TBasicAction.OnUpdate Event

Occurs when the application is idle or when the action list updates.

Pascal

property OnUpdate: TNotifyEvent;

C++

__property TNotifyEvent OnUpdate;

Description

Write an OnUpdate event handler to execute centralized code while an application is idle. For example, actions may want to update enabling and disabling, or checking and unchecking of client targets.

C++ Examples:

Copy Code

/*
When the application is idle, the OnUpdate event occurs for
every action that is linked to a visible control or menu
item that is showing. This provides an opportunity for
applications to execute centralized code for enabling and
disabling, checking and unchecking, and so on. For example,
the following code illustrates the OnUpdate event handler
for an action that is "checked" when the toolbar is visible.
This example requires a TActionList (with one TAction) and a
TToolBar on a form. This example requires a TActionList
(with one TAction) and a TToolBar on a form.  Double click
on the TActionList and create an TAction named Action1.  The
TAction has an OnUpdate event handler called Action1Update.
Then set an object's (such as a button or menu item) Action
to Action1.
*/
void __fastcall TForm1::Action1Update(TObject *Sender)
{
   // Indicate whether ToolBar1 is currently visible.
   TAction* pa = dynamic_cast<TAction*>(Sender);
   if (pa)
   {
     if (pa->Checked != ToolBar1->Visible)
     {
       lbOther->Items->Add("Event Action1Update: toolbar visibility changed");
     }
     pa->Checked = ToolBar1->Visible;
   }
}

Delphi Examples:

Copy Code

{
When the application is idle, the OnUpdate event occurs for
every action that is linked to a visible control or menu
item that is showing. This provides an opportunity for
applications to execute centralized code for enabling and
disabling, checking and unchecking, and so on. For example,
the following code illustrates the OnUpdate event handler
for an action that is "checked" when the toolbar is visible.
This example requires a TActionList (with one TAction) and a
TToolBar on a form. This example requires a TActionList
(with one TAction) and a TToolBar on a form.  Double click
on the TActionList and create an TAction named Action1.  The
TAction has an OnUpdate event handler called Action1Update.
Then set an object's (such as a button or menu item) Action
to Action1.
}
procedure TMainForm.Action1Update(Sender: TObject);
begin
  if ((Sender as TAction).Checked <> ToolBar1.Visible) then
    lbOther.Items.Add('Event Action1Update: toolbar visibility changed');
    { Indicate whether ToolBar1 is currently visible }
    (Sender as TAction).Checked := ToolBar1.Visible;
end;