Android development for a web programmer - where to start?

Question

PHP

I've been a web developer for over five years, most of the time back-end in PHP.
I know and understand design patterns, different approaches to development, I work with version control systems, etc.
In principle, I calmly read java code in the same examples of the implementation of classical design patterns.
At the moment, I became interested in developing mobile applications for andoid, first of all I started to study the official documentation, installed andoid studio and launched hallow world from the examples.
Trouble overtook me after studying the requirements for developers in vacancies for positions of mobile developers, in particular - java memory model and in general everything related to multithreading.
In the comments to the articles, I came across discussions, for example, of different behavior of the application with the same screen rotation - as far as I understand, in this example, the activity is reinitialized, which is the main class of the application, as a result of which many subtleties arise related to working with threads.
I realized that in terms of theoretical preparation, I am far from calm programming with periodic study of manuals, and therefore I ask you to tell me what and in what sequence it would be good to study before I start writing my first educational application for this platform?
Thank you!

Answer 1

Core Java - the first and part of the second volume of
Effective Java by Joshua Bloch - mandatory
Java Concurrency in Practice by Brian Goets - mandatory
from the series Pragmatic Programmer
Programming Concurrency on the JVM: Mastering Synchronization
Functional Programming in Java: Harnessing the Power of Java 8 Lambda Expressions
Pragmatic Unit Testing in Java 8 with JUnit

Answer 2

If we are talking about express immersion: then don’t read books yet, start with YouTube (just don’t get hung up on startandroid), articles on habré, built-in samples of Android Studio, study life cycles (for example, here https://github.com/xxv/android- lifecycle ), make a dozen simple applications + you can immediately feel version control together (bitbucket for example) and only after that sit down to read Java Core, OOP, Git Pro and carefully study https://developer.android.com/index.html
PS If something does not work, try to look for the correct answers immediately on SO.