Open the jni/PhysicsManager.hpp header and insert the Box2D include file.

Define a constant PHYSICS_SCALE to convert the body position from physics to game coordinates. Indeed, Box2D uses its own scale for a better precision.

Then, replace PhysicsBody with a new structure, PhysicsCollision, that will indicate which bodies entered in collision, as shown in the following:

#ifndef PACKT_PHYSICSMANAGER_HPP
#define PACKT_PHYSICSMANAGER_HPP

#include "GraphicsManager.hpp"
#include "TimeManager.hpp"
#include "Types.hpp"

#include <Box2D/Box2D.h>
#include <vector>

#define PHYSICS_SCALE 32.0f

struct PhysicsCollision {
    bool collide;

    PhysicsCollision():
        collide(false)
    {}
};
...

Then, make PhysicsManager inherit from b2ContactListener. A contact listener gets notified about new collisions each time the simulation is updated. Our PhysicsManager...