Show prgress bar when export PDF or Excel in Kendo PivotGrid

Question

I using this code to show progress bar in Kendo PivotGrid when export file:

var item = this.prepareExport(".pdf");
    item.chart.setOptions({
        pdf: {
            allPages: true,
            fileName: item.fileName,
            proxyURL: item.url
        },
        pdfExport: function (e) {
            kendo.ui.progress($(e.sender.element), true);
            e.promise
            .done(function () {
                kendo.ui.progress($(e.sender.element), false);
            });
        }
    });
    item.chart.saveAsPDF();

But this code only show progress bar in first time I export file. My question is how to every I click export file, progress bar showed.

P/s: sorry for my english.