As I see, a way to show default emojis on android is by using the following on an input text.
android:inputType=\"textMultiLine|textShortMessage\"
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 :(