How would I....? (Event Handling)

Question

Let me first start by explaining what I am needing. I am given a JFrame containing a JButton and 8 JTextFields (in the form of an array). Right now I let the button be clicked no matter what is in the fields. What I would like is to limit the button's availablility based on the fields' content. The fields are being used as a form to fill out and the button is being used to save the form. What type of event handler would I use to enable the button only if the fields' contents are not empty? I have added an ActionListener to the button but for that to work the button needs to be enabled. I would like to keep the button completely disabled until the proper fields have been filled out.

Answer 1

I'm not sure which listener is best for your situation, maybe a DocumentListener. Regardless, you will have to create a component of some sort that listens to all text fields for changes. When it detects a change it should look at whether or not all fields are empty and enable or disable the button. Implementing this is pretty easy, for example you could iterate over each field checking the length of the String getText() returns, but that wouldn't be terribly efficient, what the best solution is I'm not sure. I think I might just keep a boolean isEmpty for each field, then for each field add a different listener that modifies that boolean to true whenever the field is empty and false whenever it's not. Would be less overhead with checking every field then, you could simply have every listener call an "updateButton()" method that would check the boolean values and enable or disable the button if necessary.
This belongs in the Swing forum, post future Swing questions there, but don't repost this one please.