compmover.java

Java Thread Programming (Source

import java.awt.*;
import javax.swing.*;

public class CompMover extends Object {
	private Component comp;
	private int initX;
	private int initY;
	private int offsetX;
	private int offsetY;
	private boolean firstTime;
	private Runnable updatePositionRun;

	private Thread internalThread;
	private volatile boolean noStopRequested;

	public CompMover(Component comp, 
				int initX, int initY,
				int offsetX, int offsetY
			) {

		this.comp = comp;
		this.initX = initX;
		this.initY = initY;
		this.offsetX = offsetX;
		this.offsetY = offsetY;

		firstTime = true;

		updatePositionRun = new Runnable() {
				public void run() {
					updatePosition();
				}
			};

		noStopRequested = true;
		Runnable r = new Runnable() {
				public void run() {
					try {
						runWork();
					} catch ( Exception x ) {
						// in case ANY exception slips through
						x.printStackTrace(); 
					}
				}
			};

		internalThread = new Thread(r);
		internalThread.start();
	}

	private void runWork() {
		while ( noStopRequested ) {
			try {
				Thread.sleep(200);
				SwingUtilities.invokeAndWait(updatePositionRun);
			} catch ( InterruptedException ix ) {
				// ignore
			} catch ( Exception x ) {
				x.printStackTrace();
			}
		}
	}

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

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

	private void updatePosition() {
		// should only be called by the *event* thread

		if ( !comp.isVisible() ) {
			return;
		}

		Component parent = comp.getParent();
		if ( parent == null ) {
			return;
		}

		Dimension parentSize = parent.getSize();
		if ( ( parentSize == null ) &&
			 ( parentSize.width < 1 ) && 
			 ( parentSize.height < 1 ) 
		   ) {

			return;
		}

		int newX = 0;
		int newY = 0;

		if ( firstTime ) {
			firstTime = false;
			newX = initX;
			newY = initY;
		} else {
			Point loc = comp.getLocation();
			newX = loc.x + offsetX;
			newY = loc.y + offsetY;
		}

		newX = newX % parentSize.width;
		newY = newY % parentSize.height;

		if ( newX < 0 ) {
			// wrap around other side
			newX += parentSize.width;
		}

		if ( newY < 0 ) {
			// wrap around other side
			newY += parentSize.height;
		}

		comp.setLocation(newX, newY);
		parent.repaint();
	}

	public static void main(String[] args) {
		Component[] comp = new Component[6];

		comp[0] = new ScrollText("Scrolling Text");
		comp[1] = new ScrollText("Java Threads");
		comp[2] = new SlideShow();
		comp[3] = new SlideShow();
		comp[4] = new DigitalTimer();
		comp[5] = new DigitalTimer();

		JPanel p = new JPanel();
		p.setLayout(null); // no layout manager

		for ( int i = 0; i < comp.length; i++ ) {
			p.add(comp[i]);

			int x = (int) ( 300 * Math.random() );
			int y = (int) ( 200 * Math.random() );
			int xOff = 2 - (int) ( 5 * Math.random() );
			int yOff = 2 - (int) ( 5 * Math.random() );

			new CompMover(comp[i], x, y, xOff, yOff);
		}

		JFrame f = new JFrame("CompMover Demo");
		f.setContentPane(p);
		f.setSize(400, 300);
		f.setVisible(true);
	}
}