Showing loading animation in center of page while making a call to Action method in ASP .NET MVC

Question

My application makes several calls to an Action method (ASP .NET MVC) which returns a Json object. When the application is waiting for this method to return its data I want to display a loading animation in the center of the page. How would I accomplish this? I know that I should use JQuery but that's all I know.

Answer 1

You can do this by displaying a div (if you want to do it in a modal manner you could use blockUI - or one of the many other modal dialog plugins out there) prior to the request then just waiting until the call back succeeds as a quick example you can you $.getJSON as follows (you might want to use .ajax if you want to add proper error handling)

$("#ajaxLoader").show(); //Or whatever you want to do
$.getJSON("/AJson/Call/ThatTakes/Ages", function(result) {
    //Process your response
    $("#ajaxLoader").hide();
});

If you do this several times in your app and want to centralise the behaviour for all ajax calls you can make use of the global AJAX events:-

$("#ajaxLoader").ajaxStart(function() { $(this).show(); })
               .ajaxStop(function() { $(this).hide(); });

---

Using blockUI is similar for example with mark up like:-

<a href="/Path/ToYourJson/Action" id="jsonLink">Get JSON</a>
<div id="resultContainer" style="display:none">
And the answer is:-
    <p id="result"></p>
</div>

<div id="ajaxLoader" style="display:none">
    <h2>Please wait</h2>
    <p>I'm getting my AJAX on!</p>
</div>

And using jQuery:-

$(function() {
    $("#jsonLink").click(function(e) {
        $.post(this.href, function(result) {
            $("#resultContainer").fadeIn();
            $("#result").text(result.Answer);
        }, "json");
        return false;
    });
    $("#ajaxLoader").ajaxStart(function() {
                          $.blockUI({ message: $("#ajaxLoader") });
                     })
                    .ajaxStop(function() { 
                          $.unblockUI();
                     });
});

Answer 2

I defined two functions in Site.Master:

    <script type="text/javascript">
    var spinnerVisible = false;
    function showProgress() {
        if (!spinnerVisible) {
            $("div#spinner").fadeIn("fast");
            spinnerVisible = true;
        }
    };
    function hideProgress() {
        if (spinnerVisible) {
            var spinner = $("div#spinner");
            spinner.stop();
            spinner.fadeOut("fast");
            spinnerVisible = false;
        }
    };
</script>

And special section:

    <div id="spinner">
        Loading...
    </div>

Visual style is defined in CSS:

div#spinner
{
    display: none;
    width:100px;
    height: 100px;
    position: fixed;
    top: 50%;
    left: 50%;
    background:url(spinner.gif) no-repeat center #fff;
    text-align:center;
    padding:10px;
    font:normal 16px Tahoma, Geneva, sans-serif;
    border:1px solid #666;
    margin-left: -50px;
    margin-top: -50px;
    z-index:2;
    overflow: auto;
}