Qt: QXMLStreamReader,读XML文件实例

主要接口：

1、TokenType QXmlStreamReader::readNext()

功能：读取下一个标记，并返回其类型。

主要的类型有：

enum QXmlStreamReader::TokenType

This enum specifies the type of token the reader just read.

Constant	Value	Description
QXmlStreamReader::NoToken	0	The reader has not yet read anything.
QXmlStreamReader::Invalid	1	An error has occurred,reported in error() and errorString().
QXmlStreamReader::StartDocument	2	The reader reports the XML version number in documentVersion(),and the encoding as specified in the XML document in documentEncoding(). If the document is declared standalone,isStandaloneDocument() returns true; otherwise it returns false.
QXmlStreamReader::EndDocument	3	The reader reports the end of the document.
QXmlStreamReader::StartElement	4	The reader reports the start of an element with namespaceUri() and name(). Empty elements are also reported as StartElement,followed directly by EndElement. The convenience function readElementText() can be called to concatenate all content until the corresponding EndElement. Attributes are reported in attributes(),namespace declarations in namespaceDeclarations().
QXmlStreamReader::EndElement	5	The reader reports the end of an element with namespaceUri() and name().
QXmlStreamReader::Characters	6	The reader reports characters in text(). If the characters are all white-space,isWhitespace() returns true. If the characters stem from a CDATA section,isCDATA() returns true.
QXmlStreamReader::Comment	7	The reader reports a comment in text().
QXmlStreamReader::DTD	8	The reader reports a DTD in text(),notation declarations in notationDeclarations(),and entity declarations in entityDeclarations(). Details of the DTD declaration are reported in in dtdName(),dtdPublicId(),and dtdSystemId().
QXmlStreamReader::EntityReference	9	The reader reports an entity reference that could not be resolved. The name of the reference is reported in name(),the replacement text in text().
QXmlStreamReader::ProcessingInstruction	10	The reader reports a processing instruction in processingInstructionTarget() and processingInstructionData().

2、bool QXmlStreamReader::atEnd() const

功能：判断是否已经读到XML文件的末尾，如果是，则返回true，否则返回false.

3、QXmlStreamAttributes QXmlStreamReader::attributes() const

功能：返回StartElement.的属性。

4、QStringRef QXmlStreamReader::name() const

功能：返回StartElement,EndElement的名称。

5、void QXmlStreamReader::raiseError(const QString &message = QString())

功能：提出一个错误，

需求：

使用QXMLStreamReader，读取XML文件，并使用XML文件初始化树形控件。

效果图：

源码：

main.cpp

#include <QApplication>
#include <QTreeWidget>
#include <QLabel>
#include <QHeaderView>
#include <QObject>
#include "xmlstreamreader.h"

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

    QTreeWidget *tree = new QTreeWidget;
    tree->setHeaderLabels( QStringList()<<"Term"<<"Pages"<<"Description" );
    tree->header()->setSectionResizeMode(QHeaderView::Stretch);
    tree->setWindowTitle(QObject::tr("XML Reader"));
    tree->show();

    QString fileName("in1.xml");
    XMLStreamReader w(tree);
    w.readFile(fileName);

    return a.exec();
}

XMLStreamReader.h

#ifndef XMLSTREAMREADER_H
#define XMLSTREAMREADER_H

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

class XMLStreamReader
{

public:
    XMLStreamReader(QTreeWidget *tree);
    ~XMLStreamReader();
    bool readFile(const QString &fileName);

private:
    void readBookindexElement();
    void readEntryElement(QTreeWidgetItem *parent);
    void readPageElement(QTreeWidgetItem *parent);
    void skipUnknownElement();

    QTreeWidget *treeWidget;
    QXmlStreamReader reader;
};

#endif // XMLSTREAMREADER_H

XMLStreamReader.cpp

#include <QFile>
#include <QDebug>
#include "xmlstreamreader.h"

XMLStreamReader::XMLStreamReader(QTreeWidget *tree)
{
    treeWidget = tree;
}

XMLStreamReader::~XMLStreamReader()
{
    delete treeWidget;
}

bool XMLStreamReader::readFile(const QString &fileName)
{
    QFile file(fileName);
    if(!file.open(QFile::ReadOnly | QFile::Text))
    {
        qDebug()<<"Open XML file Error";
        return false;
    }

    reader.setDevice(&file);
    while(!reader.atEnd())
    {
        if(reader.isStartElement())
        {
            if(reader.name() == "bookindex")
            {
                readBookindexElement();
            }
            else
            {
                Q_ASSERT(reader.isStartElement() && (reader.name() == "bookindex")); //断言
                reader.raiseError(QObject::tr("Not a BookIndex file"));
            }
        }
        else
        {
            reader.readNext();
        }
    }

    file.close();
    if(reader.hasError())
    {
        qDebug()<<reader.errorString();
        return false;
    }
    else if(file.error() != QFile::NoError)
    {
        qDebug()<<file.errorString();
        return false;
    }

    return true;
}

void XMLStreamReader::readBookindexElement()
{
    reader.readNext();
    while(!reader.atEnd())
    {
        if(reader.isEndElement())
        {
            reader.readNext();
            break;
        }

        if(reader.isStartElement())
        {
            if(reader.name() == "entry")
            {
                readEntryElement(treeWidget->invisibleRootItem());
            }
            else
            {
                skipUnknownElement();
            }
        }
        else
        {
            reader.readNext();
        }
    }
}

void XMLStreamReader::readEntryElement(QTreeWidgetItem *parent)
{
    QTreeWidgetItem *item = new QTreeWidgetItem(parent);
    item->setText(0,reader.attributes().value("term").toString());
    item->setText(2,reader.attributes().value("description").toString());
    reader.readNext();
    while(!reader.atEnd())
    {
        if(reader.isEndElement())
        {
            reader.readNext();
            break;
        }

        if(reader.isStartElement())
        {
            if(reader.name() == "entry")
            {
                readEntryElement(item);
            }
            else if(reader.name() == "page")
            {
                readPageElement(item);
            }
        }
        else
        {
            reader.readNext();
        }
    }
}

void XMLStreamReader::readPageElement(QTreeWidgetItem *parent)
{
    QString page = reader.readElementText();
    if(reader.isEndElement())
        reader.readNext();

    QString allPages = parent->text(1);
    if(!allPages.isEmpty())
        allPages +=",";
    allPages += page;
    parent->setText(1,allPages);
}

void XMLStreamReader::skipUnknownElement()
{
    reader.readNext();
    while(!reader.atEnd())
    {
        if(reader.isEndElement())
        {
            reader.readNext();
            break;
        }

        if(reader.isStartElement())
        {
            skipUnknownElement();
        }
        else
        {
            reader.readNext();
        }
    }
}