Nav Host Fragment Duplicate id

Question

I already found a solution to this. But it took quite a while and a lot of references to stumble upon so I will leave this here.

This is an app that has MVVM data binding throwing error related to Nav Controller.

fragment initially gave Duplicate id error on NavHostFrament on the data binding line in my activity. Removing either android:id or android:name gave either build error or runtime error.

Activity.kt

     binding = DataBindingUtil.setContentView(this, R.layout.activity_home)
     .
     .
     .
     val navController = findNavController(R.id.nav_host_fragment)

Layout.xml

  <fragment 
    android:id="@+id/nav_host_fragment"
    android:name="androidx.navigation.fragment.NavHostFragment"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    app:defaultNavHost="true"
    app:layout_constraintLeft_toLeftOf="parent"
    app:layout_constraintRight_toRightOf="parent"
    app:layout_constraintTop_toTopOf="parent"
    app:navGraph="@navigation/mobile_navigation"/> 

while the fragment line gave me a lint check to convert to FragmentContainerView it started throwing NavController not set error.

Answer 1

I transferred the fragment tag to a separate xml file. Though I believe this is not needed.

nav_header.xml

<?xml version="1.0" encoding="utf-8"?>
<androidx.fragment.app.FragmentContainerView
    xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    android:id="@+id/nav_host_fragment"
    android:name="androidx.navigation.fragment.NavHostFragment"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    app:defaultNavHost="true"
    app:layout_constraintLeft_toLeftOf="parent"
    app:layout_constraintRight_toRightOf="parent"
    app:layout_constraintTop_toTopOf="parent"
    app:navGraph="@navigation/mobile_navigation" />

As for the Activity file. Following this link... https://issuetracker.google.com/issues/142847973#comment4

Replaced

val navController = findNavController(R.id.nav_host_fragment)

with

val navHostFragment = supportFragmentManager.findFragmentById(R.id.nav_host_fragment) as NavHostFragment
val navController = navHostFragment.navController