applet1.java

矩阵乘法的计算程序

import java.awt.*;
import java.applet.*;
import java.awt.event.*;

/**
 * This class reads PARAM tags from its HTML host page and sets
 * the color and label properties of the applet. Program execution
 * begins with the init() method. 
 */
public class Applet1 extends Applet
{
	ArcControls controls;
	public void init()
	{
		setLayout(new BorderLayout());
		ArcCanvas c=new ArcCanvas();
		add("Center",c);
		add("South",controls=new ArcControls(c));
		
	}
}	
	
	class ArcCanvas extends Canvas{
		int startAngle=0;
		int endAngle=45;
		boolean filled=false;
		Font font;
		public void paint(Graphics g){
			Rectangle r=getBounds();//获取画布的边界
			int hlines=r.height / 10;
			int vlines=r.width/10;
			
			g.setColor(Color.pink );
			for (int i=1;i<=hlines;i++){
				g.drawLine(0,i*10,r.width,i*10);
			}
			for(int i=1;i<=vlines;i++){
				g.drawLine(i*10,0,i*10,r.height );
			}
			
			g.setColor(Color.red);
			if(filled){
				g.fillArc(0,0,r.width-1,r.height-1,startAngle,endAngle);
			}else{
				g.drawArc(0,0,r.width-1,r.height-1,startAngle,endAngle);
			}
			
			g.setColor(Color.black);
			g.setFont(font);
			g.drawLine(0,r.height/2,r.width,r.height/2);
			g.drawLine(r.width/2,0,r.width/2,r.height);
			g.drawLine(0,0,r.width,r.height );
			g.drawLine(r.width,0,0,r.height);
			int sx=10;
			int sy=r.height-28;
			g.drawString("s="+startAngle,sx,sy);
			g.drawString("e="+endAngle,sx,sy+14);
		}
		
		public void redraw(boolean filled,int start,int end){
			this.filled=filled;
			this.startAngle =start;
			this.endAngle =end;
			repaint();
		}
	}
	
	class ArcControls extends Panel implements ActionListener{
		TextField s;
		TextField e;
		ArcCanvas canvas;
		
		public ArcControls(ArcCanvas canvas){
		 Button b=null;
		 this.canvas=canvas;
		 add(s=new TextField("0",4));
		 add(e=new TextField("45",4));
		 b=new Button("Fill");
		 b.addActionListener(this);
		 add(b);
		 b=new Button("Draw");
		 b.addActionListener(this);
		 add(b);
		}
		
		public void actionPerformed(ActionEvent ev){
			String label=ev.getActionCommand();
			
			canvas.redraw(label.equals("Fill"),
						  Integer.parseInt(s.getText().trim()),
						  Integer.parseInt(e.getText().trim()));
		}
	}