mograte MyListFragment to use a simple ViewModel

fixes crashes in MyListFragment if the User closes the fragment with a loading job still running, part of #56

app/src/main/java/org/mosad/teapod/ui/activity/main/fragments/MyListsFragment.kt

@@ -1,17 +1,21 @@
 package org.mosad.teapod.ui.activity.main.fragments
 
 import android.os.Bundle
+import android.util.Log
 import android.view.LayoutInflater
 import android.view.View
 import android.view.ViewGroup
 import androidx.fragment.app.Fragment
+import androidx.fragment.app.viewModels
+import androidx.lifecycle.Lifecycle
 import androidx.lifecycle.lifecycleScope
+import androidx.lifecycle.repeatOnLifecycle
 import androidx.viewpager2.adapter.FragmentStateAdapter
 import com.google.android.material.tabs.TabLayoutMediator
 import kotlinx.coroutines.launch
 import org.mosad.teapod.R
 import org.mosad.teapod.databinding.FragmentMyListsBinding
-import org.mosad.teapod.parser.crunchyroll.Crunchyroll
+import org.mosad.teapod.ui.activity.main.viewmodel.MyListsFragmentViewModel
 import org.mosad.teapod.util.toItemMediaList
 
 class MyListsFragment : Fragment() {
@@ -19,6 +23,8 @@ class MyListsFragment : Fragment() {
     private lateinit var binding: FragmentMyListsBinding
     private lateinit var pagerAdapter: FragmentStateAdapter
 
+    private val model: MyListsFragmentViewModel by viewModels()
+
     private val fragments = arrayListOf<Fragment>()
 
     override fun onCreateView(inflater: LayoutInflater, container: ViewGroup?, savedInstanceState: Bundle?): View {
@@ -33,7 +39,6 @@ class MyListsFragment : Fragment() {
         pagerAdapter = ScreenSlidePagerAdapter(this)
         binding.pagerMyLists.adapter = pagerAdapter
 
-        // TODO is position 0 always episodes? (and 1 always similar titles)
         TabLayoutMediator(binding.tabMyLists, binding.pagerMyLists) { tab, position ->
             tab.text = when(position) {
                 0 -> getString(R.string.my_list)
@@ -43,15 +48,33 @@ class MyListsFragment : Fragment() {
             }
         }.attach()
 
-        lifecycleScope.launch {
+        viewLifecycleOwner.lifecycleScope.launch {
-            val items = Crunchyroll.watchlist(50)
+            viewLifecycleOwner.repeatOnLifecycle(Lifecycle.State.STARTED) {
-
+                model.onUiState(viewLifecycleOwner.lifecycleScope) { uiState ->
-            MediaFragmentSimilar(items.toItemMediaList()).also {
+                    when (uiState) {
-                fragments.add(it)
+                        is MyListsFragmentViewModel.UiState.Normal -> bindUiStateNormal(uiState)
-                pagerAdapter.notifyItemInserted(fragments.indexOf(it))
+                        is MyListsFragmentViewModel.UiState.Loading -> bindUiStateLoading()
+                        is MyListsFragmentViewModel.UiState.Error -> bindUiStateError(uiState)
+                    }
+                }
             }
         }
+    }
 
+    private fun bindUiStateNormal(uiState: MyListsFragmentViewModel.UiState.Normal) {
+        MediaFragmentSimilar(uiState.watchlistItems.toItemMediaList()).also {
+            fragments.add(it)
+            pagerAdapter.notifyItemInserted(fragments.indexOf(it))
+        }
+    }
+
+    private fun bindUiStateLoading() {
+        // currently not used
+    }
+
+    private fun bindUiStateError(uiState: MyListsFragmentViewModel.UiState.Error) {
+        // currently not used
+        Log.e(javaClass.name, "A error occurred while loading a UiState: ${uiState.message}")
     }
 
     /**

app/src/main/java/org/mosad/teapod/ui/activity/main/viewmodel/HomeViewModel.kt

@@ -32,7 +32,7 @@ import kotlinx.coroutines.launch
 import org.mosad.teapod.parser.crunchyroll.*
 import kotlin.random.Random
 
-class HomeViewModel : ViewModel()  {
+class HomeViewModel : ViewModel() {
 
     private val WATCHLIST_LENGTH = 50
 

app/src/main/java/org/mosad/teapod/ui/activity/main/viewmodel/MyListsFragmentViewModel.kt

@@ -0,0 +1,50 @@
+package org.mosad.teapod.ui.activity.main.viewmodel
+
+import androidx.lifecycle.LifecycleCoroutineScope
+import androidx.lifecycle.ViewModel
+import androidx.lifecycle.viewModelScope
+import kotlinx.coroutines.async
+import kotlinx.coroutines.flow.MutableStateFlow
+import kotlinx.coroutines.launch
+import org.mosad.teapod.parser.crunchyroll.Crunchyroll
+import org.mosad.teapod.parser.crunchyroll.Item
+
+class MyListsFragmentViewModel : ViewModel() {
+
+    private val WATCHLIST_LENGTH = 50
+
+    private val uiState = MutableStateFlow<UiState>(UiState.Loading)
+
+    sealed class UiState {
+        object Loading : UiState()
+        data class Normal(
+            val watchlistItems: List<Item>
+        ) : UiState()
+        data class Error(val message: String?) : UiState()
+    }
+
+    init {
+        load()
+    }
+
+    fun onUiState(scope: LifecycleCoroutineScope, collector: (UiState) -> Unit) {
+        scope.launch { uiState.collect { collector(it) } }
+    }
+
+    fun load() {
+        viewModelScope.launch {
+            uiState.emit(UiState.Loading)
+            try {
+                // run the loading in parallel to speed up the process
+                val watchlistJob = viewModelScope.async { Crunchyroll.watchlist(WATCHLIST_LENGTH).data }
+                uiState.emit(
+                    UiState.Normal(watchlistJob.await())
+                )
+            } catch (e: Exception) {
+                uiState.emit(UiState.Error(e.message))
+            }
+        }
+
+    }
+
+}