来自代码分支和太阳论坛，我知道为JComboBox设置水平滚动条的技术。

然而，他们建议的解决方案局限于外观特定。

正如你所看到的，如果用户在带有GTK+look n feel的Linux机器下，或者在带有Nimbus look n fell的Windows机器下，下面的关键代码片段将不能很好地工作。

我如何才能有一种可移植的方式，使JComboBox能够有一个水平滚动条？

完整的源代码是AutoCompleteJComboBox.java

关键代码片段如下：

package org.yccheok.jstock.gui;

public class AutoCompleteJComboBox extends JComboBox {

   @Override
    public void setUI(ComboBoxUI ui)
    {
        if (ui != null)
        {
            // Let s try our own customized UI.
            Class c = ui.getClass();
            final String myClass = "org.yccheok.jstock.gui.AutoCompleteJComboBox$My" + c.getSimpleName();

            try {
                ComboBoxUI myUI = (ComboBoxUI) Class.forName(myClass).newInstance();
                super.setUI(myUI);
                return;
            } catch (ClassNotFoundException ex) {
                log.error(null, ex);
            } catch (InstantiationException ex) {
                log.error(null, ex);
            } catch (IllegalAccessException ex) {
                log.error(null, ex);
            }
        }

        // Either null, or we fail to use our own customized UI.
        // Fall back to default.
        super.setUI(ui);
    }

    // This is a non-portable method to make combo box horizontal scroll bar.
    // Whenever there is a new look-n-feel, we need to manually provide the ComboBoxUI.
    // Any idea on how to make this portable?
    //
    protected static class MyWindowsComboBoxUI extends com.sun.java.swing.plaf.windows.WindowsComboBoxUI
    {
        @Override
        protected ComboPopup createPopup()
        {
            return new MyComboPopup(comboBox);
        }
    }

    protected static class MyMotifComboBoxUI extends com.sun.java.swing.plaf.motif.MotifComboBoxUI
    {
        @Override
        protected ComboPopup createPopup()
        {
            return new MyComboPopup(comboBox);
        }
    }

    protected static class MyMetalComboBoxUI extends javax.swing.plaf.metal.MetalComboBoxUI
    {
        @Override
        protected ComboPopup createPopup()
        {
            return new MyComboPopup(comboBox);
        }
    }

    private static class MyComboPopup extends BasicComboPopup
    {
        public MyComboPopup(JComboBox combo)
        {
            super(combo);
        }

        @Override
        public JScrollPane createScroller()
        {
            return new JScrollPane(list,JScrollPane.VERTICAL_SCROLLBAR_AS_NEEDED,
                    JScrollPane.HORIZONTAL_SCROLLBAR_AS_NEEDED);
        }
    }
}