getCurrentPosition在Firefox中仅触发一次

Question

Take a look at this code:

navigator.geolocation.getCurrentPosition(function(){
    console.log("a");
});
navigator.geolocation.getCurrentPosition(function(){
    console.log("b");
});

https://jsfiddle.net/DerekL/sxb3j2bv/

After the permission is granted by the user, I would expect the console to have logged

> "a"
> "b"

and indeed this is what happened in Chrome. However on Firefox, for some reason it only fires once and only logs "b" :

> "b"

What can I do about it? Is that a bug?

Answer 1

I believe this is happening because the second call executes before the user has accepted the location permission for the first.

However, you probably want to look at

navigator.geolocation.watchPosition

rather than making multiple requests to get the position.

Answer 2

I solved it by reusing the previous request's promise:

// Note that this is using AngularJS
.service("demo_geolocation_service", function($q){
    var ongoingRequest = false; // This is to deal with strange Firefox behavior
                                //  where .getCurrentPosition only fires callback once
                                //  even when called multiple times

    return function(){
        var deferred = $q.defer();

        if(!ongoingRequest){
            // store promise
            ongoingRequest = deferred.promise;
            navigator.geolocation.getCurrentPosition(function(pos){
                deferred.resolve({latitude: pos.coords.latitude, longitude: pos.coords.longitude});
                ongoingRequest = undefined;
            }, function(){
                deferred.reject();
                ongoingRequest = undefined;
            });
        }else{
            // reuse previous promise
            ongoingRequest.then(function(latlng){
                deferred.resolve(latlng);
            }, function(){
                deferred.reject();
            });
        }

        return deferred.promise;
    };
})