按向下箭头键启动程序,首先观察字符串.这里看一下这个示例程序：
import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
public class KeyBindingExample
{
private void createAndDisplayGUI()
{
JFrame frame = new JFrame("Key Binding Example");
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
DrawingPanel contentPane = new DrawingPanel();
frame.setContentPane(contentPane);
frame.pack();
frame.setLocationByPlatform(true);
frame.setVisible(true);
contentPane.requestFocusInWindow();
}
public static void main(String... args)
{
SwingUtilities.invokeLater(new Runnable()
{
public void run()
{
new KeyBindingExample().createAndDisplayGUI();
}
});
}
}
class DrawingPanel extends JPanel
{
private int x;
private int y;
private String[] commands = {
"UP",
"DOWN",
"LEFT",
"RIGHT"
};
private ActionListener panelAction = new ActionListener()
{
@Override
public void actionPerformed(ActionEvent ae)
{
String command = (String) ae.getActionCommand();
if (command.equals(commands[0]))
y -= 1;
else if (command.equals(commands[1]))
y += 1;
else if (command.equals(commands[2]))
x -= 1;
else if (command.equals(commands[3]))
x += 1;
repaint();
}
};
public DrawingPanel()
{
x = 0;
y = 0;
for (int i = 0; i < commands.length; i++)
registerKeyboardAction(panelAction,
commands[i],
KeyStroke.getKeyStroke(commands[i]),
JComponent.WHEN_IN_FOCUSED_WINDOW);
}
@Override
public Dimension getPreferredSize()
{
return (new Dimension(500, 300));
}
@Override
public void paintComponent(Graphics g)
{
super.paintComponent(g);
String displayText = "X : " + x + " and Y : " + y;
System.out.println(displayText);
g.drawString(displayText, x, y);
}
}
