Vaadin 8 combobox implements before(!) dropdown event?

Question

Is it possible in Vaadin 8 combobox handle before(!) dropdown event?

Actually, I need to implement DataProvider that would re-read data each time when a user tries to select data from the combobox (adding new items are not allowed). CallbackDataProvider, FetchItemsCallback etc. are not an option cause they read data only once.

Any ideas?

Answer 1

Have you tried implementing AbstractBackEndDataProvider? Method fetchFromBackEnd seems to be called every time user opens the combo box.

Furthermore the is enhanced version of the ComboBox in the Vaadin's Directory https://vaadin.com/directory/component/prefixcombobox, which adds events for observing popup opening and closing. But this event is fired after popup has been opened.