/**

 * @author hpu-gs

 * 2015/11/25

 */

public class Circle {

    public static Double r;

    public static Double m;

    /**

     * 计算圆的面积

     */

    public static void main(String[] args) {

        System.out.print("请输入圆的半径：");

        Scanner in = new Scanner(System.in);

        r = in.nextDouble();

        m = Math.PI*r*r;

        System.out.println("圆的面积是："+m);

        EventQueue.invokeLater(new Runnable() {//事物分配线程，进行显示窗口

            @Override

            public void run() {

                JFrame frame = new SimpleFrame();

                frame.setTitle("求圆面积");//设置窗口的左上角标题

                frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);//设置关闭窗口事件

                Toolkit kit = Toolkit.getDefaultToolkit();

                Dimension screenSize = kit.getScreenSize();

                int screenWidth = screenSize.width;//获取屏幕的宽度

                int screenhHeight = screenSize.height;//获取屏幕的长度

                frame.setLocation(screenWidth/2-250, screenhHeight/2-100);//设置窗口在屏幕上的显示位置

                Image image = new ImageIcon("Image/image.png").getImage();//设置窗口的左上角图标

                frame.setIconImage(image);

                frame.setVisible(true);//启动显示窗口

            }

        });

    }

}

//设计窗口

class SimpleFrame extends JFrame{

    private static final int DEFAULT_WIDTH = 300;

    private static final int DEFAULT_HEIGHE = 200;

    public SimpleFrame(){

        add(new NotHelloWordComponent());//将文本填充到窗口

        pack();//调整窗口大小

//        setSize(DEFAULT_WIDTH, DEFAULT_HEIGHE);//设置窗口的大小

    }

}

//在窗口中显示文本信息

class NotHelloWordComponent extends JComponent{

    public static final int MESSAGE_X = 120;

    public static final int MESSAG_Y = 100;

    private static final int DEFAULT_WIDTH = 500;

    private static final int DEFAULT_HEIGHE = 200;

    public void paintComponent(Graphics g){

        g.drawString("半径为："+new Circle().r+"的圆，面积为："+new Circle().m, MESSAGE_X, MESSAG_Y);//在窗口中显示文字

    }

    @Override

    public Dimension getPreferredSize() {

        return new Dimension(DEFAULT_WIDTH, DEFAULT_HEIGHE);//返回组件的首选大小

    }

}