// Fig. 25.4: SliderDemo.java
// Testing SliderFrame.
import javax.swing.JFrame;
import java.awt.BorderLayout;
import java.awt.Color;
import javax.swing.JFrame;
import javax.swing.JSlider;
import javax.swing.SwingConstants;
import javax.swing.event.ChangeListener;
import javax.swing.event.ChangeEvent;
import java.awt.Graphics;
import java.awt.Dimension;
import javax.swing.JPanel;
public class SliderDemo
{
public static void main( String[] args )
{
SliderFrame sliderFrame = new SliderFrame();
sliderFrame.setDefaultCloseOperation( JFrame.EXIT_ON_CLOSE );
sliderFrame.setSize( 220, 270 ); // set frame size
sliderFrame.setVisible( true ); // display frame
} // end main
} // end class SliderDemo
class OvalPanel extends JPanel
{
private int diameter = 10; // default diameter of 10
// draw an oval of the specified diameter
public void paintComponent( Graphics g )
{
super.paintComponent( g );
g.fillOval( 10, 10, diameter, diameter ); // draw circle
} // end method paintComponent
// validate and set diameter, then repaint
public void setDiameter( int newDiameter )
{
// if diameter invalid, default to 10
diameter = ( newDiameter >= 0 ? newDiameter : 10 );
repaint(); // repaint panel
} // end method setDiameter
// used by layout manager to determine preferred size
public Dimension getPreferredSize()
{
return new Dimension( 200, 200 );
} // end method getPreferredSize
// used by layout manager to determine minimum size
public Dimension getMinimumSize()
{
return getPreferredSize();
} // end method getMinimumSize
} // end class OvalPanel
class SliderFrame extends JFrame
{
private JSlider diameterJSlider; // slider to select diameter
private OvalPanel myPanel; // panel to draw circle
// no-argument constructor
public SliderFrame()
{
super( "Slider Demo" );
myPanel = new OvalPanel(); // create panel to draw circle
myPanel.setBackground( Color.YELLOW ); // set background to yellow
// set up JSlider to control diameter value
diameterJSlider =
new JSlider( SwingConstants.HORIZONTAL, 0, 200, 10 );
diameterJSlider.setMajorTickSpacing( 10 ); // create tick every 10
diameterJSlider.setPaintTicks( true ); // paint ticks on slider
// register JSlider event listener
diameterJSlider.addChangeListener(
new ChangeListener() // anonymous inner class
{
// handle change in slider value
public void stateChanged( ChangeEvent e )
{
myPanel.setDiameter( diameterJSlider.getValue() );
} // end method stateChanged
} // end anonymous inner class
); // end call to addChangeListener
add( diameterJSlider, BorderLayout.SOUTH ); // add slider to frame
add( myPanel, BorderLayout.CENTER ); // add panel to frame
} // end SliderFrame constructor
} // end class SliderFrame
