If i am not wrong then you must be using
this grid.
this grid has Events property. so you can run your own javascript when event occurs.
you can use
.on('item:stacked', [function])
event to increment your progress counter, and
.on('grid:done', [function])
to finish the progress complete.
I hope this helps.
no need to write any code on controller for showing the loading.
and for showing loader i would recommend you to go for
NProgress