JScrollPane in Jlist

Question

hello goodevening to all i have a problem on my program with the ScrollPane in my JList i cant put an JScrollPane in my list because i am using a panel instead of Container this is my code so far its all runnable the problem is if you enter a high number in the number of times the some output will not be able to see because of the size of my list . so this is the code

import javax.swing.*;
import java.awt.*;
import java.awt.event.*;
public class MultCen extends JFrame implements ActionListener
{
    public static void main(String args [])
    {
        MultCen e = new MultCen();
        e.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        e.setVisible(true);
        e.setSize(300,450);
    }

    JTextField t1 = new JTextField();
    JTextField t2 = new JTextField();
    JButton b = new JButton("Okay");
    JButton c = new JButton("Clear");
    JList list = new JList();
    JLabel lab = new JLabel();
    DefaultListModel m = new DefaultListModel();

    public MultCen()
    {
        JPanel panel = new JPanel();
        panel.setLayout(null);



        JLabel l = new JLabel("Enter a number :");
        JLabel l1 = new JLabel("How many times :");



        l.setBounds(10,10,130,30);
        l1.setBounds(10,40,130,30);
        t1.setBounds(140,10,130,25);
        t2.setBounds(140,40,130,25);
        b.setBounds(60,90,75,30);
        c.setBounds(150,90,75,30);
        list.setBounds(30,140,220,220);

        panel.add(t1);
        panel.add(t2);
        panel.add(l);
        panel.add(l1);
        panel.add(list);
        panel.add(b);
        panel.add(c);

        getContentPane().add(panel);


        b.addActionListener(this);
        c.addActionListener(this);


    }

    public void actionPerformed(ActionEvent e)
    {
        if(e.getSource() == b)
        {
            int t3 = Integer.parseInt(t1.getText());
            int t4 = Integer.parseInt(t2.getText());
            m.addElement("The multiplication Table of "+t3);
            for (int cc =1 ; cc <=t4; cc++ )
            {

                lab.setText(t3+"*"+cc+" = "+(t3*cc));
                m.addElement(lab.getText());
                list.setModel(m);


            }



        }

        if(e.getSource() == c)
        {
            t1.setText("");
            t2.setText("");
            m.removeAllElements();
        }
    }

}

_"i cant put an JScrollPane in my list "_ - list goes in the scroll pane, not the other way around. — Paul Samsotha, Feb 27 '14 at 14:23
_"because i am using a panel instead of Container"_ - a panel _is_ a container — Paul Samsotha, Feb 27 '14 at 14:23
Don't use null layouts. Use [Layout Managers](http://docs.oracle.com/javase/tutorial/uiswing/layout/index.html) — Paul Samsotha, Feb 27 '14 at 14:24
sir in the other layout do i need to relocate those buttons and textfields ? — Batusai, Feb 27 '14 at 14:26
Using layout managers you don't need to _"locate"_ anything. You position them by either nesting panels or using a layout manager like `GridBagLayout` that helps with _"location"_. See my answer below. — Paul Samsotha, Feb 27 '14 at 14:56

score 2 · Accepted Answer · answered Feb 27 '14 at 14:21

2

JScrollPane does not work with null Layout. Use BoxLayout or any other resizeable layout instead. This is the limitation of setLayout(null).

answered Feb 27 '14 at 14:21

Masudul

21,823
5
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How sir ? can i setBounds in BoxLayout ? – Batusai Feb 27 '14 at 14:21

score 1 · Answer 2 · edited May 23 '17 at 10:31

Use Layout managers. You've asked a lot of questions here and I'm sure a few you have been advised not to use null layout. Again here is the tutorial Laying out components Within a container. Learn to use them so you don't run into the million possible problems on the road ahead. This kind of problem being one of them.

here's an example of how you could achieve the same thing with layout managers, and some empty borders for white space.

With Layout Manager

enter image description here

Without Layout Manger

enter image description here

import java.awt.BorderLayout;
import java.awt.Dimension;
import java.awt.GridLayout;
import javax.swing.*;
import javax.swing.border.EmptyBorder;

public class MultCen extends JFrame {

    public static void main(String args[]) {
        SwingUtilities.invokeLater(new Runnable() {
            public void run() {
                MultCen e = new MultCen();
                e.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
                e.setVisible(true);
                e.pack();
            }
        });

    }

    JTextField t1 = new JTextField(10);
    JTextField t2 = new JTextField(10);
    JButton b = new JButton("Okay");
    JButton c = new JButton("Clear");
    JLabel lab = new JLabel();
    DefaultListModel m = new DefaultListModel();

    public MultCen() {

        JPanel topPanel = new JPanel(new GridLayout(2, 2, 0, 5));
        JLabel l = new JLabel("Enter a number :");
        JLabel l1 = new JLabel("How many times :");
        topPanel.add(l);
        topPanel.add(t1);
        topPanel.add(l1);
        topPanel.add(t2);

        JPanel buttonPanel = new JPanel();
        buttonPanel.add(b);
        buttonPanel.add(c);
        buttonPanel.setBorder(new EmptyBorder(10, 0, 10, 0));

        JList list = new JList();
        JScrollPane scroll = new JScrollPane(list);
        scroll.setVerticalScrollBarPolicy(ScrollPaneConstants.VERTICAL_SCROLLBAR_ALWAYS);
        scroll.setPreferredSize(new Dimension(300, 300));

        JPanel panel = new JPanel(new BorderLayout());
        panel.add(topPanel, BorderLayout.NORTH);
        panel.add(buttonPanel, BorderLayout.CENTER);
        panel.add(scroll, BorderLayout.SOUTH);
        panel.setBorder(new EmptyBorder(10, 15, 10, 15));

        getContentPane().add(panel);

    }
}

Side Notes

Run Swing apps from the Event Dispatch Thread. See Initial Threads
When you do decide to use layout managers, just pack() your frame instead of setSize()
Use better variable names.
See Extends JFrame vs. creating it inside the the program

JScrollPane in Jlist

2 Answers2