Qt开发：XML文件的写入与读取

一、使用 QDomDocument操作节点

1.1 将信息写入XML文件中

#include <QDomDocument>
#include <QTextStream>
#include <QFile>
#include <QDir>void writeXmlWithStreamWriter() {QDomDocument document; // 创建对象QDomProcessingInstruction version; // 写入XML头部(添加处理命令)version = document.createProcessingInstruction("xml", "version = \"1.0\" encoding = \"utf8\"");document.appendChild(version);QDomElement root = document.createElement("Books");document.appendChild(root);// 模拟多个书for (int i = 1; i <= 3; ++i) {QDomElement book = document.createElement("Book");book.setAttribute("id", QString::number(i));QDomElement title = document.createElement("Title");QDomText text = document.createTextNode(QString("Book Title %1").arg(i));title.appendChild(text);book.appendChild(title);root.appendChild(book);}// 保存到文件QDir dir(QCoreApplication::applicationDirPath());QString strXmlPath = dir.absoluteFilePath("book_xml.xml");QFile file(strXmlPath);if (file.open(QIODevice::WriteOnly | QIODevice::Text)) {QTextStream out(&file);document.save(out, 4);file.close();}
}

输出结果：

<?xml version = "1.0" encoding = "utf8"?>
<Books><Book id="1"><Title>Book Title 1</Title></Book><Book id="2"><Title>Book Title 2</Title></Book><Book id="3"><Title>Book Title 3</Title></Book>
</Books>

1.2.从XML文件中读取信息

#include <QDomDocument>
#include <QTextStream>
#include <QFile>
#include <QDir>
#include <QDebug>void readXmlWithDom() {// 保存到文件QDir dir(QCoreApplication::applicationDirPath());QString strXmlPath = dir.absoluteFilePath("book_xml.xml");QFile file(strXmlPath);if (!file.open(QIODevice::ReadOnly)) {qDebug() << "Failed to open file";return;}QDomDocument document;if (!document.setContent(&file)) {qDebug() << "Failed to parse XML";file.close();return;}file.close();// 获取根节点QDomElement root = document.documentElement();if (root.tagName() != "Books") {qDebug() << "Invalid root element";return;}// 遍历所有 Book 节点QDomNodeList books = root.elementsByTagName("Book");for (int i = 0; i < books.count(); ++i) {QDomElement book = books.at(i).toElement();QString id = book.attribute("id");QString title = book.firstChildElement("Title").text();qDebug() << "Book id:" << id << ", title:" << title;}
}

输出结果：

二、使用 QXmlStreamWriter操作节点

2.1 将信息写入XML文件中

#include <QXmlStreamWriter>
void writeMultipleBooks() {QDir dir(QCoreApplication::applicationDirPath());QString strXmlPath = dir.absoluteFilePath("book_xml.xml");QFile file(strXmlPath);if (!file.open(QIODevice::WriteOnly | QIODevice::Truncate)) {qDebug() << "Failed to open file for writing.";return;}QXmlStreamWriter xmlWriter(&file);xmlWriter.setAutoFormatting(true); // 自动换行缩进xmlWriter.writeStartDocument();    // 写XML头部 <?xml version="1.0" encoding="UTF-8"?>xmlWriter.writeStartElement("Books"); // <Books>// 写多个<Book>子节点for (int i = 1; i <= 3; ++i) {xmlWriter.writeStartElement("Book");         // <Book>xmlWriter.writeAttribute("id", QString::number(i)); // 添加id属性xmlWriter.writeTextElement("Title", QString("Book Title %1").arg(i)); // 写<Title>内容xmlWriter.writeEndElement();                 // </Book>}xmlWriter.writeEndElement(); // </Books>xmlWriter.writeEndDocument(); // 自动结束file.close();
}

输出结果：

<?xml version="1.0" encoding="UTF-8"?>
<Books><Book id="1"><Title>Book Title 1</Title></Book><Book id="2"><Title>Book Title 2</Title></Book><Book id="3"><Title>Book Title 3</Title></Book>
</Books>

2.2 从XML文件中读取信息

#include <QXmlStreamReader>void readMultipleBooks() {QDir dir(QCoreApplication::applicationDirPath());QString strXmlPath = dir.absoluteFilePath("book_xml.xml");QFile file(strXmlPath);if (!file.open(QIODevice::ReadOnly | QIODevice::Text)) {qDebug() << "Failed to open file.";return;}QXmlStreamReader xmlReader(&file);QString currentId;QString currentTitle;while (!xmlReader.atEnd()) {xmlReader.readNext();if (xmlReader.isStartElement()) {if (xmlReader.name() == "Book") {currentId = xmlReader.attributes().value("id").toString();}else if (xmlReader.name() == "Title") {currentTitle = xmlReader.readElementText();qDebug() << "Book ID:" << currentId << "Title:" << currentTitle;}}}if (xmlReader.hasError()) {qDebug() << "XML parse error:" << xmlReader.errorString();}file.close();
}

输出结果：

解析过程详解：

• readNext() ➔ 读取下一个XML记号（元素开始、元素结束、文本等）
• isStartElement() ➔ 检查是不是开始的标签 <…>
• xmlReader.name() ➔ 得到当前节点名字
• xmlReader.attributes().value(“xxx”) ➔ 读取节点的属性，比如 <Book id=“1”>
• xmlReader.readElementText() ➔ 读取节点内的文本，比如 <Title>xxx

三、总结

QDomDocument 和 QXmlStreamWriter/Reader 的最大区别在于：

举个具体场景对比
用 QDomDocument ➔ 适合做：

• 需要随时修改某个节点
• 比如：读取配置文件，动态增加配置项，保存回去
• 编辑复杂XML（像HTML编辑器）

用 QXmlStreamReader/Writer ➔ 适合做：

• 只需要快速读一遍提取数据
• 需要生成超大XML（比如100MB+的数据导出）
• 不需要修改，只需要一条条处理