moonjframe.java

利用两个重叠的圆画出月亮的效果。且月亮的大小能够随窗口改变

//【实验6.4】  画月亮。

import java.awt.Color;
import java.awt.FlowLayout;
import java.awt.Graphics;

import java.awt.event.ComponentListener;
import java.awt.event.ComponentEvent;

import javax.swing.JFrame;

/*
import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
*/

public class MoonJFrame extends JFrame implements ComponentListener
{
    public MoonJFrame()
    {
        super("Moon");
        this.setSize(400,300);
        this.setVisible(true);
        this.setDefaultCloseOperation(EXIT_ON_CLOSE);
    }
    
    public void paint(Graphics g)                //在JFrame上作图
    {
        int x=0,y=0;                             //圆外切矩形左上角坐标
        x = this.getWidth() /4;
        y = this.getHeight() /4; 

        int diameter = Math.min(this.getWidth()/2, this.getHeight()/2);   //圆的直径

        g.setColor(Color.yellow);
        g.fillOval(x,y,diameter,diameter);       //画圆

        g.setColor(this.getBackground());        //设置为窗口背景色
        g.fillOval(x-20,y-20,diameter,diameter); //画圆
    }
    
    public void componentResized(ComponentEvent e)   //改变窗口大小时
    {
        repaint();                               //重画
    }
    
    public void componentMoved(ComponentEvent e)    {  }
    public void componentHidden(ComponentEvent e)   {  }
    public void componentShown(ComponentEvent e)    {  }
    
    public static void main(String arg[])
    {
        new MoonJFrame();
        
    }
}