private fun renderContact(uri: Uri?) {
    val contactNameView = findViewById<TextView>(R.id.contact_name)
    val contactPhoneView = findViewById<TextView>(R.id.contact_phone)
    val contactPhotoView = findViewById<ImageView>(R.id.contact_portrait)

    val name = uri?.let { getDisplayName(it, contentResolver) } ?: "Select a contact"
    val number = uri?.let { getMobileNumber(it, contentResolver) } ?: ""
    val photo = uri?.let { getPhoto(it, contentResolver)}

    contactNameView.setText(name)
    contactPhoneView.setText(number)
    contactPhotoView.setImageBitmap(photo)

} // fun renderContact