Show activity Indicator while loading a lazy loaded Module in Angular 2

Question

My scenario is as follows. I have a menu, with multiple options. Each menu should be shown depending on user permissions (already solved), most menu items are encapsulated as modules, and most of the modules are lazy loaded, so when a user clicks a menu item the first time, it loads (up to here everything works well), now my requirement is, in order to give a better user experience, I need to show activity indicator after user clicks a menu item while the lazy loaded module is loading.

Up to this, I tried using canActive, canLoad, canActivateChild interfaces from Angular Router but with no luck.

Any ideas?

Answer 1

You can listen for two router events:

• RouteConfigLoadStart
• RouteConfigLoadEnd

They fire when a lazy loaded module is being loaded. The advantage of using these over the standard router events such as NavigationStart is that they won't fire on every route change.

Listen to them in your root AppComponent to show / hide your spinner.

app.component.ts

import { Router, RouteConfigLoadStart, RouteConfigLoadEnd } from '@angular/router';  ...  export class AppComponent implements OnInit {      loadingRouteConfig: boolean;      constructor (private router: Router) {}      ngOnInit () {         this.router.events.subscribe(event => {             if (event instanceof RouteConfigLoadStart) {                 this.loadingRouteConfig = true;             } else if (event instanceof RouteConfigLoadEnd) {                 this.loadingRouteConfig = false;             }         });     } } 

app.component.html

Just a simple string here, but you could use a spinner component.

<router-outlet></router-outlet>  <ng-container *ngIf="loadingRouteConfig">Loading route config...</ng-container> 

I'm using this approach with Angular v4.2.3

Answer 2

you can do it like this

1. in app.component.html

<div class="main-loader" *ngIf="loading">   <div class="cssload-container" >       <div class="cssload-whirlpool"></div>   </div> </div> 

2. in app.component.ts

   import { Router, NavigationStart, NavigationEnd } from '@angular/router';   loading:boolean = false; constructor(private router:Router) {    router.events.subscribe(event => {     if(event instanceof NavigationStart) {       this.loading = true;       console.log("event started")     }else if(event instanceof NavigationEnd) {       this.loading = false;       console.log("event end")     }     // NavigationEnd     // NavigationCancel     // NavigationError     // RoutesRecognized   });  } 

3. in css any loading animation

hope this is useful to you. thanks