javascript side lose qt object when refresh or open new page

Can reproduce by following steps:

1： load qwebchannel.js into web page.
2： then add these JavaScript code into web page:

 new QWebChannel(qt.webChannelTransport, function(channel) {  etc..  }); 

3. add c++ code into webpage constructor (webpage derived from QWebEnginePage) ：

QWebChannel *channel = new QWebChannel(this);
    channel->registerObject(QStringLiteral("WebExtensionWin10"), &m_content);
    setWebChannel(channel);
    

It's work fine when first load web page. The developer tools display "qt is not defined(…)" when reload page or open newpage. so in the case we cannot access c++ object.