初学者提问:面板中按钮事件响应后为什么方向键事件不能响应??

Question

面板中按钮事件响应后为什么方向键事件不能响应??

Answer 1

迷宫面板
import javax.swing.*;
import java.awt.*;
import java.awt.event.*;public class DirectionPanel extends JPanel
{    private final int WIDTH=Maze.width, HEIGHT=Maze.height;   //迷宫大小 
   private final int WIDTH_RIGHT=100;
                   
   static final int JUMP = 20;      // 移动步幅,要和迷宫方格尺寸一致
   
   private final int IMAGE_SIZE = 20;
   private Maze maze;
   private ImageIcon up, down, right, left, currentImage;
   private int x, y;
   
  private JButton changeMaze;
  private JPanel tools;   public DirectionPanel()
   {  maze=new Maze();                          //创建迷宫类
    
      addKeyListener (new DirectionListener());      x = 20;                                  //移动图标初始位置
      y = 20;      up = new ImageIcon ("arrowUp21.gif");            //图标图片引用
      down = new ImageIcon ("arrowDown21.gif");
      left = new ImageIcon ("arrowLeft21.gif");
      right = new ImageIcon ("arrowRight21.gif");      currentImage = right;
                    
      setBackground (Color.white);
      setPreferredSize (new Dimension(WIDTH, HEIGHT));
      setFocusable(true);
   }
   
   public void changeMa()
   {maze=new Maze();
    x = 20;                                  //移动图标初始位置
    y = 20;
   currentImage = right;
   }public void paintComponent (Graphics page)
   {
      super.paintComponent (page);
      page.setColor(Color.GREEN);
      maze.drawMaze(page);
      currentImage.paintIcon (this, page, x, y);    }//键盘监听器,可以使用户在迷宫通道上移动箭头图标,利用Maze类的viable方法判断此坐标的特定方向是否可行
   

   private class DirectionListener implements KeyListener
   {
      public void keyPressed (KeyEvent event)
      {
         switch (event.getKeyCode())
         {
            case KeyEvent.VK_UP:
               currentImage = up;
               if(maze.viable(x,y,4)&&y>0)
               y -= JUMP;
               break;
            case KeyEvent.VK_DOWN:
               currentImage = down;
               if(maze.viable(x,y,2)&&y+20<HEIGHT)
               y += JUMP;
               break;
            case KeyEvent.VK_LEFT:
               currentImage = left;
               if(maze.viable(x,y,3)&&x>0)
               x -= JUMP;
               break;
            case KeyEvent.VK_RIGHT:
               currentImage = right;
               if(maze.viable(x,y,1)&&x<WIDTH-20)
               x += JUMP;
               break;
            case KeyEvent.VK_S:
               changeMa();
               break;   
         }         repaint();
      }      public void keyTyped (KeyEvent event) {}
      public void keyReleased (KeyEvent event) {}
   }
}主面板
import java.awt.*;
import java.awt.event.*;
import javax.swing.*;public class mainPanel extends JPanel{
private final int MAIN_WIDTH=MazeCreator.widthM*DirectionPanel.JUMP,MAIN_HEIGHT=MazeCreator.heightN*DirectionPanel.JUMP;
private final int TOOLS_WIDTH=80;
private JButton changeMaze;
private JPanel tools,MainPanel;
private DirectionPanel MazePanel;    public mainPanel() {tools=new JPanel();
    tools.setBackground(Color.lightGray);
    tools.setOpaque(true);
    
        
    changeMaze=new JButton();
    changeMazeListener changeM=new changeMazeListener();
    changeMaze.addActionListener(changeM);    
    tools.add(changeMaze);
    MazePanel=new DirectionPanel();    add(tools);
    add(MazePanel);
    
  setPreferredSize (new Dimension(MAIN_WIDTH+TOOLS_WIDTH, MAIN_HEIGHT));
    }
    
   private class  changeMazeListener implements ActionListener
   {public void actionPerformed(ActionEvent event)
      {if(event.getSource()==changeMaze)
      MazePanel.changeMa();
      repaint();   
      }
   }
}窗口驱动类就加进了那个主面板...