Question

How would I programatically set the state of a JComboBox to be selected and show its content in the drop down?

Answer 1

Try setting the selected index using: setSelectedItem(Object item) or setSelectedIndex(int index) then call on your JComboBox instance:

jComboBox.showPopup();
//or
//jComboBox.setPopupVisible(true);

If you’d like it to be visible for a certain period of time only just use a Swing Timer to call setPopupVisible(false); after a certain period of time has elapsed.

References:

• http://docs.oracle.com/javase/7/docs/api/javax/swing/JComboBox.html