Adding/Removing Listeners vs Using a flag to Enable/Disable

My ComboBox needs to have multiple listeners as Focus, Blur, TextChange, ValueChange. And these listeners needs to be enabled and disabled based on specific conditions. For Combo Box I have an issue that when I try to add and remove these listeners then when I click drop down of Combo Box it gets bank and does not show any values in combo box and second when I click it works. I noticed that the culprit seems to be adding/removing focus listener because when I comment the adding/removing of focus listener then this issue goes away. When I changed the focus listener to use a flag and I make that flag true/false to enable/disable focus listener (instead of adding/removing) then also this issue goes away.

Is it ok to use a flag to maintain enable/disable status of listener instead of adding/removing listener? What are pros and cons? Anybody came across this situation before?