Solved GraphicsView crash with GraphicsVideoItem.

[Fidchells_Eye]

Hi
I've been trying my hand at building a simple media player with the form for object placement.
But it crashes just as it starts to run.

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Constructor Code:
ui->setupUi(this);
videoItem = new QGraphicsVideoItem();

ui->GVpreview->scene()->addItem(videoItem); // << --- Trouble maker that causes crash
ui->GVpreview->show(); // GVpreview = QGraphicsView

connect(ui->hsdrDuration, SIGNAL(sliderMoved(int)), this, SLOT(setPosition(int)));
mediaPlayer.setVideoOutput(videoItem);
connect(&mediaPlayer, SIGNAL(stateChanged(QMediaPlayer::State)),this, SLOT(mediaStateChanged(QMediaPlayer::State)));

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For some reason the crash happens at ui->GVpreview->scene()->addItem(videoItem); and don't know why or how to fix it.

Thank you for your replies and time.

[Joel Bodenmann]

Is it possible that you forgot to create and/or assign the scene to the view?
Unless you can do that in the QtDesigner you have to do something like this:

// This creates the QGraphicsView, but there's still no QGraphicsScene!
ui->setupUi(this);

// Create and assign the QGraphicsScene
QGraphicsScene* scene = new QGraphicsScene(this);
ui->GVpreview->setScene(scene);

// Fun can start here
videoItem = new QGraphicsVideoItem();
ui->GVpreview->scene()->addItem(videoItem);

In general you have to check the pointer returned by QGraphicsView::scene() before accessing/using it. Most likely your app crashes because you get a nullpointer back.

[Fidchells_Eye]

Hey Joel

Thanks the code lines:
QGraphicsScene* scene = new QGraphicsScene(this);
ui->GVpreview->setScene(scene);

fixed the issue as I don't know how to do the scene view bit in the form editor.