code: private void startDialogAuth(Activity activity, String[] permissions) {
          Bundle params = new Bundle();
          if (permissions.length > 0) {
              params.putString("scope", TextUtils.join(",", permissions));
          }
          CookieSyncManager.createInstance(activity);
          dialog(activity, LOGIN, params, new DialogListener() {
  
              public void onComplete(Bundle values) {
                  // ensure any cookies set by the dialog are saved
                  CookieSyncManager.getInstance().sync();
                  setAccessToken(values.getString(TOKEN));
                  setAccessExpiresIn(values.getString(EXPIRES));
                  if (isSessionValid()) {
                      Util.logd("Facebook-authorize", "Login Success! access_token="
                              + getAccessToken() + " expires="
                              + getAccessExpires());
                      mAuthDialogListener.onComplete(values);
                  } else {
                      mAuthDialogListener.onFacebookError(new FacebookError(
                                      "Failed to receive access token."));
                  }
              }
  
              public void onError(DialogError error) {
                  Util.logd("Facebook-authorize", "Login failed: " + error);
                  mAuthDialogListener.onError(error);
              }
  
              public void onFacebookError(FacebookError error) {
                  Util.logd("Facebook-authorize", "Login failed: " + error);
                  mAuthDialogListener.onFacebookError(error);
              }
  
              public void onCancel() {
                  Util.logd("Facebook-authorize", "Login canceled");
                  mAuthDialogListener.onCancel();
              }
          });
      }
docs: Internal method to handle dialog-based authentication backend for
  authorize().
  
  @param activity
  The Android Activity that will parent the auth dialog.
  @param applicationId
  The Facebook application identifier.
  @param permissions
  A list of permissions required for this application. If you do
  not require any permissions, pass an empty String array.