canvasdemo.java

电子工业出版社出版的《java2应用开发指南》配套光盘源代码

//CanvasDemo.java
import java.awt.*;
import java.applet.*;

public class CanvasDemo extends Applet
{
	public void init()
	{
		//创建Canvas实例
		Canvas canvas=new MyCanvas();
		//在Applet容器中显示Canvas组件
		this.add(canvas);
	}
}
//这是我们扩展的Canvas类
class MyCanvas extends Canvas
{
	public void paint(Graphics g)
	{
		//得到画布的大小		
		Dimension size= this.getSize();
		//绘制画布的外围矩形区域
		g.drawRect(0,0,size.width-1,size.height-1);
		//绘制画布的三维效果
		g.setColor(Color.lightGray);
		g.draw3DRect(1,1,size.width-3,size.height-3,true);
		
		g.setColor(Color.blue);
		g.drawString("This is Canvas",120,20);
		
		g.setColor(Color.red);
		g.fillRect(10,30,60,60);
		
		g.setColor(Color.green);
		g.drawLine(120,150,20,90);
	}
	//重写该方法来设置Canvas组件的首选大小
	//这个方法必须覆盖，不然Canvas无法正确显示		
	public Dimension getPreferredSize()
	{
		return new Dimension(400,400);		
	}
}