[dewyatt]

I'm rather new to Java and I'm having some trouble with threading.
I have read the essential concurrency java docs multiple times and lots of other java threading documentation but I'm still lost.
I'm writing a JavaME MIDP 2 program which has animated GIF images.
Each image has it's own animation thread.
Basically the problem is sometimes the program just freezes up.
I'm quite certain it's a threading issue.

Code:

public class GifAnimation
{

	GifAnimation()
	{
		myAnimator = null;
		myThread = null;
		myActive = false;
		myPaused = false;
	}

	void Start(String imageFile, Canvas theCanvas)
	{
		Stop();
		myAnimator = new GifAnimator();
		myAnimator.setup(imageFile, this, theCanvas);
		myActive = true;
		myThread = new Thread(myAnimator);
		myThread.start();
	}
	
	void Stop()
	{
		myAnimator = null;
		myActive = false;
		myPaused = false;
		if (null != myThread && myThread.isAlive())
		{
			try
			{
				myThread.interrupt();
				myThread.join();
			}
			catch (InterruptedException e)
			{
			}
		}
		myThread = null;
	}

	public void Pause()
	{
		if (myPaused)
			return;

		myPaused = true;
		myThread.interrupt();
	}
	
	public void Resume()
	{
		if (!myPaused)
			return;

		myPaused = false;
		myThread.notify();
	}
	
	public synchronized Image getImage()
	{
		return myImage;
	}
	
	public synchronized void setImage(Image i)
	{
		myImage = i;
	}
	
	private GifAnimator myAnimator;
	private Thread myThread;
	boolean isActive;
	boolean isPaused;
	private Image myImage;
}

Code:

public class GifAnimator implements Runnable
{
	private GifDecoder myGifDecoder;
	private GifAnimation myAnimation;
	private Canvas myCanvas;
	
	public void setup(String imageFile, GifAnimation theAnimation, Canvas theCanvas)
	{
		myAnimation = theAnimation;
		myCanvas = theCanvas;
		
		myGifDecoder = new GifDecoder();
		myGifDecoder.read(imageFile);
		myAnimation.setImage(myGifDecoder.getImage());
	}

	public void run()
	{
		int n = myGifDecoder.getFrameCount();
		int t = 0;
		while (myAnimation.isActive())
		{
			for (int i = 0; i < n; ++i)
			{
				while (myAnimation.isPaused())
				{
					synchronized (this)
					{
						try
						{
							wait();
						}
						catch (InterruptedException e)
						{
						}
					}
				}
				myAnimation.setImage(myGifDecoder.getFrame(i));
				t = myGifDecoder.getDelay(i);
				myCanvas.repaint();
				myCanvas.serviceRepaints();
				try
				{
					Thread.sleep(t);
				}
				catch (InterruptedException e)
				{
				}
			}
		}
	}

}

My main thread is a Canvas derived class.
It has a GifAnimation member variable.
It calls GifAnimation.Next() when a certain key is pressed.
Here's the relevant bits:

Code:

public class Main extends Canvas
{
	private GifAnimation myAnimation;

	public Main()
	{
		super();
                Next();
	}
	
	protected void showNotify()
	{
		myAnimation.Resume();
	}
	
	protected void hideNotify()
	{
		myAnimation.Pause();
	}
	
	protected void paint(Graphics g)
	{
		Image img = myAnimation.getImage();
		if (null != img)
			g.drawImage(img, 0, 0, Graphics.TOP | Graphics.LEFT);

	}
	
	private void Next()
	{
                ...
		myAnimation.Start(someNewImage, this);
		repaint();
	}
	
	public void keyPressed(int keyCode)
	{
		switch (keyCode)
		{
		case Canvas.KEY_STAR:
                        Next();
			break;
		}
	}

}

I apologize for the lengthiness of it all, I've stripped it down as much as possible.
Could someone please help me synchronize things here?
I suspect I'm using wait()/notify() incorrectly but I'm not sure (though I have read about it as much as possible).
I think "Deadlock Drawing" (sonyericsson developer website) may be part (or all!) of the problem but I really don't know.

I could really use some help on this, I'm utterly lost.
This program is important to me, it's a learning aid I intend to use every day.