app18_11.java

这是大学里的 java课后题的答案

import java.awt.*;
import java.awt.event.*;
public class app18_11 extends  Frame implements ItemListener,MouseListener,MouseMotionListener
{
	static app18_11 frm=new app18_11();
	static Choice cho=new Choice();
	  int x1,x2,y1,y2;
	String str;
 public static void main (String[] args) {
	frm.setSize(200,150);
	frm.setLayout(new FlowLayout(FlowLayout.LEFT));
	frm.add(cho);
	cho.add("Red");
	cho.add("Green");
	cho.add("Blue");
	cho.add("Black");
	cho.add("Pink");
	frm.setTitle("Free drawing");
	frm.setVisible(true);
	cho.addItemListener(frm);
	frm.addMouseListener(frm);
	frm.addMouseMotionListener(frm);
 }
 
 	public void mousePressed(MouseEvent e)
 	{
 		x1=e.getX();
 		y1=e.getY();
 	}
 	public void mouseDragged(MouseEvent e)
 	{
 		
 		Graphics g=getGraphics();
 		g.setColor(Color.red);
 		x2=e.getX();
 		y2=e.getY();
 		if(str=="Red")
 			    g.setColor(Color.red);
 		else if(str=="Green")
 				g.setColor(Color.green);
 		else if(str=="Blue")
 				g.setColor(Color.blue);
 		else if(str=="Black")
 				g.setColor(Color.black);
 		else if(str=="Pink")
 				g.setColor(Color.pink);
 		g.drawLine(x1,y1,x2,y2);
 		x1=x2;
 		y1=y2;
 		 	}
  		
 	public void itemStateChanged(ItemEvent e)
 	{
 		str=cho.getSelectedItem();
 		Graphics g=getGraphics();
	 	   	update(g);
 		
 	}
	 	   
	 	   public void mouseMoved(MouseEvent e){
	 	   }
	 	   public void mouseReleased(MouseEvent e){
	 	   	
	 	   }
	 	   public void mouseEntered(MouseEvent e){
	 	   }
	 	   public void mouseExited(MouseEvent e){
	 	   }
	 	   public void mouseClicked(MouseEvent e){
	 	   }
					  
}