JMenuLazy.java

package cc.arduino.view;

import java.awt.Component;
import java.util.LinkedList;

import javax.swing.JMenu;
import javax.swing.JMenuItem;
import javax.swing.JPopupMenu;
import javax.swing.JSeparator;
import javax.swing.event.MenuEvent;
import javax.swing.event.MenuListener;

/**
 * Avoid slow rendering of menu while load full menu tree in background
 * 
 * @author Ricardo JL Rufino - (ricardo.jl.rufino@gmail.com)
 * @date 13 de mai de 2020
 */
public class JMenuLazy extends JMenu {

  private LinkedList<Component> components = new LinkedList<>();

  private boolean loading = false;

  public JMenuLazy(String s) {
    super(s);
    addMenuListener(menuListener);
  }

  public void setLoading(boolean loading) {
    this.loading = loading;
    this.setEnabled(!loading);
  }

  public boolean isLoading() {
    return loading;
  }

  @Override
  public Component add(Component c) {
    if (isLoading()) {
      components.add(c);
      return c;
    }
    return super.add(c);
  }

  @Override
  public JMenuItem add(JMenuItem c) {
    if (isLoading()) {
      components.add(c);
      return c;
    }
    return super.add(c);
  }

  @Override
  public void addSeparator() {
    if (isLoading()) {
      components.add(new JPopupMenu.Separator());
      return;
    }
    super.addSeparator();
  }

  public void removeAll() {
    super.removeAll();
    synchronized (components) {
      components.clear();
    }
  };

  private MenuListener menuListener = new MenuListener() {

    @Override
    public void menuSelected(MenuEvent e) {
      if (!isLoading()) {
        if (loading == false) {
          if (!components.isEmpty()) {
            for (Component component : components) {
              if (component instanceof JSeparator) {
                JMenuLazy.super.addSeparator();
              } else {
                JMenuLazy.super.add(component);

              }
            }
            components.clear();
          }
        }
      }
    }

    @Override
    public void menuDeselected(MenuEvent e) {

    }

    @Override
    public void menuCanceled(MenuEvent e) {

    }
  };

}