how to use QT graphic view for drawing

im trying to use the graphic veiw of QT to开发者_如何转开发 draw lines it's possible to draw a multiple objects in the scene but is it possible to do a (real time lines ) drawing inside the Qt scene , and how ?

a sample code would be highly appreciated

thanks in advance

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I'm creating a kind of "Framework" to do this. There are 2 approaches:

1. Handle mouse messages, create a QGraphicsLineItem object, add to Scene and modify it during the creation process.
2. Derive QGraphicsScene, create a QGraphicsLineItem but NOT added to scene, draw it when drawForeground, added it to scene after finished the creation.

Because QGraphicsScene will index objects in a BSP tree by default, and it will impact the performance when changing items frequently, you can get higher performance when using the 2nd approach during creation, but more code work.

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1) Create GraphicsView and Scene

m_graphScen = new QGraphicsScene;
m_graphScen->setSceneRect(0,0,790,290);

m_graphView = new QGraphicsView;
m_graphView->setFixedSize(800, 300);
m_graphView->setScene(m_graphScen);

2) Create a slot which is doing the following by handling the mouse events:

m_graphScen->addLine(0, 250, 700, 250, QPen(QBrush(Qt::black),1));
m_graphView->show();

Also if you need to write or draw text see here.