42.写入XML

 #include <QtGui>
 #include <QtXml>
 #include <iostream>

 //创建一个树结构
 void populateTree(QTreeWidget *treeWidget)
 {
     QStringList labels;
     labels << QObject::tr("Terms") << QObject::tr("Pages");

     treeWidget->setHeaderLabels(labels);
     treeWidget->header()->setResizeMode(QHeaderView::Stretch);
     treeWidget->setWindowTitle(QObject::tr("XML Stream Writer"));
     treeWidget->show();

     (void) new QTreeWidgetItem(treeWidget,
             QStringList() << "sidebearings" << "10, 34-35, 307-308");
     QTreeWidgetItem *subterm = new QTreeWidgetItem(treeWidget,
             QStringList() << "subtraction");
     (void) new QTreeWidgetItem(subterm,
             QStringList() << "of pictures" << "115, 244");
     (void) new QTreeWidgetItem(subterm,
             QStringList() << "of vectors" << "");
 }

 //生成一个新的开始标签
 void writeIndexEntry(QXmlStreamWriter *xmlWriter, QTreeWidgetItem *item)
 {
     //创建一个开始标签
     xmlWriter->writeStartElement("entry");
     //给标签添加属性
     xmlWriter->writeAttribute("term", item->text());
     //获取子树的第二个元素
     QString pageString = item->text();
     //根据','拆开
     if (!pageString.isEmpty()) {
         QStringList pages = pageString.split(", ");
         //依次写入Text元素
         foreach (QString page, pages)
             xmlWriter->writeTextElement("page", page);
     }
     //如果有子项则递归调用
     for (int i = ; i < item->childCount(); ++i)
         writeIndexEntry(xmlWriter, item->child(i));
     xmlWriter->writeEndElement();
 }

 bool writeXml(const QString &fileName, QTreeWidget *treeWidget)
 {
     QFile file(fileName);
     if (!file.open(QFile::WriteOnly | QFile::Text)) {
         std::cerr << "Error: Cannot write file "
                   << qPrintable(fileName) << ": "
                   << qPrintable(file.errorString()) << std::endl;
         return false;
     }

     //写xml
     QXmlStreamWriter xmlWriter(&file);
     xmlWriter.setAutoFormatting(true);
     //写首行<?xml version="1.0" encoding="UTF-8">
     xmlWriter.writeStartDocument();
     //生成一个开始标签
     xmlWriter.writeStartElement("bookindex");
     //对于每一个顶级项,调用writeIndexEntry函数
     for (int i = ; i < treeWidget->topLevelItemCount(); ++i)
         writeIndexEntry(&xmlWriter, treeWidget->topLevelItem(i));
     xmlWriter.writeEndDocument();

     file.close();
     if (file.error()) {
         std::cerr << "Error: Cannot write file "
                   << qPrintable(fileName) << ": "
                   << qPrintable(file.errorString()) << std::endl;
         return false;
     }
     return true;
 }

 int main(int argc, char *argv[])
 {
     QApplication app(argc, argv);
     QTreeWidget treeWidget;
     populateTree(&treeWidget);
     writeXml("out1.xml", &treeWidget);
     return app.exec();
 }