Collision between AnimatedSprite and Rectangle null pointer error

Question

I'm trying to detect a collision between an AnimatedSprite and the Rectangle floor. When they collide, I want the sprite to be removed. However, I keep getting a null pointer error. Am I doing this the wrong way?

Inside my add face function. face is an AnimatedSprite created, and ground is a rectangle.

this.mScene.registerUpdateHandler(new IUpdateHandler() {
            @Override
            public void reset() { }

            @Override
            public void onUpdate(final float pSecondsElapsed) {
                    if(face.collidesWith(ground)) {
                           Debug.d("Contact!");
                           removeFace(face);       
                    } 
            }
    });     

removeFace() is:

private void removeFace(final AnimatedSprite face) {
    final PhysicsConnector facePhysicsConnector = this.mPhysicsWorld.getPhysicsConnectorManager().findPhysicsConnectorByShape(face);

    this.mPhysicsWorld.unregisterPhysicsConnector(facePhysicsConnector);
    this.mPhysicsWorld.destroyBody(facePhysicsConnector.getBody());

    this.mScene.unregisterTouchArea(face);
    this.mScene.detachChild(face);

    System.gc();
}

The null pointer exception is inside removeFace()

Answer 1

Look at the stack trace it will tell you exactly which line has the null pointer exception. You need to invest in learning to use the debugger too, these are simple problems to debug and you can solve your own problems much faster than waiting for a reply here.

From your code I'm assuming that

this.mPhysicsWorld.getPhysicsConnectorManager().findPhysicsConnectorByShape(face)

is returning null because it's unable to find the face you specify. So it could easily throw a null pointer exception when it reaches: facePhysicsConnector.getBody(). Since you can't access a method of a null object.