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POReceiving multiple loadFinished signals for a requested web page
 

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  1. POReceiving multiple loadFinished signals for a requested web page
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    <p>I'm receiving multiple <code>loadFinished</code> signals when I attempt to load a <code>QWebPage</code> and I'm not sure what's causing the issue. There were a couple of other questions that seemed to allude to the same problem, but the solutions didn't work for me:</p> <ul> <li><a href="https://stackoverflow.com/questions/9966433/qtwebpage-loadfinished-called-multiple-times">QtWebPage - loadFinished() called multiple times</a></li> <li><a href="https://stackoverflow.com/questions/8415289/signal-qwebpageloadfinishedbool-returns-twice">Signal QWebPage::loadFinished(bool) returns twice?</a> </li> </ul> <p>In the first question, the answer was to connect signals to slots only once," but I already do that. The answer to the second question suggests that I should connect to the frame's <code>loadFinished</code> signal, but I simply don't get the necessary data when that is done.</p> <p>I attempt to load multiple pages:</p> <pre><code>int main(int argc, char *argv[]) { QApplication app(argc, argv); QList&lt;QUrl&gt; urls; urls.append(QUrl("http://www.useragentstring.com/pages/Chrome/")); urls.append(QUrl("http://www.useragentstring.com/pages/Firefox/")); urls.append(QUrl("http://www.useragentstring.com/pages/Opera/")); urls.append(QUrl("http://www.useragentstring.com/pages/Internet Explorer/")); urls.append(QUrl("http://www.useragentstring.com/pages/Safari/")); foreach(QUrl url, urls) { UA* ua = new UA(); QWebPage* page = new QWebPage(); //QObject::connect(page, SIGNAL(loadFinished(bool)), ua, SLOT(pageLoadFinished(bool))); QObject::connect(page-&gt;mainFrame(), SIGNAL(loadFinished(bool)), ua, SLOT(frameLoadFinished(bool))); // Load the page page-&gt;mainFrame()-&gt;load(url); } return app.exec(); } </code></pre> <p>The class that processes the signals looks like this:</p> <pre><code>class UA:public QObject { Q_OBJECT private: int _numPageLoadSignals; int _numFrameLoadSignals public: UA() { _numPageLoadSignals = 0; _numFrameLoadSignals = 0; } ~UA(){} public slots: void pageLoadFinished(bool ok) { _numPageLoadSignals++; QWebPage * page = qobject_cast&lt;QWebPage *&gt;(sender()); if(ok &amp;&amp; page) { qDebug() &lt;&lt; _numPageLoadSignals &lt;&lt; " loads " &lt;&lt; page-&gt;mainFrame()-&gt;documentElement().findAll("div#liste ul li a").count() &lt;&lt; " elements found on: " &lt;&lt; page-&gt;mainFrame()-&gt;requestedUrl().toString(); } } void frameLoadFinished(bool ok) { _numFrameLoadSignals++; QWebFrame * frame = qobject_cast&lt;QWebFrame *&gt;(sender()); if(ok &amp;&amp; frame) { qDebug() &lt;&lt; _numFrameLoadSignals &lt;&lt; " loads " &lt;&lt; frame-&gt;documentElement().findAll("div#liste ul li a").count() &lt;&lt; " elements found on: " &lt;&lt; frame-&gt;requestedUrl().toString(); } } }; </code></pre> <p>Here is the result of only connecting to the frame's <code>loadFinished</code> signal:</p> <pre><code>1 loads 0 elements found on: "http://www.useragentstring.com/pages/Safari/" 1 loads 0 elements found on: "http://www.useragentstring.com/pages/Chrome/" 1 loads 0 elements found on: "http://www.useragentstring.com/pages/Opera/" 1 loads 0 elements found on: "http://www.useragentstring.com/pages/Firefox/" 1 loads 241 elements found on: "http://www.useragentstring.com/pages/Internet Explorer/" </code></pre> <p>Here are the results when I connect to the page's <code>loadFinished</code> signal:</p> <pre><code>1 loads 0 elements found on: "http://www.useragentstring.com/pages/Safari/" 1 loads 0 elements found on: "http://www.useragentstring.com/pages/Chrome/" 1 loads 0 elements found on: "http://www.useragentstring.com/pages/Firefox/" 1 loads 0 elements found on: "http://www.useragentstring.com/pages/Internet Explorer/" 2 loads 576 elements found on: "http://www.useragentstring.com/pages/Safari/" 2 loads 782 elements found on: "http://www.useragentstring.com/pages/Chrome/" 2 loads 241 elements found on: "http://www.useragentstring.com/pages/Internet Explorer/" 2 loads 1946 elements found on: "http://www.useragentstring.com/pages/Firefox/" 3 loads 241 elements found on: "http://www.useragentstring.com/pages/Internet Explorer/" 3 loads 1946 elements found on: "http://www.useragentstring.com/pages/Firefox/" 3 loads 782 elements found on: "http://www.useragentstring.com/pages/Chrome/" 1 loads 964 elements found on: "http://www.useragentstring.com/pages/Opera/" 3 loads 576 elements found on: "http://www.useragentstring.com/pages/Safari/" </code></pre> <p>I don't understand the behavior, why sometimes I get relevant content and other times I don't. If I connect to the page's <code>loadFinished</code> signal, then I will eventually get the content but I don't know when it will actually happen. <strong>How do I know when my page has actually finished loading?</strong></p> <h2>Update</h2> <p>I'm assuming that most of my content will arrive in less than 3 seconds, so I've come up with a workaround: I set a timer event to signal the <code>UA::loadFinished</code> 3 seconds after the first <code>loadFinished</code> signal is received from the <code>QWebPage</code>. That's not very pretty, nor is it efficient, but it works for this situation.</p>
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