I want add user Id as visit tag so that I can identify every visit with userId, I know we can do this by manual instrumentation but I am not sure every visit will have manual logs. so I am wondering is there a possibility to tag manually or by auto instrumentation for a android app.
You can use auto-instrumentation and tag the visit manually by generating a mobile action containing the user id (similar to manual instrumentation).
When you want to use the Dynatrace Gradle plugin (for auto-instrumentation), then you have to perform the following steps:
The problem doing it manually on android mobile application is, in a given visit session if there didn't has any manual log then that visit will be without tag and there is no way i know of to track dynatrace visit session.
Please clarify what you mean with "didn't has any manual log" - do you mean when a user is already logged in and does not perform a login? In that case you can create the same action you are using for tagging the visit on login when you check if a user is already logged in.