Java 小程序 AWT-EventQueue-1 异常

Question

我用 java 小程序编写了生命游戏的简单实现。 以下是 Applet 和 模型。

当我单击按钮获取下一次迭代时，会抛出这些异常。

Z:\GameOfLife>appletviewer driver.html
Exception in thread "AWT-EventQueue-1" java.lang.ArrayIndexOutOfBoundsException:
 65
        at GameOfLifeApplet.mouseClicked(GameOfLifeApplet.java:63)
        at java.awt.Component.processMouseEvent(Component.java:6219)
        at java.awt.Component.processEvent(Component.java:5981)
        at java.awt.Container.processEvent(Container.java:2041)
        at java.awt.Component.dispatchEventImpl(Component.java:4583)
        at java.awt.Container.dispatchEventImpl(Container.java:2099)
        at java.awt.Component.dispatchEvent(Component.java:4413)
        at java.awt.EventQueue.dispatchEvent(EventQueue.java:599)
        at java.awt.EventDispatchThread.pumpOneEventForFilters(EventDispatchThre    ad.java:269)
        at java.awt.EventDispatchThread.pumpEventsForFilter(EventDispatchThread.java:184)
        at java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThre    ad.java:174)
        at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:169)
        at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:161)
        at java.awt.EventDispatchThread.run(EventDispatchThread.java:122)

Answer 1

尝试使用此代码添加一次按钮，而不是每次调用 paint()。请注意，如果您单击网格外部（而不是按钮上），此源仍然会抛出 AIOOBE，但这似乎是一个基本逻辑错误，一旦按钮修复，您应该进行调查。

// <applet code='GameOfLifeApplet' width=580 height=650></applet>
import java.awt.*;
import java.awt.event.*;
import java.applet.*;

public class GameOfLifeApplet extends Applet implements MouseListener,ActionListener
{
  //the x and y coordinates to get the location of the clicked points
  private int xCo, yCo;
  private int diff_x, diff_y;
  private GameOfLife game = new GameOfLife();
  private Button nextButton = null;
  public void init()
  {
    setLayout(null);
    nextButton = new Button("Next Stage");
    diff_x = diff_y = 600 / game.getGridSize();
    nextButton.setLocation(250, 575);
    nextButton.setSize(120, 30);
    // add the button once only!
    add(nextButton);
    addMouseListener(this);
  }

  private void drawEmptyGrid(Graphics g)
  {
    g.setColor(Color.white);
    g.fillRect(0,0,600,600);
    g.setColor(Color.black);
    for(int i=0;i<game.getGridSize();++i)
    {
      g.drawLine(0,i*diff_x,600,i*diff_x);
      g.drawLine(i*diff_x,0,i*diff_x,600);
    }
    g.setColor(Color.white);
  }

  public void paint(Graphics g)
  {
    drawEmptyGrid(g);
    g.setColor(Color.red);
    for(int i=0;i<game.getGridSize();++i)
    {
      for(int j=0;j<game.getGridSize();++j)
      {
        if( game.grid[i][j] )
        {
          g.fillRect(i*diff_x,j*diff_y,diff_x,diff_y);
        }
      }
    }
    g.setColor(Color.white);
  }

 // This method will be called when the mouse has been clicked.
 public void mouseClicked (MouseEvent me) {

  // Save the coordinates of the click lke this.
  xCo = me.getX();
  yCo = me.getY();

  int x_init = xCo / diff_x;
  int y_init = yCo / diff_y;

  System.out.println(x_init + "x" + y_init);
  game.grid[x_init][y_init] = true;
  //show the results of the click
  repaint();

 }

 // This is called when the mous has been pressed
 public void mousePressed (MouseEvent me) {}

 // When it has been released
 // not that a click also calls these Mouse-Pressed and Released.
 // since they are empty nothing hapens here.
 public void mouseReleased (MouseEvent me) {}

 // This is executed when the mouse enters the applet. it will only
 // be executed again when the mouse has left and then re-entered.
 public void mouseEntered (MouseEvent me) {}

 // When the Mouse leaves the applet.
 public void mouseExited (MouseEvent me) {}

 public void actionPerformed(ActionEvent evt)
  {
  // Here we will ask what component called this method
    if (evt.getSource() == nextButton)
    {
      System.out.println("I got clicked!");
      game.nextIteration();
      repaint();
    }
  }

}

class GameOfLife
{
  private final int GRID_SIZE = 64;
  public boolean [][] grid = new boolean[GRID_SIZE][GRID_SIZE];
  //default constructor
  public GameOfLife()
  {
    for(int i=0;i<GRID_SIZE;++i)
    {
      for(int j=0;j<GRID_SIZE;++j)
    {
      grid[i][j] = false;
    }
    }
  }

  public int getGridSize()
  {
    return GRID_SIZE;
  }

  public int getLiveNeighbors(int i,int j)
  {
    int neighbors = 0;
    for( int tmp_i = i-1; tmp_i <= i+1; ++tmp_i )
    {
      for( int tmp_j = j-1; tmp_j <= j+1; ++tmp_j )
      {
        if( tmp_i < 0 || tmp_i >= GRID_SIZE || tmp_j < 0 || tmp_j >= GRID_SIZE )
        {}
        else
        {
          if( grid[tmp_i][tmp_j] )
          {
            neighbors++;
          }
        }
      }
    }
    return neighbors;
  }

  public void nextIteration()
  {
    boolean [][] newGrid = new boolean[GRID_SIZE][GRID_SIZE];

    for(int i=0;i<GRID_SIZE;++i)
    {
      for(int j=0;j<GRID_SIZE;++j)
      {
        newGrid[i][j] = grid[i][j];
      }
    }

    for( int i=0;i<GRID_SIZE;++i)
    {
      for( int j=0;j<GRID_SIZE;++j)
      {
        int my_neighbors = getLiveNeighbors(i,j);
        if( !newGrid[i][j] && my_neighbors == 3)
        {
          grid[i][j] = true;
        }

        else if( newGrid[i][j] && ( my_neighbors == 2 || my_neighbors == 3 ) )
        {
          grid[i][j] = true;
        }

        else
        {
          grid[i][j] = false;
        }
      }
    }
    System.out.println("Change of assignment");
  }
}

进一步提示

1. 在这个世纪不要使用 AWT 组件，而应使用 Swing。
2. 不要使用 null 布局。自定义渲染区域不需要它，并且应该使用布局管理器来调整按钮的大小和位置（可能有一个边框将其填充）。

更新

此代码实现了上面“使用布局”的第二个建议，但将其作为练习留给读者，以将组件更新为本世纪可能使用的组件（即 Swing）。

下面的源代码在某种意义上“作弊”，以自然大小显示 GUI。这在小程序中很难做到，因为大小是由 HTML 设置的。但是，将 GUI 放入基于 Swing 的 JOptionPane 中，只需几行代码即可将其显示在屏幕上，并按其自然大小排列。

这是它在“自然大小”下的样子（我使用了一些数字，以使 GUI 更小）。

// <applet code='GameOfLifeApplet' width=320 height=350></applet>
import java.awt.*;
import java.awt.event.*;
import java.applet.*;

public class GameOfLifeApplet extends Applet implements ActionListener
{
    private Button nextButton = null;
    private Ecosystem ecosystem;

    public void init()
    {
        add(getGui());
    }

    public Component getGui() {
        Panel gui = new Panel(new BorderLayout(3,3));
        ecosystem = new Ecosystem();
        gui.add(ecosystem, BorderLayout.CENTER);
        nextButton = new Button("Next Stage");

        Panel p = new Panel(new FlowLayout());
        p.add(nextButton);
        gui.add(p, BorderLayout.SOUTH);
            nextButton.addActionListener(this);
        return gui;
    }

    public void actionPerformed(ActionEvent evt)
    {
        // Here we will ask what component called this method
        if (evt.getSource() == nextButton)
        {
            System.out.println("I got clicked!");
            ecosystem.nextIteration();
            ecosystem.repaint();
        }
    }

    public static void main(String[] args) {
        GameOfLifeApplet gola = new GameOfLifeApplet();
        // quick cheat to get it on-screen (packed).
        javax.swing.JOptionPane.showMessageDialog(null,gola.getGui());
    }
}

class Ecosystem extends Panel implements MouseListener {
    private GameOfLife game = new GameOfLife();
    //the x and y coordinates to get the location of the clicked points
    private int xCo, yCo;
    private int diff_x, diff_y;
    private int size = 300;

    Ecosystem() {
        diff_x = diff_y = 600 / game.getGridSize();
        setPreferredSize(new Dimension(size,size));
        addMouseListener(this);
    }

    public void nextIteration() {
        game.nextIteration();
    }

    private void drawEmptyGrid(Graphics g)
    {
        g.setColor(Color.white);
        g.fillRect(0,0,size,size);
        g.setColor(Color.black);
        for(int i=0;i<game.getGridSize();++i)
        {
            g.drawLine(0,i*diff_x,size,i*diff_x);
            g.drawLine(i*diff_x,0,i*diff_x,size);
        }
        g.setColor(Color.white);
    }

    public void paint(Graphics g)
    {
        drawEmptyGrid(g);
        g.setColor(Color.red);
        for(int i=0;i<game.getGridSize();++i)
        {
            for(int j=0;j<game.getGridSize();++j)
            {
                if( game.grid[i][j] )
                {
                    g.fillRect(i*diff_x,j*diff_y,diff_x,diff_y);
                }
            }
        }
        g.setColor(Color.white);
    }

    // This method will be called when the mouse has been clicked.
    public void mouseClicked (MouseEvent me) {
        Point point = me.getPoint();

        // Save the coordinates of the click lke this.
        xCo = (int)point.getX();
        yCo = (int)point.getY();

        int x_init = xCo / diff_x;
        int y_init = yCo / diff_y;

        System.out.println(x_init + "x" + y_init);
        game.grid[x_init][y_init] = true;
        //show the results of the click
        repaint();
    }

    // This is called when the mous has been pressed
    public void mousePressed (MouseEvent me) {}

    // When it has been released
    // not that a click also calls these Mouse-Pressed and Released.
    // since they are empty nothing hapens here.
    public void mouseReleased (MouseEvent me) {}

    // This is executed when the mouse enters the applet. it will only
    // be executed again when the mouse has left and then re-entered.
    public void mouseEntered (MouseEvent me) {}

    // When the Mouse leaves the applet.
    public void mouseExited (MouseEvent me) {}
}

class GameOfLife
{
    private final int GRID_SIZE = 60;
    public boolean [][] grid = new boolean[GRID_SIZE][GRID_SIZE];

    //default constructor
    public GameOfLife()
    {
        for(int i=0;i<GRID_SIZE;++i)
        {
            for(int j=0;j<GRID_SIZE;++j)
            {
                grid[i][j] = false;
            }
        }
    }

    public int getGridSize()
    {
        return GRID_SIZE;
    }

    public int getLiveNeighbors(int i,int j)
    {
        int neighbors = 0;
        for( int tmp_i = i-1; tmp_i <= i+1; ++tmp_i )
        {
            for( int tmp_j = j-1; tmp_j <= j+1; ++tmp_j )
            {
                if( tmp_i < 0 || tmp_i >= GRID_SIZE || tmp_j < 0 || tmp_j >= GRID_SIZE )
                {}
                else
                {
                    if( grid[tmp_i][tmp_j] )
                    {
                    neighbors++;
                    }
                }
            }
        }
        return neighbors;
    }

    public void nextIteration()
    {
        boolean [][] newGrid = new boolean[GRID_SIZE][GRID_SIZE];

        for(int i=0;i<GRID_SIZE;++i)
        {
            for(int j=0;j<GRID_SIZE;++j)
            {
                newGrid[i][j] = grid[i][j];
            }
        }

        for( int i=0;i<GRID_SIZE;++i)
        {
            for( int j=0;j<GRID_SIZE;++j)
            {
                int my_neighbors = getLiveNeighbors(i,j);
                if( !newGrid[i][j] && my_neighbors == 3)
                {
                    grid[i][j] = true;
                }
                else if( newGrid[i][j] && ( my_neighbors == 2 || my_neighbors == 3 ) )
                {
                    grid[i][j] = true;
                }
                else
                {
                    grid[i][j] = false;
                }
            }
        }
        System.out.println("Change of assignment");
    }
}

其他事项

1. 代码将自定义绘画移动到Panel。这解决了直接绘制到顶级容器的常见问题。它还允许在不同容器中轻松地重复使用相同的 GUI。在本例中，既是一个小程序，又是一个 JOptionPane 对于“应用程序”（通常放在框架中）。现在它被称为“混合小程序/应用程序”（更容易测试）。
2. 自定义绘制的组件Ecosystem（耸耸肩）通知布局它喜欢的大小。这有助于我们避免需要设置任何东西的大小或边界。
3. 按钮的大小将完全符合其需要的大小。

Answer 2

首先，我认为您错误地读取了异常跟踪。该异常是 ArrayIndexOutOfBoundsException，发生在 GameOfLifeApplet.java 的第 63 行。您的应用程序是一个小程序，或者异常发生在线程 AWT-EventQueue-1 上，这些都没有任何关系。

根本原因是您没有正确同步模型和视图关于网格中有多少单元格的想法。至少，您应该考虑在访问数组元素之前检查用户是否实际单击了网格内部。