imageanimation.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。

// ImageAnimation.java: Display a sequence of images
import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
import javax.swing.border.*;

public class ImageAnimation extends JApplet implements ActionListener
{
  private Image imageToDisplay;
  protected Image imageArray[]; // Hold images
  protected int numOfImages = 52, // Total number of images
                currentImageIndex = 0, // Current image subscript
                sleepTime = 100; // Milliseconds to sleep
  protected int direction = 1; // Image rotating direction

  // Text field for receiving speed
  protected JTextField jtfSpeed = new JTextField(5);

  // Button for reversing direction
  JButton jbtReverse = new JButton("Reverse");

  // Initialize the applet
  public void init()
  {
    // Load the image, the image files are named
    // L1 - L52 in Images directory
    imageArray = new Image[numOfImages];
    for (int i=0; i<imageArray.length; i++ )
    {
      imageArray[i] = getImage(getDocumentBase(),
        "Images/L" + (i+1) + ".gif" );
    }

    // Panel p to hold animation control
    JPanel p = new JPanel();
    p.setLayout(new BorderLayout());
    p.add(new JLabel("Animation speed in millisecond"),
      BorderLayout.WEST);
    p.add(jtfSpeed, BorderLayout.CENTER);
    p.add(jbtReverse, BorderLayout.EAST);

    // Add the image panel and p to the applet
    getContentPane().add(new PlayImage(), BorderLayout.CENTER);
    getContentPane().add(p, BorderLayout.SOUTH);

    // Register listener
    jtfSpeed.addActionListener(this);
    jbtReverse.addActionListener(this);
  }

  // Handle ActionEvent
  public void actionPerformed(ActionEvent e)
  {
    if (e.getSource() == jtfSpeed)
    {
      sleepTime = Integer.parseInt(jtfSpeed.getText());
    }
    else if (e.getSource() == jbtReverse)
    {
      direction = -direction;
    }
  }

  class PlayImage extends JPanel implements Runnable
  {
    private Thread thread = null;

    // Determine the thread status
    protected boolean suspended = false;

    // Constructor
    public PlayImage()
    {
      // Start with the first image
      currentImageIndex = 0;

      // Start the thread
      thread = new Thread(this);
      thread.start();

      // Set line border on the panel
      setBorder(new LineBorder(Color.red, 1));
    }

    public void start()
    {
      resume();
    }

    public void stop()
    {
      suspend();
    }

    public synchronized void resume()
    {
      if (suspended)
      {
        suspended = false;
        notify();
      }
    }

    public synchronized void suspend()
    {
      suspended = true;
    }

    public void destroy()
    {
      thread = null;
    }

    public void run()
    {
      while (true)
      {
        imageToDisplay =
          imageArray[currentImageIndex%numOfImages];

        // Make sure currentImageIndex is nonnegative
        if (currentImageIndex == 0) currentImageIndex = numOfImages;
        currentImageIndex = currentImageIndex + direction;
        repaint();

        try
        {
          thread.sleep(sleepTime);
          waitForNotificationToResume();
      }
      catch (InterruptedException ex)
      {
      }
    }
  }

  // Wait for notification to resume
  private synchronized void waitForNotificationToResume()
    throws InterruptedException
  {
    while (suspended)
      wait();
  }

    // Display an image
    public void paintComponent(Graphics g)
    {
      super.paintComponent(g);

      if (imageToDisplay != null)
      {
        g.drawImage(imageToDisplay, 0, 0, getSize().width,
          getSize().height, this);
      }
    }
  }
}