Question

I have an Activity A which is the landing-home screen, an Activity B which is a list of items and an Activity C which shows the detailed view of one of the items of the list.

Activity C can be started from both Activity A and Activity B. (Some elements of the list are featured in the home screen)

My question is: should the up button of Activity C always take the user to Activity B (the list, even if the user started Activity C from Activity A) or should it behave as a back button and send the user to the Activity that started Activity C?

From the design guide I read:

Navigating to screens with multiple entry points:
Sometimes a screen doesn’t have a strict position within the app’s hierarchy, and can be reached from multiple entry points—such as a settings screen that can be reached from any other screen in your app. In this case, the Up button should choose to return to the referring screen, behaving identically to Back.

Although Activity C can be reached from multiple entry points, its position inside the app hierarchy is very clear, it is the detailed view of an element of the list of Activity B.

Answer 1

Yes, your up button should return you to Activity B – as suggested by the documentation.

The Up button is used to navigate within an app based on the
hierarchical relationships between screens. For instance, if screen A
displays a list of items, and selecting an item leads to screen B
(which presents that item in more detail), then screen B should offer
an Up button that returns to screen A.