在Facebook登录Android应用程序时获取用户全名

Question

我正在尝试将facebook登录添加到Android应用程序中。虽然登录按钮和登录工作正常，但我也在尝试获取用户登录时的名字和姓氏。但是，String用户名始终保持为null。以下是此活动的完整代码：

public class FacebookLoginActivity extends BaseActivity {
private TextView info;
private LoginButton loginButton;
private CallbackManager callbackManager;
private String username;

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);


    FacebookSdk.sdkInitialize(getApplicationContext());

    callbackManager = CallbackManager.Factory.create();

    setContentView(R.layout.fb_login_activity);
    info = (TextView) findViewById(R.id.info);


    loginButton = (LoginButton) findViewById(R.id.login_button);

    loginButton.setReadPermissions(Arrays.asList("public_profile"));

    loginButton.registerCallback(callbackManager, new FacebookCallback<LoginResult>() {
        @Override
        public void onSuccess(LoginResult loginResult) {
            setData();
            if(username != null) {
                Intent intent = new Intent(FacebookLoginActivity.this, LoginActivity.class);
                Bundle bundle = new Bundle();
                bundle.putString("username", username);
                intent.putExtras(bundle);
                startActivity(intent);
            }
        }


        @Override
        public void onCancel() {
            info.setText("Login attempt canceled.");
        }

        @Override
        public void onError(FacebookException error) {
            info.setText("Login attempt failed.");
        }
    });
}

@Override
protected void onActivityResult(int requestCode, int resultCode, Intent data) {
    callbackManager.onActivityResult(requestCode, resultCode, data);
}

private void setData(){
    if(AccessToken.getCurrentAccessToken() != null){
        final GraphRequest request = GraphRequest.newMeRequest(
                AccessToken.getCurrentAccessToken(), new GraphRequest.GraphJSONObjectCallback() {
                    @Override
                    public void onCompleted(JSONObject object, GraphResponse response) {
                        if(AccessToken.getCurrentAccessToken()!=null){
                            try {
                                username = response.getJSONObject().getString("first_name")+ " " + response.getJSONObject().getString("last_name");
                            }
                            catch(JSONException e){
                                e.printStackTrace();
                            }

                        }

                    }
                });
    }
}

}