drawing1.java

这是个画直线

import java.awt.*;
import java.applet.*;
import java.awt.event.*;
import java.applet.Applet;
import java.lang.*;
public class drawing1 extends Applet implements ActionListener
{
	Point startpt,endpt;
	Button btn1,btn2,btn3,btn4;
	int a=0;
	Font fn;
	public void init()
	{
		setBackground(Color.lightGray);
		btn1=new Button("画直线");
		btn2=new Button("画矩形");
		btn3=new Button("画圆");
		btn4=new Button("画椭圆");
		fn=new Font("TimesRoman",Font.BOLD,12);
		btn1.setFont(fn);
		btn2.setFont(fn);
		btn3.setFont(fn);
		btn4.setFont(fn);
		
		add(btn1);add(btn2);add(btn3);add(btn4);
		btn1.addActionListener(this);
		btn2.addActionListener(this);
		btn3.addActionListener(this);
		btn4.addActionListener(this);
		
	}
	
	public boolean mouseDown (Event evt,int x,int y)
	{
		startpt=new Point(x,y);
		return true;
	}
	public boolean mouseDrag(Event evt,int x,int y)
	{
		endpt=new Point(x,y);
		repaint();
		return true;
	}
	public boolean mouseUp(Event evt,int x,int y)
	{
		endpt =new Point(x,y);
		repaint();
		return true;
	}
	public void paint(Graphics g)
	{
		int rectWidth,rectHeight,startX,startY;
		startX=Math.min(startpt.x,endpt.x);
	        	startY=Math.min(startpt.y,endpt.y);
	        	rectWidth=Math.abs(endpt.x-startpt.x);
	        	rectHeight=Math.abs(endpt.y-startpt.y);
		if(endpt!=null)
		if(a!=0)
		{
			if(a==1)
	        g.drawLine(startpt.x,startpt.y,endpt.x,endpt.y);
	        else if(a==2)
	         g.drawRect(startX,startY,rectWidth,rectHeight);
	         else if(a==3)
	        { rectWidth=rectHeight;g.drawOval(startX,startY,rectWidth,rectHeight);}
	           
	         else {g.drawOval(startX,startY,rectWidth,rectHeight);}
	        
	        
		}
	}

	public void actionPerformed(ActionEvent e)
	{
		
		if(e.getSource()==btn1)
		a=1;
		else if(e.getSource()==btn2)
		a=2;
		else if(e.getSource()==btn3)
		a=3;
		else 
		a=4;
	}
}