simple android touch screen move image, draw lines

//again thanks to these excellant and clear tutorials:
http://www.droidnova.com/2d-tutorial-series-part-i,770.html

package amdroid.TransformationalActivity.com;


import android.graphics.Canvas;
import android.view.SurfaceHolder;

import android.app.Activity;
import android.os.Bundle;
import android.view.Window;

import android.content.Context;
import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.graphics.Canvas;
import android.graphics.Color;
import android.graphics.Paint;
import android.view.MotionEvent;
import android.view.SurfaceHolder;
import android.view.SurfaceView;


public class TransformationalActivity extends Activity {
/** Called when the activity is first created. */
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
requestWindowFeature(Window.FEATURE_NO_TITLE);
setContentView(new Panel(this));
}
}
//////////

class Panel extends SurfaceView implements SurfaceHolder.Callback {

private Bitmap mBitmap;
private ViewThread mThread;

private int mX;
private int mY;

public Panel(Context context) {
super(context);
mBitmap = BitmapFactory.decodeResource(getResources(), R.drawable.lotus);
getHolder().addCallback(this);
mThread = new ViewThread(this);
}

public void doDraw(Canvas canvas) {
canvas.drawColor(Color.BLUE);
Paint paint = new Paint();
canvas.drawLine(33, 0, 33, 100, paint);
paint.setColor(Color.RED); paint.setStrokeWidth(10); canvas.drawLine(56, 0, 56, 100, paint);
paint.setColor(Color.GREEN); paint.setStrokeWidth(25);
for (int y = 30, alpha = 255; alpha > 2; alpha >>= 1, y += 10) {
paint.setAlpha(alpha);

canvas.drawLine(0, y, 100, y, paint);
}

canvas.drawBitmap(mBitmap, mX, mY, null);
}

@Override
public void surfaceChanged(SurfaceHolder holder, int format, int width, int height) {
// TODO Auto-generated method stub
}

@Override
public void surfaceCreated(SurfaceHolder holder) {
if (!mThread.isAlive()) {
mThread = new ViewThread(this);
mThread.setRunning(true);
mThread.start();
}
}

@Override
public void surfaceDestroyed(SurfaceHolder holder) {
if (mThread.isAlive()) {
mThread.setRunning(false);
}
}

@Override
public boolean onTouchEvent(MotionEvent event) {
mX = (int) event.getX() - mBitmap.getWidth() / 2;
mY = (int) event.getY() - mBitmap.getHeight() / 2;
return super.onTouchEvent(event);
}
}


/////////
class ViewThread extends Thread {
private Panel mPanel;
private SurfaceHolder mHolder;
private boolean mRun = false;

public ViewThread(Panel panel) {
mPanel = panel;
mHolder = mPanel.getHolder();
}

public void setRunning(boolean run) {
mRun = run;
}

@Override
public void run() {
Canvas canvas = null;
while (mRun) {
canvas = mHolder.lockCanvas();
if (canvas != null) {
mPanel.doDraw(canvas);
mHolder.unlockCanvasAndPost(canvas);
}
}
}
}