I am using google app engine as a server for my android and web application,I developed android app using Android Studio and Web application using Eclipse.I deployed two version in app engine 1st version points by android application and 2nd version points by Web application . I have my own domain name which points default version of app engine .My question is how to point 2nd version by custom domain name. I read google developer blog but i can't understand properly.Please help.
You really shouldn't attempt to run the android and the web "applications" as 2 versions of the same GAE application - that's not the intended use for versions. You'll run into trouble at least with routing traffic to the correct "application", with deploying updates and, as you already observed, with mapping to custom domains.
The proper way to run such separate "applications" as part of one GAE application is to make them separate services/modules of that GAE app. Each service can have multiple versions. Each service (actually each service's default version) can be mapped to a custom (sub)domain as needed.
It should not be very complicated to convert your current app to a multi-service app: just copying the 2 versions of the code in 2 side-by-side subdirectories of your app directory and updating the configuration files should cover over 95% of the job.
来源：https://stackoverflow.com/questions/40988295/how-to-use-custom-domain-name-in-google-app-engine-with-different-versions