问题
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.
回答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
来源：https://stackoverflow.com/questions/14305921/detecting-jtextfield-deselect-event