I'm trying to get a RecyclerView to update once I have downloaded some data from Firestore but it doesn't seem to update the UI when the data changes. Here is the main activity:

class MainActivity : AppCompatActivity() {

private lateinit var dbService: DatabaseManager
private var mBound: Boolean = false

private val restaurantListModel: RestaurantList by viewModels()

val data = ArrayList<RestaurantCardModel>()
val adapter = RestaurantListAdapter(data)

/** Defines callbacks for service binding, passed to bindService()  */
private val connection = object : ServiceConnection {

    override fun onServiceConnected(className: ComponentName, service: IBinder) {

        // We've bound to LocalService, cast the IBinder and get LocalService instance
        val binder = service as DatabaseManager.LocalBinder
        dbService = binder.getService()
        mBound = true

        dbService.read_restaurants(object: MyCallback {
            override fun onCallback(value: MutableList<Restaurant>) {
                restaurantListModel.restList.value = value
                updateView()
            }
        })
    }

    override fun onServiceDisconnected(arg0: ComponentName) {
        mBound = false
    }
}

fun updateView(){
    for (rest in restaurantListModel.restList.value!!){
        data.add(RestaurantCardModel(R.drawable.pizza_express_logo, rest.name, 5, rest.review, rest.no_review,
            R.color.colorPrimary))
    }
}

override fun onCreate(savedInstanceState: Bundle?) {
    super.onCreate(savedInstanceState)
    setContentView(R.layout.activity_main)

    // Bind to LocalService
    Intent(this, DatabaseManager::class.java).also { intent ->
        bindService(intent, connection, Context.BIND_AUTO_CREATE)
    }

    // getting the recyclerview by its id
    val recyclerview = findViewById<RecyclerView>(R.id.restaurant_recyclerview)

    // this creates a vertical layout Manager
    recyclerview.layoutManager = LinearLayoutManager(this)

    // Setting the Adapter with the recyclerview
    recyclerview.adapter = adapter
    
    if(mBound) { updateView() }
}

override fun onResume() {
    super.onResume()
    if (mBound) { updateView() }
}

override fun onStart() {
    super.onStart()
}

override fun onStop() {
    super.onStop()
    unbindService(connection)
    mBound = false
}

}

Then you have my database manager for fetching the data from firebase:

class DatabaseManager : Service() {
// Binder given to clients
private val binder = LocalBinder()

var db = FirebaseFirestore.getInstance()

override fun onStartCommand(intent: Intent?, flags: Int, startId: Int): Int {
    return super.onStartCommand(intent, flags, startId)
}

fun upload_review(review_data: String){

}

fun read_restaurants(myCallback : MyCallback): MutableList<Restaurant> {
    var restList : MutableList<Restaurant> = mutableListOf()
    db.collection("restaurant")
        .get()
        .addOnCompleteListener { task ->
            if (task.isSuccessful) {
                restList = updateRestaurantList(task.result!!)
                myCallback.onCallback(restList)
            } else {
                Log.w(TAG, "Error getting documents.", task.exception)
            }
        }
    return restList
}

private fun updateRestaurantList(restaurants: QuerySnapshot): MutableList<Restaurant> {
    var restList : MutableList<Restaurant> = mutableListOf()
    for (doc in restaurants.documents){
        Log.d(TAG, doc.toString())
        var tempRest : Restaurant? = doc.toObject(Restaurant::class.java)?.withId(doc.id)
        if (tempRest != null) {
            restList.add(tempRest)
        }
    }
    return restList
}

/**
 * Class used for the client Binder.  Because we know this service always
 * runs in the same process as its clients, we don't need to deal with IPC.
 */
inner class LocalBinder : Binder() {
    // Return this instance of LocalService so clients can call public methods
    fun getService(): DatabaseManager = this@DatabaseManager
}

override fun onBind(intent: Intent): IBinder {
    return binder
}

}

The recycler view works fine when I add the data manually in the onCreate() method but doesn't update the view once firebase is finished, any help would be appreciated.

CodePudding user response：

The recycler view works fine when I add the data manually in the onCreate() method but doesn't update the view

That's the expected behavior since you are using a .get() call, which basically means that you are getting the data only once. What you are looking for is listening for real-time updates. So you have to use addSnapshotListener() call for that.

Besides that, there is also a useful library called FirebaseUI for Android that has a specific usage for Cloud Firestore.