Pinball: Ball collision with Bumpers(objects) causes a crash. Using Box2D and have it isolated.

Hey,

I am making Pinball game that utilizes a camera to detect "buttons" that control the flippers. I got the code for the game here. Now, the buttons are actually two pieces of felt fabric, it looks like this. And when one of the pieces are cover by your hand (blocking the view of the camera), the camera will detect that and activate the corresponding flipper. This part works perfectly, and I know this because I get the same problem in the original code.

Now my problem is when the ball hits the bumper, there is a 95% chance of it crashing the game. Sometimes for some reason, the code works and the game goes smoothly but that's a rare occurrence. Also, not of the collisions cause a crash; the wall and flipper collision work great, its just the bumper collision.

This is the Ball code:

class Ball extends Drawable
{
  // Box2D body
  Body pBody;

  float diameter;

  Vec2 startPos;

  Ball(float diameter, Vec2 position)
  {
    --ballCount;
    this.startPos = position;
    this.diameter = diameter;

    // Create circle shape
    CircleShape shape = new CircleShape();
    shape.m_radius = box2d.scalarPixelsToWorld(diameter/2);

    // Create circle fixture
    FixtureDef fixture = new FixtureDef();
    fixture.shape = shape;
    fixture.density = 1.0f;
    fixture.restitution = 0.5f;

    // Define physics body
    BodyDef bodyDef = new BodyDef();
    bodyDef.type = BodyType.DYNAMIC;
    bodyDef.position.set(box2d.coordPixelsToWorld(position));

    // Add body to world
    this.pBody = box2d.createBody(bodyDef);
    this.pBody.createFixture(fixture);
    this.pBody.isBullet();

    // set the callback data to this instance
    this.pBody.setUserData(this);
  }

  void render()
  {
    super.render();

    Vec2 ballPos = box2d.getBodyPixelCoord(this.pBody);

    float angle = this.pBody.getAngle();

    pushMatrix();
    translate(ballPos.x, ballPos.y);
    rotate(-angle);
    ellipse(0, 0, diameter, diameter);
    line(0, 0, 0, diameter/2);
    popMatrix();
  }
  void bumpAway(float amount, Vec2 normal)
  {
    normal.normalize();
    Vec2 pushForce = normal.mul(-amount);
    this.pBody.applyLinearImpulse(pushForce, this.pBody.getPosition(), true);
  }
  boolean offScreen()
  {
    Vec2 ballPos = box2d.getBodyPixelCoord(this.pBody);

    return ballPos.y > height;
  }
}

And this the Bumper code:

class Bumper extends Drawable
{
  // Box2D body
  Body pBody;
  PShape pShape;
  color resetColor;
  boolean inThread;

  Bumper(Vec2 position, float radius)
  {
    // Create shape
    PolygonShape shape = new PolygonShape();

    Vec2[] vertices = new Vec2[8];
    float angleStep = PI/4;
    for (int i = 0; i < 8; i++)
    {
      vertices[i] = new Vec2(radius * cos(angleStep*i), radius * sin(angleStep*i));
    }

    // Create an array to temporarily store the box2D vertex coordinates
    Vec2[] box2DVertices = new Vec2[vertices.length];

    // Create a new PShape
    pShape = createShape();
    pShape.beginShape();

    // Iterate through every vertex
    for (int i = 0; i < vertices.length; i++)
    {
      float x = vertices[i].x;
      float y = vertices[i].y;

      // Add the vertex to the shape
      pShape.vertex(x, y);

      // Add the vertex (converted to box2D coords)
      box2DVertices[i] = new Vec2(box2d.scalarPixelsToWorld(x), -box2d.scalarPixelsToWorld(y));
    }

    // End the PShape
    pShape.endShape(CLOSE);

    // Set the box2D vertices
    shape.set(box2DVertices, box2DVertices.length);

    // Define physics body
    BodyDef bodyDef = new BodyDef();
    bodyDef.type = BodyType.STATIC;
    bodyDef.position.set(box2d.coordPixelsToWorld(position));

    // Add body to world
    this.pBody = box2d.createBody(bodyDef);
    this.pBody.createFixture(shape, 1);

    // set the callback data to this instance
    this.pBody.setUserData(this);
  }

  void render()
  {
    // Since we're using a PShape we can't just call fill and stroke
    pShape.setFill(fillColor);
    pShape.setStroke(strokeColor);

    Vec2 ballPos = box2d.getBodyPixelCoord(this.pBody);

    float angle = this.pBody.getAngle();

    pushMatrix();
    translate(ballPos.x, ballPos.y);
    rotate(-angle);
    shape(pShape);
    popMatrix();
  }
  void collide(Ball ball, color ballColor, Vec2 normal)
  {
    // Physically bump the ball away
    ball.bumpAway(100, normal);


    // Create a new thread
    Thread resetBumper = new Thread()
    {
      @Override
        public void run()
      {
        // Wait one second and change
        // The color back to it's original color
        delay(250);
        fillColor = resetColor;
        inThread = false;
      }
    };

    if (!inThread)
    {
      inThread = true;

      // Store the current color
      this.resetColor = fillColor;

      // Change the current color
      this.fillColor = ballColor;

      // Set volume to max
      gainValue.setValue(1.0f);

      // Reset the scrubber on the sound to start position
      dingSound.setToLoopStart();

      // Play the ding sound!
      dingSound.start();

      // Run the new thread
      resetBumper.start();
    }

    // Add to Player Score
    playerScore += 10;
  }
}

I have also attached the complete game so you can see what I am talking about.