Problem with colliding items with scene

[BeastBook]

Hi i am creted enemy in my game and i want when my enemy hit the end of scene to go back in different angle .I Have a problem with implementation

I want something like this

this is my move method

void Enemy::move()
{

/*Check collision with other enemies .This works fine*/
QList <QGraphicsItem *>colliding_items = collidingItems();
for(int i=0,n=colliding_items.size();i<n;i++)
{
    if(typeid (*(colliding_items[i]))==typeid (Enemy))
{
           //remove them both
        scene()->removeItem(colliding_items[i]);
        scene()->removeItem(this);

        //delete from heap
        delete colliding_items[i];
        delete this;
        return;
}
}








//moving enemy down
 setPos(x(),y()+5);


   





   if(scene()->collidingItems(this).isEmpty())
       {
           //no collision
          qDebug() << "Still no collision";
       }
       else
       {
           //collision!!!!


           //Set the position
           DoCollision();
       }

}

now goes do collision method

//Get a new position

 //Change the angle with a little randomness
 if(((qrand() %1)))
 {
     setRotation(rotation() + (180 + (qrand() % 10)));
 }
 else
 {
     setRotation(rotation() + (180 + (qrand() % -10)));
 }

 //see if the new position is in bounds
 QPointF newpoint = mapToParent(-(boundingRect().width()), -(boundingRect().width() + 2));



 if(!scene()->sceneRect().contains((newpoint)))
 {
     //move it back in bounds
     newpoint = mapToParent(0,0);
 }
 else
 {
     //set the new position
     qDebug() << "Collision";
     setPos(newpoint);


 }

this is my constructor

Enemy::Enemy():QObject(),QGraphicsPixMapItem()
{

int random_number = (rand() % 700)+80;

setPos(random_number,0);

// drew the rect
setPixmap(QPixmap(":/res/RSC/enemy.png"));
setRotation(180);

// connect
QTimer * timer = new QTimer(this);
connect(timer,SIGNAL(timeout()),this,SLOT(move()));

timer->start(50)

}