DAtabinding to custom prop

button_ticket.xml

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:layout_marginEnd="@dimen/small_margin"
    android:background="@drawable/themed_button_white_elevated"
    android:clickable="true"
    android:elevation="4dp"
    android:focusable="true"
    android:gravity="center"
    android:orientation="horizontal"
    tools:layout_height="200dp">

    <ImageView
        android:id="@+id/ticket_icon"
        android:layout_width="@dimen/ticket_icon_size"
        android:layout_height="@dimen/ticket_icon_size"
        tools:src="@drawable/ic_print_ticket_medium"
        android:scaleType="fitCenter" />

    <FrameLayout
        android:layout_width="2dp"
        android:layout_height="match_parent"
        android:layout_marginHorizontal="16dp"
        android:layout_marginVertical="32dp"
        android:background="#777" />

    <LinearLayout
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:orientation="vertical">

        <TextView
            android:id="@+id/ticket_title"
            style="@style/Text.XXLarge"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:textColor="#000"
            tools:text="Billett" />

        <TextView
            android:id="@+id/ticket_description"
            style="@style/Text.Small.Secondary"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_marginTop="2dp"
            tools:text="Egenskaper" />

    </LinearLayout>
</LinearLayout>

BuyTicketButton.kt

class BuyTicketButton(context: Context, attrs: AttributeSet?) : FrameLayout(context, attrs) {

    constructor(context: Context, attrs: AttributeSet?, defStyleAttr: Int, defStyleRes: Int) : this(context, attrs)
    constructor(context: Context, attrs: AttributeSet?, defStyleAttr: Int) : this(context, attrs)

    init {
        val view = LayoutInflater.from(context)!!.inflate(R.layout.button_ticket, this, true)
        val attributes = context.obtainStyledAttributes(attrs, R.styleable.BuyTicketButton)

        val imageSrc = attributes.getResourceId(R.styleable.BuyTicketButton_imageSrc, 0)
        view.findViewById<ImageView>(R.id.ticket_icon).setImageResource(imageSrc)
        view.findViewById<TextView>(R.id.ticket_title).text = attributes.getString(R.styleable.BuyTicketButton_title)
        view.findViewById<TextView>(R.id.ticket_description).let {
            it.text = attributes.getString(R.styleable.BuyTicketButton_description)
            it.visibility = if (it.text.isNullOrEmpty()) GONE else View.VISIBLE
        }
        attributes.recycle()
    }
}

layout-parent.xml

            <no.ruter.sales.shared.view.BuyTicketButton
                android:id="@+id/default_media_button"
                android:layout_width="0dp"
                android:layout_height="match_parent"
                android:layout_marginLeft="@dimen/small_margin"
                app:layout_constraintStart_toEndOf="@id/travel_card_button"
                app:layout_constraintEnd_toEndOf="parent"
                android:onClick="@{fragment::clickDefaultSalesMediaBtn}"
                app:imageSrc="5"
                />