dart - Flutter - How the NavigatorObserver class works? -

i'm trying detect when navigator performs basic operations (push , pop), found class achieve navigatorobserver class, can't find example on how works.

i tried implements interface:

class myclassstate extends state<myclass> navigatorobserver{      ....      @override     void didpop(route<dynamic> route, route<dynamic> previousroute) {         print('this never called');     }      @override     void didpush(route<dynamic> route, route<dynamic> previousroute) {         print('this never called');     } } 

of course i'm calling navigator.of(context).push(...); override methods, never called.

i suspect binding navigator missing, i'm not sure.

any suggestions?

thanks in advance!

edit:

i think want simple can't figure out how it.

i have page a pushes page b.

on page b have periodic timer must on there (on page b).

all want cancel timer timer.cancel() when page b popped out (with button on android or button in appbar), since when page b popped out timer still executing if page b has gone.

• i can't pass timer param navigator.pop() since don't handle buttons (the 1 in appbar , android button).

edit 2:

-i found way solves problem, did cancel timer on

@override void dispose() {   timer.cancel();   super.dispose(); } 

method. i'm not sure if best way accomplish it.

note:

with workaround timer still executing if press home button or open multitask on android, , when go app restarted again timer still executing code.

most of time don't need implement navigatorobserver. see this other stackoverflow answer explaining how use push , pop pass information between routes. in use case you've described, should addlistener animationcontroller, using tickerproviderstatemixin obtain suitable vsync object. ensures callback not fire when app suspended or after state disposed. (instead of addlistener, use animatedbuilder or animatedwidget primary purpose of callback rebuild section of widget tree.)

the main time when you'd want navigatorobserver if you're using plugin firebase analytics. can see example usage in plugins repo. pass navigatorobserver in navigatorobservers argument materialapp constructor:

static firebaseanalyticsobserver observer =   new firebaseanalyticsobserver(analytics: analytics); ... return new materialapp(   navigatorobservers: <navigatorobserver>[observer],   ... ); 

it unusual have state implements navigatorobserver because materialapp should near top of widget hierarchy. @ time you're constructing it, state objects won't exist yet you'll have hard time putting them navigatorobservers array. might instead use class isn't state. if necessary, can use globalkey<myclassstate> find state needs notified (but if you're doing this, there might easier way accomplish want).