transitionCurrentScreenOut() {
    this.keyBladeBgSprite.stopAllActions();
    this.keyBladeBgSprite.runAction(cc.fadeTo(0.2, 0.0));

    if (this.outerLayer) {
      return this.outerLayer.transitionOut().then(() => {
        this.outerLayer.destroy();
        this.outerLayer = null;
      });
    }
    return Promise.resolve();
  }
Transitions the current screen out.
@returns {Promise}