Redirecting JavaScript console messages in a Qt hybrid application

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Article

Created: isalento (25 Nov 2010)

Last edited: hamishwillee (11 Oct 2012)

Overview

One of the first things that you encounter when creating a hybrid application on top of QtWebKit is lack of JavaScript debug information. While it is easy to use Web Inspector to debug applications, on some occasions it is enough to get debug messages from the hybrid application for later inspection. This article shows how to redirect JavaScript console messages into a file or your own message handler.

Redirecting JavaScript console messages can be easily done by sub classing QWebPage and overriding virtual function called javaScriptConsoleMessage(). Writing to file can be omitted, if you have already implemented your own message handler that redirects qDebug –messages into a file

mypage.h

#ifndef MYPAGE_H
#define MYPAGE_H
#include <QObject>
#include <QWebPage>
 
class MyPage : public QWebPage
{
    Q_OBJECT
public:
    MyPage(QObject * parent = 0 );
protected:
    void javaScriptConsoleMessage(const QString& message, int lineNumber, const QString& sourceID);
};
#endif // MYPAGE_H

mypage.cpp

#include "mypage.h"
 
#include <QDebug>
#include <QFile>00
#include <QTextStream>
 
MyPage::MyPage(QObject *parent): QWebPage(parent){
}
 
void MyPage::javaScriptConsoleMessage(const QString& message, int lineNumber, const QString& sourceID){
   QString logEntry = message +" on line:"+ QString::number(lineNumber) +" Source:"+ sourceID;
   qDebug()<<logEntry;
 
   /** can be omitted */
   QFile file("C:\\Data\\debug.txt");
   if (!file.open(QIODevice::WriteOnly | QIODevice::Append | QIODevice::Text))
       return;
   QTextStream out(&file);
   out << logEntry  << endl;
}

After you have finished creating your own subclass of QWebPage, you still need to set it as active page on your QWebView.

MyPage page = new MyPage();
this->webView->setPage(page);