1、Qt: QXMLStreamReader,读XML文件实例

效果图：

需求：

打开对应格式的XML文件，读入到QTreewidget树中，并能将XML文件另存为，写入到磁盘。

源码：

main.cpp

#include "mainwindow.h"
#include <QApplication>

int main(int argc,char *argv[])
{
    QApplication a(argc,argv);

    MainWindow w;
    w.show();

    return a.exec();
}

XbelReader.h

#ifndef XBELREADER_H
#define XBELREADER_H

#include <QIcon>
#include <QXmlStreamReader>
#include <QTreeWidget>
#include <QTreeWidgetItem>
#include <QIcon>

class XbelReader
{
public:
    XbelReader(QTreeWidget *tree);
    bool read(QIODevice *device);
    QString errorString()const;

private:
    void readXBEL();
    void readTitle(QTreeWidgetItem *item);
    void readSeparator(QTreeWidgetItem *item);
    void readFolder(QTreeWidgetItem *item);
    void readBookmark(QTreeWidgetItem *item);

    QTreeWidgetItem *createChildItem(QTreeWidgetItem *item);

private:
    QXmlStreamReader xml;
    QTreeWidget *treeWidget;

    QIcon folderIcon;
    QIcon bookmarkIcon;
};

#endif // XBELREADER_H

XbelReader.cpp

#include <QStyle>
#include <QDebug>
#include "xbelreader.h"

XbelReader::XbelReader(QTreeWidget *tree)
{
    treeWidget = tree;
    QStyle *style = treeWidget->style();

    folderIcon.addPixmap(style->standardPixmap(QStyle::SP_DirClosedIcon),QIcon::Normal,QIcon::Off);
    folderIcon.addPixmap(style->standardPixmap(QStyle::SP_DirOpenIcon),QIcon::On);
    bookmarkIcon.addPixmap(style->standardPixmap(QStyle::SP_FileIcon));
}

bool XbelReader::read(QIODevice *device)
{
    xml.setDevice(device);

    if (xml.readNextStartElement())  //
    {
        if (xml.name() == "xbel" && xml.attributes().value("version") == "1.0")
            readXBEL();
        else
            xml.raiseError(QObject::tr("The file is not an XBEL version 1.0 file."));
    }

    return !xml.error(); //非运算，有错返回0，无错返回1
}

QString XbelReader::errorString() const
{
    return QObject::tr("%1\nLine %2,column %3")
            .arg(xml.errorString())
            .arg(xml.lineNumber())
            .arg(xml.columnNumber());
}

void XbelReader::readXBEL()
{
    Q_ASSERT(xml.isStartElement() && xml.name() == "xbel");

    while (xml.readNextStartElement())
    {
        if (xml.name() == "folder")
            readFolder(0);
        else if (xml.name() == "bookmark")
            readBookmark(0);
        else if (xml.name() == "separator")
            readSeparator(0);
        else
            xml.skipCurrentElement();
    }
}

void XbelReader::readTitle(QTreeWidgetItem *item)
{
    Q_ASSERT(xml.isStartElement() && xml.name() == "title");

    QString title = xml.readElementText();
    item->setText(0,title);
}

void XbelReader::readSeparator(QTreeWidgetItem *item)
{
    Q_ASSERT(xml.isStartElement() && xml.name() == "separator");

    QTreeWidgetItem *separator = createChildItem(item);
    separator->setFlags(item->flags() & ~Qt::ItemIsSelectable);
    separator->setText(0,QString(30,0xB7));
    xml.skipCurrentElement();
}

void XbelReader::readFolder(QTreeWidgetItem *item)
{
    Q_ASSERT(xml.isStartElement() && xml.name() == "folder");

    QTreeWidgetItem *folder = createChildItem(item);
    bool folded = (xml.attributes().value("folded") != "no");
    treeWidget->setItemExpanded(folder,!folded);

    while (xml.readNextStartElement())
    {
        if (xml.name() == "title")
            readTitle(folder);
        else if (xml.name() == "folder")
            readFolder(folder);
        else if (xml.name() == "bookmark")
            readBookmark(folder);
        else if (xml.name() == "separator")
            readSeparator(folder);
        else
            xml.skipCurrentElement();
    }
}

void XbelReader::readBookmark(QTreeWidgetItem *item)
{
    Q_ASSERT(xml.isStartElement() && xml.name() == "bookmark");

    QTreeWidgetItem *bookmark = createChildItem(item);
    bookmark->setFlags(bookmark->flags() | Qt::ItemIsEditable);
    bookmark->setIcon(0,bookmarkIcon);
    bookmark->setText(0,QObject::tr("Unknown title"));
    bookmark->setText(1,xml.attributes().value("href").toString());

    while(xml.readNextStartElement())
    {
        if(xml.name() == "title")
            readTitle(bookmark);
        else
            xml.skipCurrentElement();
    }
}

QTreeWidgetItem *XbelReader::createChildItem(QTreeWidgetItem *item)
{
    QTreeWidgetItem *childItem;
    if (item)
    {
        childItem = new QTreeWidgetItem(item);
    }
    else
    {
        childItem = new QTreeWidgetItem(treeWidget);
    }
    childItem->setData(0,Qt::UserRole,xml.name().toString());
    return childItem;
}

XbelWriter.h

#ifndef XBELWRITER_H
#define XBELWRITER_H

#include <QXmlStreamWriter>
#include <QTreeWidget>
#include <QTreeWidgetItem>

class XbelWriter
{
public:
    XbelWriter(QTreeWidget *tree);
    bool writeFile(QIODevice *device);

private:
    void writeItem(QTreeWidgetItem *item);
    QXmlStreamWriter xml;
    QTreeWidget *treeWidget;
};

#endif // XBELWRITER_H

XbelWriter.cpp

#include "xbelwriter.h"

XbelWriter::XbelWriter(QTreeWidget *tree)
{
    treeWidget = tree;
    xml.setAutoFormatting(true); //自动格式化文本
}

bool XbelWriter::writeFile(QIODevice *device)
{
    xml.setDevice(device);

    xml.writeStartDocument();
    xml.writeDTD("<!DOCTYPE xbel>");
    xml.writeStartElement("xbel");
    xml.writeAttribute("version","1.0");
    for(int i=0 ; i < treeWidget->topLevelItemCount() ; ++i)
        writeItem(treeWidget->topLevelItem(i));

    xml.writeEndDocument();
    return true;
}

void XbelWriter::writeItem(QTreeWidgetItem *item)
{
    QString tagName = item->data(0,Qt::UserRole).toString();
    if(tagName == "folder")
    {
        bool folded = !treeWidget->isItemExpanded(item);
        xml.writeStartElement(tagName);
        xml.writeAttribute("folded",folded ? "yes" : "no");//三目运算
        xml.writeTextElement("title",item->text(0));
        for(int i=0 ; i<item->childCount() ; ++i)
            writeItem(item->child(i));
        xml.writeEndElement();
    }
    else if(tagName == "bookmark")
    {
        xml.writeStartElement(tagName);
        if(!item->text(1).isEmpty())
            xml.writeAttribute("href",item->text(1));
        xml.writeTextElement("title",item->text(0));
        xml.writeEndElement();
    }
    else if(tagName == "separator")
    {
        xml.writeEmptyElement(tagName);
    }
}