How can I detect collision among QPixmaps and QGraphicsItems objects

DSlim

I have QGraphicsEllipse items as bullets in a scene. Targets are QPixmap images and I want just the bullets and images to interact, NOT target on target collision. Bullets are created in my scene class and QPixmaps are created in my dialog class.

This deletes my bullets that leave outside of my sceneRect. I tried adding a QList for the QPixmaps created similar to the QList QGraphicsItem * but don't think the compiler liked that. Is there a way to gather all pixmaps in scene and only have them detect bullets. Also tried collidesWithItem with no luck. Any suggestions would be appreciated.

@void Scene::advance()
{
QList <QGraphicsItem *> itemsToRemove;
foreach( QGraphicsItem * item, this->items())
{

        if( !this->sceneRect().intersects(item->boundingRect()))
        {
            // The item is no longer in the scene rect, get ready to delete it
            itemsToRemove.append(item);
        }
    }

    foreach( QGraphicsItem * item, itemsToRemove )
    {
        this->removeItem(item);
        delete(item);
    }
    QGraphicsScene::advance();

}@

Asperamanca

It should be QGraphicsPixmapItems (or similar), not QPixmap.
Collision detection can only work between subclasses of QGraphicsItem.

DSlim

If I change to a QGraphicsPixmapItem can I make another list and collide the two. i.e. collideWithItem?

Asperamanca

Yes, it should work that way.

DSlim

I understand what you're saying about collision but the issues is I have the images stored in an array.

@ main_targets[0] = QPixmap(":images/darkbluelogo.jpg");
main_targets[1] = QPixmap(":images/graylogo.jpg");
main_targets[2] = QPixmap(":images/lightbluelogo.jpg");
main_targets[3] = QPixmap(":images/lime.jpg");
main_targets[4] = QPixmap(":images/pink.jpg");
main_targets[5] = QPixmap(":images/purple.jpg");
main_targets[6] = QPixmap(":images/redlogo.jpg");
main_targets[7] = QPixmap(":images/yellow.jpg");
main_targets[8] = QPixmap(":images/brown.jpg");@

I ran into alot of errors trying to store this array in a QGraphicsPixmapItem

andreyc

@
QVector<QGraphicsPixmapItem*> targetItems;
foreach(QPixmap pix, main_targets) {
QGraphicsPixmapItem* item = QGraphicsPixmapItem(pix);
targetItems.append(item);
}
@

Hope it help.

DSlim

Thanks it helps but implementation throws @In instantiation of 'class QForeachContainer<QPixmap [9]>':@
The main_target array, QPixmap and targetitems array, QGraphicsPixmapItem seem to not play well together.

andreyc

How did you define main_targets?
Is it
@
QVector<QPixmap> main_targets;
or
QPixmap main_targets[9];
@

Qt specific keyword foreach works only with container classes like first definition. If you have second definition then you should use standard C++ for or while loop.

SGaist

Hi,

foreach must be used with a containers. A c array is not considered a container.

In your case you can use a classic for loop or change your array to a QList of QPixmap

Hope it helps

DSlim

Changing to containers I get the index is out of range error. Can I not assign each QPixmap an array value?

andreyc

If you use containers then you should use append() method to add pixmaps to your container.

DSlim

I thought the @QVector<QGraphicsPixmapItem*> targetItems;
foreach(QPixmap pix, main_targets) {
QGraphicsPixmapItem* item = QGraphicsPixmapItem(pix);
targetItems.append(item);
}@ takes each instance of the main_targets array, and creates QGraphicsPixmapItems of them.

andreyc

Could you show the code where you are getting "index is out of range" error.

DSlim

I pass the pmap to the MainTarget class by pointer, which was previously by reference. There isn't a specific line that the compiler is showing. It crashes on execution. I replaced main_targets[index] with targetItems since that should hold the QGraphicsPixmapItem items.

@void Dialog::setPixmaps()
{
//Targets are delivered every 1sec
Five_timer->start(1000);

QList<QGraphicsPixmapItem*> targetItems;
foreach(QPixmap pix, main_targets) {
QGraphicsPixmapItem* p_item = new QGraphicsPixmapItem(pix);
targetItems.append(p_item);
}

int StartY = 0;

//Random starting Y point between -140 and -389
StartY = (qrand() % (-400 + 150) -140);

index = (qrand() % 9);
{
    if(index % 2 == 0)
    {
        //When even is selected start at far right
        pmap = new MainTargets(targetItems[index], 0);
        pmap->setPos(345,StartY);
    }

    else
    {
        //When odd is selected start at far left
        pmap = new MainTargets(targetItems[index], 1);
        pmap->setPos(-325,StartY);

    }
}

scene->addItem(pmap);

}@

andreyc

Does it always crash on the same place?
Try to step through the function using a debugger.

What is the type of main_targets in line #9?

DSlim

QList<QPixmap> main_targets is the type.

Seems to fail at the QList::operator[].

That is why I think the main_target array seems to be the issue.

andreyc

How do you fill main_target?

DSlim

Guess that is where the problem is I thought the @ QList<QGraphicsPixmapItem*> targetItems;
foreach(QPixmap pix, main_targets) {
QGraphicsPixmapItem* p_item = new QGraphicsPixmapItem(pix);
targetItems.append(p_item);@ fills the main_target list. If not what is the purpose of this line?

andreyc

In this code you take the pixmaps from main_target and create qlist of qgraphicsitems.
So, the main_target must be populated by the qpixmaps before this code.

DSlim

@ main_targets[0] = QPixmap(":images/darkbluelogo.jpg");
main_targets[1] = QPixmap(":images/graylogo.jpg");
main_targets[2] = QPixmap(":images/lightbluelogo.jpg");
main_targets[3] = QPixmap(":images/lime.jpg");
main_targets[4] = QPixmap(":images/pink.jpg");
main_targets[5] = QPixmap(":images/purple.jpg");
main_targets[6] = QPixmap(":images/redlogo.jpg");
main_targets[7] = QPixmap(":images/yellow.jpg");
main_targets[8] = QPixmap(":images/brown.jpg");@

The main_targets are created and stored in the constructor initially before anything is done. So the qlist should have 9 qpixmaps.