Accessing the components from another class

Question

I am very new to java.

I have a class where i am creating gui and another class (main class), i am accessing the gui class. In the gui class i am creating some components and returning them.

gui class,

        public class Gui {

            public Component getTopPanelContent(){
                Jpanel jp = new Jpanel();
                JComboBox cbo1 = new JComboBox();
                JComboBox cbo2 = new JComboBox();
                JComboBox cbo3 = new JComboBox();
                JComboBox cbo4 = new JComboBox();
                JComboBox cbo5 = new JComboBox();
                JButton button = new JButton();

                jp.add(cbo1);
                jp.add(cbo2);
                jp.add(cbo3);
                jp.add(cbo4);
                jp.add(cbo5);
                jp.add(button);
                return jp; 
            }
        }

main class,

        public void addComponents(int id){
           Gui g = new Gui();
           Jpanel container = new Jpanel();

           if(id == 1){
               container.add(g.getTopPanelContent);     
           }
        }

upto this its working fine.

In the main class there is a JTextArea, Whenever i open a file, i have to display the country list in cbo1, the file contains the list of countries that has to be displayed,

       String[] countries = editArea.getContents().split("\n");

How to pass the country values to cbo1

Thanks

Answer 1

Well, i usually see a GUI class having the swing components as the class attributes. You made something like a 'util' class for your GUI, so you will have to hunt your JComboBox

I suggest you to go for a full featured class to represent you GUI, like:

import javax.swing.*;

public class Gui extends JPanel {

    private JComboBox cbo1 = new JComboBox();
    private JComboBox cbo2 = new JComboBox();
    private JComboBox cbo3 = new JComboBox();
    private JComboBox cbo4 = new JComboBox();
    private JComboBox cbo5 = new JComboBox();
    private JButton button = new JButton();

    public Gui() {
        add(cbo1);
        add(cbo2);
        add(cbo3);
        add(cbo4);
        add(cbo5);
        add(button); 
    }
}

Also, add getters and setters ;-).

If you wanna keep your code your way, you can search the combobox by index:

System.out.println( jp.getComponent(0) );

Or, better, you can name your JComboBox and then search for it by name:

cbo1.setName("countryCombo");
jp.add(cbo1);

and then:

public Component findCbo1() {
    for (Component comp : this.getComponents()) {
        if(comp.getName() != null && comp.getName().equals("countryCombo")) {
            return comp;
        }
    }
    return null;
}

Answer 2

Two ways to do it....

• Make the cbo1 as, static...so you will have to declare it outside the method in Class scope...

  So it will be like this..

  for(String s: countries){ 
  
   Gui.cbo1.addItem(s);
  
  
   }
  

• Or use Singleton principle to have the Gui class as Singleton, and then use Composition to get access to the JComboBox cbo1