javascript - Angularjs: How to display loading-icon when using 'resolve' in $routeProvider?

Question

The following code reads via a service and shows on the web page a list of 'page' objects for a specific 'page category' (string). Using the resolve object property in $routeProvider.when(), I am able to postpone updating the view until the new value is ready.

Two questions:

1. When asking for a new page list, I want to show a loading-icon. How can I detect (in a non-hackish way) the event when the reading from server starts (and the loading-icon should be displayed)? I guess I could do something like $('.pages-loading-icon').show() in the service, but find that to be too gui dependent too placed in the service.

2. When the new value is ready, I would like the old to fade out and the new to fade in. What is the 'angular' way to do this? I have tried to do it in the controller using $watch, but that causes the new value to be display shortly before the fadeout starts.

The code:

app.js:

$routeProvider.when('/:cat', { templateUrl: 'partials/view.html', controller: RouteCtrl, resolve: RouteCtrl.resolve});

controllers.js:

function RouteCtrl($scope, $routeParams, pages) {
        $scope.params = $routeParams;
        $scope.pages = pages;
    }

RouteCtrl.resolve={
    pages: function($routeParams, Pages){
        if($routeParams.hasOwnProperty('cat')){
            return Pages.query($routeParams.cat);
        }
    }
}

services.js: The last pages read is stored in currentPages and its category in lastCat.

factory('Pages', function($resource, $q, $timeout){
    return {
        res: $resource('jsonService/cat=:cat', {}, {
            query: {method:'GET', params:{cat:'cat'}, isArray:true}
        }),
        lastCat: null,
        currentPages: null,
        query: function(cat) {
            var res = this.res;
            if(cat != this.lastCat){
                var deferred = $q.defer();
                var p = res.query({'cat':cat}, function(){
                    deferred.resolve(p);
                });
                this.lastCat = cat;
                this.currentPages = deferred.promise;
            }
            return this.currentPages;
        }
    };
})

view.html

<ul >
    <li ng-repeat="page in pages">
        <a href="#{{params.cat}}/{{page.slug}}">{{page.title}}</a>
    </li>
</ul>

Answer 1

Not exactly sure whether this would work in your code as you have $resource integration. But it may be worth to look into angular events: $routeChangeStart and $routeChangeSuccess.

in html:

<span ng-show="isViewLoading"> loading the view... </span>

in controller (which defines the scope of the html above):

$scope.isViewLoading = false;
$scope.$on('$routeChangeStart', function() {
  $scope.isViewLoading = true;
});
$scope.$on('$routeChangeSuccess', function() {
  $scope.isViewLoading = false;
});
$scope.$on('$routeChangeError', function() {
  $scope.isViewLoading = false;
});