Thread: Java.swing JScrollPane

Hello

I 'm new to java and I have trouble adding scrollbars to the textArea of my program. The program makes a kind of magical calculation and displays the result - a lot of numbers - in a textarea: resultField. The program runs well, except for the scrollbars I want to add.

The class for the window of the program is:

 
//scrollbars.java
 
package h03;
 
import javax.swing.JFrame;
 
public class scrollbars extends JFrame
	{
	public scrollbars()
	{
		JFrame window = new JFrame();
		window.setSize(300, 300);
		window.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
		window.setTitle("scrollbars");
		window.setLocation(100, 50);
		window.add(new scrollbarsPanel());
		window.setVisible(true);
	}
 
	public static void main(String[] args)
	{
		new scrollbars();
	}
}

and for the panel the code is:

 
//scrollbarsPane.java
 
package h03;
 
import javax.swing.*;
import java.awt.event.*;
 
public class scrollbarsPanel extends JPanel implements ActionListener
{
	private JTextField inputField;
	private JTextArea resultField;
	private JButton calcButton;
	//private JScrollPane scrollArea;
	private int input;
 
	public scrollbarsPanel()
	{
		calcButton = new JButton("start calculation");
		inputField = new JTextField("000", 3);
		resultField = new JTextArea(9, 24);
		JScrollPane scrollArea = new JScrollPane(resultField);
		resultField.setLineWrap(true);
		resultField.setWrapStyleWord(true);
		this.add(scrollArea);
 
		add(new JLabel ("number"));
		add(inputField);
		inputField.addActionListener(this);
		add(calcButton);
		calcButton.addActionListener(this);
		add(resultField);
	}
 
	public void showResult(int input)
	{
		input = Integer.parseInt(inputField.getText());
		resultField.setText(input + "   ");
		while (input != 1)
		{
			if (input % 2 == 0)
			{
				resultField.append((input / 2) + "   ");
				input = input/2;
				System.out.println(input);
			}
 
			else 
			{
				resultField.append((input * 3 + 1) + "   ");
				input = input * 3 + 1;
				System.out.println(input);
			}
		}
	}
 
	public void actionPerformed(ActionEvent e)
	{
		showResult(input);
 
}
}

I really can 't figure out what I am doing wrong. Can someone help me please?

Thanks a lot!
fagus

It stops at number 1 if you other a number of 3 digits or less. But my problem is that I can 't get the scrollbars in the resultfield ... .
Fagus

You should add the JScrollPane to the panel, but NOT the JTextArea.

this.add(scrollArea); // This is good
 
add(resultField); // Take this out

Thanx but it doesn' work. Now I have a scrollbar, but no result field.

Okay
The code for the window is:

package h03;
 
import javax.swing.JFrame;
 
public class scrollbars extends JFrame
	{
	public scrollbars()
	{
		JFrame window = new JFrame();
		window.setSize(300, 300);
		window.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
		window.setTitle("scrollbars");
		window.setLocation(100, 50);
		window.add(new scrollbarsPanel());
		window.setVisible(true);
	}
 
	public static void main(String[] args)
	{
		new scrollbars();
	}
}

And for the panel:

package h03;
 
import javax.swing.*;
import java.awt.event.*;
 
public class scrollbarsPanel extends JPanel implements ActionListener
{
	private JTextField inputField;
	private JTextArea resultField;
	private JButton calcButton;
	private JScrollBar scrollArea;
	private int input;
 
	public scrollbarsPanel()
	{
		calcButton = new JButton("start calculation");
		inputField = new JTextField("000", 3);
		resultField = new JTextArea(9, 24);
		scrollArea = new JScrollBar();
		resultField.setLineWrap(true);
		resultField.setWrapStyleWord(true);
		this.add(scrollArea);
 
		add(new JLabel ("number"));
		add(inputField);
		inputField.addActionListener(this);
		add(calcButton);
		calcButton.addActionListener(this);
		//add(resultField);
	}
 
	public void showResult(int input)
	{
		input = Integer.parseInt(inputField.getText());
		resultField.setText(input + "   ");
		while (input != 1)
		{
			if (input % 2 == 0)
			{
				resultField.append((input / 2) + "   ");
				input = input/2;
				System.out.println(input);
			}
 
			else 
			{
				resultField.append((input * 3 + 1) + "   ");
				input = input * 3 + 1;
				System.out.println(input);
			}
		}
	}
 
	public void actionPerformed(ActionEvent e)
	{
		showResult(input);
 
}
}

Thanks!

okay thanks a lot I got it working finaly

the code:

package h03;
 
import javax.swing.JFrame;
 
public class Scrollbars extends JFrame
	{
	public Scrollbars()
	{
		JFrame window = new JFrame();
		window.setSize(300, 300);
		window.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
		window.setTitle("scrollbars");
		window.setLocation(100, 50);
		window.add(new ScrollbarsPanel());
		window.setVisible(true);
	}
 
	public static void main(String[] args)
	{
		new Scrollbars();
	}
}

and:

package h03;
 
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
 
import javax.swing.JButton;
import javax.swing.JLabel;
import javax.swing.JPanel;
import javax.swing.JScrollPane;
import javax.swing.JTextArea;
import javax.swing.JTextField;
 
public class ScrollbarsPanel extends JPanel implements ActionListener
{
	private JTextField inputField;
	private JTextArea resultField;
	private JButton calcButton;
	//private JScrollBar scrollArea; //
	private JScrollPane jScrollPanel;
	private int input;
 
	public ScrollbarsPanel()
	{
		calcButton = new JButton("start calculation");
		inputField = new JTextField("000", 3);
		resultField = new JTextArea(4, 24);
		//scrollArea = new JScrollBar(); //
		resultField.setLineWrap(true);
		resultField.setWrapStyleWord(true);
 
		add(new JLabel ("number"));
		add(inputField);
		inputField.addActionListener(this);
		add(calcButton);
		calcButton.addActionListener(this);
		//add(resultField);
		jScrollPanel = new JScrollPane(resultField);
		//this.add(scrollArea);
		this.add(jScrollPanel);
	}
 
	public void showResult(int input)
	{
		input = Integer.parseInt(inputField.getText());
		resultField.setText(input + "   ");
		while (input != 1)
		{
			if (input % 2 == 0)
			{
				resultField.append((input / 2) + "   ");
				input = input/2;
				System.out.println(input);
			}
 
			else 
			{
				resultField.append((input * 3 + 1) + "   ");
				input = input * 3 + 1;
				System.out.println(input);
			}
		}
	}
 
	public void actionPerformed(ActionEvent e)
	{
		showResult(input);
 
}
}

As for the remark on the endless loop: I 'm learning Java with a book in which endless loops is the next chapter. I suppose this code will be an illustration for that chapter. Anyways, I can continue with my book now. Thanks