Is it possible to add a JToolBar to JSplitPane?

Question

When I try to add Jtoolbar to JSplitPane, it gives me the following exception:
Exception in Thread "AWT-EventQueue-0" java.lang.IllegalArgumentException: cannot add to layout: unknown constraint: null
Is it not possible to add a JToolBar to a JSplitPane? Is it because I have not defined what is supposed to happen when the user clicks "next" or "previous" yet? What I ultimately want to happen is for something to move up in all the components of the split pane (it's a nested pane) when I hit "next," and to move back when i hit "prev" (buttons in the jtoolbar)

Answer 1

I believe that you don't want to add the JToolBar to the JSplitPane, but instead you want to add the JToolBar to the Panel that holds the JSplitPane. For eg:
import java.awt.BorderLayout;
import java.awt.Color;
import java.awt.Dimension;
import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.JSplitPane;
import javax.swing.JToolBar;
class FuSwing1
    private JPanel mainPanel = new JPanel();
    private JSplitPane splitpane;
    public FuSwing1()
        JToolBar toolbar = new JToolBar();
        toolbar.add(new JButton("foo 1"));
        JPanel redPanel = new JPanel();
        JPanel bluePanel = new JPanel();
        redPanel.setBackground(Color.red);
        bluePanel.setBackground(Color.blue);
        splitpane = new JSplitPane(JSplitPane.HORIZONTAL_SPLIT, redPanel, bluePanel);
        mainPanel.setPreferredSize(new Dimension(400, 400));
        mainPanel.setLayout(new BorderLayout());
        mainPanel.add(toolbar, BorderLayout.NORTH);
        mainPanel.add(splitpane, BorderLayout.CENTER);
    public JPanel getMainPanel()
        return mainPanel;
    public void setDividerLocation(double loc)
        splitpane.setDividerLocation(loc);
    private static void createAndShowUI()
        FuSwing1 fu1 = new FuSwing1();
        JFrame frame = new JFrame("FuSwing1");
        frame.getContentPane().add(fu1.getMainPanel());
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frame.pack();
        fu1.setDividerLocation(0.6);
        frame.setLocationRelativeTo(null);
        frame.setVisible(true);
    public static void main(String[] args)
        java.awt.EventQueue.invokeLater(new Runnable()
            public void run()
                createAndShowUI();
}