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MainPanel.java
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/
MainPanel.java
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// -*- mode:java; encoding:utf-8 -*-
// vim:set fileencoding=utf-8:
// @homepage@
package example;
import java.awt.*;
import java.awt.event.MouseWheelListener;
import javax.swing.*;
public final class MainPanel extends JPanel {
private MainPanel() {
super(new BorderLayout());
JPanel p = new JPanel(new GridBagLayout());
p.setBorder(BorderFactory.createTitledBorder("JComboBox"));
GridBagConstraints c = new GridBagConstraints();
c.gridx = 0;
c.insets = new Insets(5, 5, 5, 0);
c.anchor = GridBagConstraints.LINE_END;
p.add(new JLabel("Wheel:"), c);
p.add(new JLabel("Normal:"), c);
c.gridx = 1;
c.weightx = 1d;
c.fill = GridBagConstraints.HORIZONTAL;
p.add(makeComboBox(), c);
p.add(new JComboBox<>(makeModel()), c);
JTextArea textArea = new JTextArea();
add(p, BorderLayout.NORTH);
add(new JScrollPane(textArea));
setPreferredSize(new Dimension(320, 240));
}
private static JComboBox<String> makeComboBox() {
return new JComboBox<String>(makeModel()) {
private transient MouseWheelListener handler;
@Override public void updateUI() {
removeMouseWheelListener(handler);
super.updateUI();
handler = e -> {
Component c = e.getComponent();
if (c.hasFocus() && c instanceof JComboBox) {
JComboBox<?> combo = (JComboBox<?>) c;
int idx = combo.getSelectedIndex() + e.getWheelRotation();
if (idx >= 0 && idx < combo.getItemCount()) {
combo.setSelectedIndex(idx);
}
}
};
addMouseWheelListener(handler);
}
};
}
private static ComboBoxModel<String> makeModel() {
DefaultComboBoxModel<String> model = new DefaultComboBoxModel<>();
model.addElement("111111");
model.addElement("22222222");
model.addElement("3333333333");
model.addElement("444444444444");
model.addElement("5555555");
model.addElement("66666666666");
model.addElement("77777777");
model.addElement("88888888888");
return model;
}
public static void main(String[] args) {
EventQueue.invokeLater(MainPanel::createAndShowGui);
}
private static void createAndShowGui() {
try {
UIManager.setLookAndFeel(UIManager.getSystemLookAndFeelClassName());
} catch (UnsupportedLookAndFeelException ignored) {
Toolkit.getDefaultToolkit().beep();
} catch (ClassNotFoundException | InstantiationException | IllegalAccessException ex) {
ex.printStackTrace();
return;
}
JFrame frame = new JFrame("@title@");
frame.setDefaultCloseOperation(WindowConstants.EXIT_ON_CLOSE);
frame.getContentPane().add(new MainPanel());
frame.pack();
frame.setLocationRelativeTo(null);
frame.setVisible(true);
}
}