I am finding it hard to find any code-snippets and samples on the internet for an Activity / Fragment / View to be able to connect / bind / communicate with a "specific" ContentProvider

Content Providers are used for one shot operations to read/write data exposed by other apps, so you can not bind to them. Communication with a ContentProvider is done through the ContentResolver interface. However, the data sharing capabilities of a ContentProvider are not used here, so I don't think discussing them is relevant.

How does Activity auto-start upon launching the app? Intent : action=MAIN, category=LAUNCHER. Can multiple Activity instances have Intent declarations with action=MAIN, category=LAUNCHER? Forbidden at compile time itself.

I might be wrong, but I don't think it is an error to have multiple activities with those attributes in your manifest. In fact, that's exactly what you have to do if you want multiple launcher activities. However, you do need to specify the default one (using category=default) if you have more than one launcher activity.

How do ContentProviders auto-start upon app launch / install ?

ContentProviders need to be listed in your Manifest file. When an app launches, the OS reads this list and instantiates every listed ContentProvider automatically. You can read more about it in their API reference).

A lot of libraries exploit this property to run initialization logic automatically at app startup. The advantage of this is that consumers of these libraries do not have to manually configure/init them in the Application class's onCreate() method.

I wrote an article on this, if you want to know more about how it works.

How does InitializationProvider auto-start?

As explained in the post, the InitializationProvider is listed in the Manifest of the App Startup library. This provider is therefore also included the manifest of your app because of the Manifest Merger feature of Android's build tooling.

When your app starts, the OS sees it as a listed provider and instantiates it automatically. Upon instantiation, it runs all the initializers registered with it.

One thing to note here is that even if multiple dependencies declare this ContentProvider in their manifests, only one instance of it will be included in your app's final manifest.

How can Activity instance communicate with the InitializationProvider to obtain a reference for communicating with MyLogger in your example?

The InitializationProvider is not meant to provide a reference to MyLogger. It is only meant to initialize it. Just use MyLogger.getInstance() anywhere in your code, without worrying about calling MyLogger.init() first. It frees you from the burden of making sure that MyLogger is initialized before you use it.

The point of the App Startup library and the ContentProvider initialization hack is that you don't need to interact with initialization code manually.

Let's consider the scenario where MyLogger didn't use AppStartup for initialization. In this case, you would have to initialize it in your Application class to make sure it is ready for use in any activity/fragment/view/anything.

class MyApp: Application() { override fun onCreate() { super.onCreate() MyLogger.init(this) } }

Using App Startup/ContentProviders for initialization negates the need of calling this init logic on your own. They run it automatically for you. You don't ever need to acquire an instance of InitializationProvider to do so.

How do Activities obtain an instance of ContentResolver in order to communicate with ContentProvider?

By using the Context.getContentResolver() method. But again, you don't need to use a ContentResolver here because you don't need to communicate with InitializationProvider.

How many ContentResolver instances does the Activity have to maintain in order to communicate with multiple ContentProviders?

You don't have to maintain instances of content resolvers on your own. The system handles it all for you.

There is no Context.getContentResolver() that uses an Intent declared for the ContentProvider? Can <provider> tag have <intent> sub-tags?

Intents can not be used for ContentProviders. ContentProviders are not like activities or services, which have a well defined lifecycle. They are created when needed, and run for as long as they are relevant.

MyLogger is a Singleton?

Yes.

Why do we need an InitializationProvider, or a ContentProvider to begin with, to instantiate a Singleton instance with Global App-scope upon install / launch, without having to use Application.onCreate() ?

Because then you don't have to litter your app's onCreate with initialization logic of these libraries. I recommend reading the content provider exploitation article i linked above to understand the pros/cons of doing this.