qgraphicsscene save all items to file
Certainly! Here's an example of how you can save all items in a QGraphicsScene to a file in C++ using Qt:
#include <QApplication>
#include <QGraphicsScene>
#include <QGraphicsView>
#include <QGraphicsItem>
#include <QFile>
#include <QXmlStreamWriter>
void saveSceneItems(QGraphicsScene *scene, const QString &filename) {
QFile file(filename);
if (!file.open(QIODevice::WriteOnly | QIODevice::Text))
return;
QXmlStreamWriter xmlWriter(&file);
xmlWriter.setAutoFormatting(true);
xmlWriter.writeStartDocument();
xmlWriter.writeStartElement("scene");
QList<QGraphicsItem *> items = scene->items();
foreach (QGraphicsItem *item, items) {
xmlWriter.writeStartElement("item");
xmlWriter.writeAttribute("type", QString::number(item->type()));
item->write(xmlWriter);
xmlWriter.writeEndElement(); // item
}
xmlWriter.writeEndElement(); // scene
xmlWriter.writeEndDocument();
file.close();
}
int main(int argc, char *argv[]) {
QApplication app(argc, argv);
QGraphicsScene scene;
// Add items to the scene...
QGraphicsView view(&scene);
view.show();
saveSceneItems(&scene, "scene_items.xml");
return app.exec();
}
Explanation of steps:
1. Include necessary headers: Include the required Qt headers for working with QGraphicsScene, QGraphicsView, QGraphicsItem, QFile, and QXmlStreamWriter.
2. saveSceneItems function: This function saves all items in a QGraphicsScene to an XML file. It takes a QGraphicsScene pointer and a filename as parameters.
3. Open file for writing: Open the specified file for writing the XML data.
4. Create XML writer: Create a QXmlStreamWriter object to write XML data to the file.
5. Write XML document: Begin writing the XML document with writeStartDocument()
.
6. Write scene start element: Write the <scene>
start element.
7. Iterate through scene items: Get a list of all items in the scene using scene->items()
. Iterate through each item.
8. Write item elements: For each item, create an <item>
element with a "type" attribute containing the item's type. Use item->write(xmlWriter)
to write the item's data to the XML file.
9. Close item and scene elements: Close the <item>
and <scene>
elements.
10. End writing the document: End writing the XML document with writeEndDocument()
.
11. Close the file: Close the file after writing the XML data.
12. main function: In the main function, create a QApplication object. Create a QGraphicsScene, add items to it, create a QGraphicsView to visualize the scene, display the view, call the saveSceneItems
function to save the scene items to an XML file, and run the application loop with app.exec()
.
This code illustrates the process of iterating through the items in a QGraphicsScene, extracting their data, and saving it to an XML file using Qt's XML writing capabilities.