By "events", if you mean things like whether the app became active, entered the background etc, you can have the app subscribe to TApplicationEventMessage:
http://docwiki.embarcadero.com/Libraries/Sydney/en/FMX.Platform.TApplicationEventMessage
Use TMessageManager to subscribe to the event, e.g:
TMessageManager.DefaultManager.SubscribeToMessage(TApplicationEventMessage, ApplicationEventMessageHandler);
..and to unsubscribe when you no longer wish to receive the messages:
TMessageManager.DefaultManager.Unsubscribe(TApplicationEventMessage, ApplicationEventMessageHandler);
Example handler:
procedure TMyClass.ApplicationEventMessageHandler(const Sender: TObject; const M: TMessage);
var
LMessage: TApplicationEventMessage;
begin
LMessage := TApplicationEventMessage(M);
case LMessage.Value.Event of
TApplicationEvent.BecameActive:
DoAppBecameActive;
TApplicationEvent.EnteredBackground:
DoAppEnteredBackground;
// etc
end;
end;