How to get a reference to an object in a NavigationView Header

Question

In my activity, I am inflating the layout via data binding. The binding itself works correctly, and I am able to get references to objects in the layout file easily.

One of those objects is a NavigationView. It has a headerLayout:

<com.google.android.material.navigation.NavigationView
    android:id="@+id/nav_view"
    android:layout_width="wrap_content"
    android:layout_height="match_parent"
    android:layout_gravity="start"
    android:background="@android:color/white"
    android:fitsSystemWindows="true"
    app:itemIconTint="@color/navigation_view_color"
    app:itemTextColor="@color/navigation_view_color"
    app:headerLayout="@layout/nav_view_header" />

The header layout looks like this (extra objects removed for simplicity):

<androidx.constraintlayout.widget.ConstraintLayout 
    xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:background="@color/menu_blue"
    android:paddingBottom="32dp">

    <ImageView
        android:id="@+id/navViewLogOutButton"
        android:layout_width="48dp"
        android:layout_height="48dp"
        android:padding="12dp"
        android:src="@drawable/logout"
        app:tint="@color/white"
        app:layout_constraintTop_toTopOf="parent"
        app:layout_constraintEnd_toEndOf="parent"
        android:layout_marginTop="16dp"
        android:contentDescription="@string/sz.proApp.support.logOut" />

</androidx.constraintlayout.widget.ConstraintLayout>

I need to set a click listener on this image view, but I can't get a reference to it. This is what I am using:

binding.navView.findViewById<ImageView>(R.id.navViewLogOutButton)?.setOnClickListener{
    doSomething()
}

I've verified that binding.navView is not null. Also, by setting a break point there, I can see what the memory address for this ImageView is. When I change that line to this:

binding.navView.findViewById<ImageView>(213123403)

I get the reference that I want. But obviously, I can't just use the integer since that is dynamic. The code compiles and the app launches. But when it hits that line, findViewById returns null every time.

I read that findViewById may not work with data binding in a activity, but if that is true, then how can I get this reference so that I can set the listener?

Answer 1

app:headerLayout="@layout/nav_view_header"

So, the generated binding class should beNavViewHeaderBinding, you can get the binding with:

val headerBinding = NavViewHeaderBinding.bind(binding.navView.getHeaderView(0))

And access the header views through headerBinding:

headerBinding.navViewLogOutButton