[webkit-qt] problem when using QtWebKit to get elements from page

Mon Sep 27 20:04:06 PDT 2010

Hi Qichao. Let me try to explain the problem.

void View::loadFinished(bool ok)

{

    Q_UNUSED(ok);

    QWebFrame *frame = page()->mainFrame();

    QWebElement element = frame->findFirstElement("div");

    qDebug() << frame->toHtml();

    QWebView webView;

    webView.setUrl(QUrl("http://www.google.com"));

    qDebug() << webView.page()->mainFrame()->toHtml();

}

You have two QWebViews here. One that is the current "this" element (we'll call that one A) and one that you instantiate inline with the variable you call webView (we'll call that one B). You've reached this signal once (A) was loaded, and then you try to load a URL into (B). The difference is that you access the HTML of (A) after it's already loaded, but you access the HTML of (B) before it's fully loaded. You can't expect google.com to be loaded from the network immediately after you request for it, networks still take some time - and this is an asynchronous API. :)

If you want this to work, you should keep a live pointer to your webView (B), and connect its loadFinished signal to another slot, instead of calling webView.page()->mainFrame()->toHtml() synchronously after setting the URL.

If you have questions, please reply to the list and not to me directly, there might be others interested in your question :)
Regards
No'am

From: webkit-qt-bounces at lists.webkit.org [mailto:webkit-qt-bounces at lists.webkit.org] On Behalf Of ext qichao zhu
Sent: Monday, September 27, 2010 7:32 PM
To: webkit-qt at lists.webkit.org
Subject: [webkit-qt] problem when using QtWebKit to get elements from page

Hi all,
I am using Qt SDK by Nokia v2010.04 (open source). I want to get webelement from page through webkit component but the result confuses me.

If using code like this:

main.h

#ifndef MAIN_H

#define MAIN_H

#include <QtGui>

#include <QtWebKit>

class View : public QWebView

{

    Q_OBJECT

public:

    View(QWidget *parent = 0);

private slots:

    void loadFinished(bool ok);

};

#endif // MAIN_H

main.cpp

#include "main.h"

View::View(QWidget *parent) : QWebView(parent)

{

    setUrl(QUrl("http://www.google.com"));

    connect(this, SIGNAL(loadFinished(bool)), SLOT(loadFinished(bool)));

}

void View::loadFinished(bool ok)

{

    Q_UNUSED(ok);

    QWebFrame *frame = page()->mainFrame();

    QWebElement element = frame->findFirstElement("div");

    qDebug() << element.toPlainText();

}

int main(int argc, char *argv[])

{

    QApplication app(argc, argv);

    View view;

    view.show();

    return app.exec();

}

The debug output will print out some html. But if I change main.cpp code as follow:

#include "main.h"

View::View(QWidget *parent) : QWebView(parent)

{

    setUrl(QUrl("http://www.google.com"));

    connect(this, SIGNAL(loadFinished(bool)), SLOT(loadFinished(bool)));

}

void View::loadFinished(bool ok)

{

    Q_UNUSED(ok);

    QWebFrame *frame = page()->mainFrame();

    QWebElement element = frame->findFirstElement("div");

    qDebug() << frame->toHtml();

    QWebView webView;

    webView.setUrl(QUrl("http://www.google.com"));

    qDebug() << webView.page()->mainFrame()->toHtml();

}

int main(int argc, char *argv[])

{

    QApplication app(argc, argv);

    View view;

    view.show();

    return app.exec();

}

The second debug output is "<html><head></head><body></body></html>". Why can't I just create a simple QWebView instance for retrieving elements? I have created a post on forum Nokia for this issue (http://discussion.forum.nokia.com/forum/showthread.php?210271-webelement-can-t-be-retrieved-in-Simple-Selector-Example&p=779849#post779849). Thanks.

regards,

qichao

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