Android : How to programmatically open the soft keyboard in Emoji View
Maybe this will help you:
https://blog.swiftkey.com/tech-blog-android-input-method-subtypes/
There is something like an Emoji Subtype as you can see following the link below.
public static RichInputMethodSubtype getEmojiSubtype()
TextView
Using TextView's input type does not contain what you want...
Keyboards
Seems you can show the user a list of available keyboards. (the ones that are available on that device)
And with that, see if it has an Emoji Key Board available. But needs at least Android 4.1 it seems.
Force Part of Key Board
Not possible as far as I can see. You can disable them, it seems.
*I would love to show how to do this, it looks like a neat thing to be able to do. But my google-fu does not show anything close :(
After trying for a while I didn't achieved this goal even injecting a keyevent.
Looking in Google Allo, that looks as a custom implementation. I have switftkey themed keyboard and on KitKat Moto G (1st gen) it's very remarkeable. I tested also on a Marshmallow Moto G (2nd gen) with native keyboard, but contracted, and you can see that isn't the real soft keyboard :
I think there is no way to achieve this without a custom emoji's implementation.