控制面板的組件,其實就是一個地地道道的DLL文件,所不同的是其后綴名為.CPL而已.控制面板組件對外必須要實現一個CPlApplet接口,其原型為:LONG CALLBACK CPlApplet(HWND hwndCPL,UINT message, LPARAM lParam1, LPARAM lParam2).而在此函數之中,為了使組件正常運作,我們必須要處理如下消息:CPL_INIT(初始化,可以在這分配內存等等),CPL_GETCOUNT(顯示的組件數目),CPL_NEWINQUIRE(獲取組件的信息,才能正常顯示),CPL_DBLCLK(雙擊圖標時執行).
為方便觀看,將此函數體列出:

// =-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=
// The entry point to the Control Panel application.
// =-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=
extern "C"? LONG CALLBACK CPlApplet(HWND hwndCPL,UINT message, LPARAM lParam1, LPARAM lParam2)
{
? switch (message)
? {
??? case CPL_INIT:
????? ?// Perform global initializations, especially memory
????? ?// allocations, here.
????? ?// Return 1 for success or 0 for failure.
????? ?// Control Panel does not load if failure is returned.
????? ?return 1;

??? case CPL_GETCOUNT:
????? ?// The number of actions supported by this Control
????? ?// Panel application.
????? ?return 1;

??? case CPL_NEWINQUIRE:
??? ?{
??? ?// This message is sent once for each dialog box, as
??? ?// determined by the value returned from CPL_GETCOUNT.
??? ?// lParam1 is the 0-based index of the dialog box.
??? ?// lParam2 is a pointer to the NEWCPLINFO structure.
????return 0; //means CPLApplet succeed
????return 1;? // Nonzero value means CPlApplet failed.
???}
??? case CPL_DBLCLK:
???{
??? ?// The user has double-clicked the icon for the
??? ?// dialog box in lParam1 (zero-based).
????return 0;???? // CPlApplet succeed.
????return 1;???? // CPlApplet failed.
???}
???
??? case CPL_STOP:
????// Called once for each dialog box. Used for cleanup.
????
??? case CPL_EXIT:
????// Called only once for the application. Used for cleanup.
????
??? default:
????? ?return 0;
? }

? return 1;? // CPlApplet failed.
}? // CPlApplet

組件要進行相關操作,一般在.cpl文件內部進行操作;但我們完全可以把.CPL文件當成一個外殼,其作用只是在"控制面板"中顯示一個圖標,真正的處理是調用另外一個EXE文件.這樣的好處是,此.CPL代碼通用性強,如果想再添加別的組件,只要更改.CPL少量代碼;并且,功能模塊的分離,使得我們如果要更改相關功能,也只要修改相應的EXE文件,調試也更加方便.

現在就讓我們看一下如何在控制面板中調用EXE文件.
我們需要的是,在控制面板中雙擊我們顯示的圖標就調用我們相應的EXE程序;很顯然,我們只需要在CPL_DBLCLK消息中添加調用代碼即可.
extern "C"? LONG CALLBACK CPlApplet(HWND hwndCPL,UINT message, LPARAM lParam1, LPARAM lParam2)
{
? switch (message)
? ?
? ?....
????
??? case CPL_DBLCLK:
??{
???//-----------------------------------------------------------------
???//關于FindWindow函數的說明:
???//原型:HWND FindWindow(LPCTSTR lpClassName,LPCTSTR lpWindowName);?
???//lpClassName:要賦的值是類的字符串名稱,在ce下可以運行Remote Spy++進行查看;在本例子中采用此工具看到的是"Dialog".
???//此參數也可以為NULL,前提是所有在運行的窗口標題不同
???//lpWindowName:窗口的標題字符串名稱,也即是我們可以看到的窗口標題???
???//------------------------------------------------------------------
???//由于我們的這個exe文件只有一個窗口,下面這個函數也可以這樣寫FindWindow (NULL,TEXT("背光調節"))
???HWND hWnd = FindWindow (L"Dialog",TEXT("背光調節"));?
???if (hWnd)?
???{???????
????//如果已經運行過一個實例,則把它提到窗口前
????SetForegroundWindow (hWnd);
????CloseHandle(hWnd);
????return 0;???
???}
???else
???{
????//調用exe文件.
????if (CreateProcess(_T("\\Windows\\Backlight.exe"), NULL, NULL,NULL, FALSE, 0, NULL, NULL, NULL, &pi))
????{
?????CloseHandle(pi.hThread);
?????CloseHandle(pi.hProcess);
?????return 0;
????}
???}
???return 1;???? // CPlApplet failed.
??}
??
??....
??
}

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