Android data binding: cannot inject an attribute into "include" tag

Question

I'm trying to create a reusable layout included.xml which then could be injected into other layouts and customized via tag attributes. Here's what I have:

res/layout/parent.xml:

<?xml version="1.0" encoding="utf-8"?>
<layout
    xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/com.myself.fancyapp"
    >

    <include layout="@layout/included"
            app:src123="@drawable/my_icon" />

</layout>

res/layout/included.xml:

<?xml version="1.0" encoding="utf-8"?>
<layout
    xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    >
    <data>
        <variable name="src123" type="android.graphics.drawable.Drawable" />
    </data>

    <android.support.design.widget.FloatingActionButton
        android:src="@{src123}" />
</layout>

app/build.gradle:

android {
    compileSdkVersion 23
    buildToolsVersion "23.0.2"

    dataBinding {
        enabled = true
    }
    ....
}

dependencies {
    compile 'com.android.support:appcompat-v7:23.1.1'
    compile 'com.android.support:design:23.1.1'
}

As an outcome, the button which I try to inject doesn't contain any image at all.

If in parent.xml I change xmlns:app to res-auto, I have the following error in app/build/intermediate/data-binding-layout-out/debug/layout/parent.xml:

Error:(17) No resource identifier found for attribute 'src123' in package 'com.myself.fancyapp'

Does anybody have an idea why this happens and how to fix this? Thanks.

Answer 1

The problem is that you're not using binding syntax for the variable:

<include layout="@layout/included"
        app:src123="@drawable/my_icon" />

should be:

<include layout="@layout/included"
        app:src123="@{@drawable/my_icon}" />

Unrelated, but I don't think that includes are allowed as the root element of a layout. I believe that you're going to have to have a normal View surrounding the include.

<?xml version="1.0" encoding="utf-8"?>
<layout
    xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/com.myself.fancyapp"
    >

    <FrameLayout android:layout_width="match_parent"
                 android:layout_height="match_parent">
        <include layout="@layout/included"
                app:src123="@{@drawable/my_icon}" />
    </FrameLayout>
</layout>