Java Applet卡在浏览器中加载

Question

我想让一个applet加载到网页上，但它不会正确加载。下面是页面的小程序标记：

<applet codebase="classes" code="Simulation.class" width="600" height="600"></applet> 

我已经能够得到加载，没有问题的网站上的其他小应用程序，但是这一个要么什么都不做，或者不能让过去的载入画面（见你自己here）。小程序需要其他类，但它们仍然在“classes”目录下，所以我不认为这是问题。这里是Simulation.java文件的代码：

import java.applet.Applet; 
import java.awt.Color; 
import java.awt.Font; 
import java.awt.Graphics; 
import java.awt.Point; 
import java.awt.Rectangle; 
import java.awt.event.KeyEvent; 
import java.awt.event.KeyListener; 
import java.awt.event.MouseEvent; 
import java.awt.event.MouseListener; 
import java.awt.event.MouseMotionListener; 
import java.io.BufferedReader; 
import java.io.InputStreamReader; 
import java.text.DecimalFormat; 
import java.util.ArrayList; 

public class Simulation 
    extends Applet 
    implements Runnable, MouseListener, MouseMotionListener, KeyListener{ 

private static final long serialVersionUID = -1914559969027349635L; 

private boolean threadSuspended; 
private Thread t = null; 
private int startX; 
private int startY; 
private int endX; 
private int endY; 

private Environment env; 
private int numAgents = -1; 
private int width; 
private int height; 
private int stepTime; 
private int currentParam; 
private boolean start; 
private boolean instructions; 

private final double START_RANGE = 70.0; 
private final double START_BUFFER = 5.0; 
private int speed; 
private final int[] SPEEDS = {4, 5, 6, 7, 8, 
           10, 12, 15, 18, 22, 
           26, 30, 35, 40, 50, 
           65, 80, 100, 150, 300}; 

public void init() { 
    start = true; 
    currentParam = 1; 
    initParams(); 
    env = new Environment(width, height, numAgents, START_RANGE, START_BUFFER); 
    env.init(); 
    resize(width, height); 
    setBackground(Color.WHITE); 
    addMouseListener(this); 
    addMouseMotionListener(this); 
    addKeyListener(this); 
    repaint(); 
} 

public void restart() { 
    stop(); 
    start = true; 
    double tempVD = env.getVelocityDiscount(); 
    double tempHD = env.getHeadingDiscount(); 
    env = new Environment(width, height, numAgents, env.getRange(), env.getBuffer()); 
    env.init(); 
    env.setVelocityDiscount(tempVD); 
    env.setHeadingDiscount(tempHD); 
    repaint(); 
} 

private void initParams() { 
    start = true; 
    width = 600; 
    height = 600; 
    stepTime = 15; 
    speed = 8; 
    getNumAgents(); 
} 

private void getNumAgents() { 
    BufferedReader reader = new BufferedReader(new InputStreamReader(System.in)); 
    try { 
     if (numAgents < 1) { 
      System.out.print("Number of agents: "); 
      numAgents = Integer.parseInt(reader.readLine()); 
     } 
    } 
    catch (Exception e) { 
     System.err.println("Error reading input. Please enter only positive integers."); 
     try { 
      Thread.sleep(500); 
     } catch (InterruptedException e1) { 
      System.err.println("Thread interrupted."); 
      System.exit(1); 
     } 
     getNumAgents(); 
    } 
    if (numAgents < 1) { 
     System.err.println("Error reading input. Please enter only positive integers."); 
     getNumAgents(); 
    } 
} 

public void start(){ 
    if (t == null){ 
     t = new Thread(this); 
     threadSuspended = false; 
     t.start(); 
    } 
    else{ 
     if(threadSuspended){ 
      threadSuspended = false; 
      synchronized(this){ 
       notify(); 
      } 
     } 
    } 
} 

public void stop(){ 
    threadSuspended = true; 
} 

public void run(){ 
    numAgents = env.getAgents().size(); 
    width = env.getWidth(); 
    height = env.getHeight(); 
    try { 
     stop(); 
     while (true) { 
      if (threadSuspended){ 
       synchronized(this){ 
        while (threadSuspended){ 
         wait(); 
        } 
       } 
      } 
      if (this.getWidth() != env.getWidth() || this.getHeight() != env.getHeight()) { 
       env.setWidth(this.getWidth()); 
       env.setHeight(this.getHeight()); 
      } 
      env.cycle(); 
      repaint(); 
      for (int i = 0; i < stepTime/5; i++) { 
       Thread.sleep(5); 
      } 
     } 
    } 
    catch (InterruptedException e) { 
     System.err.println("Runtime Error"); 
     e.printStackTrace(); 
    } 
} 

public void paint(Graphics g){ 
    g.setFont(new Font("SansSerif", Font.PLAIN, 15)); 
    ArrayList<Agent> agents = env.getAgents(); 
    for (Agent i : agents) { 
     if (i.isSelected()) { 
      g.setColor(Color.RED); 
      g.fillOval((int) i.getX() - 2, (int) i.getY() - 2, 5, 5); 
     } 
     else { 
      switch (i.getGroup()) { 
      case 0: 
       g.setColor(Color.BLACK); 
       break; 
      case 1: 
       g.setColor(Color.BLUE); 
       break; 
      case 2: 
       g.setColor(Color.YELLOW); 
       break; 
      case 3: 
       g.setColor(Color.RED); 
       break; 
      case 4: 
       g.setColor(Color.GREEN); 
       break; 
      case 5: 
       g.setColor(Color.ORANGE); 
       break; 
      case 6: 
       g.setColor(Color.CYAN); 
       break; 
      case 7: 
       g.setColor(Color.PINK); 
       break; 
      case 8: 
       g.setColor(Color.MAGENTA); 
       break; 
      case 9: 
       g.setColor(Color.DARK_GRAY); 
       break; 
      } 
      g.drawOval((int) i.getX() - 1, (int) i.getY() - 1, 3, 3); 
     } 
    } 
    if (startX != -1 && startY != -1 && endX != -1 && endY != -1) { 
     g.setColor(Color.LIGHT_GRAY); 
     Rectangle r = getDraggedRect(); 
     g.drawRect((int) r.getMinX(), (int) r.getMinY(), r.width, r.height); 
    } 
    g.setColor(Color.LIGHT_GRAY); 
    switch (currentParam) { 
    case 1: 
     g.drawString("Speed: " + (SPEEDS.length - speed), 2, 12); 
     break; 
    case 2: 
     g.drawString("Sensing range: " + env.getRange(), 2, 12); 
     break; 
    case 3: 
     g.drawString("Velocity discount: " + env.getVelocityDiscount(), 2, 12); 
     break; 
    case 4: 
     g.drawString("Heading discount: " + env.getHeadingDiscount(), 2, 12); 
     break; 
    case 5: 
     g.drawString("Buffer: " + env.getBuffer(), 2, 12); 
     break; 
    } 
    if (start || instructions) { 
     drawInstructions(g); 
    } 
} 

private void drawInstructions(Graphics g) { 
    Color c = new Color(50, 50, 50, 200); 
    g.setColor(c); 
    int startX = (width/2) - 152; 
    int startY = (width/2) - 152; 
    g.fill3DRect(startX, startY, 304, 304, true); 
    g.setColor(Color.WHITE); 
    g.setFont(new Font("SansSerif", Font.PLAIN, 10)); 
    g.drawString("Please set parameters before starting (parameters can be", startX + 3, startY + 13); 
    g.drawString("altered at any time - current selected parameter is in the", startX + 3, startY + 26); 
    g.drawString("upper left corner at all times):", startX + 3, startY + 39); 
    g.drawString("Press 'S' to change simulation speed", startX + 3, startY + 52); 
    g.drawString("Press 'R' to change sensing range", startX + 3, startY + 65); 
    g.drawString("Press 'V' to change velocity discount", startX + 3, startY + 78); 
    g.drawString("Press 'H' to change header discount", startX + 3, startY + 91); 
    g.drawString("Press 'B' to change buffer size", startX + 3, startY + 104); 
    g.drawString("Use the UP and DOWN arrow keys to alter parameters", startX + 3, startY + 117); 
    g.drawString("Press the FORWARD arrow while paused to move one step", startX + 3, startY + 143); 
    g.drawString("Press SPACEBAR to pause or resume", startX + 3, startY + 156); 
    g.drawString("Reset the simulation by pressing ENTER", startX + 3, startY + 169); 
    g.drawString("Groups:", startX + 3, startY + 195); 
    g.drawString("Assign agents to any group by pressing 0-9 when selected.", startX + 3, startY + 208); 
    g.drawString("CLICK on any agent to select it, or select several agents", startX + 3, startY + 221); 
    g.drawString("at once by DRAGGING a selection box around them.", startX + 3, startY + 234); 
    g.drawString("Agents will only cohere to others in their group, but will", startX + 3, startY + 247); 
    g.drawString("still avoid collisions with all agents in the simulation.", startX + 3, startY + 260); 
    g.drawString("Press SPACEBAR to begin", startX + 3, startY + 286); 
    g.setFont(new Font("SansSerif", Font.ITALIC, 10)); 
    g.drawString("NOTE: these instructions can be brought up by pressing i", startX + 3, startY + 299); 
} 

private Rectangle getDraggedRect() { 
    int xS; 
    int width; 
    int yS; 
    int height; 
    if (startX > endX) { 
     xS = endX; 
     width = startX - endX; 
    } 
    else { 
     xS = startX; 
     width = endX - startX; 
    } 
    if (startY > endY) { 
     yS = endY; 
     height = startY - endY; 
    } 
    else { 
     yS = startY; 
     height = endY - startY; 
    } 
    return new Rectangle(xS - 3, yS - 3, width + 7, height + 7); 
} 

private double roundTwo(double d) { 
    DecimalFormat twoDForm = new DecimalFormat("#.##"); 
    return Double.valueOf(twoDForm.format(d)); 
} 

public void mouseClicked(MouseEvent e) {} 

public void mouseEntered(MouseEvent e) {} 

public void mouseExited(MouseEvent e) {} 

public void mousePressed(MouseEvent e) { 
    stop(); 
    startX = e.getX(); 
    startY = e.getY(); 
} 

public void mouseReleased(MouseEvent e) { 
    endX = e.getX(); 
    endY = e.getY(); 
    Rectangle r = getDraggedRect(); 
    Point temp; 
    for (Agent i : env.getAgents()) { 
     temp = new Point((int) i.getX(), (int) i.getY()); 
     if (r.contains(temp)) { 
      i.select(); 
     } 
     else { 
      i.setSelected(false); 
     } 
    } 
    startX = -1; 
    startY = -1; 
    endX = -1; 
    endY = -1; 
    repaint(); 
} 

public void mouseDragged(MouseEvent e) { 
    endX = e.getX(); 
    endY = e.getY(); 
    repaint(); 
} 

public void mouseMoved(MouseEvent e) {} 

public void keyPressed(KeyEvent e) { 
    int code = e.getKeyCode(); 
    switch (code) { 
    case 10: 
     restart(); 
     break; 
    case 32: 
     start = false; 
     if (threadSuspended) { 
      start(); 
     } 
     else { 
      stop(); 
     } 
     break; 
    case 39: 
     if (threadSuspended && !start) { 
      env.cycle(); 
      repaint(); 
     } 
     break; 
    case 83: 
     currentParam = 1; 
     repaint(); 
     break; 
    case 82: 
     currentParam = 2; 
     repaint(); 
     break; 
    case 86: 
     currentParam = 3; 
     repaint(); 
     break; 
    case 72: 
     currentParam = 4; 
     repaint(); 
     break; 
    case 66: 
     currentParam = 5; 
     repaint(); 
     break; 
    case 65: 
     env.setAllSelected(); 
     repaint(); 
     break; 
    case 73: 
     if (!start) { 
      instructions = !instructions; 
      repaint(); 
     } 
     break; 
    case 48: 
     env.setSelectedGroup(0); 
     break; 
    case 49: 
     env.setSelectedGroup(1); 
     break; 
    case 50: 
     env.setSelectedGroup(2); 
     break; 
    case 51: 
     env.setSelectedGroup(3); 
     break; 
    case 52: 
     env.setSelectedGroup(4); 
     break; 
    case 53: 
     env.setSelectedGroup(5); 
     break; 
    case 54: 
     env.setSelectedGroup(6); 
     break; 
    case 55: 
     env.setSelectedGroup(7); 
     break; 
    case 56: 
     env.setSelectedGroup(8); 
     break; 
    case 57: 
     env.setSelectedGroup(9); 
     break; 
    } 
    switch (currentParam) { 
    case 1: 
     if (code == 38 && speed > 0) { 
      speed--; 
      stepTime = SPEEDS[speed]; 
      repaint(); 
     } 
     if (code == 40 && speed < SPEEDS.length - 1) { 
      speed++; 
      stepTime = SPEEDS[speed]; 
      repaint(); 
     } 
     break; 
    case 2: 
     if (code == 38 && env.getRange() < 200) { 
      env.setRange(env.getRange() + 5); 
      repaint(); 
     } 
     if (code == 40 && env.getRange() > 5) { 
      env.setRange(env.getRange() - 5); 
      repaint(); 
     } 
     break; 
    case 3: 
     if (code == 38 && env.getVelocityDiscount() < 0.99) { 
      env.setVelocityDiscount(roundTwo(env.getVelocityDiscount() + 0.01)); 
      repaint(); 
     } 
     if (code == 40 && env.getVelocityDiscount() > 0.00) { 
      env.setVelocityDiscount(roundTwo(env.getVelocityDiscount() - 0.01)); 
      repaint(); 
     } 
     break; 
    case 4: 
     if (code == 38 && env.getHeadingDiscount() < 0.99) { 
      env.setHeadingDiscount(roundTwo(env.getHeadingDiscount() + 0.01)); 
      repaint(); 
     } 
     if (code == 40 && env.getHeadingDiscount() > 0.01) { 
      env.setHeadingDiscount(roundTwo(env.getHeadingDiscount() - 0.01)); 
      repaint(); 
     } 
     break; 
    case 5: 
     if (code == 38 && env.getBuffer() < 100) { 
      env.setBuffer(env.getBuffer() + 5); 
      repaint(); 
     } 
     if (code == 40 && env.getBuffer() > 0) { 
      env.setBuffer(env.getBuffer() - 5); 
      repaint(); 
     } 
     break; 
    } 
} 

public void keyReleased(KeyEvent e) {} 

public void keyTyped(KeyEvent e) {} 
} 

任何帮助或建议为什么这不是正确加载赞赏。谢谢！

Answer 1

与小程序一起启动Java控制台并监视异常。

Answer 2

我想通了。当小程序初始化时，它要求用户的输入：

private void getNumAgents() { 
    BufferedReader reader = new BufferedReader(new InputStreamReader(System.in)); 
    try { 
     if (numAgents < 1) { 
      System.out.print("Number of agents: "); 
      numAgents = Integer.parseInt(reader.readLine()); 
     } 
    } 
... 

这引起了小程序在浏览器中运行时熄火。在Eclipse中进行测试时，我最初是这样设置它的，并且希望在上传之前将其取出。

感谢大家的帮助。