JCombobox在另一个动作中执行了action

I'm trying to make a Combobox with actionperformed in another actionperformed. The idea is that you start with a screen with a button, and after the button is clicked the combobox is added. When I try to add the combobox, the error says "vlaggenlijst cannot be resolved to a variable".I'm trying to make a Combobox with actionperfor