TApplicationEvents.OnActionUpdate Event

Occurs when an action's Update method is called and its action list has not already handled it.

Pascal

property OnActionUpdate: TActionEvent;

C++

__property TActionEvent OnActionUpdate;

Description

Use the OnActionUpdate event handler to update the properties of an action when the application is idle if the action's action list does not handle it in an OnUpdate event handler. OnActionUpdate occurs after the OnIdle event.

If the action list that contains the action does not update it in an OnUpdate event handler, the action is routed to the Application object's OnActionUpdate event. The application events object hooks this event and responds with its own OnActionUpdate event handler.

The Handled parameter of the event handler returns false by default. If the handler updates the event, it should change Handled to true, thereby ending the processing of the action. When the event handler exits with Handled set to false, the event first goes to any other application events objects, and then the action's OnUpdate event occurs. If the action is not updated after that, the active control's UpdateAction method is called to allow the target to update the action. Finally, the active form's UpdateAction method is called if all other handlers do not handle the action.

Note: Call the CancelDispatch method from an OnActionUpdate event handler to prevent the application from forwarding the event to any other application events objects.

C++ Examples:

Copy Code

/*
This example requires a TApplicationEvents and a TListBox
in the form.  Select the TApplicationEvents, double click
on the OnActionUpdate event and add the following code to
the handler.  Create other TApplicationEvents the same way.
When these events update this event is triggered.  The
Handled parameter of the event handler returns false by
default. If the handler handles the event, it should change
Handled to true, thereby preventing further attempts to
*/
void __fastcall TAppEventForm::ApplicationEventsActionUpdate(
      TBasicAction *Action, bool &Handled)
{
     lbActionUpdate->Items->Add("Event OnActionUpdate");
}

Delphi Examples:

Copy Code

{
This example requires a TApplicationEvents and a TListBox
in the form.  Select the TApplicationEvents, double click
on the OnActionUpdate event and add the following code to
the handler.  Create other TApplicationEvents the same way.
When these events update this event is triggered.  The
Handled parameter of the event handler returns false by
default. If the handler handles the event, it should change
Handled to true, thereby preventing further attempts to
handle the action.
}
procedure TMainForm.ApplicationEventsActionUpdate(Action: TBasicAction;
  var Handled: Boolean);
begin
  lbActionUpdate.Items.Add('Event OnActionUpdate');
end;