How do I apply a style to all buttons of an Android application

For Material components theme it would be like this:

<style name="AppTheme" parent="Theme.MaterialComponents.Light.NoActionBar">
    <item name="colorPrimary">@color/colorPrimary</item>
    <item name="colorPrimaryDark">@color/colorPrimaryDark</item>
    <item name="colorAccent">@color/colorAccent</item>

    <item name="materialButtonStyle">@style/AppTheme.Button</item>
</style>

For Android styles, you reference the preset attributes that Android has laid out in R.attr. In this case, it looks like you want to to reference android:buttonStyle. I think this would work:

<style name="ApplicationStyle" parent="android:Theme">
  <item name="android:buttonStyle">@style/CKButton</item>
</style>