How to set Android DataBinding in nested layouts

DataBindingUtils.setContentView() does exactly how it is named: It sets the current view to the given parameter. I don't think you want your AppBar as the whole view, or do you?

Nevertheless, I assume that you include your layouts in your layout_activity_main.xml. George Mount has written a whole blog post about this feature. The code examples are from this post.

The first example would be your layout_activity_main.xml (Or however you have named it), where you include your AppBar, your Content and so on.

hello_world.xml
<layout xmlns:android="http://schemas.android.com/apk/res/android">
    <LinearLayout
            android:layout_width="match_parent"
            android:layout_height="match_parent"
            android:orientation="vertical">

        <TextView
                android:id="@+id/hello"
                android:layout_width="wrap_content"
                android:layout_height="wrap_content"/>
        <include
                android:id="@+id/world1"
                layout="@layout/included_layout"/>
        <include
                android:id="@+id/world2"
                layout="@layout/included_layout"/>
    </LinearLayout>
</layout>


included_layout.xml
<?xml version="1.0" encoding="utf-8"?>
<layout xmlns:android="http://schemas.android.com/apk/res/android">
    <TextView
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:id="@+id/world"/>
</layout>

Now that the used layouts are clear, you'll need to jump into your ActivityMain, initialize the DataBinding and access your fields:

//This works if you have used a variable in your <data> tag and you have built your project afterwards, if you don't have an activity
HelloWorldBinding binding = HelloWorldBinding.inflate(getLayoutInflater());

 //if you have an activity, you can use setContentView from the DataBindingUtils. Don't forget to delete the generic setContentView
HelloWorldBinding binding = DataBindingUtil.setContentView(this, R.layout.activity_my_activity);


//Once you have accomplished the above, you can access your data-bound fields like this:
binding.hello.setText(“Hello”);
binding.world1.world.setText(“First World”);
binding.world2.world.setText(“Second World”);

It is important to set Ids to your <include> tags to access them correctly i your Activity.

One can pass the objects in XML ... the xmlns:bind namespace is required (similar to xmlns:app).

<?xml version="1.0" encoding="utf-8"?>
<layout
    xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:bind="http://schemas.android.com/apk/res-auto">
    
   <data>
       <variable name="user" type="com.example.User"/>
   </data>

   <LinearLayout
       android:orientation="vertical"
       android:layout_width="match_parent"
       android:layout_height="match_parent">

       <include
           layout="@layout/name"
           bind:user="@{user}"/>

       <include
           layout="@layout/contact"
           bind:user="@{user}"/>

   </LinearLayout>

</layout>

source of the example: Layouts and binding expressions.