Handy solution to support non-removable prefix for https://github.com/RedMadRobot/input-mask-android library

NonRemovePrefixTextChangedListener

import android.text.Editable
import android.text.TextWatcher
import android.widget.EditText
import com.redmadrobot.inputmask.MaskedTextChangedListener
import com.redmadrobot.inputmask.helper.AffinityCalculationStrategy
import com.redmadrobot.inputmask.model.Notation

class NonRemovePrefixTextChangedListener(
    primaryFormat: String,
    affineFormats: List<String> = emptyList(),
    customNotations: List<Notation> = emptyList(),
    affinityCalculationStrategy: AffinityCalculationStrategy = AffinityCalculationStrategy.WHOLE_STRING,
    autocomplete: Boolean = true,
    autoskip: Boolean = false,
    val field: EditText,
    listener: TextWatcher? = null,
    valueListener: ValueListener? = null,
    private val nonRemovePrefix: String
) : MaskedTextChangedListener(
    primaryFormat,
    affineFormats,
    customNotations,
    affinityCalculationStrategy,
    autocomplete,
    autoskip,
    field,
    listener,
    valueListener
) {

    override fun afterTextChanged(edit: Editable?) {
        val text = field.text.toString()
        if (!text.startsWith(nonRemovePrefix)) {
            setText(nonRemovePrefix, field)
        } else {
            super.afterTextChanged(edit)
        }
    }

    companion object {

        fun installOn(
            editText: EditText,
            primaryFormat: String,
            affineFormats: List<String> = emptyList(),
            customNotations: List<Notation> = emptyList(),
            affinityCalculationStrategy: AffinityCalculationStrategy = AffinityCalculationStrategy.WHOLE_STRING,
            autocomplete: Boolean = true,
            autoskip: Boolean = false,
            listener: TextWatcher? = null,
            valueListener: ValueListener? = null,
            nonRemovePrefix: String

        ): NonRemovePrefixTextChangedListener {
            val maskedListener = NonRemovePrefixTextChangedListener(
                primaryFormat,
                affineFormats,
                customNotations,
                affinityCalculationStrategy,
                autocomplete,
                autoskip,
                editText,
                listener,
                valueListener,
                nonRemovePrefix
            )
            editText.addTextChangedListener(maskedListener)
            editText.onFocusChangeListener = maskedListener
            return maskedListener
        }
    }

}