Qt Write and Read XML File 读写XML文件

在Qt中，我们有时候需要把一些参数写入xml文件，方便以后可以读入，类似一种存档读档的操作，例如，我们想生成如下的xml文件：

<?xml version="1.0" encoding="UTF-8"?>

<Parameters>

    <para1>1</para1>

    <para2>2</para2>

    <para3>3</para3>

</Parameters>

那么写入的操作请参见如下代码：

void QtMainWindow::on_actionSave_triggered() {

    QString filename = QFileDialog::getSaveFileName(this,

        tr("Save Xml"), ".",

        tr("Xml files (*.xml)"));

    QFile file(filename);

    file.open(QIODevice::WriteOnly);

    QXmlStreamWriter xmlWriter(&file);

    xmlWriter.setAutoFormatting(true);

    xmlWriter.writeStartDocument();

    xmlWriter.writeStartElement("Parameters");

    xmlWriter.writeTextElement("para1",QString::number());

    xmlWriter.writeTextElement("para2",QString::number());

    xmlWriter.writeTextElement("para3",QString::number());

    xmlWriter.writeEndElement();

    xmlWriter.writeEndDocument();

    file.close();

}

读入的操作请参见如下：

void QtMainWindow::on_actionLoad_triggered() {

    QString filename = QFileDialog::getOpenFileName(this,

        tr("Open Xml"), ".",

        tr("Xml files (*.xml)"));

    QFile file(filename);

    if (!file.open(QFile::ReadOnly | QFile::Text)) {

        std::cerr << "Error: Cannot read file " << qPrintable(filename)

            << ": " << qPrintable(file.errorString())

            << std::endl;

    }

    QXmlStreamReader xmlReader(&file);

    xmlReader.readNext();

    while(!xmlReader.atEnd()) {

        if(xmlReader.isStartElement()) {

            if(xmlReader.name() == "Parameters") {

                xmlReader.readNext();

            } else if (xmlReader.name() == "para1") {

                int para1 = xmlReader.readElementText().toInt();

                xmlReader.readNext();

            } else if (xmlReader.name() == "preFilterCap") {

                int para2 = xmlReader.readElementText().toInt();

                xmlReader.readNext();

            } else if (xmlReader.name() == "SADWindowSize") {

                int para3 = xmlReader.readElementText().toInt();

                xmlReader.readNext();

            } else {

                xmlReader.raiseError(QObject::tr("Not a options file"));

            }

        } else {

            xmlReader.readNext();

        }

        file.close();

        if (xmlReader.hasError()) {

            std::cerr << "Error: Failed to parse file "

                << qPrintable(filename) << ": "

                << qPrintable(xmlReader.errorString()) << std::endl;

        } else if (file.error() != QFile::NoError) {

            std::cerr << "Error: Cannot read file " << qPrintable(filename)

                << ": " << qPrintable(file.errorString())

                << std::endl;

        }

    }

}