I am new in developement android apps and java. Now I have developed a app, that stores entries in a mysql-db. My api-language ist php. Until now I was the only user, that used that app, so it was easy to store and receive the data into and from the db. Now I want to give some other my app and I only want to use this one db, that I used before. My app doesn't have a login-system, so my question is, how to identify a user, so that the app gives that user-identification to my php-api and last to my db-query.
Do you have some ideas for me?
A good way would be a device-way to identify the user. A better way would be a user-way to identify, so that that user could use more than one device for his db-entries to get.