BBjControl::setCallback

Description

This method registers the callback routine for a specified event of the BBjControl.

Syntax

Return Value	Method
void	setCallback(int `eventType`, string subRoutineName)
void	setCallback(int `eventType`, CustomObject customObj, string methodName)

Parameters

Variable	Description
eventType	Event type for which the callback is to be registered.
subRoutineName	Subroutine name to be executed in PROCESS_EVENTS.
customObj	A CustomObject containing the method to be called when the event is processed by PROCESS_EVENTS.
methodName	The name of the method that is to be called when the event is processed by PROCESS_EVENTS.

Return Value

None.

Remarks

A callback can only be registered for event types that a specific control can trigger. The documentation for each control contains a list of events for which callbacks can be registered.

The CALLBACK verb will implicitly GOSUB to the subroutine specified in subroutineName. Since the block of code executed at subroutineName is arrived at via an implicit GOSUB, a RETURN is required at the end of the subroutine.

The CALLBACK implicitly CALLs the publicProgram at the given EntryPoint when the CALLBACK VERB uses the publicProgramEntryPoint syntax (ie: "publicProgram::EntryPoint"). Since a CALL has been made to a public program, an ENTER may optionally be used at the beginning, and an EXIT is required at the end.

The setCallback method must be called before the PROCESS_EVENTS verb, or within a subroutine that is called in response to an event.

If more than one callback is registered for a specific BBjControl event, the most recent will be used in PROCESS_EVENTS.

When a foreign interpreter invokes this method, an !ERROR=208 Multi Thread results. See Accessing Objects From Different Interpreters.

Example

rem 'Set a Callback using <control>.setCallBack

rem 'Obtain the instance of the BBjAPI object
let myAPI! = BBjAPI()

rem 'Open the SysGui device
SYSGUI = UNT
OPEN (SYSGUI) "X0"

rem 'Obtain the instance of the BBjSysGui object
let mySysGui! = myAPI!.getSysGui()

rem 'Set addWindow param values
X = 10
Y = 10
WIDTH = 200
HEIGHT = 200
TITLE$="BBj Window"

rem 'Set the current context
mySysGui!.setContext(0)

rem 'Create a window
myWindow! = mySysGui!.addWindow(X,Y,WIDTH,HEIGHT,TITLE$)

rem 'Add a button on the window
myRedButton! = myWindow!.addButton(101,50,100,90,30,"Red",$0800$)

rem 'Register the CALLBACK routines
myRedButton!.setCallback(myRedButton!.ON_BUTTON_PUSH,"RED_BUTTON_PUSHED")
myWindow!.setCallback(myWindow!.ON_CLOSE,"APP_CLOSE")

rem 'Process Events
process_events

rem 'Callback routine called when the red button is pressed
RED_BUTTON_PUSHED:
    rem 'Create the BBjColor Object using colorNum constant
    myColorRed! = mySysGui!.makeColor(mySysGui!.RED)

    rem 'Set the button colors to RED
    myRedButton!.setBackColor(myColorRed!)
return

rem 'Callback routine called when the user closes the application window
APP_CLOSE:
release