In my Fragment, I’m trying to fetch data from Firebase Database using coroutines where data is retrieving properly. Here is my code
@ExperimentalCoroutinesApi //Fragment Class code
override fun onStart() {
super.onStart()
checkOutViewModel.viewModelScope.launch {
try{
if (isActive){
checkOutViewModel.getCartDataFromFirebaseNetwork().collect{
tempList.add(it)
}
}
}catch (ex : Exception){
Log.d("exception message",ex.cause?.message!!) //Fatal Exception: Main
}
orderListAdapter?.submitList(tempList)
binding.progress.visibility = View.GONE
binding.recycler.visibility = View.VISIBLE
}
}
@ExperimentalCoroutinesApi //Viewmodel class code
suspend fun getCartDataFromFirebaseNetwork()= firebaseNetwork.getCartFromFirebase()
@ExperimentalCoroutinesApi //Repository class code
suspend fun getCartFromFirebase() = callbackFlow<Cart> {
ensureActive()
val counterList = myFlow.toList()
val itemList = myFlow.mapBasketToItemsList().toList()
val pairs = myFlow.mapBasketListToQuantity().toList()
if(itemList.isNotEmpty() && pairs.isNotEmpty()){
for ((current,item) in itemList.withIndex()) {
val cart = Cart(counterList[current].basketId!!,item.id!!,item.url!!,item.name!!,pairs[current].first,pairs[current].second,counterList[current].itemCounter!!,pairs[current].second)
offer(cart)
}
channel.close()
}
}
@ExperimentalCoroutinesApi
val myFlow = callbackFlow<Basket> {
databaseReference.child("Cart").child(getCurrentUserUid())
.addListenerForSingleValueEvent(object : ValueEventListener {
override fun onCancelled(p0: DatabaseError) {
}
override fun onDataChange(dataSnapshot: DataSnapshot) {
if (dataSnapshot.exists()) {
for (data in dataSnapshot.children) {
val basket = Basket()
basket.basketId = data.key
basket.itemId = data.child("itemId").value as String
basket.itemCounter = data.child("itemCounter").value as String
basket.itemWeight = data.child("itemWeight").value as String
offer(basket)
}
channel.close()
}
}
})
awaitClose()
}
@ExperimentalCoroutinesApi
private fun Flow<Basket>.mapBasketToItemsList() : Flow<Items> = map{basket ->
suspendCoroutine<Items> {continuation ->
databaseReference.child("Items").child(basket.itemId!!)
.addListenerForSingleValueEvent(object : ValueEventListener {
override fun onCancelled(p0: DatabaseError) {
}
override fun onDataChange(dataSnapshot: DataSnapshot) {
if (dataSnapshot.exists()) {
val items = dataSnapshot.getValue(Items::class.java)!!
continuation.resume(items)
}
}
})
}
}
@ExperimentalCoroutinesApi
private fun Flow<Basket>.mapBasketListToQuantity() : Flow<Pair<String,String>> = map{basket ->
suspendCoroutine<Pair<String,String>> {continuation ->
databaseReference.child("Quantities").child(basket.itemId!!)
.child(basket.itemWeight!!)
.addListenerForSingleValueEvent(object : ValueEventListener {
override fun onCancelled(p0: DatabaseError) {
}
override fun onDataChange(dataSnapshot: DataSnapshot) {
if (dataSnapshot.exists()) {
val key = dataSnapshot.key
val value = dataSnapshot.value as String
val myPair = Pair(key!!, value)
continuation.resume(myPair)
}
}
})
}
}
I’m also using isActive method to check whether the job is still active or not before retrieving any data. I get " Fatal Exception: Main, Job was Cancelled " if i pressed back button before recyclerview shows the data. How should i handle this issue? Can somebody tell me to solve it?
Edited:
This is my Navigation Flow of Fragments
OnBoarding-Authentication-MainFragment-CheckItemListFragment
override fun onStart() { //OnBoarding Fragment
super.onStart()
try {
if(viewModel.checkAuth()){
updateUI()
}
}catch (ex : Exception){
println("In onBoarding Fragment")
Log.d("exception message",ex.cause?.message!!)
}
}
override fun onStart() { //Authentication Fragment
super.onStart()
try {
if(mAuth.currentUser == null){
showShortToast("Please Login")
}else{
updateUI()
}
}catch (ex : Exception){
println("In authentication Fragment")
Log.d("exception message",ex.cause?.message!!)
}
}
override fun onStart() { //MainFragment
super.onStart()
try {
if(mainFragmentViewModel.checkSignIn() == null)
findNavController().navigateUp()
binding.toolbar.add_to_cart.setOnClickListener {
it.findNavController().navigate(R.id.action_mainFragment_to_checkoutItemsList)
}
}catch (ex : Exception){
println("In Main Fragment")
Log.d("exception",ex.message!!)
}
}
@ExperimentalCoroutinesApi
override fun onStart() { //CheckItemList Fragment
super.onStart()
try {
binding.addToCart.setOnClickListener {
checkOutViewModel.viewModelScope.launch {
val message = orderListAdapter?.getList()?.let { it1 -> checkOutViewModel.submitFinalCart(it1) }
if(message!!){
findNavController().navigate(R.id.action_checkoutItemsList_to_finalCarts)
}
}
}
viewLifecycleOwner.lifecycleScope.launch {
ensureActive()
checkOutViewModel.getCartDataFromFirebaseNetwork().collect {
tempList.add(it)
orderListAdapter?.submitList(tempList)
binding.progress.visibility = View.GONE
binding.recycler.visibility = View.VISIBLE
}
}
}catch (ex : Exception){
println("In checkItemList Fragment")
Log.d("exception message",ex.cause?.message!!)
}
}
Edited : My Logcat is :-
--------- beginning of crash
07-10 21:18:40.605 30715-30715/com.example.groceryapp E/AndroidRuntime: FATAL
EXCEPTION: main
Process: com.example.groceryapp, PID: 30715
f.d
at com.example.groceryapp.checkout.CheckoutItemsList$e.a(:73)
at f.z.k.a.a.b(:33)
at kotlinx.coroutines.u0.run(:334)
at kotlinx.coroutines.z0.k(:68)
at kotlinx.coroutines.r0.b(:354)
at f.z.i.b(:42)
at com.example.groceryapp.f.a$r$a$b.a(:262)
at com.google.firebase.database.m$a.a(:179)
at com.google.firebase.database.u.a0.a(:75)
at com.google.firebase.database.u.i0.d.a(:63)
at com.google.firebase.database.u.i0.g$a.run(:55)
at android.os.Handler.handleCallback(Handler.java:742)
at android.os.Handler.dispatchMessage(Handler.java:95)
at android.os.Looper.loop(Looper.java:157)
at android.app.ActivityThread.main(ActivityThread.java:5603)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:774)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:652)
This is how i used my Try Catch block in every Fragments to handle this issue but it is also not working at all. So far I couldn’t find any possible answer that will solve my issue. I also posted the issue on Stack Overflow android - How do i fix "Job was Cancelled" exception? - Stack Overflow but couldn’t find any correct solution. Please tell me how do i fix it?