Q:

How to save private string values in android apk?

I know i can save strings in res/values/strings.xml but if someone disassembles the dex file or the apk file then he will be able to see HARDCODED strings or res/values/strings.xml strings.
Is there a way to store strings that wont be read if disassembled?

A:

Briefly - no. 

If you can decrypt/extract any string from your apk, potentially anyone with enough knowledge may look through your code and re-cosntruct the algorithm you use to extract those strings. And then extract them by herself.
Of course you may use some tricks to make it harder. What tricks can be used is actually up to you, Android doesn't provide any by default (AFAIK).

