import java.awt.*;
import java.awt.event.*;
import java.awt.font.*;
import java.util.*;
import java.text.*;
import javax.swing.*;
import javax.swing.plaf.*;

public class DigitalClock extends JPanel
{
	public DigitalClock()
	{
		//指定一個UI對象
		this.setUI(DigitalClockPanelUI.createUI(this));
		//設定panel為不透明
		this.setOpaque(true);
	}
	
	
 public static void main(String []args)
	{
		JFrame frame=new JFrame();
		frame.setLocation(200,200);
		frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
		DigitalClock panel=new DigitalClock();
		frame.getContentPane().add(panel);
		frame.pack();
		frame.setVisible(true);
	}
}
//繼承PanelUI類，該類在所有平臺都能用
class DigitalClockPanelUI extends PanelUI implements ActionListener
{
	protected final static Font clockFont=new Font("Arial",Font.BOLD,24);
	//時間顯示格式
	
	protected final static SimpleDateFormat dateFormat=new SimpleDateFormat("hh::mm::ss a");
    protected final static FontRenderContext frc=new FontRenderContext(null,true,true);
    //字體之間空格
    protected final static int FUDGE=6;
    //含當前時間的AttribuedString
    protected   AttributedString  timeString=null;
    protected   TextLayout textLayout=null;
    //每秒一次的timer控件
    protected  javax.swing.Timer timer=new javax.swing.Timer(1000,this);
    protected   DigitalClock  panel;
    private  DigitalClockPanelUI(DigitalClock panel)
    {
    	this.panel=panel;
    	panel.setBackground(Color.BLACK);
    	actionPerformed(null);
    	timer.start();
    }
    public static ComponentUI creatUI(JComponent  component)
    {
    	return new  DigitalClockPanelUI((DigitalClock)component);
    }
    public void paint(Graphics g,JComponent c)
     {
     	//沒有時間或沒有textLayout時，不進行重繪
     	if(this.timeString==null||this.textLayout==null)
     	return;
     	Graphics2D g2=(	Graphics2D)g;
     	g2.setRenderingHint(RenderingHints.KEY_ANTIALIASING,RenderingHints.VALUE_ANTIALIAS_ON);
     	//在textLayout指示位置上顯示字符串
     	g2.drawString(timeString.getIterator(),1,(int)(textLayout.getAscent()));
     	g2.setRenderingHint(RenderingHints.KEY_ANTIALIASING,RenderingHints.VALUE_ANTIALIAS_DEFAULT);
     	
     }
     //當間隔時間到時，timer會自動調用此方法
     public void actionPerformed(ActionEvent event)
     {
     	timeString=new AttributedString (dateFormat.format(new Date()));
        timeString.addAttribute(TextAttribute.FONT,clockFont);
        timeString.addAttribute(TextAttribute.FOREGROUND,Color.red);
        timeString.addAttribute(TextAttribute.FOREGROUND,Color.yellow,2,3);
        timeString.addAttribute(TextAttribute.FOREGROUND,Color.yellow,5,6);
        textLayout=new  TextLayout(timeString.getIterator(),frc);
        panel.repaint();
     }
     public Dimension getPreferredSize(JComponent c)
     {
     	Dimension size=textLayout.getBounds().getBounds().getSize();
     	size.height+=FUDGE;
     	size.width+=(FUDGE+2);
     	return size;
     }
}