How to find reference resource implementation in Android studio?

Question

I mean, is it possible now to see platform's(exact sdk) implementation of reference attr?

This time I'm using Android Studio v2.3 and 3.0

Answer 1

selectableItemBackground is an attribute, that is specified in themes.

For a reference you can see how topmost Theme style specifies that attribute, which is declared in themes.xml.

<style name="Theme">
    ...
    <item name="selectableItemBackground">@drawable/item_background</item>
    <item name="selectableItemBackgroundBorderless">?attr/selectableItemBackground</item>
    ...
</style>

As to the question: "How to find reference resource implementation in Android studio?" - what you can do, is perform a search inside Android Studio with query "theme_material". That file, as the name applies, contains material themes, alternatively you can search for "themes" for non-material themes.

Also, you can make use of Android Studio's "Find in Path" feature:

In above screenshot you can see that I've specified search directory to point to SDK sources (in my case it's "/Users/azizbekian/Library/Android/sdk/platforms/android-27") and search query "selectableitembackground">