Java 小程序无法正确绘制

Question

这是主要代码

import java.awt.*;  

import javax.swing.*;  
import java.awt.event.*;  
import java.applet.Applet;  

import java.applet.*;  
import java.awt.image.*;  
import java.util.*;  
import java.net.*;  
public class AlcatrazBreakout extends JApplet implements KeyListener, FocusListener  {  
    int choice=0,curloc=0;  
    boolean focus = false;  
    boolean left=false, right=false, up=false, down=false, space=false, enter=false;  

    public double randNum(Graphics canvas)
    {
        double x;
        x=Math.random()*100;
        return x;
    }
    public void init()
    {

        addKeyListener(this);
        addFocusListener(this);
        play(getCodeBase(), "SpyHunter.mid");

    }
    public void paint(Graphics canvas)
    {
        clearScreen(canvas);

        canvas.setColor(Color.BLACK);  // Must do this so words will
                                       // display on the screen

         if (!focus)
         {
            canvas.setColor(Color.WHITE);
            canvas.drawString("Welcome to Alcatraz Breakout! The objective of the game is to escape Alcatraz.",10,10);
            canvas.drawString("Click the screen to begin the game.",10,30);
            return;
         }
         else if (focus)
         {
             startbody(canvas);
         }


     }
    public void showstats(Graphics canvas)
    {
        int hp=10,hpmax=10,defense=0,attack=0;
        canvas.drawString("HP: " + hp ,1750,10);
        canvas.drawString("/" + hpmax,1790,10);
        canvas.drawString("Attack: " + attack,1750,30);
        canvas.drawString("Defense: " + defense,1750,50);
    }
    public void startbody(Graphics canvas)
    {
        space=enter=left=right=up=down=false;
        clearScreen(canvas);
        canvas.setColor(Color.WHITE);
        showstats(canvas);
        canvas.drawString("You are in your cell.",0,10);
        canvas.drawString("Left: To the Training Room.",0,30);
        canvas.drawString("Right: To the Showers",0,50);
        curloc=0;
        makeMove(canvas,curloc, left,right,up,down);
        canvas.drawString(" "+curloc,0,70);
    }
    public void train(Graphics canvas)
    {
        System.out.println("You are at train");
        space=enter=left=right=up=down=false;
        clearScreen(canvas);
        canvas.setColor(Color.WHITE);
        showstats(canvas);
        canvas.drawString("You are in the training room.",0,10);
        canvas.drawString("Right: To your cell.",0,30);
        makeMove(canvas,curloc,left,right,up,down);

    }
    public void showers(Graphics canvas)
    {
        System.out.println("You are in the showers");
        space=enter=left=right=up=down=false;
        clearScreen(canvas);
        canvas.setColor(Color.WHITE);
        showstats(canvas);
        canvas.drawString("You are in the showers.",0,10);
        canvas.drawString("Left: To your cell.",0,30);
        curloc=1;
        makeMove(canvas,curloc, left,right,up,down);
    }
    public void cellBlockC(Graphics canvas)
    {
        space=enter=left=right=up=down=false;
        clearScreen(canvas);
        canvas.setColor(Color.WHITE);
        canvas.drawString("You are in CellBlock C", 0, 10);
        canvas.drawString("Left: Back to your cell",0,20);
        canvas.drawString("Up: to security room 1", 0, 40);
        curloc=2;
        makeMove(canvas,curloc, left,right,up,down);
    }
    public void SecRoom1(Graphics canvas)
    {
        space=enter=left=right=up=down=false;
        clearScreen(canvas);
        canvas.setColor(Color.WHITE);
        canvas.drawString("Your in Secrity room 1.", 0, 10);
        canvas.drawString("Down: Back to Cell Block C",0,20);
        canvas.drawString("Up: Left to Guard Post", 0, 40);
        curloc=3;
        makeMove(canvas,curloc, left,right,up,down);
    }
    public void tunnel(Graphics canvas)
    {
        space=enter=left=right=up=down=false;
        clearScreen(canvas);
        canvas.setColor(Color.WHITE);
        canvas.drawString("Your in Secrity room 1.", 0, 10);
        canvas.drawString("Down: Back to Cell Block C",0,20);
        canvas.drawString("Up: Left to Guard Post", 0, 40);
        curloc=7;
        makeMove(canvas,curloc, left,right,up,down);
    }
    public void guardPost(Graphics canvas)
    {
        space=enter=left=right=up=down=false;
        clearScreen(canvas);
        canvas.setColor(Color.WHITE);
        canvas.drawString("Your in the Guard Post.", 0, 10);
        canvas.drawString("Left: to go to the Court Yard",0,20);
        canvas.drawString("Right: to go to Security room 1", 0, 40);
        canvas.drawString("Up: to go to Solitary Confinement",0,60);
        curloc=4;
        makeMove(canvas,curloc, left,right,up,down);
    }
    public void courtyard(Graphics canvas)
    {
        space=enter=left=right=up=down=false;
        clearScreen(canvas);
        canvas.setColor(Color.WHITE);
        canvas.drawString("Your in the Court Yard", 0, 10);
        canvas.drawString("Down: to Security Room 2.",0,20);
        canvas.drawString("Up: To Guard Post", 0, 40);
        curloc=8;
        makeMove(canvas,curloc, left,right,up,down);
    }
    public void SecRoom2(Graphics canvas)
    {
        space=enter=left=right=up=down=false;
        clearScreen(canvas);
        canvas.setColor(Color.WHITE);
        canvas.drawString("Your in Security Room 2.", 0, 10);
        canvas.drawString("Up: To the Court Yard", 0, 40);
        curloc=9;
        makeMove(canvas,curloc, left,right,up,down);
    }
    public void fight(Graphics canvas)
    {
        space=enter=left=right=up=down=false;
        clearScreen(canvas);
        canvas.setColor(Color.WHITE);
        canvas.drawString("Your at the Final Fight!!!", 0, 10);
        curloc=11;
        makeMove(canvas,curloc, left,right,up,down);
    }
    public void free(Graphics canvas)
    {
        space=enter=left=right=up=down=false;
        clearScreen(canvas);
        canvas.setColor(Color.WHITE);
        canvas.drawString("You Won!!!!", 0, 10);
        curloc=11;
        makeMove(canvas,curloc, left,right,up,down);
    }
    public void solitaryConfinement(Graphics canvas)
    {
        space=enter=left=right=up=down=false;
        clearScreen(canvas);
        canvas.setColor(Color.WHITE);
        canvas.drawString("Your in Solitary Confinement.", 0, 10);
        canvas.drawString("Down: Guard Post",0,20);
        curloc=5;
        makeMove(canvas,curloc, left,right,up,down);
    }
    public void makeMove(Graphics canvas,int curloc,boolean left, boolean right, boolean up, boolean down )
    {
        if (curloc==0)
        {
            if(left)
            {
                train(canvas);
                left=right=up=down=false;
            }
        }
    }
     public void delayGame(int numSecs)
     {
        int delayTime = 1000 * numSecs;
        long startDelay = System.currentTimeMillis();
        long endDelay = 0;

        while (endDelay - startDelay < delayTime)
        {
          endDelay = System.currentTimeMillis();
        }
     }
     public void clearScreen(Graphics g)
     {
        g.setColor(Color.BLACK);
        g.fillRect(0,0,5000,5000);
     }
     public void keyPressed(KeyEvent e)
     {
      int key = e.getKeyCode();


      if (key == KeyEvent.VK_LEFT)
      {
        left = true;
        repaint();
      }

      if (key == KeyEvent.VK_DOWN)
      {
        down = true;
        repaint();
      }

      if (key == KeyEvent.VK_RIGHT)
      {
        right = true;
        repaint();
      }

      if (key == KeyEvent.VK_UP)
      {
        up = true;
        repaint();
      }

      if (key == KeyEvent.VK_SPACE)
      {
        space = true;
        repaint();
      }

      if (key == KeyEvent.VK_ENTER)
      {
        enter = true;
        repaint();
      }

     }
     public void focusGained(FocusEvent evt) {focus=true; repaint();}
     public void focusLost(FocusEvent evt) {focus=false;}
     public void keyReleased(KeyEvent e){}
     public void keyTyped(KeyEvent e) {}
     public void restart(Graphics g){}

}  

，因此 curloc 的编号不会传递到 makeMove 中，并且程序键不起作用。
谢谢
chris

编辑：

You are at train
[message repeated 1075 time]
You are at train
Exception in thread "AWT-EventQueue-1" java.lang.StackOverflowError
    at sun.nio.cs.SingleByteEncoder.encodeArrayLoop(Unknown Source)
    at sun.nio.cs.SingleByteEncoder.encodeLoop(Unknown Source)
    at java.nio.charset.CharsetEncoder.encode(Unknown Source)
    at sun.nio.cs.StreamEncoder.implWrite(Unknown Source)
    at sun.nio.cs.StreamEncoder.write(Unknown Source)
    at java.io.OutputStreamWriter.write(Unknown Source)
    at java.io.BufferedWriter.flushBuffer(Unknown Source)
    at java.io.PrintStream.write(Unknown Source)
    at java.io.PrintStream.print(Unknown Source)
    at java.io.PrintStream.println(Unknown Source)
    at AlcatrazBreakout.train(AlcatrazBreakout.java:75)
    at AlcatrazBreakout.makeMove(AlcatrazBreakout.java:196)
    at AlcatrazBreakout.train(AlcatrazBreakout.java:81)
    at AlcatrazBreakout.makeMove(AlcatrazBreakout.java:196)
    at AlcatrazBreakout.train(AlcatrazBreakout.java:81)
    at AlcatrazBreakout.makeMove(AlcatrazBreakout.java:196)
    at AlcatrazBreakout.train(AlcatrazBreakout.java:81)
    at AlcatrazBreakout.makeMove(AlcatrazBreakout.java:196)
    at AlcatrazBreakout.train(AlcatrazBreakout.java:81)
    at AlcatrazBreakout.makeMove(AlcatrazBreakout.java:196)
    at AlcatrazBreakout.train(AlcatrazBreakout.java:81)
    at AlcatrazBreakout.makeMove(AlcatrazBreakout.java:196)
    at AlcatrazBreakout.train(AlcatrazBreakout.java:81)
    at AlcatrazBreakout.makeMove(AlcatrazBreakout.java:196)
    at AlcatrazBreakout.train(AlcatrazBreakout.java:81)
    at AlcatrazBreakout.makeMove(AlcatrazBreakout.java:196)
    at AlcatrazBreakout.train(AlcatrazBreakout.java:81)

这是我在 Eclipse 中的控制台输出

Answer 1

我发现的两个问题：

1. 在 paint() 中，您要么绘制初始化屏幕（'欢迎来到...'），要么调用 startbody()，具体取决于在焦点上。在 startbody 中您要做的第一件事是 space = Enter = left = right = up = down = false; 即“清除”所有“键”的值。这就是为什么您的程序键没有任何作用。您似乎在游戏中不同“位置”的所有方法中都执行此操作

2. 您还将 curloc 重置为 0。同样的问题。而且您实际上不需要将 curloc 作为参数传递给不同的方法，因为它是一个实例变量，并且在代码中的任何位置都可见。

Answer 2

您不应该：

1. 覆盖小程序的paint()方法。自定义绘制是通过重写 JPanel 的paintComponent() 方法来完成的，然后将面板添加到小程序中。

2. 使用紧密循环来“延迟”游戏。相反，请使用 Swing Timer 来安排游戏的下一步。

Answer 3

在 AWT/Swing（或任何 GUI）程序（包括小程序）中，您必须将程序逻辑（即在房间之间移动）与绘画分离。

这意味着，您的 keyPress 和类似的事件驱动方法应该（可能通过调用其他方法间接）更改程序的某些内部状态（即我现在在哪个房间），然后调用repaint()，然后就完成了。

您的 paint 方法应该查看状态，根据此状态绘制小程序，然后完成。

您正在做的是在没有递归结束条件的情况下从自身递归调用某些方法，这会导致您观察到的 StackOverflowError （这也是该网站的同名）。

---

因此，这里是一个对用户输入做出反应的示例小程序：

class ExampleApplet extends JApplet {

   /** our game state. */
   private int colorCode = 0;

   /**
    * This method will be called by the applet environment on loading the applet.
    */    
   public void init() {
      EventQueue.invokeLater(new Runnable() { public void run() {
         JApplet app = ExampleApplet.this;
         app.setContentPane(new Painter());
         app.addKeyListener(new Listener());
      }});
   }

   /**
    * An object of this class is registered as a key listener for our applet.
    * It changes the game state whenever a key is typed, and then invokes repaint().
    */
   class Listener extends KeyAdapter {
      public void keyTyped(KeyEvent e) {
         colorCode ++;
         repaint();
      }
   }

   /** This class is the contentPane of the applet, and responsible for the painting. */
   class Painter extends JPanel {

      private Color chooseColor() {
          switch(colorCode % 11) {
             case  0: return Color.WHITE;
             case  1: return Color.BLUE;
             case  2: return Color.YELLOW;
             case  3: return Color.RED;
             case  4: return Color.CYAN;
             case  5: return Color.LIGHT_GRAY;
             case  6: return Color.MAGENTA;
             case  7: return Color.GREEN;
             case  8: return Color.ORANGE;
             case  9: return Color.PINK;
             case 10: return Color.BLACK;
          }
          throw new IllegalStateException("colorCode is negative: " + colorCode);
      }

      /**
       * Paints the component dependent on the current state of the game.
       */
      public void paintComponent(Graphics g) {
         g.setColor(chooseColor());
         g.fillRectangle(0,0, getHeight(), getWidth());
      }
   }

}

当然，在游戏中您不想用某种颜色绘制矩形，但您会为当前所在的房间调用正确的绘制方法。您的内部状态将包括房间，按右键会更改为其他房间之一。