Xamarin.forms / Android Facebook获得好友

Question

Hi everyone I'm using Xamarin.Forms to create an application. I've been able to create a facebook login and retrieve user ID. I'm now trying to get the friendlist of the user. I understood that only user who have accepted the app can be shown, however I cant see the one who identified in my app ( I have a friend as test user) Here's my code:

    private void getFriends() {
        FacebookClient fb = new FacebookClient (App.Token);

        fb.GetTaskAsync ("me/friends").ContinueWith (t => {
            try {
                var result = (IDictionary<string, object>)t.Result;
                var data = (IList<object>)result ["data"];

                foreach (IDictionary<string, object> friend in data) {
                    App.addFriendToList ((string)friend ["name"], (string)friend["id"]);
                }
            } catch {
                App.addFriendToList ("No Friends Using imin", "0000");
            }
        });
    }

The code is for android. The code is inspired (not to say copy pasted) from the Xamarin Facebook SDK. So it should work. It is working however the list supposed to display friend remain empty ( note that i do not catch any errors).

Thanks for the answers!

Answer 1

The callback in ContinueWith actually runs on a different synchronization context. The UI probably doesn't get updated. Try doing this:

private void getFriends() {
    FacebookClient fb = new FacebookClient (App.Token);

    // There call for "Result" here will wait for the task to complete before returning.
    var result = (IDictionary<string, object>)fb.GetTaskAsync ("me/friends").Result;
    var data = (IList<object>)result ["data"];

    foreach (IDictionary<string, object> friend in data) {
        App.addFriendToList ((string)friend ["name"], (string)friend["id"]);
    }
}

Please not that this WILL block the UI thread and the application will remain unresponsive during the Get call. Something like this would be preferable:

private async Task getFriends() {
    FacebookClient fb = new FacebookClient (App.Token);

    //Here the call to ConfigureAsync(true) will force the synchronization context back to the one before the call (the UI thread in this case)
    var result = (IDictionary<string, object>)(await fb.GetTaskAsync ("me/friends").ConfigureAsync(true));
    var data = (IList<object>)result ["data"];

    foreach (IDictionary<string, object> friend in data) {
        App.addFriendToList ((string)friend ["name"], (string)friend["id"]);
    }
}

Answer 2

Alright i just made a silly mistake, did not init the List I used to store the friends, should have checked twice. My initial code is working fine with that.