259 lines
8.3 KiB
C++
259 lines
8.3 KiB
C++
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/****************************************************************************
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**
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** Copyright (C) 2016 The Qt Company Ltd.
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** Contact: https://www.qt.io/licensing/
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**
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** This file is part of the examples of the Qt Toolkit.
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**
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** $QT_BEGIN_LICENSE:BSD$
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** Commercial License Usage
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** Licensees holding valid commercial Qt licenses may use this file in
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** accordance with the commercial license agreement provided with the
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** Software or, alternatively, in accordance with the terms contained in
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** a written agreement between you and The Qt Company. For licensing terms
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** and conditions see https://www.qt.io/terms-conditions. For further
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** information use the contact form at https://www.qt.io/contact-us.
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**
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** BSD License Usage
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** Alternatively, you may use this file under the terms of the BSD license
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** as follows:
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**
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** "Redistribution and use in source and binary forms, with or without
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** modification, are permitted provided that the following conditions are
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** met:
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** * Redistributions of source code must retain the above copyright
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** notice, this list of conditions and the following disclaimer.
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** * Redistributions in binary form must reproduce the above copyright
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** notice, this list of conditions and the following disclaimer in
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** the documentation and/or other materials provided with the
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** distribution.
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** * Neither the name of The Qt Company Ltd nor the names of its
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** contributors may be used to endorse or promote products derived
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** from this software without specific prior written permission.
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**
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**
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** THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
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** "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
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** LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
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** A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
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** OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
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** SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
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** LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
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** DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
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** THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
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** (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
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** OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE."
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**
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** $QT_END_LICENSE$
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**
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****************************************************************************/
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/*
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rsslisting.cpp
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Provides a widget for displaying news items from RDF news sources.
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RDF is an XML-based format for storing items of information (see
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http://www.w3.org/RDF/ for details).
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The widget itself provides a simple user interface for specifying
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the URL of a news source, and controlling the downloading of news.
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The widget downloads and parses the XML asynchronously, feeding the
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data to an XML reader in pieces. This allows the user to interrupt
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its operation, and also allows very large data sources to be read.
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*/
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#include <QtCore>
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#include <QtWidgets>
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#include <QtNetwork>
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#include "rsslisting.h"
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/*
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Constructs an RSSListing widget with a simple user interface, and sets
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up the XML reader to use a custom handler class.
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The user interface consists of a line edit, a push button, and a
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list view widget. The line edit is used for entering the URLs of news
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sources; the push button starts the process of reading the
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news.
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*/
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RSSListing::RSSListing(QWidget *parent)
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: QWidget(parent), currentReply(0)
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{
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lineEdit = new QLineEdit(this);
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lineEdit->setText("http://blog.qt.io/feed/");
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fetchButton = new QPushButton(tr("Fetch"), this);
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treeWidget = new QTreeWidget(this);
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connect(treeWidget, SIGNAL(itemActivated(QTreeWidgetItem*,int)),
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this, SLOT(itemActivated(QTreeWidgetItem*)));
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QStringList headerLabels;
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headerLabels << tr("Title") << tr("Link");
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treeWidget->setHeaderLabels(headerLabels);
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treeWidget->header()->setSectionResizeMode(QHeaderView::ResizeToContents);
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connect(&manager, SIGNAL(finished(QNetworkReply*)),
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this, SLOT(finished(QNetworkReply*)));
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connect(lineEdit, SIGNAL(returnPressed()), this, SLOT(fetch()));
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connect(fetchButton, SIGNAL(clicked()), this, SLOT(fetch()));
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QVBoxLayout *layout = new QVBoxLayout(this);
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QHBoxLayout *hboxLayout = new QHBoxLayout;
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hboxLayout->addWidget(lineEdit);
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hboxLayout->addWidget(fetchButton);
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layout->addLayout(hboxLayout);
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layout->addWidget(treeWidget);
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setWindowTitle(tr("RSS listing example"));
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resize(640,480);
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}
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/*
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Starts the network request and connects the needed signals
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*/
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void RSSListing::get(const QUrl &url)
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{
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QNetworkRequest request(url);
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if (currentReply) {
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currentReply->disconnect(this);
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currentReply->deleteLater();
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}
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currentReply = manager.get(request);
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connect(currentReply, SIGNAL(readyRead()), this, SLOT(readyRead()));
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connect(currentReply, SIGNAL(metaDataChanged()), this, SLOT(metaDataChanged()));
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connect(currentReply, SIGNAL(errorOccurred(QNetworkReply::NetworkError)), this, SLOT(error(QNetworkReply::NetworkError)));
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}
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/*
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Starts fetching data from a news source specified in the line
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edit widget.
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The line edit is made read only to prevent the user from modifying its
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contents during the fetch; this is only for cosmetic purposes.
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The fetch button is disabled, the list view is cleared, and we
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define the last list view item to be 0, meaning that there are no
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existing items in the list.
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A URL is created with the raw contents of the line edit and
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a get is initiated.
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*/
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void RSSListing::fetch()
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{
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lineEdit->setReadOnly(true);
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fetchButton->setEnabled(false);
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treeWidget->clear();
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xml.clear();
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QUrl url(lineEdit->text());
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get(url);
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}
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void RSSListing::metaDataChanged()
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{
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QUrl redirectionTarget = currentReply->attribute(QNetworkRequest::RedirectionTargetAttribute).toUrl();
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if (redirectionTarget.isValid()) {
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get(redirectionTarget);
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}
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}
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/*
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Reads data received from the RDF source.
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We read all the available data, and pass it to the XML
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stream reader. Then we call the XML parsing function.
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*/
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void RSSListing::readyRead()
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{
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int statusCode = currentReply->attribute(QNetworkRequest::HttpStatusCodeAttribute).toInt();
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if (statusCode >= 200 && statusCode < 300) {
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QByteArray data = currentReply->readAll();
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xml.addData(data);
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parseXml();
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}
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}
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/*
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Finishes processing an HTTP request.
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The default behavior is to keep the text edit read only.
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If an error has occurred, the user interface is made available
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to the user for further input, allowing a new fetch to be
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started.
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If the HTTP get request has finished, we make the
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user interface available to the user for further input.
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*/
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void RSSListing::finished(QNetworkReply *reply)
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{
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Q_UNUSED(reply);
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lineEdit->setReadOnly(false);
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fetchButton->setEnabled(true);
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}
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/*
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Parses the XML data and creates treeWidget items accordingly.
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*/
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void RSSListing::parseXml()
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{
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while (!xml.atEnd()) {
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xml.readNext();
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if (xml.isStartElement()) {
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if (xml.name() == "item")
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linkString = xml.attributes().value("rss:about").toString();
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currentTag = xml.name().toString();
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} else if (xml.isEndElement()) {
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if (xml.name() == "item") {
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QTreeWidgetItem *item = new QTreeWidgetItem;
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item->setText(0, titleString);
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item->setText(1, linkString);
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treeWidget->addTopLevelItem(item);
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titleString.clear();
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linkString.clear();
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}
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} else if (xml.isCharacters() && !xml.isWhitespace()) {
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if (currentTag == "title")
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titleString += xml.text();
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else if (currentTag == "link")
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linkString += xml.text();
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}
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}
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if (xml.error() && xml.error() != QXmlStreamReader::PrematureEndOfDocumentError) {
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qWarning() << "XML ERROR:" << xml.lineNumber() << ": " << xml.errorString();
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}
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}
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/*
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Open the link in the browser
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*/
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void RSSListing::itemActivated(QTreeWidgetItem * item)
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{
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QDesktopServices::openUrl(QUrl(item->text(1)));
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}
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void RSSListing::error(QNetworkReply::NetworkError)
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{
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qWarning("error retrieving RSS feed");
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currentReply->disconnect(this);
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currentReply->deleteLater();
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currentReply = 0;
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}
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