Android :: Black Screen Problem With Graphics Update Using UnlockCanvasAndPost()

I am working on a game for Android. I'm following the general program layout of Lunar Lander, where a SurfaceView has a worker thread that runs the main game loop. That loop updates the physics and redraws the screen by creating and drawing to a canvas.

From the thread class:

CODE:.........

I believe surfaceHolder.unlockCanvasAndPost(canvas); is supposed to release the canvas and force the screen to redraw correct? That's not what I'm seeing. I'm getting strange behavior where the final draw works, but each previous draw only shows a black screen.

For a better example: I draw a small character sprite at the left side of the screen. Then, for each successive frame of 100 frames I translate the image one to the right. So I expect to see the sprite slide to the right as the program runs. Instead, the screen is black the whole time until the end, when the sprite appears already on the right side of the screen. It's as if the very last call to unlockCanvasAndPost() is applied to the screen, but the others are hidden or not drawn. I've verified that they are, in deed, being executed.