The NavController and its
navigation graph is contained within a single activity. Therefore, when
migrating an existing project to use the Navigation Architecture Component,
focus on migrating one Activity at a time by creating a navigation graph for
the destinations within each Activity.
Separate Activities can then be linked by adding activity destinations to the
navigation graph, replacing existing usages of startActivity() throughout the
code base.
In cases where multiple Activities share the same layout, the navigation graphs can be combined, replacing navigate calls to the activity destination to navigate calls directly between the two navigation graphs.
