app.js

app.config(function($routeProvider, $httpProvider) {
  var numLoadings = 0,
		loadingScreen = $('.processing');

	$httpProvider.interceptors.push(function() {
		return {
			request: function(config) {
				++numLoadings;
				loadingScreen.show();

				return config;
			},
			response: function(response) {
				--numLoadings;
				if (numLoadings == 0)
					loadingScreen.hide();

				return response;
			}
		}
	});
});