Home > Language Reference > Classes > Form

KeyPress Event

Event raised when a character is entered or a key is pressed.

Syntax

Protected Event KeyPress(ByRef iChar As Integer, ByRef iKeyCode As Integer, ByRef eModifiers As HbKeyModifier, ByRef bForward As Boolean)

Remarks

The KeyPress event is raised each time the user draws a character in the writing recognition area, or each time a key is pressed. Even if a control has the focus, the form always receives this event, before the character is sent to the control.

The iChar parameter indicates the character code recognized or the key pressed. If the value is less than 256, the character is an ANSI standard character. Otherwise, it represents a control key or code, for which HB++ has the following built-in constants:

Numerous other codes are possible, depending on the Palm OS^® version and the handheld device model being used.

The iKeyCode parameter is the virtual code for the entered character. It is unused on most platforms; its value only matters when handling 5-way navigators, and other special hard keys. Unfortunately, most devices do not agree on its signification. You should refer to the each licensee's developer documentation for more information.

The eModifiers parameter specifies additional information about the entered character, and can be zero, one, or more of the following:

The bForward parameter allows handling of the event by the system to be blocked. If you sets its value to False, when this event is being handled, the character or key pressed is ignored. If a control has the focus, it does not receive the character entered. If a key is pressed, it has no effect.

The following example uses this functionality to prevent a user from exiting the current application. All the keys apart from on/off are blocked:

Private Sub Form_KeyPress(ByRef iChar As Integer, ByRef iKeyCode As Integer, ByRef iModifiers As HbKeyModifier, ByRef bForward As Boolean)
  If iChar>=256 And iChar<>hbCharHardPower Then bForward=False
End Sub

Note that the iChar, iKeyCode, and eModifiers parameters are passed by reference. This means that your application can change the value of those parameters on the fly, before the system processes the event.

System requirements