Home / Questions / 522411
Accepted
eMihl
Asked: 2022-08-19 04:20:10 +0800 CST 2022-08-19 04:20:10 +0800 CST

Coroutines in Kotlin, how to make the thread wait for the result of the get() thrown to FIREBASE?

  • 772

I have created a coroutine inside a function to achieve, through the withContext, that the thread waits for the result of the get() launched to firestore. However, it seems that the get() method creates a separate thread, so I can't get the coroutine to wait for the variables to be assigned their corresponding values. The execution continues, and the variables are left with their default values, not with the values ​​collected in firestore.

How should I use the coroutine so that it expects the result requested from the firestore via the get() method? Is there an alternative way to do what I want?

GlobalScope.launch(Dispatchers.Main) {

      val recyclerView: RecyclerView = view.findViewById(R.id.recycler1)
      recyclerView.layoutManager = LinearLayoutManager(context)

      val database = FirebaseFirestore.getInstance()

      withContext(Dispatchers.IO) {
         database.collection("grupos").document("2").get().addOnSuccessListener {
           nombreEvent = it.getString("name")
           artista = it.getString("artista")
           descripcion = it.getString("descripcion")
           lugar = it.getString("lugar")
           imagen = it.getString("imagen")
         }
       }

       val adapterRec = RecyclerAdapter( listOf(Grupo("id", nombreEvent, artista, descripcion, lugar,imagen)))
       recyclerView.adapter = adapterRec
            
}
firebase

1 Answers

  1. Best Answer

    I have already found the solution to the problem I was posing with this coroutine; First, I had to use the await() function so that the main thread would wait for the response of the query launched. On top of that, I had to wrap everything inside a try..catch to catch the exception if no data was found in the query.

    try{
      val database = FirebaseFirestore.getInstance()

      withContext(Dispatchers.IO) {
         database.collection("grupos").document("2").get().addOnSuccessListener {
           nombreEvent = it.getString("name")
           artista = it.getString("artista")
           descripcion = it.getString("descripcion")
           lugar = it.getString("lugar")
           imagen = it.getString("imagen")
         }
       }.await()
} catch (e: Exception) {
            println("exception: ${e.message}")
}

       val adapterRec = RecyclerAdapter( listOf(Grupo("id", nombreEvent, artista, descripcion, lugar,imagen)))
       recyclerView.adapter = adapterRec
    • 1