how to get an ordered list of selected items in GraphicsScene

Hey, guys. I'm writing a program with pyqt4 and met a problem.

In the class QGraphicsScene, there's a method "selectedItems()" which returns a list of all currently selected items. But the items are returned in no particular order. What if I want to get the first and second items that I selected? Is there any way to know the order when the items are selected?

Thanks a lot!

I guess you will need to evaluate that yourself. One way is to monitor the QGraphicsItem::GraphicsItemChange , and keep a list of items that are selected.

Also what do you want to do with first and second items selected ? If you can tell more, may be theres another solution :rolleyes:

Quote:

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Originally Posted by aamer4yu

I guess you will need to evaluate that yourself. One way is to monitor the QGraphicsItem::GraphicsItemChange , and keep a list of items that are selected.

Also what do you want to do with first and second items selected ? If you can tell more, may be theres another solution :rolleyes:

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This is what I'm thinking about! I wrote something and I know currently it's still not right. I want to connect two graphicsItem with an arrow, pointing from the first selected item to the second one. So I need the order.

def itemChange(self, change, variant):
if change == QGraphicsItem.ItemSelectedChange:
## I need some code here to give me a list "slctItems" of the currently selected items. I have a QGraphicsScene in a class called MainWindow which can get the selected items by calling selectedItems(). But this method (itemChange) is in another class. How could I call other class' method in one class? By the way, itemList will be used in another class too. So I made it global. Is it right?

if len(slctItems) == 0:
itemList = []
if len(slctItems) == 1:
itemList = slctItems
if len(slctItems) == 2:
if slctItems[0] == itemList[0]:
itemList[1] = slctItems[1]
else:
itemList[1] = slctItems[0]
if len(slctItems) > 2:
itemList = []
return QGraphicsItem.itemChange(self, change, variant)

Really appreciate your help.

Quote:

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I want to connect two graphicsItem with an arrow, pointing from the first selected item to the second one. So I need the order.

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I bet you haven't looked at Qt Demos completely. Look in the Diagram Scene example under Qt Demos-->>GraphicsView ;)

That's a good example. I'll read it and find out how it works.

Many thanks!

Problem solved.

I used my own way because the methods in Qt Demos will change too much of my code.

Thanks anyway.

Would it be an option to override QGraphicsScene::mousePressEvent to get the selected item and store the pointer in a list? If the length of the list == 2, draw a line from first to second item. From there it depends on what behavior you want: you could clear the list every time a line is drawn or copy the second element into the first and just keep refreshing the second element with the newly selected item, drawing line to line to line.