Java处理敲击键盘事件 Etch-A-Sketch玩具实现 光标画笔画图程序 Java核心技术

Java处理敲击键盘事件 Etch-A-Sketch玩具实现 光标画笔画图程序 Java核心技术

 

source code:

 

package com.sunnyykn.chapter08;import java.awt.*;import java.awt.geom.*;import java.util.*;import java.awt.event.*;import javax.swing.*;class SketchPanel extends JPanel{private Point2D last;private ArrayList<Line2D> lines;private static final int SMALL_INCREMENT = 1;private static final int LARGE_INCREMENT = 5;public SketchPanel(){last = new Point2D.Double(100,100);lines = new ArrayList<Line2D>();KeyHandler listener = new KeyHandler();addKeyListener(listener);setFocusable(true);}/** * Add a new line segment to the sketch * @param dx the movement in x direction * @param dy the movement in y direction */public void add (int dx ,int dy){//compute new end pointPoint2D end = new Point2D.Double(last.getX() + dx, last.getY() + dy);//add line segmentLine2D line = new Line2D.Double(last, end);lines.add(line);repaint();//remember new end pointlast = end;}public void paintComponent(Graphics g){super.paintComponent(g);Graphics2D g2 = (Graphics2D) g;//draw all linesfor (Line2D l : lines)g2.draw(l);}private class KeyHandler implements KeyListener{public void keyPressed(KeyEvent event){int KeyCode = event.getKeyCode();//set distanceint d;if (event.isShiftDown())d = LARGE_INCREMENT;elsed = SMALL_INCREMENT;//add line segmentif (KeyCode == KeyEvent.VK_LEFT) add(-d,0);else if (KeyCode == KeyEvent.VK_RIGHT) add(d,0);else if (KeyCode == KeyEvent.VK_UP) add(0,-d);else if (KeyCode == KeyEvent.VK_DOWN) add(0,d);}public void keyReleased(KeyEvent event){}public void keyTyped(KeyEvent event){char keyChar = event.getKeyChar();//set distanceint d;if (Character.isUpperCase(keyChar)){d = LARGE_INCREMENT;keyChar = Character.toLowerCase(keyChar);}elsed = SMALL_INCREMENT;//add line segmentif (keyChar == 'h') add(-d,0);else if (keyChar == 'l') add(d,0);else if (keyChar == 'k') add(0,-d);else if (keyChar == 'j') add(0,d);}}}/** * A frame with a panel for sketching a figure * @author sunnyykn * */class SketchFrame extends JFrame{public static final int DEFAULT_WIDTH = 300;public static final int DEFAULT_HEIGHT = 200;public SketchFrame(){setTitle("Sketch Sunnyykn");setSize(DEFAULT_WIDTH,DEFAULT_HEIGHT);//add panel to frame SketchPanel panel = new SketchPanel();add(panel);}}public class Sketch {public static void main(String args[]){SketchFrame frame = new SketchFrame();frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);frame.setVisible(true);}}