fontviewer | Providing an easy way | Animation library

First of all: Please clean up your code before asking questions on StackOverflow. This serves two main reasons:

• cleaner code is more easily understood by yourself. In most cases after cleaning up the problem is obvious and you even don't have to ask.
• second: everyone reading your question has to do it to understand it. Now you have 20 people potentially trying to help and everyone of them has to do it. This scales badly.

Now to your problem: Since you don't wrote what it is you are having trouble with I'm guessing that you don't get the button pressed event.

The reason for that is, that you instantiate your listener = new Calculator() after creating your fields/panels. But you use it in creating them here: inputField.addActionListener(listener); where listener is still null. So try moving it some lines to the top and you get your event.

(This would be obvious with cleaner code, did I mention?)

There are more problems in this code but with this change you will get at least some error messages when clicking the button so I will leave you with that.