XML文件读取、显示、更改、删除、查找demo

（该例子参考《Qt Creator快速入门 第三版》src\17\17-10）

1、pro中添加如下代码

QT       += xml

2、UI界面设计如下图所示

3、代码部分

#ifndef MAINWINDOW_H
#define MAINWINDOW_H

#if _MSC_VER >=1600    // MSVC2015>1899,对于MSVC2010以上版本都可以使用
#pragma execution_character_set("utf-8")
#endif

#include <QMainWindow>

QT_BEGIN_NAMESPACE
namespace Ui { class MainWindow; }
QT_END_NAMESPACE

class MainWindow : public QMainWindow
{
    Q_OBJECT

public:
    MainWindow(QWidget *parent = nullptr);
    ~MainWindow();

    void doXml(const QString operate);  // 用于功能判断

private slots:
    void on_showBtn_clicked();

    void on_addBtn_clicked();

    void on_deleteBtn_clicked();

    void on_updateBtn_clicked();

    void on_findBtn_clicked();

private:
    Ui::MainWindow *ui;
};
#endif // MAINWINDOW_H

#include "mainwindow.h"#include "ui_mainwindow.h"#include<QtXml>#include<QFile>

#if _MSC_VER >=1600    // MSVC2015>1899,对于MSVC2010以上版本都可以使用
#pragma execution_character_set("utf-8")
#endif

MainWindow::MainWindow(QWidget *parent)
    : QMainWindow(parent)
    , ui(new Ui::MainWindow)
{
    ui->setupUi(this);

    QDomDocument doc;
    QDomProcessingInstruction instruction;
    instruction = doc.createProcessingInstruction("xml",
                                                  "version = \"1.0\"  encoding = \"UTF-8\"");
    doc.appendChild(instruction);

    // 添加根元素
    QDomElement root = doc.createElement("library");
    doc.appendChild(root);
    QDomElement book = doc.createElement("book");
    QDomAttr id = doc.createAttribute("id");
    QDomElement title = doc.createElement("name");
    QDomElement author = doc.createElement("author");
    QDomText text;
    id.setValue(QString("1"));
    book.setAttributeNode(id);
    text = doc.createTextNode("Qt");
    title.appendChild(text);
    text = doc.createTextNode("shiming");
    author.appendChild(text);
    book.appendChild(title);
    book.appendChild(author);
    root.appendChild(book);

    book = doc.createElement("book");
    id = doc.createAttribute("id");
    title = doc.createElement("name");
    author = doc.createElement("author");
    id.setValue(QString("2"));
    book.setAttributeNode(id);
    text = doc.createTextNode("Linux");
    title.appendChild(text);
    text = doc.createTextNode("zk");
    author.appendChild(text);
    book.appendChild(title);
    book.appendChild(author);
    root.appendChild(book);

    QFile file("my.xml");
    if(!file.open(QIODevice::WriteOnly | QIODevice::Truncate)) return ;
    QTextStream out(&file);
    doc.save(out, 4);
    file.close();
}

MainWindow::~MainWindow()
{
    delete ui;
}

void MainWindow::doXml(const QString operate)
{
    ui->listWidget->clear();
    ui->listWidget->addItem("没有找到相关内容");
    QFile file("my.xml");
    if(!file.open(QIODevice::ReadOnly)) return ;
    QDomDocument doc;
    if(!doc.setContent(&file))
    {
        file.close();
        return ;
    }
    file.close();
    QDomNodeList list = doc.elementsByTagName("book");

    for (int i = 0; i < list.count(); i++)
    {
        QDomElement e = list.at(i).toElement();

        if(e.attribute("id") == ui->lineEdit->text())　　// 判断节点
        {
            if(operate == "delete")
            {
                QDomElement root = doc.documentElement();
                root.removeChild(list.at(i));

                QFile file("my.xml");
                if(!file.open(QIODevice::WriteOnly | QIODevice::Truncate)) return;
                QTextStream out(&file);
                doc.save(out, 4);
                file.close();

                ui->listWidget->clear();
                ui->listWidget->addItem("删除成功~");
            }
            else if(operate == "update")　　// 更新节点内容
            {
                QDomNodeList child = list.at(i).childNodes();
                child.at(0).toElement().firstChild().setNodeValue(
                            ui->lineEdit_2->text());
                child.at(1).toElement().firstChild().setNodeValue(
                            ui->lineEdit_3->text());

                QFile file("my.xml");
                if(!file.open(QIODevice::WriteOnly | QIODevice::Truncate)) return;
                QTextStream out(&file);
                doc.save(out, 4);
                file.close();

                ui->listWidget->clear();
                ui->listWidget->addItem("更新成功~");
            }
            else if(operate == "find")
            {
                ui->listWidget->clear();

                ui->listWidget->addItem(e.tagName() + e.attribute("id"));
                QDomNodeList list = e.childNodes();
                for(int i = 0; i< list.count(); i++)
                {
                    QDomNode node = list.at(i);
                    if(node.isElement())
                        ui->listWidget->addItem("    " + node.toElement().tagName()
                                                + " : " + node.toElement().text());
                }
            }
        }
    }
}


void MainWindow::on_showBtn_clicked()
{
    ui->listWidget->clear();

    QFile file("my.xml");
    if(!file.open(QIODevice::ReadOnly)) return ;
    QDomDocument doc;
    if(!doc.setContent(&file))
    {
        file.close();
        return ;
    }
    file.close();
    QDomElement docElem = doc.documentElement();
    ui->listWidget->addItem(docElem.tagName());
    QDomNode n = docElem.firstChild();
    while (!n.isNull())
    {
        if(n.isElement())
        {
            QDomElement e = n.toElement();
            ui->listWidget->addItem("    " + e.tagName() + e.attribute("id"));
            QDomNodeList list = e.childNodes();
            for(int i = 0; i< list.count(); i++)
            {
                QDomNode node = list.at(i);
                if(node.isElement())
                    ui->listWidget->addItem("        " + node.toElement().tagName()
                                            + " : " + node.toElement().text());
            }
        }
        n = n.nextSibling();
    }
}

void MainWindow::on_addBtn_clicked()
{
    ui->listWidget->clear();
    ui->listWidget->addItem("无法添加...");
    QFile file("my.xml");
    if(!file.open(QIODevice::ReadOnly)) return ;
    QDomDocument doc;
    if(!doc.setContent(&file))
    {
        file.close();
        return ;
    }
    file.close();

    QDomElement root = doc.documentElement();
    QDomElement book = doc.createElement("book");
    QDomAttr id = doc.createAttribute("id");
    QDomElement title = doc.createElement("name");
    QDomElement author = doc.createElement("author");

    QDomText text;
    QString num = root.lastChild().toElement().attribute("id");
    int count = num.toInt() + 1;
    id.setValue(QString::number(count));
    book.setAttributeNode(id);

    text = doc.createTextNode(ui->lineEdit_2->text());
    title.appendChild(text);

    text = doc.createTextNode(ui->lineEdit_3->text());
    author.appendChild(text);

    book.appendChild(title);
    book.appendChild(author);
    root.appendChild(book);

    if(!file.open(QIODevice::WriteOnly | QIODevice::Truncate)) return;
    QTextStream out(&file);
    doc.save(out, 4);
    file.close();

    ui->listWidget->clear();
    ui->listWidget->addItem("添加成功~");
}

void MainWindow::on_deleteBtn_clicked()
{
    doXml("delete");
}

void MainWindow::on_updateBtn_clicked()
{
    doXml("update");
}

void MainWindow::on_findBtn_clicked()
{
    doXml("find");
}