如何检查Cloud Firestore数据是否已缓存？

Question

经过阅读后，我了解了Cloud Firestore的isFromCache（）来检查数据是否来自缓存。但是，我不知道如何使用它，并且文档中也没有太多关于如何使用它的细节。

我使用FirestoreRecyclerView，以下是我的onViewCreated（）：

override fun onViewCreated(view: View, savedInstanceState: Bundle?) {
    super.onViewCreated(view, savedInstanceState)

    val recyclerView = view.firestoreRecyclerView

    val db = Firebase.firestore

    val query : Query = db.collectionGroup("fire")

    val options : FirestoreRecyclerOptions<FireModel> =
        FirestoreRecyclerOptions.Builder<FireModel>()
            .setQuery(query, FireModel::class.java)
            .build()

    adapter = object : FirestoreRecyclerAdapter<FireModel, FireViewHolder>(options) {

        override fun onCreateViewHolder(parent: ViewGroup, viewType: Int): FireViewHolder{

            val v : View = LayoutInflater.from(parent.context).inflate(R.layout.fire_cardview, parent, false)

            return FireViewHolder(v)
        }

        override fun onBindViewHolder(
            holder: FireViewHolder,
            position: Int,
            model: FireModel
        ) {
            holder.name.text = model.name.name
            holder.address.text = model.address.unitName
            holder.age.text = model.age.toString()
}


class FireViewHolder(v : View) : RecyclerView.ViewHolder (v) {

    var name : TextView = v.nameTextView
    var address: TextView = v.addressTextView
    var age: TextView = v.ageValueTextView
}

和我的模型班：

@Keep
@Parcelize
class FireModel (

    var name : String = "",
    var address : String = "",
    var age : Int = 0
) : Parcelable