DialogFragment расширяет XML на весь экран?

я реализовал DialogFragment , но это выглядит так:

вместо этого (из предварительного просмотра XML):

фрагмент onViewCreated

val button = view.findViewById(R.id.button_register) as Button
button.setOnClickListener{
    Log.d(TAG, "Clicked")
    val dialog = SuccessDialog()
    dialog.show(fragmentManager, "success dialog")
}

Класс SuccessDialog

class SuccessDialog: DialogFragment() {
    override fun onCreateView(inflater: LayoutInflater, container: ViewGroup?, savedInstanceState: Bundle?): View? {
        val view = inflater.inflate(R.layout.dialog_success, container, false)
        val button: Button = view.findViewById(R.id.button_ok)
        button.setOnClickListener{
            dialog.dismiss()
        }
        return view
    }
}

XML диалога:

<?xml version = "1.0" encoding = "utf-8"?>
<android.support.constraint.ConstraintLayout 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:orientation = "vertical"
    android:layout_width = "250dp"
    android:layout_height = "200dp"
    android:background = "@color/colorPrimaryDark"
    android:padding = "5dp"
    android:layout_gravity = "center">

    <ImageView
        android:id = "@+id/imageView"
        android:layout_width = "47dp"
        android:layout_height = "46dp"
        android:layout_marginStart = "8dp"
        android:layout_marginLeft = "8dp"
        android:layout_marginEnd = "8dp"
        android:layout_marginRight = "8dp"
        app:layout_constraintEnd_toEndOf = "parent"
        app:layout_constraintStart_toStartOf = "parent"
        app:layout_constraintTop_toTopOf = "parent"
        tools:srcCompat = "@drawable/ic_check_mark_24dp"
        android:contentDescription = "@string/checkmark" />

    <TextView
        android:id = "@+id/textView3"
        android:layout_width = "wrap_content"
        android:layout_height = "wrap_content"
        android:layout_marginStart = "8dp"
        android:layout_marginLeft = "8dp"
        android:layout_marginTop = "8dp"
        android:layout_marginEnd = "8dp"
        android:layout_marginRight = "8dp"
        android:text = "@string/success"
        android:textColor = "@android:color/white"
        android:textSize = "18sp"
        android:textStyle = "bold"
        app:layout_constraintEnd_toEndOf = "parent"
        app:layout_constraintStart_toStartOf = "parent"
        app:layout_constraintTop_toBottomOf = "@+id/imageView" />

    <TextView
        android:id = "@+id/textView6"
        android:layout_width = "match_parent"
        android:layout_height = "wrap_content"
        android:layout_marginStart = "8dp"
        android:layout_marginLeft = "8dp"
        android:layout_marginTop = "8dp"
        android:layout_marginEnd = "8dp"
        android:layout_marginRight = "8dp"
        android:gravity = "center"
        android:text = "@string/thank_you"
        android:textColor = "@android:color/white"
        android:textStyle = "italic"
        app:layout_constraintEnd_toEndOf = "parent"
        app:layout_constraintStart_toStartOf = "parent"
        app:layout_constraintTop_toBottomOf = "@+id/textView3" />

    <Button
        android:id = "@+id/button_ok"
        android:layout_width = "86dp"
        android:layout_height = "40dp"
        android:layout_marginStart = "8dp"
        android:layout_marginLeft = "8dp"
        android:layout_marginTop = "8dp"
        android:layout_marginEnd = "8dp"
        android:layout_marginRight = "8dp"
        android:layout_marginBottom = "8dp"
        android:text = "@string/ok"
        app:layout_constraintBottom_toBottomOf = "parent"
        app:layout_constraintEnd_toEndOf = "parent"
        app:layout_constraintStart_toStartOf = "parent"
        app:layout_constraintTop_toBottomOf = "@+id/textView6" />
</android.support.constraint.ConstraintLayout>