AccessToken.getCurrentAccessToken() is null
<p>I Integrated Facebook in my app and getting the proper token. If the token already exists then it assigns it, and if it's the first time then it will make a request for the token. However, the token is not being received.</p>

<p>Here is my code: </p>

<pre><code>@Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        FacebookSdk.sdkInitialize(this.getApplicationContext());
        callbackManager = CallbackManager.Factory.create();

        accessTokenTracker = new AccessTokenTracker() {
            @Override
            protected void onCurrentAccessTokenChanged(
                    AccessToken oldAccessToken,
                    AccessToken currentAccessToken) {
                // Set the access token using
                // currentAccessToken when it's loaded or set.
            }
        };
        // If the access token is available already assign it.
        accessToken = AccessToken.getCurrentAccessToken();
        setContentView(R.layout.activity_signup);
</code></pre>