Java JScrollBar Example

Java JScrollBar Example

Java JScrollBar is used to add vertical or horizontal scroll bars.ScrollBar inherits methods from JComponent class.

How to Declare Java JScrollBar

[class JScrollBar extends JComponent implements Adjustable, Accessible]

Java JScrollBar  used constructors

• JScrollBar()-creates vertical scrollbar with initial values.
• JScrollBar(int orientation)-creates scrollbar with a certain orientation and initial values.
• JScrollBar(int orientation,int v,int extent,int max,int min)-creates JScrollBar with specified values.

Java JScrollBar Example

[

import javax.swing.JFrame;
import javax.swing.JScrollBar;
public class JavaJScrollBarExample extends JFrame {
    JavaJScrollBarExample ()
    {
        super("JavaJScrollBarExample ");

        JScrollBar scroll=new JScrollBar();
        scroll.setBounds(50,50, 50,100);
        add(scroll);


        setSize(400,400);
        setLayout(null);
        setLocationRelativeTo(null);
        setDefaultCloseOperation(EXIT_ON_CLOSE);
        setVisible(true);

    }
    public static void main(String args[])
    {
        new JavaJScrollBarExample ();
    }

}

]

Code Explanation

[ super("JavaJScrollBarExample ");] -this code calls the JFrame constructor which has been extended in this class.

[ JScrollBar scroll=new JScrollBar();]-Creates JScrollbar object.

[setDefaultCloseOperation(EXIT_ON_CLOSE);]-exits application when the close button is clicked.

Java JScrollBar Example with Adjustment Listener

[

import javax.swing.JFrame;
import javax.swing.JScrollBar;
import java.awt.event.AdjustmentEvent;
import java.awt.event.AdjustmentListener;
import javax.swing.JOptionPane;
public class JavaJScrollBarExample extends JFrame
        implements AdjustmentListener {
    JavaJScrollBarExample ()
    {
        super("JavaJScrollBarExample ");

        JScrollBar scroll=new JScrollBar();
        scroll.setBounds(50,50, 50,100);
        add(scroll);

        scroll.addAdjustmentListener(this);

        setSize(400,400);
        setLayout(null);
        setLocationRelativeTo(null);
        setDefaultCloseOperation(EXIT_ON_CLOSE);
        setVisible(true);

    }
    public void adjustmentValueChanged(AdjustmentEvent evt)
    {
        JOptionPane.showMessageDialog(null, "Vertical scrollbar "                  

      +evt.getValue(),"JScrollBar Example",
                JOptionPane.INFORMATION_MESSAGE);
    }
    public static void main(String args[])
    {
        new JavaJScrollBarExample ();
    }

}

]

Output

Code Explanation
Above class extends JFrame and implement AdjustmentListener interface [public class JavaJScrollBarExample extends JFrame
implements AdjustmentListener ]

If a non abstract class implements a certain interface,the class is required to override all interface abstract methods.For example AdjustmentListener abstract method is [public void adjustmentValueChanged(AdjustmentEvent evt)

    {
        JOptionPane.showMessageDialog(null, "Vertical scrollbar "                     

   +evt.getValue(),"JScrollBar Example",
                JOptionPane.INFORMATION_MESSAGE);
    }

]

The user scrolls the JScrollBar action is picked which invokes [ JOptionPane.showMessageDialog()] method.JOptionPane pop ups showing value of vertical scrollbar position.

Other methods used in this program

[setBounds(50,50, 50,100);]-positions java.swing components in JFrame or JPanel.

[setDefaultCloseOperation(EXIT_ON_CLOSE);]-exits application when close button is clicked.

[ setLocationRelativeTo(null);]-positions JFrame at the center of the screen.