Detecting JTextField “deselect” event

Question

Is there some way to detect if a JTextField is deselected, i.e. the field WAS selected but now you have selected something else. The reason why I want to do this is because I want to check my users forms for any illegal characters before they try to submit their data. If there is some easier way to do that, instead of the way I'm trying to solve it, I'll gladly accept enlightenment.

Answer 1

At first though use a FocusAdapter and override focusLost(FocusEvent fe) which will be called when JTextField loses focuses, i.e another component is selected.

However because you have a purpose:

I want to check my users forms for any illegal characters before they try to submit their data

Id suggest a read on How to Use the Focus Subsystem - Validating Input

Better options than a FocusAdapter - tailored made for validating/restricting user input:

• DocumentFilter. See here and this variation for an example.
• InputVerifier. See here for an example
• JFormattedTextField. See here for an example