nativescript | call ngOnInit after android back button Navigation

Question

I have a problem handling the back button , when the user taping the back button the ngOnInit is not triggered and the component is not working as wanted . from what i saw i understand that when taping back its only make the ngOnDestroy fire but not the ngOnInit

this is the lifecycle

open App --> ngOnInit() called

click on some anther component --> ngOnInit() of the new component called

tap back --> ngOnDestroy

Did someone had the same problem and how did you handle it ? thank you

Answer 1

After some search i decided to use this solution

in components that i need the ngOnInit to run even if the navigate is from the back button or function i added this

constructor(private location : PlatformLocation) {}

ngOnInit() {
    this.location.onPopState(() => {
    this.initComponent();
});
}

Answer 2

Why do you think ngOnInit should run on back ? it doesn't

Solution is to use router events :

For example : A Solution to detect back from "/beatles/john/songs/strawberryfields" to "/doors/jim/girlfriend/pam"

Doors page --------> Beatles page.....(back tapped)----------->Doors

Is :

Add this method into a shared service :

 public onNavigatePreviousToCurrent(pre: string, current: string  ): Observable<any>
        {
            return this.router.events.pipe(filter(e => e instanceof NavigationEnd), pairwise(), filter((f: [any, any]) =>
                                                                                                       {
                                                                                                           return f[0].url.toLowerCase()
                                                                                                                      .indexOf(pre.toLowerCase()) > -1 &&
                                                                                                                  f[1].url.toLowerCase()
                                                                                                                      .indexOf(current.toLowerCase()) > -1;
                                                                                                       })  );
        }

In the Doors page call it :

 ngOnInit()
        {
            let f = this._routingService.onNavigatePreviousToCurrent("john", "pam") //or doors or jim
                        .subscribe((res) =>
                                   {
                                    //do what you want here !!!
                                   }, (error) =>
                                   {
                                   });

   //don't forget to unsubscribe `f`
       }

Notice that you can use any token from /beatles/john/songs/strawberryfields ( beatles,john,songs,strawberryfields , atles)----> also in Doors. (substring)

Basically this methods detects where you came from and what is the destination after back.

BTW you might want to say : "well , I don't know where I am , I only want a situation where a user tapped "back".

Answer :

this._routingService.onNavigatePreviousToCurrent("/", "pam") ;
// "/" will always be present , so basically this ^ detects back from anywhere to Doors page