Add a listener on collpase event in day Vaadin Calendar

i’m new in Vaadin framework. I don’t have any ideas how can set up collapse event listeners to show the popupView with the description of the event.

Not sure I understand completely what you’re trying to achieve. Care to elaborate a bit? :slight_smile:

Perhaps chapters 5.27.12 and forward will help you out:
https://vaadin.com/book/-/page/components.calendar.html
.