绑定在 GridBagLayout 中不起作用

为什么items组件没有附加到上一行的底部？

    public static void main(String[] args) {
        JFrame frame = new JFrame();
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        JTextField name = new JTextField("Name");
        JButton submit = new JButton("Search");
        JScrollPane items = new JScrollPane();
        items.setVerticalScrollBarPolicy(JScrollPane.VERTICAL_SCROLLBAR_AS_NEEDED);
        items.setHorizontalScrollBarPolicy(JScrollPane.HORIZONTAL_SCROLLBAR_AS_NEEDED);

        frame.setLayout(new GridBagLayout());
        frame.add(name, new GridBagConstraints  (0,  0, 1, 1,  2, 1, GridBagConstraints.NORTHEAST,  GridBagConstraints.HORIZONTAL,new Insets(5, 2, 2, 2),0,0));
        frame.add(submit, new GridBagConstraints(-1, 0, 1, 1,  1, 1, GridBagConstraints.NORTHWEST,  GridBagConstraints.HORIZONTAL,new Insets(0, 0, 0, 0),0,0));
        frame.add(items, new GridBagConstraints (0, -1, 2, 1, -1, 2, GridBagConstraints.NORTH,      GridBagConstraints.BOTH,new Insets(0, 0, 0, 0),0,0));

        frame.setPreferredSize(new Dimension(800, 600));
//      frame.setResizable(false);
        frame.pack();
        frame.setVisible(true);
    }