When user input emoji into EditText, it's count like 2 symbols. How to count emoji like 1 symbol?

I have InputEditText from Google Material. And when I enter emoji from soft keyboard, on counter instead of 1 symbol shows 2 symbols per emoji. How to avoid it and count emoji like 1 symbol?

<com.google.android.material.textfield.TextInputLayout
    android:id="@+id/optionalInputLayout"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:layout_marginTop="@dimen/padding_default_vertical"
    android:focusable="true"
    android:hint="@string/spend_visit_note"
    app:counterEnabled="false"
    app:counterMaxLength="100"
    app:errorEnabled="true"
    app:hintTextAppearance="@style/TextAppearance.AppCompat.Medium.Inverse">

    <com.google.android.material.textfield.TextInputEditText
        android:id="@+id/optionalEditText"
        style="@style/AppTheme.Widget.EditText"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:imeOptions="actionDone"
        android:inputType="textNoSuggestions"
        android:maxLength="101"
        android:singleLine="true" />
</com.google.android.material.textfield.TextInputLayout>

optionalEditText
    .afterTextChangeEvents()
    .skipInitialValue()
    .throttleFirst(100, TimeUnit.MICROSECONDS)
    .map {
        Action.OptionalEdited(
            it.editable?.toString() ?: String.empty
        )
    }
    .bindToUiActions()

I try to find smth in methods or documentation, but I found nothing

The issue you're encountering is related to how emojis are represented in the input field. Emojis, especially the newer ones, can be made up of multiple Unicode characters, which can lead to discrepancies in character counting. To count emojis as a single character, you need to take into account the variation in Unicode character lengths.

To handle this, you can use the breakIterator class from java.text package, which can help you get the correct character count even for emojis.

Here's a code snippet that shows how you can modify your existing code to count emojis as single characters:

import java.text.BreakIterator;

// Inside your existing code:
optionalEditText
    .afterTextChangeEvents()
    .skipInitialValue()
    .throttleFirst(100, TimeUnit.MICROSECONDS)
    .map {
        val inputText = it.editable?.toString() ?: String.empty
        val emojiCount = countEmojis(inputText)
        Action.OptionalEdited(inputText, emojiCount)
    }
    .bindToUiActions()

// Function to count emojis as single characters
private fun countEmojis(inputText: String): Int {
    var count = 0
    val breakIterator = BreakIterator.getCharacterInstance()

    breakIterator.setText(inputText)
    var prevIndex = 0
    var index = breakIterator.first()

    while (index != BreakIterator.DONE) {
        val char = inputText.substring(prevIndex, index)
        if (char.isEmoji()) {
            count++
        }
        prevIndex = index
        index = breakIterator.next()
    }

    return count
}

// Extension function to check if a string is an emoji
private fun String.isEmoji(): Boolean {
    return this.codePointCount(0, this.length) == 1 && this.matches(Regex("\\p{So}"))
}

This code introduces a countEmojis function that uses BreakIterator to properly count emojis as single characters. The isEmoji extension function is used to determine whether a string represents an emoji.

By using this approach, you should now see the correct character count in the TextInputLayout. Note that you may need to adapt the code to your specific Android/Kotlin environment if needed.