Mouse-wheel events tell you when the wheel on the mouse rotates.
/*
*
* Copyright (c) 1998 Sun Microsystems, Inc. All Rights Reserved.
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import java.awt.BorderLayout;
import java.awt.Dimension;
import java.awt.event.MouseWheelEvent;
import java.awt.event.MouseWheelListener;
import javax.swing.BorderFactory;
import javax.swing.JComponent;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.JScrollPane;
import javax.swing.JTextArea;
public class MouseWheelEventDemo extends JPanel implements MouseWheelListener {
JTextArea textArea = new JTextArea();
JScrollPane scrollPane = new JScrollPane(textArea);
final static String newline = "\n";
public MouseWheelEventDemo() {
super(new BorderLayout());
textArea.setEditable(false);
scrollPane.setVerticalScrollBarPolicy(JScrollPane.VERTICAL_SCROLLBAR_ALWAYS);
scrollPane.setPreferredSize(new Dimension(400, 250));
add(scrollPane, BorderLayout.CENTER);
textArea.append("This text area displays information " + "about its mouse wheel events."
+ newline);
textArea.addMouseWheelListener(this);
setPreferredSize(new Dimension(450, 350));
setBorder(BorderFactory.createEmptyBorder(20, 20, 20, 20));
}
public void mouseWheelMoved(MouseWheelEvent e) {
String message;
int notches = e.getWheelRotation();
if (notches < 0) {
message = "Mouse wheel moved UP " + -notches + " notch(es)" + newline;
} else {
message = "Mouse wheel moved DOWN " + notches + " notch(es)" + newline;
}
if (e.getScrollType() == MouseWheelEvent.WHEEL_UNIT_SCROLL) {
message += " Scroll type: WHEEL_UNIT_SCROLL" + newline;
message += " Scroll amount: " + e.getScrollAmount() + " unit increments per notch"
+ newline;
message += " Units to scroll: " + e.getUnitsToScroll() + " unit increments" + newline;
message += " Vertical unit increment: "
+ scrollPane.getVerticalScrollBar().getUnitIncrement(1) + " pixels" + newline;
} else { // scroll type == MouseWheelEvent.WHEEL_BLOCK_SCROLL
message += " Scroll type: WHEEL_BLOCK_SCROLL" + newline;
message += " Vertical block increment: "
+ scrollPane.getVerticalScrollBar().getBlockIncrement(1) + " pixels" + newline;
}
saySomething(message, e);
}
void saySomething(String eventDescription, MouseWheelEvent e) {
textArea.append(e.getComponent().getClass().getName() + ": " + eventDescription);
textArea.setCaretPosition(textArea.getDocument().getLength());
}
public static void main(String[] args) {
JFrame frame = new JFrame("MouseWheelEventDemo");
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
JComponent newContentPane = new MouseWheelEventDemo();
newContentPane.setOpaque(true); // content panes must be opaque
frame.setContentPane(newContentPane);
frame.pack();
frame.setVisible(true);
}
}