鼠标滚轮监听器API
虽然MouseWheelListener
只有一个方法,但它有相应的适配器类-MouseAdapter
。这种能力使得应用程序只需为组件管理来自鼠标指针的所有类型事件拥有一个适配器类实例。
mouseWheelMoved(MouseWheelEvent) //Called when the mouse wheel is rotated.
以下代码片段与鼠标滚轮事件处理相关:
import java.awt.BorderLayout;
import java.awt.Color;
import java.awt.Dimension;
import java.awt.event.MouseWheelEvent;
import java.awt.event.MouseWheelListener;
import javax.swing.*;
public class MouseWheelEventDemo extends JPanel
implements MouseWheelListener {
JTextArea textArea;
JScrollPane scrollPane;
static final String NEWLINE = System.getProperty("line.separator");
public static void main(String[] args) {
try {
UIManager.setLookAndFeel("javax.swing.plaf.metal.MetalLookAndFeel");
} catch (UnsupportedLookAndFeelException ex) {
ex.printStackTrace();
} catch (IllegalAccessException ex) {
ex.printStackTrace();
} catch (InstantiationException ex) {
ex.printStackTrace();
} catch (ClassNotFoundException ex) {
ex.printStackTrace();
}
UIManager.put("swing.boldMetal", Boolean.FALSE);
javax.swing.SwingUtilities.invokeLater(new Runnable() {
public void run() {
createAndShowGUI();
}
});
}
private static void createAndShowGUI() {
JFrame frame = new JFrame("MouseWheelEventDemo");
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
JComponent newContentPane = new MouseWheelEventDemo();
newContentPane.setOpaque(true);
frame.setContentPane(newContentPane);
frame.pack();
frame.setVisible(true);
}
public MouseWheelEventDemo() {
super(new BorderLayout());
textArea = new JTextArea();
textArea.setEditable(false);
scrollPane = new JScrollPane(textArea);
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));
}
void eventOutput(String eventDescription, MouseWheelEvent e) {
textArea.append(e.getComponent().getClass().getName()
+ ": "
+ eventDescription);
textArea.setCaretPosition(textArea.getDocument().getLength());
}
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 {
message += " Scroll type: WHEEL_BLOCK_SCROLL" + NEWLINE;
message += " Vertical block increment: "
+ scrollPane.getVerticalScrollBar().getBlockIncrement(1)
+ " pixels" + NEWLINE;
}
eventOutput(message, e);
}
}
对于使用鼠标滚轮的单位增量的系统,MouseWheelEventDemo 的输出可能如下所示:
javax.swing.JTextArea: Mouse wheel moved UP 1 notch(es)
Scroll type: WHEEL_UNIT_SCROLL
Scroll amount: 3 unit increments per notch
Units to scroll: -3 unit increments
Vertical unit increment: 16 pixels