Why does this code work for a stationary object, but not a moving one?

Question

I use the following chunk of code to make bullets that fire towards the player's ship:

@Override
public void onTimePassed(final TimerHandler pTimerHandler)
{
    pTimerHandler.reset();
    if(spawnBullets){
        for(int i = 0; i < enemies.size(); i++){
            if(enemies.get(i).isShooter()){
                //shoot from this enemy to ship
                final Vector2 v = new Vector2(ship.getX() - enemies.get(i).getSprite().getX(),ship.getY() - enemies.get(i).getSprite().getY());
                v.nor();
                v.mul(BULLET_SPEED);
                createEnemyBullet(enemies.get(i).getSprite().getX(),enemies.get(i).getSprite().getY(), v);
            }
        }
    }
}

This works fine if the enemy is stationary, i.e. just a Sprite with no Body, but when the enemy is moving, my game completely freezes up. Sometimes it will happen immediately (on the first attempt to fire), or sometimes 1 or 2 bullets later.

It gets through this code (a log output after createEnemyBullet works fine), but locks up somewhere before anything else happens. Disabling this section of code makes the problem go away. What could be going wrong?

Edit

Here is createEnemyBullet():

private void createEnemyBullet(float x, float y, Vector2 v){
    //remove old bullet
    if(enemyBullets[enemyBulletCounter] != null){
        makeBulletExplosion(bullets[i].getX(),bullets[i].getY());
        mScene.detachChild(bullets[i]);
        mBulletPhysicsWorld.destroyBody(bulletsPhysical[i]);
        bullets[i] = null;
    }
    //create new bullet 
    enemyBullets[enemyBulletCounter] = new AnimatedSprite(x +8, y +8, this.mEnemyBulletTextureRegion); //Nasty magic number, oh well
    enemyBulletsBody[enemyBulletCounter] = PhysicsFactory.createCircleBody(this.mBulletPhysicsWorld, enemyBullets[enemyBulletCounter], BodyType.KinematicBody, BULLET_FIXTURE_DEF);

    enemyBullets[enemyBulletCounter].animate(55);
    enemyBulletsBody[enemyBulletCounter].setLinearVelocity(v);

    this.mBulletPhysicsWorld.registerPhysicsConnector(new PhysicsConnector(enemyBullets[enemyBulletCounter], enemyBulletsBody[enemyBulletCounter], true, true));
    this.mScene.attachChild(enemyBullets[enemyBulletCounter]);
    //update counter
    enemyBulletCounter = enemyBulletCounter < ENEMY_BULLET_MAX -1 ? enemyBulletCounter + 1 : 0;
}

Answer 1

I'm going to write an answer instead of a comment.

Looking at your CreateBullet method: You are creating two new objects for each new bullet: AnimatedSprite and CircleBody You will have many short-lived instances of them. Better to recycle them. Have an object pool of both classes and initialize them as invisible/disabled. Each time a new bullet is requested just retrieve an unused object from each pool, initialize them and activate them. Bullets objects that are destroyed are returned to the pool for reuse.

A brute force "debugging" tip: To narrow the line causing the issue. Print to console between each line. This is not pretty, but will quickly show which line causes the hanging.

You also said the code works fine, if the enemy has no physical body. Could it be that you spawn new bullets inside the enemies body? That might trip the collision resolution of the physics engine.