Android Navigation Graph, Nested Graph Issue

Question

I hope you're all doing well.

I have a problem about navigation graphs. You can see the structure in the image below;

So we have 2 different navigation graphs; navigation_A and navigation_B .

I need to navigate to Fragment Y and Fragment Z from a fragment in nested graph which is navigation_B .

The problem is;

• If I use <include> for navigation_B , I can not use it as NavHost .
• If I use different navigation graph and add it as nested graph like above, I can not use navigation destination for Fragment Y or Fragment Z .

I need to use navigation_B as NavHost , also i need to be able to navigate to Fragment Y and Fragment Z . How can I achieve that?

Thank you!

Answer 1

Your navigation graph structure breaks the recommended navigation pattern!

But for your needs, I have a way to workaround.

Method 1: First, FragmentY and FragmentZ need to have their own deeplink.

    <fragment
      android:id="@+id/fragY"
      android:name=".FragmentY"
      tools:layout="@layout/frag_y>
      <deepLink
        android:id="@+id/"
        app:uri="any-app://internal_navigation_frag_y" />
    </fragment>

    <fragment
      android:id="@+id/fragZ"
      android:name=".FragmentZ"
      tools:layout="@layout/frag_z>
      <deepLink
        android:id="@+id/dlink_frag_z"
        app:uri="any-app://internal_navigation_frag_z" />
    </fragment>

Then, Inside a Fragment that lives in navigation_b. Let's call it FragmentB

// navigate to FramgmentY
val deeplinkY = Uri.parse("any-app://internal_navigation_frag_y")
findNavController().navigate(deeplinkY)

// navigate to FramgmentZ
val deeplinkZ = Uri.parse("any-app://internal_navigation_frag_z")
findNavController().navigate(deeplinkZ)

You can store the string any-app://internal_navigation_frag_y and any-app://internal_navigation_frag_z in string.xml file though.

Check this out: https://developer.android.com/guide/navigation/navigation-navigate#uri

Method 2: Inside the nested graph navigation_B, define 2 global actions that point to fragmentY and fragmentZ. Since navigation_B is a NavHost, so it will know about FragmentY and FragmnentZ

Check this: https://developer.android.com/guide/navigation/navigation-global-action

Answer 2

When you use nested navigation graph the inner graph should not know anything about the outside graph. In this case graph_B should not know about the existence of a FragmentY or FragmentZ. What you should do is deliver a result from your graph_B to whomever launched it. Then at that point decide whether to go FragmentY or FragmentZ.