利用键盘画线

昨天在论坛上看到有网友问关于如何用键盘中的方向键画直线的问题，感觉挺有意思就

写了一个比较简单的实现该功能的例子，具体代码如下：

package demo;
import java.awt.Color;
import java.awt.Graphics;
import java.awt.event.KeyEvent;
import java.awt.event.KeyListener;
import java.util.ArrayList;
import javax.swing.JFrame;
import javax.swing.JPanel;

public class DemoForDrawLineByKey extends JFrame {

 /**
  * <p>功能描述:[字段功能描述]</p>
  */
 private static final long serialVersionUID = -8155745524182056025L;
 private ArrayList<MyPoint> pointArrayList;
 private int intNowX = 10;
 private int intNowY = 10;
 private MyPanelForDrawLine panel;
 private int oldCode = 0;
 private int movePx = 3;
 private JPanel mainpanel;
 /**
  * Launch the application
  *
  * @param args
  */
 public static void main(String args[]) {
  DemoForDrawLineByKey frame = new DemoForDrawLineByKey();
  frame.setBounds(100, 100, 500, 375);
  frame.setVisible(true);
  frame.init();
 }
 public void init() {
  panel.requestFocusInWindow();
 }
 /**
  * Create the frame
  */
 public DemoForDrawLineByKey() {
  super();
  setTitle("利用键盘画线");
  pointArrayList = new ArrayList<MyPoint>();
  getContentPane().setLayout(null);
  setBounds(100, 100, 500, 375);
  setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

  mainpanel = new JPanel();
  mainpanel.setBounds(0, 0, 492, 341);
  getContentPane().add(mainpanel);
  mainpanel.setLayout(null);
  panel = new MyPanelForDrawLine();
  panel.setBounds(0, 0, 492, 341);
  panel.requestFocusInWindow();
  mainpanel.add(panel);

 }
 class MyPanelForDrawLine extends JPanel {
  private static final long serialVersionUID = 3470945714820691208L;
  KeyListenerForPanel mKeyListenerForPanel = new KeyListenerForPanel();
  public MyPanelForDrawLine() {
   super();
   addKeyListener(mKeyListenerForPanel);
  }
  public void paintComponent(Graphics g) {
   super.paintComponents(g);
   g.setColor(Color.WHITE);
   g.fillRect(0, 0, getWidth(), getHeight());
   g.setColor(Color.BLACK);
   drawOldLine(g);
   g.fillRect(intNowX, intNowY, 3, 3);
  }
  public void drawOldLine(Graphics g) {
   if (pointArrayList.size() > 0) {
    Object tmpObj[] = pointArrayList.toArray();
    MyPoint lasePoint = null;
    if (tmpObj.length >= 1) {
     lasePoint = (MyPoint) tmpObj[tmpObj.length - 1];
    }
    for (int i = 0; i < tmpObj.length - 1; i++) {
     MyPoint tmpPoint1 = (MyPoint) tmpObj[i];
     MyPoint tmpPoint2 = (MyPoint) tmpObj[i + 1];
     g.drawLine(tmpPoint1.getPx(), tmpPoint1.getPy(), tmpPoint2
       .getPx(), tmpPoint2.getPy());
    }
    g.drawLine(lasePoint.getPx(), lasePoint.getPy(), intNowX,
      intNowY);
   }
  }
 }
 class MyPoint {
  int px = 0;
  int py = 0;
  public MyPoint(int x, int y) {
   px = x;
   py = y;
  }
  public int getPx() {
   return px;
  }
  public void setPx(int px) {
   this.px = px;
  }
  public int getPy() {
   return py;
  }
  public void setPy(int py) {
   this.py = py;
  }
 }
 class KeyListenerForPanel implements KeyListener {
  public void keyPressed(KeyEvent e) {
   int keycodeOfKey = e.getKeyCode();
   if (keycodeOfKey != oldCode) {
    oldCode = keycodeOfKey;
    MyPoint tmpPoint = new MyPoint(intNowX, intNowY);
    pointArrayList.add(tmpPoint);
   } else {
    switch (keycodeOfKey) {

     // 向上
     case KeyEvent.VK_UP :
      intNowY = intNowY - movePx;

      break;
     // 向下
     case KeyEvent.VK_DOWN :
      intNowY = intNowY + movePx;
      break;
     // 向左
     case KeyEvent.VK_LEFT :
      intNowX = intNowX - movePx;
      break;
     // 向右
     case KeyEvent.VK_RIGHT :
      intNowX = intNowX + movePx;
      break;
    }
   }
   panel.repaint();
  }

  public void keyReleased(KeyEvent e) {
   int keycodeOfKey = e.getKeyCode();
   if (keycodeOfKey != oldCode) {
    oldCode = keycodeOfKey;
    MyPoint tmpPoint = new MyPoint(intNowX, intNowY);
    pointArrayList.add(tmpPoint);
   } else {
    switch (keycodeOfKey) {
     // 向上
     case KeyEvent.VK_UP :
      intNowY = intNowY - movePx;
      break;
     // 向下
     case KeyEvent.VK_DOWN :
      intNowY = intNowY + movePx;
      break;
     // 向左
     case KeyEvent.VK_LEFT :
      intNowX = intNowX - movePx;
      break;
     // 向右
     case KeyEvent.VK_RIGHT :
      intNowX = intNowX + movePx;
      break;
    }
   }
   panel.repaint();
  }
  public void keyTyped(KeyEvent e) {
  }
 }

}