Question

I have a JFrame, which is the toplevel container for a window, and a single JComponent (that I have implemented) which is contained in the JFrame.

In part of my JComponent’s logic, I need to resize the window to a specific size, but now matter what I try, it has not worked. I have tried calling setPreferredSize and setSize on the JFrame, the JComponent, and on the Container returned from calling getParent() on the component.

I have a feeling this has something to do with not calling pack after changing the size, but I cannot figure out how to access the JFrame from the JComponent to call pack on it (I am no swing expert).

Thank you

Answer 1

You can always get the top level window by calling the SwingUtilities#getWindowAncestor method:

Window topLevelWindow = SwingUtilities.getWindowAncestor(myComponent);
topLevelWindow.pack();

passing in your component. Just make sure that you only call this after the GUI has been rendered, else you’ll get a nasty NullPointerException.