sketch.java

一个J2SE的简单入门

package 第八章;
import java.awt.*;
import java.awt.geom.*;
import java.util.*;
import java.awt.event.*;
import javax.swing.*;

public class Sketch {
	public  static  void main(String[] args)
	{
		SketchFrame frame= new SketchFrame();
		frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
		frame.show();
		
	}
}
class SketchFrame extends JFrame{
	public SketchFrame(){
		setTitle("键盘事件");
		setSize(DEFAULT_WIDTH, DEFAULT_HEIGHT );
		SketchPanel panel= new SketchPanel();
		Container contentPane= getContentPane();
		contentPane.add(panel);
	}
	public static final int DEFAULT_WIDTH = 300;
	public static final int DEFAULT_HEIGHT= 200;
}
class SketchPanel extends JPanel
{
	public SketchPanel()
	{
		last= new Point2D.Double(100,100);
		lines= new ArrayList();
		KeyHandler listener= new KeyHandler();
		addKeyListener(listener);
		setFocusable(true);
	}
	public void add( int dx,int dy)
	{
		Point2D end= new Point2D.Double(last.getX()+dx,last.getY()+ dy);
		Line2D line= new Line2D.Double(last,end);
		lines.add(line);
		repaint();
		last=end;
	}
	public void paintComponent(Graphics g)
	{
		super.paintComponent(g);
		Graphics2D g2= (Graphics2D)g;
		//draw all lines
		for(int i=0;i<lines.size();i++)
		{
			g2.draw((Line2D)lines.get(i));
			
		}
	}
	private Point2D last;
	private ArrayList  lines;
	private static final int INCREMENT= 10;
	private class KeyHandler implements KeyListener
	{
		public void keyPressed(KeyEvent event)
		{
			int keyCode= event.getKeyCode();
			//set distance
			int d;
	
			d=INCREMENT;
					
			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();
			int d;
			if(Character.isUpperCase(keyChar))
			{
				d=INCREMENT;
				keyChar= Character.toLowerCase(keyChar);
			}
			else 
				d=INCREMENT;
			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);
		}
	}
	
}