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What Is The OnActionUpdate Event In DelphiVCL.Application?


In this post, we’ll use OnActionUpdate or DelphiVCL.Application.OnActionUpdate event occurs when an action’s Update method is called and its action list has not already handled it. Learning how to do it will allow you to easily build GUIs and test it with Python Testing Tools.

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.

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 UpdateAction method, which invokes the OnActionUpdate event handler (the application’s UpdateAction method applies to all actions in the application).

What does the “handled” parameter do?

The Handled parameter of the event handler returns false by default. If the handler updates the event, it should set Handled to true, ending the action’s processing. The action’s OnUpdate event occurs when the event handler exits with Handled set to false. 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: OnActionUpdate occurs after the application’s OnIdle event.

Note: You can also respond to this event using the TApplicationEvents component, which allows you to assign an event handler using the IDE.

Let’s browse all the properties and methods of the DelphiVCL.Application.OnActionUpdate using dir() command:

See the responses in our Windows command prompt:


You can also read short information about the DelphiVCL.Application.OnActionUpdate using the print() command:

See the responses in our Windows command prompt:



Check out DelphiVCL which easily allows you to build GUIs for Windows using Python.

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