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 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(); 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 point Point2D end = new Point2D.Double(last.getX() + dx, last.getY() + dy); //add line segment Line2D line = new Line2D.Double(last, end); lines.add(line); repaint(); //remember new end point last = end; } public void paintComponent(Graphics g) { super.paintComponent(g); Graphics2D g2 = (Graphics2D) g; //draw all lines for (Line2D l : lines) g2.draw(l); } private class KeyHandler implements KeyListener { public void keyPressed(KeyEvent event) { int KeyCode = event.getKeyCode(); //set distance int d; if (event.isShiftDown()) d = LARGE_INCREMENT; else d = SMALL_INCREMENT; //add line segment if (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 distance int d; if (Character.isUpperCase(keyChar)) { d = LARGE_INCREMENT; keyChar = Character.toLowerCase(keyChar); } else d = SMALL_INCREMENT; //add line segment if (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); } }