// we want to take in account now what was already mentioned in Lesson3:
// forces must be applied for each physics step if you want a constant
// force applied
// thus we create an input handler that gets invoked each physics step
physicsStepInputHandler = new InputHandler();
getPhysicsSpace().addToUpdateCallbacks(new PhysicsUpdateCallback() {
public void beforeStep(PhysicsSpace space, float time) {
physicsStepInputHandler.update(time);
}
public void afterStep(PhysicsSpace space, float time) {