auth.statusChange doesn't fire during FB.init if the user isn't logged in to facebook

问题

I wondered if anyone has found a workaround to the behaviour that I'm experiencing.

Take the example of the below code:

<script>
window.fbAsyncInit = function() {
        FB.init({
          appId      : '[----removed-------]', // App ID
          channelUrl : 'http://localhost/channel.html', // Channel File
          status     : true, // check login status
          cookie     : true, // enable cookies
          xfbml      : true  // parse XFBML
        });     
        // Additional initialization code here

        FB.Event.subscribe('auth.statusChange',fbLoginStatus);

        console.log("getloginstatus");

        FB.getLoginStatus(fbLoginStatus);
</script>

Using FB.init with status set to true, essentially calls getLoginStatus() according to the facebook documentation. However, it is apparently intended behaviour that this will not trigger the event auth.statusChange, because the default value is 'unknown', and the value for 'not logged in' is also 'unknown' (even though it can be known!!)

Therefore I have had to make a call to FB.getLoginStatus() explicitly as well as having the status set to true if I want to also respond to users who are not logged in to facebook.

The problem is, this results in the function being called twice if the user is anything other than "logged out".

Is there a neat way to stop this happening? I think my only option might be to call a different function to handle auth change events..

回答1:

My best solution for this was to set status to 'false' in the fb.init options, then to explicitly call getloginstatus separately.

IF get loginstatus came back as unknown (i.e. logged out), I subscribed to the status change event, as well as doing the usual of displaying the login button. Then when the user logs in, status change fires as expected.

回答2:

A better solution that theoretically should save you a roundtrips is as follows (coffeescript, but easily translatable to javascript):

FB.init
  appId: appId
  channelUrl: channelUrl
  status: true     # Check Facebook Login status on init
  cookies: true
  xfbml: false

FB.getLoginStatus (response) =>
  @parseResponse(response)
  FB.Event.subscribe 'auth.statusChange', @parseResponse
  FB.Event.subscribe 'auth.authResponseChange', @parseResponse

We're still using a manual getLoginStatus to fire when the user is unknown, but this time we still use 'status: true' so that the login status is already cached when getLoginStatus is called. By subscribing to the relevant events only after getLoginStatus has fired, we make sure the handling method parseResponse is only called once on load.

回答3:

You can check the response you get back after you pass a true parameter in the getLoginStatus:

window.fbAsyncInit = function() {
    FB.init({
        appId  : '',
        status : true,
        cookie : true,
        xfbml  : true,
    });

    FB.getLoginStatus( function(response) {
        //console.log(response);
        if (response.status === 'connected') {
            var accessToken = response.authResponse.accessToken;
            alert(accessToken);
        } else if (response.status === 'not_authorized') {
            //login function
        } else {
            //login function
        }
    }, true);

    FB.Event.subscribe('auth.authResponseChange', function(response) {
        //console.log('The status of the session changed to: '+response.status);
        window.location.reload();
    });
};

If you set the status to true, the FB.getLoginStatus response object will be cached by the SDK and subsequent calls to FB.getLoginStatus will return data from this cached response.

To get around this, you have to call FB.getLoginStatus with the second parameter set to true to force a roundtrip to Facebook - effectively refreshing the cache of the response object.

FB Docs: https://developers.facebook.com/docs/reference/javascript/FB.getLoginStatus/

来源：https://stackoverflow.com/questions/10643918/auth-statuschange-doesnt-fire-during-fb-init-if-the-user-isnt-logged-in-to-fac