After researching for a while there is still something unclear for me:
When is it worth to implement Parcelable rather than just getting the variables and send them to a new Activity? If i search for example for something like "RecyclerView click open new Activity", almost everyone posts code that extracts the values with getter methods in Activity 1 and sends them via multiple .putExtra calls to Activity 2. Almost no one seems to suggest to implement Parcelable. I also fail to see where Parcelable saves effort or makes the code more maintainable, since i have to call .getXXX for every value in the target Activity anyways.
So let's say I have a RecyclerView, I want to open a new Activity on Button click and i want to send 3 variables out of 1 Object from 1 ArrayList. Should i send the variables directly over 3 .putExtra calls or implement Parcelable and send the whole Object?
In your case sending the 3 primitive values with putExtra should be enough. Parcelable is to send objects. Normally these objects contain objects which contain other objects or array of objects. In summary it is used to send complex objects. It's also necessary if you need to send an object to your service as part of the body of a request.