted and is now available.
DBT_DEVICEQUERYREMOVE Permission is requested to remove a device. Any application can deny this request and cancel the removal.
DBT_DEVICEQUERYREMOVEFAILED A request to remove a device has been canceled.
DBT_DEVICEREMOVECOMPLETE A device has been removed.
DBT_DEVICEREMOVEPENDING A device is about to be removed. Cannot be denied.
DBT_DEVICETYPESPECIFIC A device-specific event has occurred.
DBT_QUERYCHANGECONFIG Permission is requested to change the current configuration (dock or undock).
DBT_USERDEFINED The meaning of this message is user-defined.
dwData
Address of a structure that contains event-specific data. Its meaning depends on the given event.
Return Values
Return TRUE to grant a requested action.
Return QUERY_BROADCAST_DENY to deny a requested action.
Remarks
For devices that offer software-controllable features, such as ejection and locking, the operating system typically sends a DBT_DEVICEREMOVEPENDING message to let applications and device drivers end their use of the device gracefully.
If the operating system forcibly removes a device, it may not send a DBT_DEVICEQUERYREMOVE message before doing so.
DBT_CONFIGCHANGECANCELED, DBT_CONFIGCHANGED, DBT_DEVICEARRIVAL, DBT_DEVICEQUERYREMOVE, DBT_DEVICEQUERYREMOVEFAILED, DBT_DEVICEREMOVECOMPLETE, DBT_DEVICEREMOVEPENDING, DBT_DEVICETYPESPECIFIC, DBT_QUERYCHANGECONFIG, DBT_USERDEFINED
不过我在使用这个函数时,已经使CDROM打开了,
这样使用:
procedure tform1.wmdevicechange(var msg:tmessage);
begin
if msg.wparam=DBT_DEVICEREMOVEPENDING then
msg.result:=true;
而delphi5系统却是报出错,DBT_DEVICEREMOVEPENDING 出现什么错误!
我已经在开头声明了这个函数了!
希望大家能给我一个解答,谢谢!