mMediaRouteSelector = new MediaRouteSelector.Builder() .addControlCategory(CastMediaControlIntent.categoryForCast("YOUR_APPLICATION_ID")) .build();
If I pay $5 for google cast sdk then I can use this sdk for multiple devices for testing purpose or not or If any other way to connect the android application with any TV or projector.
If you register your application, you'll get an Application Id and then you can register your Cast devices for testing without publishing your app and then publish your app when ready. If you don't want to register to get your own Application Id, you can use the Default Receiver (app id=CastMediaControlIntent.DEFAULT_MEDIA_RECEIVER_APPLICATION_ID)