自定义的进度条

jdk自带的JProgressBar效果不太符合需求，如下是一个跑马灯式渐进效果的progressbar，效果就是一段渐进色的矩形来回滚动。
实现原理很简单，就是用一个线程循环绘制一个矩形区域，并用渐进色填充。详细代码如下。

public class ProcessBar extends JComponent implements ActionListener {

	private static final long serialVersionUID = 1L;

	private String showText;



	private final int TIMER_DELAY = 41;

	private final Dimension PREFERRED_SIZE = new Dimension(240, 16);

	private int tailLength;

	private int increment;

	private boolean movingRight;

	private int currentPosition;

	private Timer timer;

	private boolean constructed;

	public ProcessBar() {
		tailLength = 120;
		increment = 13;
		movingRight = true;
		currentPosition = 0;
		constructed = false;
		timer = new Timer(TIMER_DELAY, this);
		timer.setRepeats(true);
		setAttributes();
		Insets insets = getBorder().getBorderInsets(this);
		Dimension d = PREFERRED_SIZE;
		d.width += insets.left + insets.right;
		d.height += insets.top + insets.bottom;
		setPreferredSize(d);
		setMinimumSize(d);
		constructed = true;
	}

	public void setShowText(String text) {
		this.showText = text;		
	}

	public void removeNotify() {
		super.removeNotify();
		if (timer != null) {
			timer.stop();
			timer.removeActionListener(this);
			timer = null;
		}
	}

	public void addNotify() {
		super.addNotify();
		if (timer == null) {
			timer = new Timer(41, this);
			timer.setRepeats(true);
		}
	}

	public void actionPerformed(ActionEvent e) {
		repaint();
	}

	public void updateUI() {
		super.updateUI();
		if (constructed)
			setAttributes();
	}

	public void setIncrement(int increment) {
		if (increment > 0 && increment < 500)
			this.increment = increment;
	}

	public int getIncrement() {
		return increment;
	}

	public void setTailLength(int tailLength) {
		if (tailLength > 0 && tailLength < 500)
			this.tailLength = tailLength;
	}

	public int getTailLength() {
		return tailLength;
	}

	protected void setAttributes() {
		setOpaque(true);
		if (getBackground() == null
				|| (getBackground() instanceof ColorUIResource))
			setBackground(new ColorUIResource(UIManager.getColor("control")));
		if (getForeground() == null
				|| (getForeground() instanceof ColorUIResource))
			setForeground(new ColorUIResource(UIManager
					.getColor("ProgressBar.foreground")));
		if (getBorder() == null || (getBorder() instanceof BorderUIResource))
			setBorder(createDefaultBorder());
	}

	protected Border createDefaultBorder() {
		return new BorderUIResource(BorderFactory.createCompoundBorder(
				BorderFactory.createEtchedBorder(0, UIManager
						.getColor("controlLtHighlight"), UIManager
						.getColor("controlShadow")),
				BorderFactory.createCompoundBorder(new GradientBorder(),
						BorderFactory.createLineBorder(GradientBorder.getBrighterColor(
								UIManager.getColor("controlShadow"), 0.4F)))));
	}

	public void paintComponent(Graphics g) {
		Graphics2D g2 = (Graphics2D) g;
		Color background = getBackground();
		Color foreground = getForeground();
		Insets insets = getInsets();
		Rectangle rect = getBounds();
		int height = rect.height - (insets.top + insets.bottom);
		int width = rect.width - (insets.left + insets.right);
		currentPosition += increment;
		if (currentPosition > (rect.width - (insets.left + insets.right))
				+ tailLength + increment * 2) {
			currentPosition = 0;
			movingRight = !movingRight;
		}
		g2.setColor(background);
		g2.fillRect(g.getClipBounds().x, g.getClipBounds().y,
				g.getClipBounds().width, g.getClipBounds().height);		
		int x = 0;
		background = new Color(foreground.getRed(), foreground.getGreen(),
				foreground.getBlue(), 0);
		if (movingRight) {
			x = (insets.left + currentPosition) - tailLength;
			Color temp = foreground;
			foreground = background;
			background = temp;
		} else {
			x = (insets.left + rect.width) - currentPosition;
		}
		GradientPaint gp = new GradientPaint(x, (float) insets.top
				+ (float) (height / 2), foreground, x + tailLength, insets.top
				+ height / 2, background, false);
		g2.setPaint(gp);
		Rectangle r = new Rectangle(x, insets.top, tailLength, height);
		r = r
				.intersection(new Rectangle(insets.left, insets.top, width,
						height));
		r = r.intersection(g.getClipBounds());
		g2.fillRect(r.x, r.y, r.width, r.height);

		g2.setPaint(Color.black);
		if(showText != null){
			g2.drawString(showText, 170, 16);
		}		
		if (timer != null && !timer.isRunning())
			timer.start();
	}


}