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I'm trying to keep my application clean by breaking functionality into multiple modules.

:App
:Features:Foo
:Features:Bar
:Ux

I've defined my application's theme in themes.xml in the :Ux module, and then it's used throughout the application.

<style name="Theme.MyApp" parent="Theme.MaterialComponents.Light">
   ...
</style>

Some of my features have custom attributes I want to add to the theme and use throughout just that feature, however. So I've added an attrs.xml and themes.xml to each of :Features:Foo and :Features:Bar.

<style name="Theme.MyApp.Foo" parent="Theme.MaterialComponents.Light">
   <item name="customFooViewColor">@android:color/holo_orange_dark</item>   
</style>

and

<style name="Theme.MyApp.Bar" parent="Theme.MaterialComponents.Light">
   <item name="customBarViewColor">@android:color/holo_green_light</item>   
</style>

But now I'd like to add a new feature in :Features:Baz that can host fragments from both :Features:Foo and :Features:Bar, so its theme needs to include the custom attributes defined in :Feature:Foo's attrs.xml and :Feature:Bar's attrs.xml, and the same values of those attributes defined in :Feature:Foo's themes.xml and :Feature:Bar's themes.xml.

One solution is to move those custom attributes and their values into the :Ux module, but that pollutes the entire app with feature-specific properties that only are only required in a couple modules.

As @ritesh4302 points out, I can access the attrs.xml files in :Feature:Foo and :Feature:Bar from :Feature:Baz by adding dependencies on those modules, so another solution is to duplicate all the fields in each of :Features:Foo and :Features:Bar into :Features:Baz.

In :Features:Foo

<style name="Theme.MyApp.Foo" parent="Theme.MaterialComponents.Light">
   <item name="customFooViewColor">@android:color/holo_orange_dark</item>   
</style>

In :Features:Bar

<style name="Theme.MyApp.Bar" parent="Theme.MaterialComponents.Light">
   <item name="customBarViewColor">@android:color/holo_green_light</item>   
</style>

In :Features:Baz

<style name="Theme.MyApp.Baz" parent="Theme.MaterialComponents.Light">
   <item name="customFooViewColor">@android:color/holo_orange_dark</item>   
   <item name="customBarViewColor">@android:color/holo_green_light</item>   
</style>

Obviously this duplication of values is problematic because now I need to update values in multiple places whenever they change.

Is there a way to avoid the duplication without placing everything in :Ux? Has anyone written a build plugin that can achieve this?

Aidan64
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1 Answers1

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If :Feature:Baz needs to use code written in :Feature:Foo and :Feature:Bar then you need to added them as a dependency and once they are added as dependency you must be able to use the custom attrs defined in base package.

ritesh4302
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    Makes sense. Any ideas how I can have two custom themes include the same values for those attributes without inheriting from one another? – Aidan64 Jul 14 '21 at 13:57