我JPopupMenu
在鼠标右键单击时显示。我希望JPopupMenu'
右上角位于click location
(默认情况下不是左上角)。为此,我需要将X
坐标设置为mouseEvent.getX() - popupMenu.getWidth()
。问题是,在第一次显示弹出窗口之前,它的宽度等于 0。
SSCCE:
public class PopupTest2 {
public static void main(String[] a) {
final JFrame frame = new JFrame();
frame.setSize(500, 500);
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
final JPanel panel = new JPanel(new BorderLayout());
panel.setBorder(BorderFactory.createLineBorder(Color.RED));
final JPopupMenu menu = new JPopupMenu();
for (int i = 0; i < 10; i++) {
JMenuItem item = new JMenuItem("Item #"+String.valueOf(i));
menu.add(item);
}
panel.addMouseListener(new MouseAdapter() {
@Override
public void mouseClicked(MouseEvent e) {
if (e.getButton() == MouseEvent.BUTTON3) {
// first time works wrong
menu.show(panel, e.getX() - menu.getWidth(), e.getY());
}
}
});
frame.setContentPane(panel);
frame.setUndecorated(true);
frame.setBackground(new Color(50, 50, 50, 200));
SwingUtilities.invokeLater(new Runnable() {
@Override
public void run() {
frame.setVisible(true);
}
});
}
}