Using App namespace in style

I am going to give an example to demonstrate the greater point.

Imagine my app has a number of FloatingActionButtons. Consequently, I want to create one style and reuse it. So I do the following:

<style name="FabStyle” parent ="Widget.Design.FloatingActionButton">
    <item name="android:layout_width">wrap_content</item>
    <item name="android:layout_height">wrap_content</item>
    <item name="android:layout_margin">16dp</item>
    <item name="app:backgroundTint">@color/accent</item>
    <item name="app:layout_anchorGravity">end|bottom</item>
</style>

The problem I am having is that the code is not compiling because it is complaining about

Error:(40, 5) No resource found that matches the given name: attr 'app:backgroundTint'.

I tried bringing the namespace in through the resources tag but that is not working

<resources
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:android="http://schemas.android.com/apk/res/android"
    >

Any ideas how I might get this to work?

For app namespace you don't need to specify app:<property name>. Just <property name> is enough.

For example

<style name="FabStyle" parent="Widget.Design.FloatingActionButton"> 
    <item name="android:layout_width">wrap_content</item>
    <item name="android:layout_height">wrap_content</item>
    <item name="android:layout_margin">16dp</item>
    <item name="backgroundTint">@color/accent</item>
    <item name="layout_anchorGravity">end|bottom</item>
</style>

And for layout_anchorGravity you need to set it in XML file where you are defining Floating action button.

You can directly use the property without app

<style name="FabStyle” parent ="Widget.Design.FloatingActionButton">
    <item name="android:layout_width">wrap_content</item>
    <item name="android:layout_height">wrap_content</item>
    <item name="android:layout_margin">16dp</item>
    <item name="backgroundTint">@color/accent</item>
    <item name="layout_anchorGravity">end|bottom</item>
</style>