Question

I have a jpanel and inner jpannels in it.
When I set the panel background dynamically the inner colors dont change.
to init :

 myPanel.setOpaque(true)

and then

 myPanel.setBackground(...)

Is there a solution to set the background to all of the inner frames without looping or direct set?
Thank you.

Answer 1

No, but if you set the inner panels to non-opaque (transparent) you can change the outer panels directly:

inner.setOpaque(false);

You can always craete a class that you can use instead of JPanel:

class TransparentJPanel extends JPanel {
    {
        setOpaque(false);
    }
}

---

Full example:

static class TransparentJPanel extends JPanel {{
    setOpaque(false);
}}

public static void main(String... args) throws Exception {

    JFrame frame = new JFrame("Test");

    final JPanel panel;

    frame.add(panel = new JPanel() {{
        add(new TransparentJPanel());
        add(new TransparentJPanel());
        add(new TransparentJPanel());
    }}, BorderLayout.CENTER);

    frame.add(new JButton(new AbstractAction("Toggle") {

        @Override
        public void actionPerformed(ActionEvent e) {
            if (panel.getBackground().equals(Color.RED))
                panel.setBackground(Color.GREEN);
            else
                panel.setBackground(Color.RED);
        }
    }), BorderLayout.SOUTH);


    frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    frame.setSize(400, 300);
    frame.setVisible(true);
}