Context: It is my first Android project and maybe my second with Kotlin so I am quite limited and I fill I am asking some silly question but I can’t find any direction on it (certainly I am messing up some previous knowledge of Angular/Srping with Android/Kotlin)
Goal: Android App will get a Firestore customtoken from certain backend microservice and then start to listen a document. So far so good. I read about good practices of how close/detach the listen and I believe I have successfully done this by passing Android activity as first argument to snapshot. So far also so good. But in my case, I have to close/detach the snapshot listen either after 10 minutes or after a especific value from document is received. Now I really got stuck.
I tried the simplest first step as imagined and I am getting the naive warnning form this topic. So my straght question is: why it is complaining as ALWAYS TRUE condition? A complementaty comment from someone expert on Android would be how to close/detach the snapshot after 10 minutes and if I receive a specific value from the listened document. Please accept the idea that either one of these two conditions needs to stops listen and still keep in same MainActivity.kt.
Here is the code with warning when trying to check during onStop cycle phase
package com.mycomp.appfirestore
import android.os.Bundle
import android.util.Log
import android.widget.Button
import android.widget.TextView
import android.widget.Toast
import androidx.appcompat.app.AppCompatActivity
import com.google.firebase.auth.FirebaseAuth
import com.google.firebase.firestore.DocumentSnapshot
import com.google.firebase.firestore.EventListener
import com.google.firebase.firestore.FirebaseFirestore
import com.mycomp.appfirestore.data.service.Endpoint
import com.mycomp.appfirestore.data.service.NetworkUtils
import com.mycomp.appfirestore.model.Transfer
import kotlinx.android.synthetic.main.activity_main.*
import retrofit2.Call
import retrofit2.Callback
import retrofit2.Response
class MainActivity : AppCompatActivity() {
lateinit var auth: FirebaseAuth
lateinit var listenerReg : FirebaseFirestore
override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
setContentView(R.layout.activity_main)
val btnTransfer = findViewById(R.id.btnTransfer) as Button
val textViewTransfer = findViewById(R.id.textViewTransfer) as TextView
btnTransfer.setOnClickListener {
getToken()
}
}
fun getToken() {
val retrofitClient = NetworkUtils
.getRetrofitInstance("http://192.168.15.13:8080/")
val endpoint = retrofitClient.create(Endpoint::class.java)
...
callback.enqueue(object : Callback<Transfer> {
override fun onFailure(call: Call<Transfer>, t: Throwable) {
Toast.makeText(baseContext, t.message, Toast.LENGTH_SHORT).show()
}
override fun onResponse(call: Call<Transfer>, response: Response<Transfer>) {
listenStatus()
}
})
}
fun listenStatus() {
val TAG = "ListenStatus"
auth = FirebaseAuth.getInstance()
// to make simple for this question let's say the backend returned a valid customtoken used here
auth.signInWithCustomToken("eyJ **** gXsQ")
.addOnCompleteListener(this) { task ->
if (task.isSuccessful) {
Log.d(TAG, "*** signInWithCustomToken:success")
startSnapshot()
} else {
// If sign in fails, display a message to the user.
Log.w(TAG, "signInWithCustomToken:failure", task.exception)
Toast.makeText(
baseContext, "Authentication failed.",
Toast.LENGTH_SHORT
).show()
}
}
}
fun startSnapshot() {
val TAG = "StartSnapshot"
//Try to pass this(activity context) as first parameter.It will automatically handle acivity life cycle.
// Example if you are calling this listener in onCreate() and passing this as a first parameter then
// it will remove this listener in onDestroy() method of activity.
listenerReg = FirebaseFirestore.getInstance()
listenerReg.collection("transfer")
.document("sDme6IRIi4ezfeyfrU7y")
.addSnapshotListener(
this,
EventListener<DocumentSnapshot?> { snapshot, e ->
if (e != null) {
Log.w(TAG, "Listen failed.", e)
return@EventListener
}
if (snapshot != null && snapshot.exists()) {
textViewTransfer.text = snapshot.data!!["status"].toString()
//Log.d(TAG, snapshot.data!!["status"].toString())
} else {
Log.d(TAG, "Current data: null")
}
})
}
//here I get the warnning: 'listenerReg != null' is always 'true' when trying to detach/close Firestore snapshot (certainly I am messing up here some Java concept with Kotlin concept)
fun stopSnapshot() {
if (listenerReg != null) {
listenerReg.remove()
}
}
}
I am aware that since I added the activity as first argument of snapshot soon the activity is left it will detached automatically the listen. But I have two more condition to stop listen:
1 - after 10 minutes
2 - if I get a specific returned value
So as imaginary solution I would try more or less
…
EventListener<DocumentSnapshot?> { snapshot, e ->
if (e != null) {
Log.w(TAG, "Listen failed.", e)
return@EventListener
}
if (snapshot != null && snapshot.exists()) {
textViewTransfer.text = snapshot.data!!["status"].toString()
**** imagined solution ****
if (snapshot.data!!["status"].toString() == "FINISH"){
stopSnapshot()
}
//Log.d(TAG, snapshot.data!!["status"].toString())
} else {
Log.d(TAG, "Current data: null")
}
})
...
**** imagined solution ***
listenerReg.timeout(10000, stopSnapshot())
PS.: this question was originally posted in stackoverflow