Method to Use The Pixmap Currently Visible Inside a QGraphicsScene/View in an Unrelated slot

[mrjj]

Hi
Im not sure why you cant make it a member of the class that has the slot.
Like he does here.
http://www.bogotobogo.com/Qt/Qt5_QGraphicsView_QGraphicsScene.php

It is completely other class than where you create the scene?

[brazz]

@mrjj If I use this line in each slot scene = new QGraphicsScene(this); will it be referring to the same scene everytime? I'm not entirely what "this" points to specifically in Qt.

[mrjj]

@brazz
No no that would create a new one each time.
You just do it ONCE. Like he does in sample
("this" is used as parent/owner)

class Dialog : public QDialog
{
private:
    QGraphicsScene *scene; <<< define

and then in constructor
Dialog::Dialog(QWidget *parent) :
{
    scene = new QGraphicsScene(this); <<< set it to point to an instance

Then in any slot in Dialog class, you can use the variable scene to access it

In your case QDialog is most likely QMainwindow but 100% same way.

[brazz]

@mrjj Works perfectly, thank you. I figured it would have to do with adding code to the Qt auto generated stuff, I just didn't have to toolset/knowledge to do that yet. This trick will be make my life so much easier now.

[mrjj]

@brazz
Super. :)
Well adding code to any of the auto generated files is
not fun as they are overwritten
often. (like moc_xx files)

But the file the project wizard creates for you are for your use.
So that is fine to add code to. its never re-created again.

[brazz]

@mrjj any idea why this bit of code says that the List is never used/declared

QList<QGraphicsItem*> graphicsItemList(wavesScene->items());
   QGraphicsPixmapItem pixmapItem(graphicsItemList.at(0));

[mrjj]

@brazz said in Method to Use The Pixmap Currently Visible Inside a QGraphicsScene/View in an Unrelated slot:

QList<QGraphicsItem*> graphicsItemList(wavesScene->items());
QGraphicsPixmapItem pixmapItem(graphicsItemList.at(0));

Ehh no as it's both declared and used.

What is the exact error ?
(you can right click and get it)

Same code in test project is not showing any warning.

also just to be sure u mean it
QGraphicsPixmapItem pixmapItem(graphicsItemList.at(0))
This makes a new QGraphicsPixmapItem (locally) and set
graphicsItemList.at(0) as parent.
Its not same as
QGraphicsPixmapItem *pixmapItem = graphicsItemList.at(0);
That would point to the first item in the list.

[brazz]

@mrjj D:\SEGYView\segyview.cpp:209: error: 'graphicsItemList' was not declared in this scope
QGraphicsPixmapItem* pixmapItem = graphicsItemList.at(0);

                                   ^

I tried I did mean to use the line that you provided, however it still gave the same error

[brazz]

this is how I added the first item in my actionOpen triggered() slot

        wavesScene->addItem(pixmapGraphicsItem);

        ui->PixmapView->setScene(wavesScene);

[mrjj]

@brazz

D:\SEGYView\segyview.cpp:209: error: 'graphicsItemList' was not declared in this scope

but those two lines are RIGHT next to each other or ?

just like you show ?

QList<QGraphicsItem*> graphicsItemList(wavesScene->items());
QGraphicsPixmapItem pixmapItem(graphicsItemList.at(0));

[brazz]

Exactly like that. Could it be that I'm missing some inclusions? I included <QGraphicsPixmapItem> <QList> <QGraphicsItem>