概要
JComboBoxの右側にPopupMenuが表示されるように設定します。
サンプルコード
class RightPopupMenuListener implements PopupMenuListener {
@Override public void popupMenuWillBecomeVisible(final PopupMenuEvent e) {
EventQueue.invokeLater(new Runnable() {
@Override public void run() {
JComboBox combo = (JComboBox) e.getSource();
Accessible a = combo.getUI().getAccessibleChild(combo, 0);
if (a instanceof BasicComboPopup) {
BasicComboPopup pop = (BasicComboPopup) a;
Point p = new Point(combo.getSize().width, 0);
SwingUtilities.convertPointToScreen(p, combo);
pop.setLocation(p);
}
}
});
}
@Override public void popupMenuWillBecomeInvisible(PopupMenuEvent e) {}
@Override public void popupMenuCanceled(PopupMenuEvent e) {}
}
解説
JComboBoxのドロップダウンリストであるPopupMenuが開くとき、その位置を変更するPopupMenuListenerを作成JComboBox#addPopupMenuListener(...)メソッドで追加
JComboBoxの矢印アイコンも、以下のように変更combo2.setUI(new WindowsComboBoxUI() { @Override protected JButton createArrowButton() { JButton button = new JButton(icon) { @Override public Dimension getPreferredSize() { return new Dimension(14, 14); } }; button.setRolloverIcon(makeRolloverIcon(icon)); button.setFocusPainted(false); button.setContentAreaFilled(false); return button; } });