I've been following the docs from Navigation Architecture Component to understand how this new navigation system works.
To go/back from one screen to another you need a component which implements NavHost
interface.
The NavHost is an empty view whereupon destinations are swapped in and out as a user navigates through your app.
But, it seems that currently only Fragments implement NavHost
The Navigation Architecture Component’s default NavHost implementation is NavHostFragment.
So, my questions are:
Even if I have a very simple screen which can be implemented with an Activity
, in order to work with this new navigation system, a Fragment
needs to be hosted containing the actual view?
Will Activity
implement NavHost
interface in a near future?
--UPDATED--
Based on ianhanniballake's answer, I understand that every activity contains its own navigation graph. But if I want to go from one activity to another using the nav component (replacing "old" startActivity
call), I can use activity destinations
. What is activity destinations
is not clear to me because the docs for migration don't go into any detail:
Separate Activities can then be linked by adding activity destinations to the navigation graph, replacing existing usages of startActivity() throughout the code base.
ActivityNavigator
instead of startActivity
? The navigation graph only exists within a single activity. As per the Migrate to Navigation guide, <activity>
destinations can be used to start an Activity from within the navigation graph, but once that second activity is started, it is totally separate from the original navigation graph (it could have its own graph or just be a simple activity).
You can add an Activity destination to your navigation graph via the visual editor (by hitting the + button and then selecting an activity in your project) or by manually adding the XML:
<activity
android:id="@+id/secondActivity"
android:name="com.example.SecondActivity" />
Then, you can navigate to that activity (i.e., start the activity) by using it just like any other destination:
Navigation.findNavController(view).navigate(R.id.secondActivity);