QT QXmlStreamReader流处理解析XML

来源https://www.devbean.net/2013/07/qt-study-road-2-read-xml-with-stream/
建立XML文档

<bookindex>    <entry term="sidebearings">        <page>10</page>        <page>34-35</page>        <page>307-308</page>    </entry>    <entry term="subtraction">        <entry term="of pictures">            <page>115</page>            <page>244</page>        </entry>        <entry term="of vectors">            <page>9</page>        </entry>    </entry></bookindex>

在Pro文件中声明XML

QT       += core gui xml

头文件

public:    MainWindow(QWidget *parent = 0);    ~MainWindow();    //读取file    bool readFile(const QString &fileName);private:    //读取截点    //父节点    //子节点(QTreeWidgetItem *parent)    //读取bookindex节点    void readBookindexElement();    //读取entry节点    void readEntryElement(QTreeWidgetItem *parent);    //读取page节点    void readPageElement(QTreeWidgetItem *parent);    //无关节点跳过    void skipUnknownElement();    QTreeWidget *treeWidget;    QXmlStreamReader reader;

方法依次为：
1.读取文件
2.读取父节点bookindex
3.读取子节点entry（接受传过来的父节点 bookindex）
4.读取子节点page（接受传过来的父节点 entry）
5.跳过无关节点
读取文件:

bool MainWindow::readFile(const QString &fileName){    QFile file(fileName);    if(!file.open(QFile::ReadOnly | QFile::Text)){        QMessageBox::information(this,tr("open error"),tr("connot read file %1").arg(fileName));        qDebug()<<"error";        return false;    }    qDebug()<<QDir::currentPath();    //将file设置为QXmlStreamReader的设备(Stream从file中读取内容)    //Sets the current device to device.    //Setting the device resets the stream to its initial state.    reader.setDevice(&file);    //判断文件是否读到末尾    while(!reader.atEnd()){        //判断是否是开始元素        if(reader.isStartElement()){            //判断读取的根标签是否是bookindex            if(reader.name() == "bookindex"){                //是bookindex 往下读取                readBookindexElement();            }else {                reader.raiseError(tr("Not a valid book file"));            }        }else {            reader.readNext();        }    }    //文件记得关闭    file.close();    if(reader.hasError()){        QMessageBox::information(this,tr("Error"),tr("Filed to parse file %1").arg(fileName));        return false;    }else if(file.error() != QFile::NoError){        QMessageBox::information(this,tr("Error"),tr("Cannot read file %1").arg(fileName));        return false;    }    return true;}

读取bookindex节点：

void MainWindow::readBookindexElement(){    //Q_ASSERT()加断言  若进函数的时候 StartElement状态，或者说标签不是 bookindex，就认为出错    Q_ASSERT(reader.isStartElement() && reader.name()=="bookindex");    //往下读取    reader.readNext();    while (!reader.atEnd()) {        //判断是结束节点，跳出        if(reader.isEndElement()){            reader.readNext();            break;        }        if(reader.isStartElement()){            //(bookindex的子元素为entry)开始处理entry            if(reader.name() == "entry"){                //读取entry节点，(隐藏根节点)                readEntryElement(treeWidget->invisibleRootItem());            }else {                //没读到entry节点 跳过                skipUnknownElement();            }        }else {            reader.readNext();        }    }}

读取entry节点

//接受一个QTreeWidgetItem指针作为根节点.这个节点被当做这个 entry 标签在QTreeWidget中的根节点。void MainWindow::readEntryElement(QTreeWidgetItem *parent){    QTreeWidgetItem *item = new QTreeWidgetItem(parent);    //item index=0 属性为"term"的值    //QXmlStreamReader::attributes() Returns the attributes of a StartElement.    item->setText(0,reader.attributes().value("term").toString());    reader.readNext();    while (!reader.atEnd()) {        if(reader.isEndElement()){            reader.readNext();            break;        }        if(reader.isStartElement()){            //读到entry节点            if(reader.name() == "entry"){                readEntryElement(item);                //page节点            }else if(reader.name() == "page"){                readPageElement(item);            }else{                //无节点  跳过                skipUnknownElement();            }        }else {            reader.readNext();        }    }}

读取page

void MainWindow::readPageElement(QTreeWidgetItem *parent){    //获取文本    QString page = reader.readElementText();    if(reader.isEndElement()){        reader.readNext();    }    //QTreeWidgetItem::text(int column)返回指定列的text    QString allPages = parent->text(1);    if(!allPages.isEmpty()){        //用","分割        allPages += ",";    }    allPages += page;    parent->setText(1,allPages);}

无关节点跳过

void MainWindow::skipUnknownElement(){    reader.readNext();    //没有结束    while (!reader.atEnd()) {        //结束        if(reader.isEndElement()){            reader.readNext();            break;        }        //继续跳过读取。        if(reader.isStartElement()){            skipUnknownElement();        }else {            reader.readNext();        }    }}

在MainWindow函数中 声明

setWindowTitle(tr("xml reader"));    treeWidget = new QTreeWidget(this);    QStringList headers;    //设置头 Items Pages    headers<<"Items"<<"Pages";    treeWidget->setHeaderLabels(headers);    setCentralWidget(treeWidget);    //读取不到  用绝对路径读取成功  添加到资源路径读取成功    //readFile("D:/lei_project/qtproject/XMLdemo/books.xml");    readFile(":/xml/books.xml");    //readFile("books.xml")