Android Data Binding using include tag

The problem is that the included layout isn’t being thought of as a data-bound layout. To make it act as one, you need to pass a variable:

buttons.xml:

<layout xmlns:andr...>
  <data>
    <variable name="foo" type="int"/>
  </data>
  <Button
    android:id="@+id/button"
    ...." />

main.xml:

<layout xmlns:andr...
...
   <include layout="@layout/buttons"
            android:id="@+id/buttons"
            app:foo="@{1}"/>
....

Then you can access buttons indirectly through the buttons field:

MainBinding binding = MainBinding.inflate(getLayoutInflater());
binding.buttons.button

As of 1.0-rc4 (just released), you no longer need the variable. You can simplify it to:

buttons.xml:

<layout xmlns:andr...>
  <Button
    android:id="@+id/button"
    ...." />

main.xml:

<layout xmlns:andr...
...
   <include layout="@layout/buttons"
            android:id="@+id/buttons"/>
....