rsslisting.cpp Example File

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    /*
     rsslisting.cpp

     Provides the business logic for retrieving news items from RDF news sources.
     RDF is an XML-based format for storing items of information (see
     http://www.w3.org/RDF/ for details).

     The class downloads and parses the XML asynchronously, feeding the
     data to an XML reader in pieces. This allows the user to interrupt
     its operation, and also allows very large data sources to be read.
     */

    #include "rsslisting.hpp"

    /*
     Constructs an RSSListing object and connects the needed signals.
     */
    RSSListing::RSSListing(QObject *parent)
        : QObject(parent)
        , m_url("http://feeds.feedburner.com/blackberry/CAxx")
        , m_active(false)
        , m_currentReply(0)
    {
        // Invoke the finished() method whenever the download job has been finished
        connect(&m_manager, SIGNAL(finished(QNetworkReply*)),
                this, SLOT(finished(QNetworkReply*)));
    }

    /*
     Starts the network request and connects the needed signals
     */
    void RSSListing::get(const QUrl &url)
    {
        QNetworkRequest request(url);
        if (m_currentReply) {
            m_currentReply->disconnect(this);
            m_currentReply->deleteLater();
        }

        m_currentReply = m_manager.get(request);
        connect(m_currentReply, SIGNAL(readyRead()), this, SLOT(readyRead()));
        connect(m_currentReply, SIGNAL(metaDataChanged()), this, SLOT(metaDataChanged()));
        connect(m_currentReply, SIGNAL(error(QNetworkReply::NetworkError)),
                this, SLOT(error(QNetworkReply::NetworkError)));
    }

    /*
     Starts fetching data from a news source specified in m_url.

     The UI is made read only to prevent the user from modifying its
     contents during the fetch; this is only for cosmetic purposes.

     A URL is created with the raw contents of m_url and
     a get is initiated.
     */

    void RSSListing::fetch()
    {
        m_active = true;
        emit activeChanged();

        m_xml.clear();

        const QUrl url(m_url);
        get(url);
    }

    /*
     If we got a redirect response from the server, trigger a new download
     with the redirect URL.
     */
    void RSSListing::metaDataChanged()
    {
        const QUrl redirectionTarget = m_currentReply->attribute(QNetworkRequest::RedirectionTargetAttribute).toUrl();
        if (redirectionTarget.isValid()) {
            get(redirectionTarget);
        }
    }

    /*
     Reads data received from the RDF source.

     We read all the available data, and pass it to the XML
     stream reader.
     */

    void RSSListing::readyRead()
    {
        const int statusCode = m_currentReply->attribute(QNetworkRequest::HttpStatusCodeAttribute).toInt();
        if (statusCode >= 200 && statusCode < 300) {
            const QByteArray data = m_currentReply->readAll();
            m_xml.addData(data);
        }
    }

    /*
     Finishes processing an HTTP request.

     If an error has occurred, the user interface is made available
     to the user for further input, allowing a new fetch to be
     started.

     If the HTTP get request has finished, we make the
     user interface available to the user for further input.
     */

    void RSSListing::finished(QNetworkReply *reply)
    {
        Q_UNUSED(reply);

        parseXml();

        m_active = false;
        emit activeChanged();
    }

    void RSSListing::setUrl(const QString &url)
    {
        if (m_url == url)
            return;

        m_url = url;
        emit urlChanged();
    }

    QString RSSListing::url() const
    {
        return m_url;
    }

    QString RSSListing::feeds() const
    {
        return m_feeds;
    }

    bool RSSListing::active() const
    {
        return m_active;
    }

    /*
     Parses the XML data and fill feeds string accordingly.
     */
    void RSSListing::parseXml()
    {
        m_feeds.clear();

        QString currentTag;
        QString linkString;
        QString titleString;

        while (!m_xml.atEnd()) {
            m_xml.readNext();
            if (m_xml.isStartElement()) {
                if (m_xml.name() == "item")
                    linkString = m_xml.attributes().value("rss:about").toString();
                currentTag = m_xml.name().toString();
            } else if (m_xml.isEndElement()) {
                if (m_xml.name() == "item") {

                    m_feeds.append(QString::fromLatin1("%1\n      %2\n\n").arg(titleString, linkString));

                    titleString.clear();
                    linkString.clear();
                }

            } else if (m_xml.isCharacters() && !m_xml.isWhitespace()) {
                if (currentTag == "title")
                    titleString += m_xml.text().toString();
                else if (currentTag == "link")
                    linkString += m_xml.text().toString();
            }
        }

        if (m_xml.error() && m_xml.error() != QXmlStreamReader::PrematureEndOfDocumentError) {
            m_feeds.append(
                    QString::fromLatin1("XML ERROR: %1: %2").arg(m_xml.lineNumber()).arg(m_xml.errorString()));
        }

        emit feedsChanged();
    }

    void RSSListing::error(QNetworkReply::NetworkError)
    {
        m_feeds = QLatin1String("error retrieving RSS feed");
        emit feedsChanged();

        m_currentReply->disconnect(this);
        m_currentReply->deleteLater();
        m_currentReply = 0;
    }