Learning Java
Chapter 14: Using Swing Components
Scrollbars and Sliders
JScrollPane is such a handy component that you may not ever
need to use scrollbars by themselves. In fact, if you ever do find yourself
using a scrollbar by itself, chances are you really want to use another
component called a slider.
There's not much point in describing the appearance and functionality of
scrollbars and sliders. Instead, let's jump right in with an example that
includes both components. Figure 14-9 shows a simple example with both a
scrollbar and a slider.
Figure 14-9. Using a scrollbar and a slider
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Here is the source code for this example:
//file: Slippery.java
import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
import javax.swing.event.*;
public class Slippery extends JFrame {
public Slippery( ) {
super("Slippery v1.0");
setSize(220, 160);
setLocation(200, 200);
Container content = getContentPane( );
JPanel main = new JPanel(new GridLayout(2, 1));
JPanel scrollBarPanel = new JPanel( );
final JScrollBar scrollBar =
new JScrollBar(JScrollBar.HORIZONTAL, 0, 48, 0, 255);
int height = scrollBar.getPreferredSize( ).height;
scrollBar.setPreferredSize(new Dimension(175, height));
scrollBarPanel.add(scrollBar);
main.add(scrollBarPanel);
JPanel sliderPanel = new JPanel( );
final JSlider slider =
new JSlider(JSlider.HORIZONTAL, 0, 255, 128);
slider.setMajorTickSpacing(48);
slider.setMinorTickSpacing(16);
slider.setPaintTicks(true);
sliderPanel.add(slider);
main.add(sliderPanel);
content.add(main, BorderLayout.CENTER);
final JLabel statusLabel =
new JLabel("Welcome to Slippery v1.0");
content.add(statusLabel, BorderLayout.SOUTH);
// wire up the event handlers
scrollBar.addAdjustmentListener(new AdjustmentListener( ) {
public void adjustmentValueChanged(AdjustmentEvent e) {
statusLabel.setText("JScrollBar's current value = "
+ scrollBar.getValue( ));
}
});
slider.addChangeListener(new ChangeListener( ) {
public void stateChanged(ChangeEvent e) {
statusLabel.setText("JSlider's current value = "
+ slider.getValue( ));
}
});
}
public static void main(String[] args) {
JFrame f = new Slippery( );
f.addWindowListener(new WindowAdapter( ) {
public void windowClosing(WindowEvent e) { System.exit(0); }
});
f.setVisible(true);
}
}
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