Automatically open and close JPopupMenu without mouse click

• download example.jar
• download src.zip
• repository

Code

/* If the mouse cursor goes out of the region at high speed, JPopupMenu may not close, use AWTEventListener to work around this problem. */
class AutoClosePopupMenu extends JPopupMenu {
  private transient PopupMenuListener listener;

  @Override public void updateUI() {
    removePopupMenuListener(listener);
    super.updateUI();
    listener = new AwtPopupMenuListener();
    addPopupMenuListener(listener);
  }

  private void checkAutoClose(MouseEvent e) {
    Component c = e.getComponent();
    Rectangle r = getBounds();
    r.grow(0, 5);
    Point pt = SwingUtilities.convertPoint(c, e.getPoint(), this);
    if (!r.contains(pt) && !(c instanceof JButton)) {
      setVisible(false);
    }
  }

  private final class AwtPopupMenuListener implements PopupMenuListener {
    private final AWTEventListener handler = e -> {
      if (e instanceof MouseEvent) {
        int id = e.getID();
        if (id == MouseEvent.MOUSE_MOVED || id == MouseEvent.MOUSE_EXITED) {
          checkAutoClose((MouseEvent) e);
        }
      }
    };

    @Override public void popupMenuWillBecomeVisible(PopupMenuEvent e) {
      long mask = AWTEvent.MOUSE_EVENT_MASK | AWTEvent.MOUSE_MOTION_EVENT_MASK;
      Toolkit.getDefaultToolkit().addAWTEventListener(handler, mask);
    }

    @Override public void popupMenuWillBecomeInvisible(PopupMenuEvent e) {
      Toolkit.getDefaultToolkit().removeAWTEventListener(handler);
    }

    @Override public void popupMenuCanceled(PopupMenuEvent e) {
      /* not needed */
    }
  }
}

Set up an event listener to automatically open JPopupMenu when the mouse cursor enters the JButton area and automatically close it when the mouse cursor leaves the JButton or JPopupMenu area.

References

• Automatically open and close JPopupMenu without mouse click(Japanese)