Question

I’ m using this code in my mobile application built with phonegap and jQuery I want to show pictures from server but I couldn’t integrate showPageLoadingMsg function and I ‘m not convinced that this type of Ajax call is useful and powerful. So I want really know what type of Ajax call I should use and how to use showPageLoadingMsg() function in my Android phone application .

server = "http://monserveur.com/upload.php";
var wid = $(window).width();
    if (server) {
        var xmlhttp = new XMLHttpRequest();
        xmlhttp.onreadystatechange=function(){
            if(xmlhttp.readyState == 4){
        alert('ready');

                if (xmlhttp.status == 200  ) {
        alert('200');
                    document.getElementById('ousa').innerHTML = xmlhttp.responseText;
                }
                else {
                    document.getElementById('ousa').innerHTML = "Error retrieving pictures from server.";
                }
            }
        };
        xmlhttp.open("GET", server+"?wid="+wid, true);
        xmlhttp.send();

Answer 1

Have you tried
http://api.jquery.com/ajaxStart/

http://api.jquery.com/ajaxStop/

and couple them with a logic like found here

http://www.w3schools.com/jquery/ajax_ajaxstart.asp

$("div").ajaxStart(function(){
  $(this).html("<img src='demo_wait.gif' />");
})ajaxStop(function(){
   $(this).empty();
});

This will basically add a listener if added to a self executing function or the dom ready logic of your script this listener will wait for anything ajax related to run.

$.post()
$.get()
$.ajax()
$.getJSON()
$.postJSON()
//any I missed?

also I notice you mention phonegap, are you currently using the xhr.js they suggest using with AJAX requests? If not its something I suggest looking into, due to the same domain policy your AJAX may just be failing silently and very quickly. the xhr.js over comes the bounds of the same domain policy.