scrolltext.java

Java Thread Programming (Source

import java.awt.*;
import java.awt.image.*;
import java.awt.font.*;
import java.awt.geom.*;
import javax.swing.*;

public class ScrollText extends JComponent {
	private BufferedImage image;
	private Dimension imageSize;
	private volatile int currOffset;

	private Thread internalThread;
	private volatile boolean noStopRequested;

	public ScrollText(String text) {
		currOffset = 0;
		buildImage(text);

		setMinimumSize(imageSize);
		setPreferredSize(imageSize);
		setMaximumSize(imageSize);
		setSize(imageSize);

		noStopRequested = true;
		Runnable r = new Runnable() {
				public void run() {
					try {
						runWork();
					} catch ( Exception x ) {
						x.printStackTrace(); 
					}
				}
			};

		internalThread = new Thread(r, "ScrollText");
		internalThread.start();
	}

	private void buildImage(String text) {
		// Request that the drawing be done with anti-aliasing
		// turned on and the quality high.
		RenderingHints renderHints = new RenderingHints(
			RenderingHints.KEY_ANTIALIASING,
			RenderingHints.VALUE_ANTIALIAS_ON);

		renderHints.put(
			RenderingHints.KEY_RENDERING,
			RenderingHints.VALUE_RENDER_QUALITY);

		// Create a scratch image for use in determining
		// the text dimensions.
		BufferedImage scratchImage = new BufferedImage(
				1, 1, BufferedImage.TYPE_INT_RGB);

		Graphics2D scratchG2 = scratchImage.createGraphics();
		scratchG2.setRenderingHints(renderHints);

		Font font = 
			new Font("Serif", Font.BOLD | Font.ITALIC, 24);

		FontRenderContext frc = scratchG2.getFontRenderContext();
		TextLayout tl = new TextLayout(text, font, frc);
		Rectangle2D textBounds = tl.getBounds();
		int textWidth = (int) Math.ceil(textBounds.getWidth());
		int textHeight = (int) Math.ceil(textBounds.getHeight());

		int horizontalPad = 10;
		int verticalPad = 6;

		imageSize = new Dimension(
				textWidth + horizontalPad,
				textHeight + verticalPad
			);

		// Create the properly-sized image
		image = new BufferedImage(
				imageSize.width,
				imageSize.height,
				BufferedImage.TYPE_INT_RGB);

		Graphics2D g2 = image.createGraphics();
		g2.setRenderingHints(renderHints);

		int baselineOffset = 
			( verticalPad / 2 ) - ( (int) textBounds.getY());

		g2.setColor(Color.white);
		g2.fillRect(0, 0, imageSize.width, imageSize.height);

		g2.setColor(Color.blue);
		tl.draw(g2, 0, baselineOffset);

		// Free-up resources right away, but keep "image" for
		// animation.
		scratchG2.dispose();
		scratchImage.flush();
		g2.dispose();
	}

	public void paint(Graphics g) {
		// Make sure to clip the edges, regardless of curr size
		g.setClip(0, 0, imageSize.width, imageSize.height);

		int localOffset = currOffset; // in case it changes
		g.drawImage(image, -localOffset, 0, this);
		g.drawImage(
			image, imageSize.width - localOffset, 0, this);

		// draw outline
		g.setColor(Color.black);
		g.drawRect(
			0, 0, imageSize.width - 1, imageSize.height - 1);
	}

	private void runWork() {
		while ( noStopRequested ) {
			try {
				Thread.sleep(100);  // 10 frames per second
				
				// adjust the scroll position
				currOffset = 
					( currOffset + 1 ) % imageSize.width;

				// signal the event thread to call paint()
				repaint();
			} catch ( InterruptedException x ) {
				Thread.currentThread().interrupt(); 
			}
		}
	}

	public void stopRequest() {
		noStopRequested = false;
		internalThread.interrupt();
	}

	public boolean isAlive() {
		return internalThread.isAlive();
	}

	public static void main(String[] args) {
		ScrollText st = 
			new ScrollText("Java can do animation!");

		JPanel p = new JPanel(new FlowLayout());
		p.add(st);

		JFrame f = new JFrame("ScrollText Demo");
		f.setContentPane(p);
		f.setSize(400, 100);
		f.setVisible(true);
	}
}