movemessagedemo.java

此源码为机械工业出版社出版的《Java语言程序设计》第三版所配套的书中所有源代码。

// MoveMessageDemo.java: Move a message in a panel
// by dragging the mouse
import java.awt.*;
import java.awt.event.*;
import javax.swing.*;

public class MoveMessageDemo extends JApplet
{
  // Initialize the applet
  public void init()
  {
    // Create a MoveMessagePanel instance for drawing a message
    MoveMessagePanel p = new MoveMessagePanel("Welcome to Java");

    // Place the message panel in the frame
    getContentPane().setLayout(new BorderLayout());
    getContentPane().add(p);
  }

  // This main method enables the applet to run as an application
  public static void main(String[] args)
  {
    // Create a frame
    JFrame frame = new JFrame("Move Message Using Mouse");

    // Create an instance of the applet
    MoveMessageDemo applet = new MoveMessageDemo();

    // Add the applet instance to the frame
    frame.getContentPane().add(applet, BorderLayout.CENTER);

    // Invoke init() and start()
    applet.init();
    applet.start();

    // Display the frame
    frame.setSize(300, 300);
    // frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    frame.setVisible(true);
  }

  // MoveMessagePanel draws a message
  // This class is defined as inner class
  class MoveMessagePanel extends MessagePanel
    implements MouseMotionListener
  {
    // Construct a panel to draw string s
    public MoveMessagePanel(String s)
    {
      super(s);
      this.addMouseMotionListener(this);
    }

    // Tell the panel how to draw things
    public void paintComponent(Graphics g)
    {
      // Invoke the paintComponent method in the MessagePanel class
      super.paintComponent(g);
    }

    // Handler for mouse moved event
    public void mouseMoved(MouseEvent e)
    {
    }

    // Handler for mouse dragged event
    public void mouseDragged(MouseEvent e)
    {
      // Get the new location and repaint the screen
      setXCoordinate(e.getX());
      setYCoordinate(e.getY());
      repaint();
    }
  }
}