'Change the page, and show the information that was stored in
self.responses
If OK, the responses are saved like this:
self.responses.append((True, http_resp.get_id()))
else:
self.responses.append((False, realreq, realbody, error_msg))
:return: None.'

def page_change(self, page):

    info = self.responses[page]
    if info[0]:
        reqid = info[1]
        try:
            historyItem = self.historyItem.read(reqid)
        except IndexError:
            error_msg = 'Error    searching    the    request    database'
            self.resultReqResp.request.show_raw(error_msg, error_msg)
            self.resultReqResp.response.show_error(error_msg)
            self.title0.set_markup('<b>Error</b>')
        else:
            self.resultReqResp.request.show_object(historyItem.request)
            self.resultReqResp.response.show_object(historyItem.response)
            self.title0.set_markup(('<b>Id:    %d</b>' % reqid))
    else:
        (realreq, realbody, error_msg) = info[1:]
        self.resultReqResp.request.show_raw(realreq, realbody)
        self.resultReqResp.response.show_error(error_msg)
        self.title0.set_markup('<b>Error</b>')
