Migrate various usages of LiveData to Flow

Change-Id: I1f502003973fe2147253babf58398daa68a8568b

Author: JoseAlcerreca

mobile/lint.xml

@@ -45,7 +45,4 @@
         <!-- Map markers are referenced by name at runtime -->
         <ignore regexp="res/drawable/map_marker_.+\.xml" />
     </issue>
-
-    <!-- TODO: remove this check (b/181732250) -->
-    <issue id="NullSafeMutableLiveData" severity="warning" />
 </lint>

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

@@ -17,12 +17,16 @@
 package com.google.samples.apps.iosched.ui
 
 import androidx.lifecycle.ViewModel
+import androidx.lifecycle.viewModelScope
 import com.google.samples.apps.iosched.shared.domain.prefs.OnboardingCompletedUseCase
+import com.google.samples.apps.iosched.shared.result.Result.Loading
 import com.google.samples.apps.iosched.shared.result.data
 import com.google.samples.apps.iosched.ui.LaunchNavigatonAction.NavigateToMainActivityAction
 import com.google.samples.apps.iosched.ui.LaunchNavigatonAction.NavigateToOnboardingAction
 import dagger.hilt.android.lifecycle.HiltViewModel
+import kotlinx.coroutines.flow.SharingStarted.Companion.Eagerly
 import kotlinx.coroutines.flow.map
+import kotlinx.coroutines.flow.stateIn
 import javax.inject.Inject
 
 /**
@@ -38,7 +42,7 @@ class LaunchViewModel @Inject constructor(
         } else {
             NavigateToMainActivityAction
         }
-    }
+    }.stateIn(viewModelScope, Eagerly, Loading)
 }
 
 sealed class LaunchNavigatonAction {

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

@@ -17,12 +17,12 @@
 package com.google.samples.apps.iosched.ui
 
 import android.content.Intent
-import androidx.lifecycle.repeatOnLifecycle
 import android.os.Bundle
 import androidx.activity.viewModels
-import androidx.lifecycle.Lifecycle
 import androidx.appcompat.app.AppCompatActivity
+import androidx.lifecycle.Lifecycle
 import androidx.lifecycle.lifecycleScope
+import androidx.lifecycle.repeatOnLifecycle
 import com.google.samples.apps.iosched.ui.LaunchNavigatonAction.NavigateToMainActivityAction
 import com.google.samples.apps.iosched.ui.LaunchNavigatonAction.NavigateToOnboardingAction
 import com.google.samples.apps.iosched.ui.onboarding.OnboardingActivity

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

@@ -25,15 +25,16 @@ import androidx.core.view.isVisible
 import androidx.core.view.updatePadding
 import androidx.fragment.app.activityViewModels
 import androidx.fragment.app.viewModels
-import androidx.lifecycle.Observer
 import com.google.common.collect.ImmutableMap
 import com.google.samples.apps.iosched.databinding.FragmentAnnouncementsBinding
 import com.google.samples.apps.iosched.shared.analytics.AnalyticsHelper
 import com.google.samples.apps.iosched.ui.MainActivityViewModel
 import com.google.samples.apps.iosched.ui.MainNavigationFragment
 import com.google.samples.apps.iosched.ui.signin.setupProfileMenuItem
 import com.google.samples.apps.iosched.util.doOnApplyWindowInsets
+import com.google.samples.apps.iosched.util.launchAndRepeatWithViewLifecycle
 import dagger.hilt.android.AndroidEntryPoint
+import kotlinx.coroutines.flow.collect
 import javax.inject.Inject
 
 @AndroidEntryPoint
@@ -85,12 +86,11 @@ class AnnouncementsFragment : MainNavigationFragment() {
             v.updatePadding(bottom = padding.bottom + systemInsets.bottom)
         }
 
-        model.announcements.observe(
-            viewLifecycleOwner,
-            Observer {
+        launchAndRepeatWithViewLifecycle {
+            model.announcements.collect {
                 (binding.recyclerView.adapter as FeedAdapter).submitList(it)
             }
-        )
+        }
     }
 
     private fun createAdapter(): FeedAdapter {

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

@@ -16,16 +16,19 @@
 
 package com.google.samples.apps.iosched.ui.feed
 
-import androidx.lifecycle.LiveData
 import androidx.lifecycle.ViewModel
-import androidx.lifecycle.liveData
+import androidx.lifecycle.viewModelScope
 import com.google.samples.apps.iosched.shared.domain.feed.LoadAnnouncementsUseCase
 import com.google.samples.apps.iosched.shared.domain.settings.GetTimeZoneUseCase
 import com.google.samples.apps.iosched.shared.result.Result.Loading
 import com.google.samples.apps.iosched.shared.result.successOr
 import com.google.samples.apps.iosched.shared.time.TimeProvider
 import com.google.samples.apps.iosched.shared.util.TimeUtils
 import dagger.hilt.android.lifecycle.HiltViewModel
+import kotlinx.coroutines.flow.SharingStarted.Companion.Eagerly
+import kotlinx.coroutines.flow.StateFlow
+import kotlinx.coroutines.flow.flow
+import kotlinx.coroutines.flow.stateIn
 import org.threeten.bp.ZoneId
 import javax.inject.Inject
 
@@ -36,7 +39,7 @@ class AnnouncementsViewModel @Inject constructor(
     timeProvider: TimeProvider
 ) : ViewModel() {
 
-    val announcements: LiveData<List<Any>> = liveData {
+    val announcements: StateFlow<List<Any>> = flow {
         val loadAnnouncementsResult = loadAnnouncementsUseCase(timeProvider.now())
         if (loadAnnouncementsResult is Loading) {
             emit(listOf(LoadingIndicator))
@@ -48,14 +51,14 @@ class AnnouncementsViewModel @Inject constructor(
                 emit(listOf(AnnouncementsEmpty))
             }
         }
-    }
+    }.stateIn(viewModelScope, Eagerly, emptyList())
 
-    val timeZoneId: LiveData<ZoneId> = liveData {
+    val timeZoneId: StateFlow<ZoneId> = flow {
         val timeZoneResult = getTimeZoneUseCase(Unit)
         if (timeZoneResult.successOr(true)) {
             emit(TimeUtils.CONFERENCE_TIMEZONE)
         } else {
             emit(ZoneId.systemDefault())
         }
-    }
+    }.stateIn(viewModelScope, Eagerly, TimeUtils.CONFERENCE_TIMEZONE)
 }

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

@@ -22,13 +22,13 @@ import android.view.ViewGroup
 import android.widget.TextView
 import androidx.databinding.BindingAdapter
 import androidx.lifecycle.LifecycleOwner
-import androidx.lifecycle.LiveData
 import androidx.recyclerview.widget.RecyclerView.ViewHolder
 import com.google.samples.apps.iosched.R
 import com.google.samples.apps.iosched.databinding.ItemFeedAnnouncementBinding
 import com.google.samples.apps.iosched.databinding.ItemFeedAnnouncementsHeaderBinding
 import com.google.samples.apps.iosched.model.Announcement
 import com.google.samples.apps.iosched.shared.util.TimeUtils
+import kotlinx.coroutines.flow.StateFlow
 import org.threeten.bp.ZoneId
 import org.threeten.bp.ZonedDateTime
 
@@ -86,7 +86,7 @@ class AnnouncementsPreviewViewHolder(
 
 // For Announcement items
 class AnnouncementViewBinder(
-    private val timeZoneId: LiveData<ZoneId>,
+    private val timeZoneId: StateFlow<ZoneId>,
     private val lifecycleOwner: LifecycleOwner
 ) : FeedItemViewBinder<Announcement, AnnouncementViewHolder>(
     Announcement::class.java
@@ -115,7 +115,7 @@ class AnnouncementViewBinder(
 class AnnouncementViewHolder(
     private val binding: ItemFeedAnnouncementBinding,
     private val lifecycleOwner: LifecycleOwner,
-    private val timeZoneId: LiveData<ZoneId>
+    private val timeZoneId: StateFlow<ZoneId>
 ) : ViewHolder(binding.root) {
 
     fun bind(announcement: Announcement) {

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

@@ -172,7 +172,7 @@ class FeedFragment : MainNavigationFragment() {
             val momentViewBinder = MomentViewBinder(
                 eventListener = model,
                 userInfo = model.userInfo,
-                themeLiveData = model.theme
+                theme = model.theme
             )
             val sessionsViewBinder = FeedSessionsViewBinder(model)
             val feedAnnouncementsHeaderViewBinder =

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

@@ -63,13 +63,13 @@ class CountdownViewBinder : FeedItemViewBinder<CountdownItem, CountdownViewHolde
 class MomentViewBinder(
     private val eventListener: FeedEventListener,
     private val userInfo: StateFlow<AuthenticatedUserInfo?>,
-    private val themeLiveData: StateFlow<Theme>
+    private val theme: StateFlow<Theme>
 ) : FeedItemViewBinder<Moment, MomentViewHolder>(Moment::class.java) {
 
     override fun createViewHolder(parent: ViewGroup): MomentViewHolder {
         val binding =
             ItemFeedMomentBinding.inflate(LayoutInflater.from(parent.context), parent, false)
-        return MomentViewHolder(binding, eventListener, userInfo, themeLiveData)
+        return MomentViewHolder(binding, eventListener, userInfo, theme)
     }
 
     override fun bindViewHolder(model: Moment, viewHolder: MomentViewHolder) {

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

@@ -17,7 +17,6 @@
 package com.google.samples.apps.iosched.ui.feed
 
 import androidx.lifecycle.ViewModel
-import androidx.lifecycle.asLiveData
 import androidx.lifecycle.viewModelScope
 import androidx.navigation.NavDirections
 import com.google.samples.apps.iosched.R
@@ -55,6 +54,7 @@ import com.google.samples.apps.iosched.util.WhileViewSubscribed
 import dagger.hilt.android.lifecycle.HiltViewModel
 import kotlinx.coroutines.channels.Channel
 import kotlinx.coroutines.flow.Flow
+import kotlinx.coroutines.flow.SharingStarted.Companion.Eagerly
 import kotlinx.coroutines.flow.StateFlow
 import kotlinx.coroutines.flow.combine
 import kotlinx.coroutines.flow.flatMapLatest
@@ -94,9 +94,7 @@ class FeedViewModel @Inject constructor(
         // View All sessions and go to schedule to view the full list
         private const val MAX_SESSIONS = 10
 
-        // Indicates there is no header to show at the current time. We need this sentinel value
-        // because our LiveData.combine extension functions interpret null values to mean the
-        // LiveData has not returned a result, but null for the current Moment is valid.
+        // Indicates there is no header to show at the current time.
         private object NoHeader
 
         // Indicates there is no sessions related display on the home screen as the conference is
@@ -115,17 +113,13 @@ class FeedViewModel @Inject constructor(
     var isMapEnabledByRemoteConfig: Boolean = false
 
     // Exposed to the view as a StateFlow but it's a one-shot operation.
-    // TODO: Rename with timeZoneId when ScheduleViewModel is migrated
-    val timeZoneIdFlow = flow<ZoneId> {
+    val timeZoneId = flow<ZoneId> {
         if (getTimeZoneUseCase(Unit).successOr(true)) {
             emit(TimeUtils.CONFERENCE_TIMEZONE)
         } else {
             emit(ZoneId.systemDefault())
         }
-    }.stateIn(viewModelScope, WhileViewSubscribed, TimeUtils.CONFERENCE_TIMEZONE)
-
-    // TODO: Replace with timeZoneIdFlow when ScheduleViewModel is migrated
-    val timeZoneId = timeZoneIdFlow.asLiveData()
+    }.stateIn(viewModelScope, Eagerly, TimeUtils.CONFERENCE_TIMEZONE)
 
     private val loadSessionsResult: StateFlow<Result<List<UserSession>>> =
         signInViewModelDelegate.userId
@@ -177,7 +171,7 @@ class FeedViewModel @Inject constructor(
     }.stateIn(viewModelScope, WhileViewSubscribed, emptyList())
 
     private val feedSessionsContainer: Flow<FeedSessions> = loadSessionsResult
-        .combine(timeZoneIdFlow) { sessions, timeZone ->
+        .combine(timeZoneId) { sessions, timeZone ->
             createFeedSessionsContainer(sessions, timeZone)
         }
 

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

@@ -22,7 +22,6 @@ import android.view.LayoutInflater
 import android.view.ViewGroup
 import androidx.appcompat.app.AppCompatDialogFragment
 import androidx.fragment.app.viewModels
-import androidx.lifecycle.Observer
 import androidx.recyclerview.widget.DiffUtil
 import androidx.recyclerview.widget.LinearLayoutManager
 import androidx.recyclerview.widget.ListAdapter
@@ -32,9 +31,12 @@ import com.google.samples.apps.iosched.R
 import com.google.samples.apps.iosched.databinding.FragmentSessionFeedbackBinding
 import com.google.samples.apps.iosched.databinding.ItemQuestionBinding
 import com.google.samples.apps.iosched.model.SessionId
+import com.google.samples.apps.iosched.shared.result.data
+import com.google.samples.apps.iosched.util.launchAndRepeatWithViewLifecycle
 import com.google.samples.apps.iosched.widget.SimpleRatingBar
 import dagger.hilt.android.AndroidEntryPoint
 import kotlinx.coroutines.ExperimentalCoroutinesApi
+import kotlinx.coroutines.flow.collect
 
 @ExperimentalCoroutinesApi
 @AndroidEntryPoint
@@ -59,21 +61,16 @@ class SessionFeedbackFragment : AppCompatDialogFragment() {
             layoutManager = LinearLayoutManager(context)
             adapter = questionAdapter
         }
-        // The lifecycle owner has to be the DialogFragment itself here.
-        viewModel.questions.observe(
-            this,
-            Observer { questions ->
-                if (questions != null && questions.isNotEmpty()) {
-                    questionAdapter.submitList(questions)
+
+        questionAdapter.submitList(viewModel.questions)
+
+        launchAndRepeatWithViewLifecycle {
+            viewModel.userSession.collect {
+                it.data?.let {
+                    dialog?.setTitle(it.session.title)
                 }
             }
-        )
-        viewModel.userSession.observe(
-            this,
-            Observer { userSession ->
-                dialog?.setTitle(userSession.session.title)
-            }
-        )
+        }
         return MaterialAlertDialogBuilder(requireContext())
             // The actual title is set asynchronously, but there has to be some title to
             // initialize the view first.