ticker.java

java编程开发技巧与实例的编译测试通过的所有例程

import java.awt.*;

public class Ticker extends Canvas implements Runnable
{
	private int xPos, yPos;
	private int height, width;
	
	private Thread runner		=	null;
	private String text			=	null;
	private FontMetrics metrics	=	null;
	private Font font	=	new Font("Monospaced", Font.BOLD, 12);
	
	public Ticker(String _text)
	{
		metrics	=	getFontMetrics(font);
		text	=	_text;
		width	=	metrics.stringWidth(text);
		height	=	metrics.getHeight();
		xPos	=	getSize().width;
		yPos	=	height;
		
		start();
	}
	public void start()
	{
		if (runner == null)
		{
			runner	=	new Thread(this);
			runner.start();
		}
	}
	public void stop()
	{
		runner = null;
	}
	public void run()
	{
		Thread currentThread = Thread.currentThread();
		while (runner == currentThread)
		{
			computeCoordinates();
			repaint();
			try
			{
				runner.sleep(50);
			}
			catch (InterruptedException ie)
			{
				System.err.println("Errr: " + ie);
			}
		}
	}
	public void paint (Graphics g)
	{
		g.setFont(font);
		g.drawString(text, xPos, yPos);
	}
	private void computeCoordinates()
	{
		if (xPos < - width)
			xPos	=	getSize().width;
		else
			xPos	-=	2;
	}
	public Dimension getPreferredSize()
	{
		return new Dimension(width, height + 3);
	}
}