java – error upon assigning Layout: BoxLayout cant be shared

java – error upon assigning Layout: BoxLayout cant be shared

Your problem is that youre creating a BoxLayout for a JFrame (this), but setting it as the layout for a JPanel (getContentPane()). Try:

getContentPane().setLayout(
    new BoxLayout(getContentPane(), BoxLayout.PAGE_AXIS)
);

Ive also found this error making this:

JPanel panel = new JPanel(new BoxLayout(panel, BoxLayout.PAGE_AXIS));

The JPanel isnt initialized yet when passing it to the BoxLayout. So split this line like this:

JPanel panel = new JPanel();
panel.setLayout(new BoxLayout(panel, BoxLayout.PAGE_AXIS));

This will work.

java – error upon assigning Layout: BoxLayout cant be shared

I think that one important thing to highlight from the previous answers is that the BoxLayouts target (the first parameter) should be the same Container that the setLayout method is being called upon as in the following example:

JPanel XXXXXXXXX = new JPanel();
XXXXXXXXX.setLayout(new BoxLayout(XXXXXXXXX, BoxLayout.Y_AXIS));