IssueTracker

If you need to add a custom Navigator but don't want to subclass NavHost (which we expect will be needed in most cases), the correct approach is to add it before you set your graph:
1) Don't use app:navGraph in your XML
2) Get a reference to your NavController
3) Add your Navigator to the NavController
4) Call setGraph on the NavController

This relies on the fact that NavController waits until the graph is set before restoring state / doing anything at all.

Technically, the createFragmentNavigator() call in NavHostFragment is already called at the same time as your proposed onNavControllerCreated() method so as a workaround, you could override that method, add your Navigator, then return super.createFragmentNavigator().

The first solution does not work, because after screen rotation, the graph (probably a restored graph) is set when Activity.setContentView() is called.

The workaround with createFragmentNavigator() works, though it's not very elegant. Maybe the method could be renamed to createNavigators() and return a list or an array of Navigators?
Anyway, it is a good enough solution for now, so it is not very urgent.

In conclusion:
* I think that a better support for custom destinations should be provided before final release.
* I would suggest describing the "Add support for new destination types" section in the documentation in more details.

Thank you

I suspect the issue you're running into for the first solution is that you're using the setGraph(R.navigation.graph) method, which does indeed cause it to automatically inflate the graph by id on rotation. Using setGraph(navGraph) where navGraph is a navGraph object you've inflated with navController.getNavInflater().inflate(R.navigation.graph) will never automatically be recreated.

Definitely something we can do better on though :)

Project: platform/frameworks/support
Branch: androidx-master-dev

commit a2e68921841727237528c4ac7076d50af64663c8
Author: Ian Lake <ilake@google.com>
Date:   Wed Oct 17 16:46:28 2018

    Make setGraph(int) and setGraph(NavGraph) act identically
   
    Remove the auto restore functionality from NavController's
    setGraph(int) method so that it functions identically to
    setGraph(NavGraph).
   
    This ensures that developers that manually are calling
    setGraph() after adding custom navigators don't get
    recreated too early.
   
    Test: updated NavController test
    BUG: 110763345
    Change-Id: I51ae7c74451669d6bfed0fe84df445c2ff272e6e

M       navigation/runtime/src/androidTest/java/androidx/navigation/NavControllerTest.kt
M       navigation/runtime/src/main/java/androidx/navigation/NavController.java

https://android-review.googlesource.com/792819
https://goto.google.com/android-sha1/a2e68921841727237528c4ac7076d50af64663c8

We've decided to remove the automatic recreation that was unique to setGraph(int) - it now acts identically to setGraph(NavGraph), so the flow in #2 can be used to ensure that you have custom Navigators added before calling setGraph.

This fix will be available in 1.0.0-alpha07

Project: platform/frameworks/support
Branch: androidx-master-dev

commit f40bad0faef05bded2d226711338e489309885ba
Author: Ian Lake <ilake@google.com>
Date:   Tue Oct 23 21:03:24 2018

    Ensure NavHostFragment calls setGraph on restore
   
    If a graph is set on NavHostFragment via
    NavHostFragment.create() or through
    app:navGraph, it should be restored immediately
    after the call to restoreState.
   
    Test: testapp now works
    BUG: 110763345
    Change-Id: I7a0c656480e27a66637667519eabe61820b09a6c

M       navigation/fragment/src/main/java/androidx/navigation/fragment/NavHostFragment.java

https://android-review.googlesource.com/799721
https://goto.google.com/android-sha1/f40bad0faef05bded2d226711338e489309885ba