为菜单增加热键

Using MFC in C++ Part 2: Menus - Adding accelerator keys
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Accelerator keys allow a user to accessmenu items quicker by pressing a pre-defined combination of keys,instead of having to click on a specific menu item everytime it isrequred. An accelerator table, which contains a list accelerator keys,has the following structure:

[TableName] ACCELERATORS

{

KeyCode, Message Id [, Type, Options]

KeyCode, Message Id [, Type, Options]

KeyCode, Message Id [, Type, Options]

}

KeyCode: The KeyCode value should contain the key combination that will trigger the accelerator. The key code can be either:

• Any alphanumeric character enclosed in quotes, such as “a”, “C”, “6”. These are case sensitive.
• The header file afxres.h defines several macrosfor “virtual keys”. Virtual key macros allow keys such as F1 and F2(VK_F1 to VK_F12) to be used as accelerator keys. If a virtual key isused as the key code, then the type should be set to VIRTKEY.
• The ASCII code number of a character. If an ASCII key code is used, then the type should be set to ASCII.

Message Id:The message Id should contain an ID declared as part of an ON_COMMAND()macro for a windows message map. For example, our application would useIDM_1, IDM_2 and IDM_3.

Type: Can be either empty, VIRTKEY or ASCII, as described above.

Options: If CONTROL is specified, then the control keymust be pressed to trigger this accelerator key. If SHIFT is specified,then the shift key must be pressed to trigger this accelerator key. IfALT is specified, then the alt key must be pressed to trigger thisaccelerator key.

Adding an accelerator key for a menu item iseasy. To make the CMainWin::OnItem1() function execute when we pressthe Control key and the 1 (one) key, we would add the following code tothe end of our resource file, menu.rc:

MyKeys ACCELERATORS

{

"1", IDM_1, CONTROL, VIRTKEY

}

To trigger the CMainWin::OnItem2() function when we prress the F2 key, we would add this accelerator key:

VK_F2, IDM_2, VIRTKEY

To trigger our the CMainWin::OnItem3() function when we press the “3” key, we would add this accelerator key:

51, IDM_3, ASCII // 51 is the ascii code for the 3 key

Wecan’t actually use these accelerator keys yet. We need to load theaccelerator table. Double click on menu.cpp and add the following linejust before the end of the CMainWin constructor:

if(!LoadAccelTable("MyKeys"))

MessageBox("Couldn't load the accelerator table");

TheLoadAccelTable function is a member of the CFrameWnd class, accepts oneparameter, the name of the menu (in quotes), and returns a BOOL value.It loads our accelerator table into memory and sends the notificationmessages to our application when the right combination of keys ispressed.

To make sure our accelerator keys work, compile and runour app. First, press Cntl+1. Next, press the F2 key. Lastly, pressjust the “3” key. Each different OnItem function should be triggered.

To make our menu items display the accelerator keys they respond to, change the MENU table in menu.rc, like this:

MyMenu MENU

{

POPUP "Popup"

{

MENUITEM "Item One/tCntl+1", IDM_1

MENUITEM "Item Two/tF2", IDM_2

MENUITEM SEPARATOR

MENUITEM "Item Three/t3", IDM_3

}

}