setInterval ajax调用不起作用

Question

我有一个ajax调用将文件上传到服务器端。它似乎工作正常。

之间我在setInterval中再发送一个ajax调用来更新进度条宽度。我的期望是第一次调用将文件保存到服务器之间setInterval ajax调用将响应上传的字节到webUI。

setInterval ajax调用非常有效。但我无法得到该电话的回复。因为setInterval所有的ajax调用都会在第一次调用（FileUpload）完成后返回响应。

我在这里提到了我的代码。为此，我使用了MVC 4框架。

客户端代码：

---

//handleFileUpload() :: consolidate the files and send to server side..
        function handleFileUpload(files) {
            formData = new FormData();
            $("#errorStatus").text('');
            for (var i = 0; i < files.length; i++) {
                filename = files[i].name;
                filesize = files[i].size;
                fileExtension = filename.split('.');
                if ($.inArray(fileExtension[1], ['ppt', 'pptx', 'doc', 'docx','pdf'])==-1)
                 {
                    $("#errorStatus").text('We are not supporting this file types : ' + 
                    files[i].name + '. \n Only support the following file extensions: 
                    .ppt, .pptx, .doc, .docx, .pdf.');
                    return;
                 }
                formData.append('file', files[i]);
            }
            formData.append('queueName', $(btnDDC).val());           
            setInterval('generateProgressBar()', 500);            
            sendFileToServer(formData);
        }

    //sendFileToServer() :: send job files to server side..
    function sendFileToServer(formData) {
        var uploadURL = "/JobSubmission/DragandDropPrintFromFile/";             
        jqXHR = $.ajax({
            url: uploadURL,
            type: "POST",      
            processData: false, 
            contentType: false,
            data: formData,               
            success: function (data) {  
             //doing some success activities..               
            },
            error: function (data) {     
              //doing some error activities..          
            }
        });
    }     

generateProgressBar = function () {
            $.ajax({
                type: "get",
                data: {},               
                url: "/jobsubmission/UploadProgressChanged/"),              
                success: function (data) {
                    var result = jquery.parsejson(data);
                    if (result != null && result != undefined) {
                        if (result.error == 0) {
                            var totalwidth = ((200 / result.countcheck) * result.count)+20;
                            var progresswidth = (result.count);
                            $(".progressbar div").css('width', totalwidth + 'px');
                            $(".sizeprog").html(progresswidth + ' mb');                           
                        }                       
                    }
                },
                error: function (data) {
                    console.log("couldn't reach the file..");
                }
            });
        }