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| |
| /* |
| rsslisting.cpp |
| |
| Provides a widget for displaying 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 widget itself provides a simple user interface for specifying |
| the URL of a news source, and controlling the downloading of news. |
| |
| The widget 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 <QtCore> |
| #include <QtWidgets> |
| #include <QtNetwork> |
| |
| #include "rsslisting.h" |
| |
| |
| /* |
| Constructs an RSSListing widget with a simple user interface, and sets |
| up the XML reader to use a custom handler class. |
| |
| The user interface consists of a line edit, a push button, and a |
| list view widget. The line edit is used for entering the URLs of news |
| sources; the push button starts the process of reading the |
| news. |
| */ |
| |
| RSSListing::RSSListing(QWidget *parent) |
| : QWidget(parent), currentReply(0) |
| { |
| |
| lineEdit = new QLineEdit(this); |
| lineEdit->setText("http://blog.qt.io/feed/"); |
| |
| fetchButton = new QPushButton(tr("Fetch"), this); |
| |
| treeWidget = new QTreeWidget(this); |
| connect(treeWidget, SIGNAL(itemActivated(QTreeWidgetItem*,int)), |
| this, SLOT(itemActivated(QTreeWidgetItem*))); |
| QStringList headerLabels; |
| headerLabels << tr("Title") << tr("Link"); |
| treeWidget->setHeaderLabels(headerLabels); |
| treeWidget->header()->setSectionResizeMode(QHeaderView::ResizeToContents); |
| |
| connect(&manager, SIGNAL(finished(QNetworkReply*)), |
| this, SLOT(finished(QNetworkReply*))); |
| |
| connect(lineEdit, SIGNAL(returnPressed()), this, SLOT(fetch())); |
| connect(fetchButton, SIGNAL(clicked()), this, SLOT(fetch())); |
| |
| QVBoxLayout *layout = new QVBoxLayout(this); |
| |
| QHBoxLayout *hboxLayout = new QHBoxLayout; |
| |
| hboxLayout->addWidget(lineEdit); |
| hboxLayout->addWidget(fetchButton); |
| |
| layout->addLayout(hboxLayout); |
| layout->addWidget(treeWidget); |
| |
| setWindowTitle(tr("RSS listing example")); |
| resize(640,480); |
| } |
| |
| /* |
| Starts the network request and connects the needed signals |
| */ |
| void RSSListing::get(const QUrl &url) |
| { |
| QNetworkRequest request(url); |
| if (currentReply) { |
| currentReply->disconnect(this); |
| currentReply->deleteLater(); |
| } |
| currentReply = manager.get(request); |
| connect(currentReply, SIGNAL(readyRead()), this, SLOT(readyRead())); |
| connect(currentReply, SIGNAL(metaDataChanged()), this, SLOT(metaDataChanged())); |
| connect(currentReply, SIGNAL(error(QNetworkReply::NetworkError)), this, SLOT(error(QNetworkReply::NetworkError))); |
| } |
| |
| /* |
| Starts fetching data from a news source specified in the line |
| edit widget. |
| |
| The line edit is made read only to prevent the user from modifying its |
| contents during the fetch; this is only for cosmetic purposes. |
| The fetch button is disabled, the list view is cleared, and we |
| define the last list view item to be 0, meaning that there are no |
| existing items in the list. |
| |
| A URL is created with the raw contents of the line edit and |
| a get is initiated. |
| */ |
| |
| void RSSListing::fetch() |
| { |
| lineEdit->setReadOnly(true); |
| fetchButton->setEnabled(false); |
| treeWidget->clear(); |
| |
| xml.clear(); |
| |
| QUrl url(lineEdit->text()); |
| get(url); |
| } |
| |
| void RSSListing::metaDataChanged() |
| { |
| QUrl redirectionTarget = 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. Then we call the XML parsing function. |
| */ |
| |
| void RSSListing::readyRead() |
| { |
| int statusCode = currentReply->attribute(QNetworkRequest::HttpStatusCodeAttribute).toInt(); |
| if (statusCode >= 200 && statusCode < 300) { |
| QByteArray data = currentReply->readAll(); |
| xml.addData(data); |
| parseXml(); |
| } |
| } |
| |
| /* |
| Finishes processing an HTTP request. |
| |
| The default behavior is to keep the text edit read only. |
| |
| 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); |
| lineEdit->setReadOnly(false); |
| fetchButton->setEnabled(true); |
| } |
| |
| |
| /* |
| Parses the XML data and creates treeWidget items accordingly. |
| */ |
| void RSSListing::parseXml() |
| { |
| while (!xml.atEnd()) { |
| xml.readNext(); |
| if (xml.isStartElement()) { |
| if (xml.name() == "item") |
| linkString = xml.attributes().value("rss:about").toString(); |
| currentTag = xml.name().toString(); |
| } else if (xml.isEndElement()) { |
| if (xml.name() == "item") { |
| |
| QTreeWidgetItem *item = new QTreeWidgetItem; |
| item->setText(0, titleString); |
| item->setText(1, linkString); |
| treeWidget->addTopLevelItem(item); |
| |
| titleString.clear(); |
| linkString.clear(); |
| } |
| |
| } else if (xml.isCharacters() && !xml.isWhitespace()) { |
| if (currentTag == "title") |
| titleString += xml.text(); |
| else if (currentTag == "link") |
| linkString += xml.text(); |
| } |
| } |
| if (xml.error() && xml.error() != QXmlStreamReader::PrematureEndOfDocumentError) { |
| qWarning() << "XML ERROR:" << xml.lineNumber() << ": " << xml.errorString(); |
| } |
| } |
| |
| /* |
| Open the link in the browser |
| */ |
| void RSSListing::itemActivated(QTreeWidgetItem * item) |
| { |
| QDesktopServices::openUrl(QUrl(item->text(1))); |
| } |
| |
| void RSSListing::error(QNetworkReply::NetworkError) |
| { |
| qWarning("error retrieving RSS feed"); |
| currentReply->disconnect(this); |
| currentReply->deleteLater(); |
| currentReply = 0; |
| } |