Android draw using SurfaceView and Thread

I am trying to draw a ball to my screen using 3 classes. I have read a little about this and I found a code snippet that works using the 3 classes on one page, Playing with graphics in Android

I altered the code so that I have a ball that is moving and shifts direction when hitting the wall like the picture below (this is using the code in the link).

Now I like to separate the classes into 3 different pages for not making everything so crowded, everything is set up the same way.

Here are the 3 classes I have.

1. BallActivity.java
2. Ball.java
3. BallThread.java

package com.brick.breaker;
import android.app.Activity;
import android.os.Bundle;
import android.view.Window;
import android.view.WindowManager;


public class BallActivity extends Activity {

private Ball ball;

@Override
protected void onCreate(Bundle savedInstanceState) {

    super.onCreate(savedInstanceState);

    requestWindowFeature(Window.FEATURE_NO_TITLE);
    getWindow().setFlags(WindowManager.LayoutParams.FLAG_FULLSCREEN,WindowManager.LayoutParams.FLAG_FULLSCREEN);

    ball = new Ball(this);
    setContentView(ball);
}

@Override
protected void onPause() {

    super.onPause();

    setContentView(null);
    ball = null;

    finish();
}

}

package com.brick.breaker;

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

public class Ball extends SurfaceView implements SurfaceHolder.Callback {

private BallThread ballThread = null;

private Bitmap bitmap;

private float x,