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ON KEY LABEL Command

  • Artikel

Specifies a command that executes when you press a specific key or key combination or click the mouse button.

ON KEY [LABEL KeyLabelName] [Command]

Parameters

  • LABEL KeyLabelName
    Specifies the key label name assigned to the key. The KeyLabelName is the letter or digit on the key or a special name assigned to the key. The following table lists the special key label names.

    Visual FoxPro key label assignments

    For this key Specify this KeyLabelName value
    LEFTARROW
    RIGHTARROW
    UPARROW
    DNARROW
    HOME HOME
    END END
    PAGE UP PGUP
    PAGE DOWN PGDN
    DEL DEL
    BACKSPACE BACKSPACE
    SPACEBAR SPACEBAR
    INS INS
    TAB TAB
    SHIFT+TAB BACKTAB
    Left Brace LBRACE
    Right Brace RBRACE
    ENTER ENTER
    F1 to F12 F1, F2, F3 ...
    CTRL+F1 to CTRL+F12 CTRL+F1, CTRL+F2 ...
    SHIFT+F1 to SHIFT+F12 SHIFT+F1, SHIFT+F2 ...
    ALT+F1 to ALT+F12 ALT+F1, ALT+F2, ALT+F3 ...
    ALT+0 to ALT+9 ALT+0, ALT+1, ALT+2 ...
    ALT+A to ALT+Z ALT+A, ALT+B, ALT+C ...
    CTRL+LEFT ARROW CTRL+LEFTARROW
    CTRL+RIGHT ARROW CTRL+RIGHTARROW
    CTRL+HOME CTRL+HOME
    CTRL+END CTRL+END
    CTRL+PAGE UP CTRL+PGUP
    CTRL+PAGE DOWN CTRL+PGDN
    CTRL+A TO CTRL+Z CTRL+A, CTRL+B, CTRL+C ...
    CTRL+0 CTRL+0
    RIGHT MOUSE BUTTON RIGHTMOUSE
    LEFT MOUSE BUTTON LEFTMOUSE
    MOUSE BUTTON MOUSE
    ESC ESC

  • Command
    Specifies the command that executes when you press the specified key or key combination or click the mouse button.

    You can include parameter or parameter expressions with the command that you assign to the key, as in the following example:

    ON KEY LABEL ALT+V WAIT WINDOW "Version: " + VERSION()

    You can include variables in the assignment, but they must be public. For example:

    PUBLIC message
message = "Default drive: " + SYS(5)
ON KEY LABEL ALT+D WAIT WINDOW message

Remarks

ON KEY LABEL typically uses DO to execute a procedure.

ON KEY LABEL executes the command immediately during the execution of READ, BROWSE, EDIT, CHANGE, and user-defined menus. If a program is executing when you press the key or click the mouse button, Visual FoxPro executes the current program line and then executes the ON KEY LABEL command. Any ON KEY LABEL key assignments created in a program remain in effect after the program is run. You can also create key assignments in the Command window.

To restore the behavior of a specific key to normal, issue ON KEY LABEL KeyLabelName. To restore all keys to their default behavior, issue ON KEY.

Tip   To prevent recursive calls during the execution of an ON KEY LABEL procedure, include PUSH KEY CLEAR early in the procedure to disable all active ON KEY LABEL commands. Issue POP KEY at the end of the procedure to enable the ON KEY LABEL commands.

The ON KEY LABEL key assignments aren't in effect in the Visual FoxPro system menu bar, system menus, dialog boxes, alerts, and so on. The key assignments are effective in the Visual FoxPro system windows — the Visual FoxPro text editor, the Command window, the Trace window, and so on.

Unlike ON KEY, there can be multiple active ON KEY LABEL commands. For example, you can assign a command to each of the arrow keys and a mouse button.

Executing an ON KEY LABEL resets PARAMETERS( ) to 0. For more information, see PARAMETERS( ).

In Visual FoxPro, certain events cannot be trapped because they are under the control of Windows. In particular, ON KEY LABEL MOUSE, ON KEY LABEL LEFTMOUSE, and ON KEY LABEL RIGHTMOUSE are not executed when you click a Windows control such as a Control menu, scroll bar, or the like. Also, CTRL+0 is supported in ON KEY LABEL in Visual FoxPro, allowing you to redefine the key combination used to enter a null value into a field.

Note that ON KEY LABEL operates outside of the scope of a form; the KeyPress event can be used within forms to execute code when a key is pressed.

Example

The following example displays a message when an arrow key is pressed.

CLEAR
PUBLIC msg
msg = CHR(13) + CHR(13) + "Press F9 to " + ;
   "restore default key definition."
ON KEY LABEL RIGHTARROW Wait Window "Right Arrow " + msg NOWAIT
ON KEY LABEL LEFTARROW Wait Window "Left Arrow " + msg NOWAIT
ON KEY LABEL UPARROW Wait Window "Up Arrow " + msg NOWAIT
ON KEY LABEL DNARROW Wait Window "Down Arrow " + msg NOWAIT

* Press F9 to clear the ON KEY LABEL assignments
ON KEY LABEL F9 ON KEY

See Also

INKEY( ) | KeyPress Event | ON( ) | POP KEY | PUSH KEY