How to better understand start app package and activity class

[maes....@gmail.com]

I can start app's using the start app block.
But now I'm strying to do specific thing with the app's on start.
I understand I can do that with the package and activity options, but is there a way to know what every package does?

[Henrik "The Developer" Lindqvist]

An package is an app, try the app to know what it does?

[maes....@gmail.com]

Yes I understand that.
And I was able to automatically plan a Spotify playlist by looking at the flow of someone else, using a class, action and an uri.
But I want to shuffle the playlist.
And use the connect to other device function in Spotify.
But I don't know where to start searching for these functions.
Is it an activity class?
Because the action seem to be app independent?

[scintillating luminescence]

I think when OP said "what every package does", they meant "for a given package of interest, how is it possible to know/learn/discover what the various activity classes do?"

This is a question I'm also curious about.  If this were Windows I'd say it's probably something like Spy++ to uncover the name of the window I wanted to send a message to.

For example, if I wanted to open a Hangouts conversation with a particular contact... where do I start?  I mean, the package of interest is Hangouts.  But I tried looking at all the activity classes, and the long-form names were being left-justified in the textbox - meaning I couldn't even tell what the full name of the activity class was, all I saw was the same "com.google.android.apps.hangout" before the text is cut off.  Some of them have short-form names but the majority do not.  But even if I could see the long-form name, I would still need some way to know what values to pass into it, how to format them, etc.

I'm not saying I need someone to give me an API reference, I'm none too shabby at reversing, I'm just unfamiliar with the tools I need to explore this domain.  Any way to help identify arbitrary activity class would be appreciated.

[Henrik "The Developer" Lindqvist]

Create a simple flow to find out the foreground activity:
     Flow beginning
           |
+--------->+
|   App in foreground
| Foreground activity: a
|          |
|      Toast show
|      Message= a     
+----------+

[bensperso...@gmail.com]

What do you mean when you say:

Flow beginning
|
+--------->+
| App in foreground
| Foreground activity: a
| |
| Toast show
| Message= a
+----------+

Specifically "Foreground activity: a" and Message = a". I'm trying to start a Google Play playlist when my alarm goes off, and I don't know how to specifically link to a playlist such as "Morning Music" playlist.

[Henrik "The Developer" Lindqvist]

That's just an simple example flow to that show a Toast when the foreground activity changes.