Adding JScrollPane on a JList without using JPanel

Question

I need help on my program. I need to have a JScrollPane on a JList without putting JList on a JPanel.

import java.awt.*;
import java.awt.event.*;
import java.util.*;
import javax.swing.*;

public class refurbished extends JFrame implements ActionListener {
    ArrayList<String> names;
    JButton add;
    JTextField inputName;
    JScrollPane scrollName;
    JList nameList;

public refurbished() {
    setSize(700,500);
    setLayout(null);

    names = new ArrayList<String>();

    add = new JButton("Add");
    add.setBounds(25,200,90,30);
    add.setBackground(Color.WHITE);
    add.addActionListener(this);

    inputName = new JTextField();
    inputName.setBounds(150,350,150,30);

    nameList = new JList(names.toArray());

    scrollName = new JScrollPane(nameList);
    scrollName.setBounds(150,75,150,200);

    getContentPane().add(add);
    getContentPane().add(inputName);
    getContentPane().add(scrollName);

    setVisible(true);
}

public void actionPerformed (ActionEvent buttonclick) {
    if (buttonclick.getSource() == add) {
        names.add(inputName.getText().toLowerCase());
        nameList = new JList(names.toArray());
        scrollName = new JScrollPane(nameList);
        scrollName.setBounds(150,75,150,200);
}
}

public static void main (String[] args) {
    refurbished r = new refurbished();
}

}

Can you help me? I really need your help because this is the only missing feature in my code.

Your help is really appreciated.

Answer 1

Yout haven't added the lists to the scroll panes. You've only added the lists to the contentpane.

scrollName = new JScrollPane();
scrollNumber = new JScrollPane();

getContentPane().add(nameList);      <-- Get rid of this
getContentPane().add(numberList);    <-- Get rid of this

You need this instead

scrollName = new JScrollPane(nameList);
scrollNumber = new JScrollPane(numberList);

getContentPane().add(scrollName);      
getContentPane().add(scrollNumber);

Also as @Alex2410 noted in his comment below, "Also you need to use LayoutManager, or set Bounds to JScrollPane rather then to JList"

Update: to original poster update

You need to both revalidate() and repaint() after adding or removing components. Add revalidate() before where you have repaint(). You only need to revalidate() repaint() once in the method

---

Edit: If you want to update the list, use a ListModel. You don't need to replace the entire list with a new list

See this code. What I've done is used a DefaultListModel and set that model to the Jlist. Then you can add element to the list dynamically. I fixed your code and it works. I commented on the adds and what I removed

import java.awt.*;
import java.awt.event.*;
import java.util.*;
import javax.swing.*;

public class refurbished extends JFrame implements ActionListener {

    ArrayList<String> names;
    JButton add;
    JTextField inputName;
    JScrollPane scrollName;
    JList nameList;
    DefaultListModel model;          <-- declare DefaultListModel

    public refurbished() {
        setSize(700, 500);
        setLayout(null);

        names = new ArrayList<String>();

        add = new JButton("Add");
        add.setBounds(25, 200, 90, 30);
        add.setBackground(Color.WHITE);
        add.addActionListener(this);

        inputName = new JTextField();
        inputName.setBounds(150, 350, 150, 30);

        model = new DefaultListModel();                <-- Initialize model
        nameList = new JList(model);                   <-- set model to list

        scrollName = new JScrollPane(nameList);
        scrollName.setBounds(150, 75, 150, 200);

        getContentPane().add(add);
        getContentPane().add(inputName);
        getContentPane().add(scrollName);

        setVisible(true);
    }

    public void actionPerformed(ActionEvent buttonclick) {
        if (buttonclick.getSource() == add) {
            //names.add(inputName.getText().toLowerCase());   
            //nameList = new JList(names.toArray());        <-- don't need all this
            //scrollName = new JScrollPane(nameList);
            //scrollName.setBounds(150, 75, 150, 200);
            String name = inputName.getText();           <-- get input
            names.add(name);                             
            model.addElement(name);                      <-- add name to model      
        }
    }

    public static void main(String[] args) {
        refurbished r = new refurbished();
    }
}

Take a look at Using Models. You should take time to learn the MVC (Model, View, Controller) paradigm.