How do I add components to a JPanel at runtime

Question

I have a JPanel that I want to add some components. in particular JButtons to at runtime based on the content of a user supplied file.

I can add compontents to panel if I call it from the constructor of the JFrame derived form class, even after everything else have been constructed, but If I read the file first and then add components to the panel the call succeds but the added components are never shown.

Does anybody know how I force Java to do as I want?

Answer 1

Call the method validate() on the JPanel after you have added the JButtons to it.