Question

So i have a swing GUI where i change it’s default look and feel based upon some input from another GUI Class using something like this:

javax.swing.UIManager.setLookAndFeel("newlook&feel");
SwingUtilities.updateComponentTreeUI(this);
pack();

This works fine, but however on the console i see everytime this is called an exception is thrown with message like:

Exception in thread "AWT-EventQueue-0" java.lang.NullPointerException

and it refers to line numbers from classes which are internal Java classes. What could be the problem here or i am missing something.

Just a point, SwingUtilities.isEventDispatchThread() returns false in this scenario.

Answer 1

Just a point, SwingUtilities.isEventDispatchThread() returns false in
this scenario.

Maybe that is the problem, have you tried invoking the L&F change inside the EDT Thread?

    SwingUtilities.invokeLater(new Runnable() {
       public void run() {
         javax.swing.UIManager.setLookAndFeel("newlook&feel");
         SwingUtilities.updateComponentTreeUI(OuterClassName.this);
         pack();
        }
      });