Ripple when view has alpha background

btn_alpha_bg.xml

<?xml version="1.0" encoding="utf-8"?>

<shape xmlns:android="http://schemas.android.com/apk/res/android"
       android:shape="rectangle">

  <solid android:color="#66000000"/>
  <corners android:radius="4dp"/>

</shape>

btn_mask.xml

<?xml version="1.0" encoding="utf-8"?>
<shape xmlns:android="http://schemas.android.com/apk/res/android"
       android:shape="rectangle">

  <solid android:color="@android:color/black"/>
  <corners android:radius="4dp"/>

</shape>

btn_normal_bg.xml

<?xml version="1.0" encoding="utf-8"?>

<shape xmlns:android="http://schemas.android.com/apk/res/android"
       android:shape="rectangle">

  <solid android:color="#316C41"/>
  <corners android:radius="4dp"/>

</shape>

ripple_alpha_drawable.xml

<?xml version="1.0" encoding="utf-8"?>
<!-- Ripple effect does not work, but the drawable background does -->
<!-- http://d.pr/i/1fQTf -->
<ripple android:color="#1A000000" xmlns:android="http://schemas.android.com/apk/res/android">
  <item android:drawable="@drawable/btn_alpha_bg" />
</ripple>

ripple_alpha_drawable_masked.xml

<?xml version="1.0" encoding="utf-8"?>
<!-- Ripple effect works, but the drawable background is gone -->
<!-- http://d.pr/i/15hka -->
<ripple android:color="#1A000000" xmlns:android="http://schemas.android.com/apk/res/android">
  <item android:id="@android:id/mask" android:drawable="@drawable/btn_alpha_bg" />
</ripple>

ripple_normal_drawable.xml

<?xml version="1.0" encoding="utf-8"?>
<!-- Ripple effect does work as well the drawable background -->
<!-- http://d.pr/i/1lEb9 -->
<ripple android:color="#1A000000" xmlns:android="http://schemas.android.com/apk/res/android">
  <item android:drawable="@drawable/btn_normal_bg" />
</ripple>

ripple_working_alpha_drawable.xml

<?xml version="1.0" encoding="utf-8"?>
<!-- WORKING SOLUTION -->
<!-- Ripple effect does work as well as the alpha drawable background -->
<ripple android:color="#1A000000">
  <item android:id="@android:id/mask" android:drawable="@drawable/btn_mask"/>
  <item android:drawable="@drawable/btn_alpha_bg" />
</ripple>

🙏 big thanks. this was driving me mad