As I see, a way to show default emojis on android is by using the following on an input text.
android:inputType=\"textMultiLine|textShortMessage\"
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()
https://android.googlesource.com/platform/packages/inputmethods/LatinIME/+/master/java/src/com/android/inputmethod/latin/RichInputMethodSubtype.java