Surfaceview animation instance

package game.test;

import android.content.Context;
import android.graphics.Canvas;
import android.graphics.Color;
import android.graphics.Paint;
import android.graphics.Rect;
import android.view.SurfaceHolder;
import android.view.SurfaceView;
import android.view.SurfaceHolder.Callback;

public class TestSurfaceView extends SurfaceView implements Callback, Runnable {

private SurfaceHolder surfaceHolder;
private int width, height;
private boolean bExit;
private Paint paint;
private Rect rect;

public TestSurfaceView(Context context) {
super(context);
        surfaceHolder = this.getHolder();
        surfaceHolder.addCallback(this);
        rect = new Rect(100, 0, 120, 20);
        paint = new Paint();  
        paint.setAntiAlias(true);  
        paint.setColor(Color.WHITE);  
this.setKeepScreenOn(true);
        bExit = false;
    }

private void draw() {
        Canvas canvas = surfaceHolder.lockCanvas();
        canvas.drawColor(Color.BLACK);
        rect.top += 10;
if(rect.top > height)
            rect.top = 0;
        rect.bottom = rect.top + 20;
        canvas.drawRect(rect, paint);
        surfaceHolder.unlockCanvasAndPost(canvas);
    }

    @Override
public void surfaceChanged(SurfaceHolder holder, int format, int width,
int height) {

    }

    @Override
public void surfaceCreated(SurfaceHolder holder) {
        width = this.getWidth();
        height = this.getHeight();
new Thread(this).start();
    }

    @Override
public void surfaceDestroyed(SurfaceHolder holder) {

    }

    @Override
public void run() {
while(!bExit) {
            draw();
try {
                Thread.sleep(1000);
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
        }
    }
}