Migrate MainActivity to Flow

Fixes: b/187703234
Change-Id: I60df7e2f211f5dab6534a7187ffbc4a6e615e6a8

Author: Manuel Vivo

mobile/src/main/java/com/google/samples/apps/iosched/ui/MainActivity.kt

@@ -24,7 +24,9 @@ import android.view.Menu
 import androidx.activity.viewModels
 import androidx.appcompat.app.AppCompatActivity
 import androidx.appcompat.widget.Toolbar
-import androidx.lifecycle.Observer
+import androidx.lifecycle.Lifecycle
+import androidx.lifecycle.lifecycleScope
+import androidx.lifecycle.repeatOnLifecycle
 import androidx.navigation.NavController
 import androidx.navigation.fragment.NavHostFragment
 import androidx.navigation.ui.AppBarConfiguration
@@ -39,7 +41,6 @@ import com.google.samples.apps.iosched.shared.di.CodelabsEnabledFlag
 import com.google.samples.apps.iosched.shared.di.ExploreArEnabledFlag
 import com.google.samples.apps.iosched.shared.di.MapFeatureEnabledFlag
 import com.google.samples.apps.iosched.shared.domain.ar.ArConstants
-import com.google.samples.apps.iosched.shared.result.EventObserver
 import com.google.samples.apps.iosched.ui.messages.SnackbarMessage
 import com.google.samples.apps.iosched.ui.messages.SnackbarMessageManager
 import com.google.samples.apps.iosched.ui.signin.SignInDialogFragment
@@ -48,6 +49,8 @@ import com.google.samples.apps.iosched.util.HeightTopWindowInsetsListener
 import com.google.samples.apps.iosched.util.signin.FirebaseAuthErrorCodeConverter
 import com.google.samples.apps.iosched.util.updateForTheme
 import dagger.hilt.android.AndroidEntryPoint
+import kotlinx.coroutines.flow.collect
+import kotlinx.coroutines.launch
 import timber.log.Timber
 import java.util.UUID
 import javax.inject.Inject
@@ -107,10 +110,6 @@ class MainActivity : AppCompatActivity(), NavigationHost {
     private lateinit var navHostFragment: NavHostFragment
     private var currentNavId = NAV_ID_NONE
 
-    // For sending pinned sessions as JSON to the AR module
-    private var pinnedSessionsJson: String? = null
-    private var canSignedInUserDemoAr: Boolean = false
-
     override fun onCreate(savedInstanceState: Bundle?) {
         super.onCreate(savedInstanceState)
 
@@ -149,42 +148,36 @@ class MainActivity : AppCompatActivity(), NavigationHost {
             navigateTo(requestedNavId)
         }
 
-        viewModel.theme.observe(this, Observer(::updateForTheme))
-
-        viewModel.navigateToSignInDialogAction.observe(
-            this,
-            EventObserver {
-                openSignInDialog()
-            }
-        )
-
-        viewModel.navigateToSignOutDialogAction.observe(
-            this,
-            EventObserver {
-                openSignOutDialog()
-            }
-        )
-        viewModel.arCoreAvailability.observe(
-            this,
-            Observer {
-                // Start observing ArCoreAvailability otherwise the value isn't updated
-                Timber.d("ArCoreAvailability = $it")
-            }
-        )
-        viewModel.pinnedSessionsJson.observe(
-            this,
-            Observer {
-                // Need to observe the pinnedSessions otherwise it's considered as inactive
-                pinnedSessionsJson = it
-            }
-        )
-        viewModel.canSignedInUserDemoAr.observe(
-            this,
-            Observer {
-                Timber.d("Signed in user can demo ar = $it")
-                canSignedInUserDemoAr = it
+        lifecycleScope.launch {
+            lifecycle.repeatOnLifecycle(Lifecycle.State.STARTED) {
+                launch {
+                    viewModel.navigationActions.collect { action ->
+                        when (action) {
+                            MainNavigationAction.OpenSignIn -> openSignInDialog()
+                            MainNavigationAction.OpenSignOut -> openSignOutDialog()
+                        }
+                    }
+                }
+                launch {
+                    viewModel.theme.collect { theme ->
+                        updateForTheme(theme)
+                    }
+                }
+                // AR-related Flows
+                launch {
+                    viewModel.arCoreAvailability.collect { result ->
+                        // Do nothing - activate flow
+                        Timber.d("ArCoreAvailability = $result")
+                    }
+                }
+                launch {
+                    viewModel.pinnedSessionsJson.collect { /* Do nothing - activate flow */ }
+                }
+                launch {
+                    viewModel.canSignedInUserDemoAr.collect { /* Do nothing - activate flow  */ }
+                }
             }
-        )
+        }
     }
 
     private fun configureNavMenu(menu: Menu) {
@@ -275,8 +268,8 @@ class MainActivity : AppCompatActivity(), NavigationHost {
             ArActivity::class.java
         ).apply {
             addFlags(Intent.FLAG_ACTIVITY_SINGLE_TOP)
-            putExtra(ArConstants.CAN_SIGNED_IN_USER_DEMO_AR, canSignedInUserDemoAr)
-            putExtra(ArConstants.PINNED_SESSIONS_JSON_KEY, pinnedSessionsJson)
+            putExtra(ArConstants.CAN_SIGNED_IN_USER_DEMO_AR, viewModel.canSignedInUserDemoAr.value)
+            putExtra(ArConstants.PINNED_SESSIONS_JSON_KEY, viewModel.pinnedSessionsJson.value)
         }
         startActivity(intent)
     }

mobile/src/main/java/com/google/samples/apps/iosched/ui/MainActivityViewModel.kt

@@ -17,21 +17,26 @@
 package com.google.samples.apps.iosched.ui
 
 import android.content.Context
-import androidx.lifecycle.LiveData
-import androidx.lifecycle.MutableLiveData
 import androidx.lifecycle.ViewModel
-import androidx.lifecycle.liveData
-import androidx.lifecycle.switchMap
+import androidx.lifecycle.viewModelScope
+import com.google.ar.core.ArCoreApk
 import com.google.samples.apps.iosched.shared.domain.ar.LoadArDebugFlagUseCase
 import com.google.samples.apps.iosched.shared.domain.sessions.LoadPinnedSessionsJsonUseCase
-import com.google.samples.apps.iosched.shared.result.Event
 import com.google.samples.apps.iosched.shared.result.Result
-import com.google.samples.apps.iosched.ui.ar.ArCoreAvailabilityLiveData
+import com.google.samples.apps.iosched.shared.util.tryOffer
 import com.google.samples.apps.iosched.ui.signin.SignInViewModelDelegate
 import com.google.samples.apps.iosched.ui.theme.ThemedActivityDelegate
+import com.google.samples.apps.iosched.util.WhileViewSubscribed
 import dagger.hilt.android.lifecycle.HiltViewModel
 import dagger.hilt.android.qualifiers.ApplicationContext
+import kotlinx.coroutines.channels.Channel
+import kotlinx.coroutines.delay
+import kotlinx.coroutines.flow.StateFlow
 import kotlinx.coroutines.flow.collect
+import kotlinx.coroutines.flow.flow
+import kotlinx.coroutines.flow.receiveAsFlow
+import kotlinx.coroutines.flow.stateIn
+import kotlinx.coroutines.flow.transformLatest
 import javax.inject.Inject
 
 @HiltViewModel
@@ -45,47 +50,54 @@ class MainActivityViewModel @Inject constructor(
     SignInViewModelDelegate by signInViewModelDelegate,
     ThemedActivityDelegate by themedActivityDelegate {
 
-    private val _navigateToSignInDialogAction = MutableLiveData<Event<Unit>>()
-    val navigateToSignInDialogAction: LiveData<Event<Unit>>
-        get() = _navigateToSignInDialogAction
+    private val _navigationActions = Channel<MainNavigationAction>(Channel.CONFLATED)
+    val navigationActions = _navigationActions.receiveAsFlow()
 
-    private val _navigateToSignOutDialogAction = MutableLiveData<Event<Unit>>()
-    val navigateToSignOutDialogAction: LiveData<Event<Unit>>
-        get() = _navigateToSignOutDialogAction
-
-    val pinnedSessionsJson: LiveData<String> = currentUserInfo.switchMap { user ->
+    val pinnedSessionsJson: StateFlow<String> = currentUserInfoFlow.transformLatest { user ->
         val uid = user?.getUid()
-        liveData {
-            if (uid != null) {
-                loadPinnedSessionsUseCase(uid).collect { result ->
-                    if (result is Result.Success) {
-                        emit(result.data)
-                    }
-                }
-            } else {
-                emit("")
-            }
-        }
-    }
-
-    val canSignedInUserDemoAr: LiveData<Boolean> = currentUserInfo.switchMap {
-        liveData {
-            emit(false)
-            loadArDebugFlagUseCase(Unit).collect { result ->
+        if (uid != null) {
+            loadPinnedSessionsUseCase(uid).collect { result ->
                 if (result is Result.Success) {
                     emit(result.data)
                 }
             }
+        } else {
+            emit("")
         }
-    }
+    }.stateIn(viewModelScope, WhileViewSubscribed, "")
+
+    val canSignedInUserDemoAr: StateFlow<Boolean> = currentUserInfoFlow.transformLatest {
+        val result = loadArDebugFlagUseCase(Unit)
+        if (result is Result.Success) {
+            emit(result.data)
+        }
+    }.stateIn(viewModelScope, WhileViewSubscribed, false)
 
-    val arCoreAvailability = ArCoreAvailabilityLiveData(context)
+    val arCoreAvailability: StateFlow<ArCoreApk.Availability?> = flow<ArCoreApk.Availability> {
+        var result: ArCoreApk.Availability? = null
+        while (result == null) {
+            val availability = ArCoreApk.getInstance().checkAvailability(context)
+            // If the availability is transient, we need to call availability check again
+            // as in https://developers.google.com/ar/develop/java/enable-arcore#check_supported
+            if (availability.isTransient) {
+                delay(1000)
+            } else {
+                result = availability
+                emit(result)
+            }
+        }
+    }.stateIn(viewModelScope, WhileViewSubscribed, null)
 
     fun onProfileClicked() {
         if (isSignedIn()) {
-            _navigateToSignOutDialogAction.value = Event(Unit)
+            _navigationActions.tryOffer(MainNavigationAction.OpenSignOut)
         } else {
-            _navigateToSignInDialogAction.value = Event(Unit)
+            _navigationActions.tryOffer(MainNavigationAction.OpenSignIn)
         }
     }
 }
+
+sealed class MainNavigationAction {
+    object OpenSignIn : MainNavigationAction()
+    object OpenSignOut : MainNavigationAction()
+}

mobile/src/main/java/com/google/samples/apps/iosched/ui/ar/ArCoreAvailabilityLiveData.kt

@@ -34,6 +34,7 @@ import com.google.samples.apps.iosched.model.Moment.Companion.CTA_SIGNIN
 import com.google.samples.apps.iosched.model.Theme
 import com.google.samples.apps.iosched.shared.data.signin.AuthenticatedUserInfo
 import com.google.samples.apps.iosched.util.executeAfter
+import kotlinx.coroutines.flow.StateFlow
 
 // Countdown is shown before the Keynote
 object CountdownItem
@@ -63,7 +64,7 @@ class CountdownViewBinder : FeedItemViewBinder<CountdownItem, CountdownViewHolde
 class MomentViewBinder(
     private val eventListener: FeedEventListener,
     private val userInfoLiveData: LiveData<AuthenticatedUserInfo?>,
-    private val themeLiveData: LiveData<Theme>
+    private val themeLiveData: StateFlow<Theme>
 ) : FeedItemViewBinder<Moment, MomentViewHolder>(Moment::class.java) {
 
     override fun createViewHolder(parent: ViewGroup): MomentViewHolder {
@@ -88,7 +89,7 @@ class MomentViewHolder(
     private val binding: ItemFeedMomentBinding,
     private val eventListener: FeedEventListener,
     private val userInfoLiveData: LiveData<AuthenticatedUserInfo?>,
-    private val themeLiveData: LiveData<Theme>
+    private val themeLiveData: StateFlow<Theme>
 ) : ViewHolder(binding.root) {
 
     fun bind(item: Moment) {

mobile/src/main/java/com/google/samples/apps/iosched/ui/feed/FeedHeaderViewBinders.kt

@@ -16,15 +16,17 @@
 
 package com.google.samples.apps.iosched.ui.theme
 
-import androidx.lifecycle.LiveData
-import androidx.lifecycle.liveData
 import com.google.samples.apps.iosched.model.Theme
+import com.google.samples.apps.iosched.shared.di.ApplicationScope
 import com.google.samples.apps.iosched.shared.domain.settings.GetThemeUseCase
 import com.google.samples.apps.iosched.shared.domain.settings.ObserveThemeModeUseCase
 import com.google.samples.apps.iosched.shared.result.Result.Success
 import com.google.samples.apps.iosched.shared.result.successOr
-import kotlinx.coroutines.ExperimentalCoroutinesApi
-import kotlinx.coroutines.flow.collect
+import kotlinx.coroutines.CoroutineScope
+import kotlinx.coroutines.flow.SharingStarted
+import kotlinx.coroutines.flow.StateFlow
+import kotlinx.coroutines.flow.map
+import kotlinx.coroutines.flow.stateIn
 import kotlinx.coroutines.runBlocking
 import javax.inject.Inject
 
@@ -45,7 +47,7 @@ interface ThemedActivityDelegate {
     /**
      * Allows observing of the current theme
      */
-    val theme: LiveData<Theme>
+    val theme: StateFlow<Theme>
 
     /**
      * Allows querying of the current theme synchronously
@@ -54,16 +56,14 @@ interface ThemedActivityDelegate {
 }
 
 class ThemedActivityDelegateImpl @Inject constructor(
-    private val observeThemeUseCase: ObserveThemeModeUseCase,
+    @ApplicationScope externalScope: CoroutineScope,
+    observeThemeUseCase: ObserveThemeModeUseCase,
     private val getThemeUseCase: GetThemeUseCase
 ) : ThemedActivityDelegate {
 
-    @ExperimentalCoroutinesApi
-    override val theme: LiveData<Theme> = liveData {
-        observeThemeUseCase(Unit).collect {
-            emit(it.successOr(Theme.SYSTEM))
-        }
-    }
+    override val theme: StateFlow<Theme> = observeThemeUseCase(Unit).map {
+        it.successOr(Theme.SYSTEM)
+    }.stateIn(externalScope, SharingStarted.Eagerly, Theme.SYSTEM)
 
     override val currentTheme: Theme
         get() = runBlocking { // Using runBlocking to execute this coroutine synchronously

mobile/src/main/java/com/google/samples/apps/iosched/ui/theme/ThemedActivityDelegate.kt

@@ -22,6 +22,7 @@
     <data>
 
         <import type="androidx.lifecycle.LiveData" />
+        <import type="kotlinx.coroutines.flow.StateFlow" />
 
         <variable
             name="moment"
@@ -33,7 +34,7 @@
 
         <variable
             name="theme"
-            type="LiveData&lt;com.google.samples.apps.iosched.model.Theme&gt;" />
+            type="StateFlow&lt;com.google.samples.apps.iosched.model.Theme&gt;" />
 
         <variable
             name="eventListener"