Implementing dialog action handlers

How to execute user code in ON ACTION blocks when an action is fired.

Actions handlers are typically defined in dialog instructions with the ON ACTION interaction block. You must specify the name of the action after the ON ACTION keywords:

INPUT BY NAME ...
   ...
   ON ACTION print
      -- user code
   ...

Action handlers can also be defined with the COMMAND syntax in MENU and DIALOG instructions:

MENU ...
   ...
   COMMAND "Print" "Print the current record"
      -- user code
   ...

ON ACTION blocks provide better abstraction than COMMAND blocks by using simple action identifiers and leaving the decoration in the form files or action defaults files.

The ON ACTION block defines an action handler with a simple action name.

Built-in class methods such as ui.Dialog.setActionActive() take an action name as parameter. For more details, see Identifying actions in ui.Dialog methods.

The COMMAND block defines an action handler with an action name, but it also defines decoration attributes, such as the label and comment. Keyboard accelerators and help topic numbers can also be defined.

Action views controlled by ON ACTION handlers cannot get the focus. When using the COMMAND action handler, action views such as a BUTTON defined in the form layout can get the focus and are part of the tabbing item list.

Action handlers are bound to action views by name.