KeyDown Event

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Defined By: Indented List

Description:

Occurs on the downstroke when the user presses a key while an object has the keyboard focus and is sent repeatedly as long as the key is held down. It is commonly used in combination with the KeyUp event to process the press and/or release of any key (compare to the KeyPress event, which receives only ANSI characters).

Usage:

Sub KeyDown (keyCode As Integer, ByVal shift As Integer)

Syntax Description

KeyCode Provides a unique number identifier, or key code, for the key pressed. The key code is the virtual-key value as defined by the Win32 API. Constants are provided with Phoenix to make key event handling code more readable, e.g. KEY_DELETE (Del key) and KEY_F2 (F2 key). Key code constants are defined in the “KEYCODES” module.

Shift Indicates the status of the SHIFT, CTRL, and ALT keys at the time the event was called. Each of these keys has a corresponding bit-flag value. SHIFT has a value of 1, CTRL is 2, and ALT is 4. To indicate which key or keys were pressed, the key values are summed in the Shift argument. For example, if both CTRL and ALT are pressed, the value of Shift is 6.

Details:

The object with the keyboard focus receives all keystrokes. Generally, this object is a control. A form receives key events only if it has no active controls or if the form's KeyPreview property is set to True. When a form's KeyPreview property is set to True, the form receives key events before the controls on the form, and can modify the key that will be seen by the control when it receives the event. This is useful for creating form-specific keyboard-handling routines, such as special shortcuts or accelerators.

The KeyDown event can process all keys, not just character keys. However, it is most commonly used to distinguish between the numeric keypad and regular numbers or to react to users pressing:

images/Phx90000.gif Extended character keys such as function keys.

images/Phx90000.gif Navigation keys such as arrow keys.

images/Phx90000.gif Key combinations such as CTRL-SHIFT-key.

To test for the Shift argument, you can declare constants that define the bits within the argument. The Shift constants have the following values:

Constant Value Bit

SHIFT_MASK 1 0

CTRL_MASK 2 1

ALT_MASK 4 2

You can use these constants to test for any combination of modifiers.

Note: To interpret ANSI characters, use the KeyPress event.

Pressing and holding a key down activates this event repeatedly until the key is released.