The NativeScript companion app is a test utility for iOS and Android devices which allows you to quickly run and test a NativeScript application on a mobile device. Its main advantage is acting as a container that doesn't interfere with the look and feel of your app, which is why you can get a behavior that closely mimics the real behavior of the app when it runs directly on a device. It is mostly helpful if you want to quickly test your app and code sign it later on during your development process.
However, the NativeScript companion app is not designed to run on Android emulators. However, you should see the Genymotion Android emulator in the AppBuilder Devices tab. If that is indeed the case on your side, then you should be able to use the Build and Deploy option to directly run the app in the emulator. Please give this a try and let me know if it helps.
Another option you have is to go through the AppBuilder Command-Line Interface. Since you're developing your app in the Windows client of AppBuilder, you can set up your project for collaboration as described here. Once configured, the project can be opened from different AppBuilder clients.
In order to test a NativeScript
app in a Genymotion
emulator, you can run the following command in the AppBuilder CLI
appbuilder emulate android --geny <
You can find more info about the steps you can follow in this tutorial