Mega Code Archive
How to Write a Mouse-Wheel Listener
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Mouse-wheel events tell you when the wheel on the mouse rotates.
/*
*
* Copyright (c) 1998 Sun Microsystems, Inc. All Rights Reserved.
*
* Sun grants you ("Licensee") a non-exclusive, royalty free, license to use,
* modify and redistribute this software in source and binary code form,
* provided that i) this copyright notice and license appear on all copies of
* the software; and ii) Licensee does not utilize the software in a manner
* which is disparaging to Sun.
*
* This software is provided "AS IS," without a warranty of any kind. ALL
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* IMPLIED WARRANTY OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE OR
* NON-INFRINGEMENT, ARE HEREBY EXCLUDED. SUN AND ITS LICENSORS SHALL NOT BE
* LIABLE FOR ANY DAMAGES SUFFERED BY LICENSEE AS A RESULT OF USING, MODIFYING
* OR DISTRIBUTING THE SOFTWARE OR ITS DERIVATIVES. IN NO EVENT WILL SUN OR ITS
* LICENSORS BE LIABLE FOR ANY LOST REVENUE, PROFIT OR DATA, OR FOR DIRECT,
* INDIRECT, SPECIAL, CONSEQUENTIAL, INCIDENTAL OR PUNITIVE DAMAGES, HOWEVER
* CAUSED AND REGARDLESS OF THE THEORY OF LIABILITY, ARISING OUT OF THE USE OF
* OR INABILITY TO USE SOFTWARE, EVEN IF SUN HAS BEEN ADVISED OF THE
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*
* This software is not designed or intended for use in on-line control of
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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);
}
}
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