No reference documentation in Android Studio

Question

A new problem just popped up yesterday. When I hover over a method or press Ctrl-Q, I used to get documentation info for that particular method.

But now I just get (pressing Ctrl-Q on SharedPreferences.getLong()):

Following external urls were checked:
            http://developer.android.com/reference/android/content/SharedPreferences.html#getLong-java.lang.String-long-
            http://developer.android.com/reference/android/content/SharedPreferences.html#getLong(java.lang.String, long) 

    The documentation for this element is not found. Please add all the needed paths to API docs in Project Settings.
        android.content.SharedPreferences
        public abstract long getLong(String s, long l)

I googled a lot, but couldn't find an answer. Which paths do I need to add and where?

Answer 1

Note: as of AS 3.6.2 (or, maybe, even earlier) this is irrelevant and does not answer the question.

Answer for older Android Studio versions:

You Must Download Documentation for Android SDK from SDK Manager

Answer 2

So for me the solution in Android Studio 4.1.1 was that I forgot to download the sources for SDK 30.

1. Go to Tools > SDK Manager
2. Check Show Package Details
3. See if Sources for Android 30 is checked