How can I detect collision among QPixmaps and QGraphicsItems objects

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.

andreyc

If I'm not mistaken you need to use .append() method to add elements to the QList. QList::opeartor[] does not work for adding new elements.

EDIT: Yep, you have to use append() or operator+=() to extend a list "operator[]":http://qt-project.org/doc/qt-5/qlist.html#operator-5b-5d requires an index to be valid (0 <= i < qlist.size())

DSlim

Thank you finally have it switched over to QGraphicsPixmapItems. Now the initial problem and see if I can get the collision working.

DSlim

Ok the original problem of colliding the two objects. My thinking at the beginning of this post was to have something along the lines of:

@if(pellets->collidesWithItem(targets){
remove(pellets)
remove(targets)

}@

Asperamanca

I wouldn't delete the items right away, but only hide them, and delete them later on. But otherwise, it might be something like this.

Have you taken a look at the Colliding Mice example?

DSlim

Yeah I've looked at that example a lot. Doesn't seem to be in the realm of what I'm trying to accomplish.