Introduce start/onStart methods on ViewModel, when you want to delay observing db

vector/src/main/java/im/vector/app/core/platform/VectorViewModel.kt

@@ -16,6 +16,7 @@
 
 package im.vector.app.core.platform
 
+import androidx.lifecycle.viewModelScope
 import com.airbnb.mvrx.Async
 import com.airbnb.mvrx.BaseMvRxViewModel
 import com.airbnb.mvrx.Fail
@@ -26,6 +27,9 @@ import im.vector.app.core.utils.DataSource
 import im.vector.app.core.utils.PublishDataSource
 import io.reactivex.Observable
 import io.reactivex.Single
+import kotlinx.coroutines.launch
+import timber.log.Timber
+import java.util.concurrent.atomic.AtomicBoolean
 
 abstract class VectorViewModel<S : MvRxState, VA : VectorViewModelAction, VE : VectorViewEvents>(initialState: S)
     : BaseMvRxViewModel<S>(initialState, false) {
@@ -37,6 +41,27 @@ abstract class VectorViewModel<S : MvRxState, VA : VectorViewModelAction, VE : V
     // Used to post transient events to the View
     protected val _viewEvents = PublishDataSource<VE>()
     val viewEvents: DataSource<VE> = _viewEvents
+    private val isStarted = AtomicBoolean(false)
+
+    /**
+     * Call this method when you are ready to grab data for your ViewModel.
+     * Mostly to be used at the end of onCreateView from fragment.
+     * It's safe to be called multiple time.
+     */
+    fun start() {
+        if (!isStarted.getAndSet(true)) {
+            Timber.v("Start viewModel ${this.javaClass.name}")
+            viewModelScope.launch {
+                onStarted()
+            }
+        }
+    }
+
+    /**
+     * This is the method where you want to start observing rx data, subscribe to state...
+     * Will be called only once. It's bound the viewModelScope and is launched on Main thread
+     */
+    protected open suspend fun onStarted() = Unit
 
     /**
      * This method does the same thing as the execute function, but it doesn't subscribe to the stream

vector/src/main/java/im/vector/app/features/grouplist/GroupListFragment.kt

@@ -56,6 +56,7 @@ class GroupListFragment @Inject constructor(
                 is GroupListViewEvents.OpenGroupSummary -> sharedActionViewModel.post(HomeActivitySharedAction.OpenGroup)
             }.exhaustive
         }
+        viewModel.start()
     }
 
     override fun onDestroyView() {

vector/src/main/java/im/vector/app/features/grouplist/GroupListViewModel.kt

@@ -26,14 +26,14 @@ import com.squareup.inject.assisted.AssistedInject
 import im.vector.app.R
 import im.vector.app.core.platform.VectorViewModel
 import im.vector.app.core.resources.StringProvider
+import io.reactivex.Observable
+import io.reactivex.functions.BiFunction
 import org.matrix.android.sdk.api.NoOpMatrixCallback
 import org.matrix.android.sdk.api.query.QueryStringValue
 import org.matrix.android.sdk.api.session.Session
 import org.matrix.android.sdk.api.session.group.groupSummaryQueryParams
 import org.matrix.android.sdk.api.session.group.model.GroupSummary
 import org.matrix.android.sdk.api.session.room.model.Membership
-import io.reactivex.Observable
-import io.reactivex.functions.BiFunction
 import org.matrix.android.sdk.rx.rx
 
 const val ALL_COMMUNITIES_GROUP_ID = "+ALL_COMMUNITIES_GROUP_ID"
@@ -60,7 +60,7 @@ class GroupListViewModel @AssistedInject constructor(@Assisted initialState: Gro
 
     private var currentGroupId = ""
 
-    init {
+    override suspend fun onStarted() {
         observeGroupSummaries()
         observeSelectionState()
     }

vector/src/main/java/im/vector/app/features/home/HomeDetailFragment.kt

@@ -53,10 +53,6 @@ import org.matrix.android.sdk.internal.crypto.model.rest.DeviceInfo
 import timber.log.Timber
 import javax.inject.Inject
 
-private const val INDEX_PEOPLE = 0
-private const val INDEX_ROOMS = 1
-private const val INDEX_CATCHUP = 2
-
 class HomeDetailFragment @Inject constructor(
         val homeDetailViewModelFactory: HomeDetailViewModel.Factory,
         private val serverBackupStatusViewModelFactory: ServerBackupStatusViewModel.Factory,
@@ -123,6 +119,8 @@ class HomeDetailFragment @Inject constructor(
                     activeCallViewHolder.updateCall(it, webRtcPeerConnectionManager)
                     invalidateOptionsMenu()
                 })
+
+        viewModel.start()
     }
 
     override fun onResume() {

vector/src/main/java/im/vector/app/features/home/HomeDetailViewModel.kt

@@ -27,9 +27,9 @@ import im.vector.app.core.platform.VectorViewModel
 import im.vector.app.core.resources.StringProvider
 import im.vector.app.features.grouplist.SelectedGroupDataSource
 import im.vector.app.features.ui.UiStateRepository
+import io.reactivex.schedulers.Schedulers
 import org.matrix.android.sdk.api.session.Session
 import org.matrix.android.sdk.api.session.room.model.Membership
-import io.reactivex.schedulers.Schedulers
 import org.matrix.android.sdk.rx.rx
 
 /**
@@ -65,7 +65,7 @@ class HomeDetailViewModel @AssistedInject constructor(@Assisted initialState: Ho
         }
     }
 
-    init {
+    override suspend fun onStarted() {
         observeSyncState()
         observeSelectedGroupStore()
         observeRoomSummaries()

vector/src/main/java/im/vector/app/features/home/UnknownDeviceDetectorSharedViewModel.kt

@@ -30,6 +30,10 @@ import im.vector.app.core.platform.EmptyViewEvents
 import im.vector.app.core.platform.VectorViewModel
 import im.vector.app.core.platform.VectorViewModelAction
 import im.vector.app.features.settings.VectorPreferences
+import io.reactivex.Observable
+import io.reactivex.functions.Function3
+import kotlinx.coroutines.Dispatchers
+import kotlinx.coroutines.withContext
 import org.matrix.android.sdk.api.NoOpMatrixCallback
 import org.matrix.android.sdk.api.extensions.orFalse
 import org.matrix.android.sdk.api.session.Session
@@ -39,8 +43,6 @@ import org.matrix.android.sdk.api.util.toMatrixItem
 import org.matrix.android.sdk.internal.crypto.model.CryptoDeviceInfo
 import org.matrix.android.sdk.internal.crypto.model.rest.DeviceInfo
 import org.matrix.android.sdk.internal.crypto.store.PrivateKeysInfo
-import io.reactivex.Observable
-import io.reactivex.functions.Function3
 import org.matrix.android.sdk.rx.rx
 import timber.log.Timber
 import java.util.concurrent.TimeUnit
@@ -57,7 +59,7 @@ data class DeviceDetectionInfo(
 )
 
 class UnknownDeviceDetectorSharedViewModel @AssistedInject constructor(@Assisted initialState: UnknownDevicesState,
-                                                                       session: Session,
+                                                                       private val session: Session,
                                                                        private val vectorPreferences: VectorPreferences)
     : VectorViewModel<UnknownDevicesState, UnknownDeviceDetectorSharedViewModel.Action, EmptyViewEvents>(initialState) {
 
@@ -84,12 +86,13 @@ class UnknownDeviceDetectorSharedViewModel @AssistedInject constructor(@Assisted
 
     private val ignoredDeviceList = ArrayList<String>()
 
-    init {
-
-        val currentSessionTs = session.cryptoService().getCryptoDeviceInfo(session.myUserId)
-                .firstOrNull { it.deviceId == session.sessionParams.deviceId }
-                ?.firstTimeSeenLocalTs
-                ?: System.currentTimeMillis()
+    override suspend fun onStarted() {
+        val currentSessionTs = withContext(Dispatchers.Default) {
+            session.cryptoService().getCryptoDeviceInfo(session.myUserId)
+                    .firstOrNull { it.deviceId == session.sessionParams.deviceId }
+                    ?.firstTimeSeenLocalTs
+                    ?: System.currentTimeMillis()
+        }
         Timber.v("## Detector - Current Session first time seen $currentSessionTs")
 
         ignoredDeviceList.addAll(

vector/src/main/java/im/vector/app/features/home/room/breadcrumbs/BreadcrumbsFragment.kt

@@ -43,6 +43,7 @@ class BreadcrumbsFragment @Inject constructor(
         super.onViewCreated(view, savedInstanceState)
         setupRecyclerView()
         sharedActionViewModel = activityViewModelProvider.get(RoomDetailSharedActionViewModel::class.java)
+        breadcrumbsViewModel.start()
     }
 
     override fun onDestroyView() {

vector/src/main/java/im/vector/app/features/home/room/breadcrumbs/BreadcrumbsViewModel.kt

@@ -49,7 +49,7 @@ class BreadcrumbsViewModel @AssistedInject constructor(@Assisted initialState: B
         }
     }
 
-    init {
+    override suspend fun onStarted() {
         observeBreadcrumbs()
     }
 

vector/src/main/java/im/vector/app/features/home/room/detail/RoomDetailFragment.kt

@@ -365,6 +365,7 @@ class RoomDetailFragment @Inject constructor(
                 is RoomDetailViewEvents.RequestNativeWidgetPermission    -> requestNativeWidgetPermission(it)
             }.exhaustive
         }
+        roomDetailViewModel.start()
     }
 
     private fun requestNativeWidgetPermission(it: RoomDetailViewEvents.RequestNativeWidgetPermission) {

vector/src/main/java/im/vector/app/features/home/room/detail/RoomDetailViewModel.kt

@@ -170,7 +170,7 @@ class RoomDetailViewModel @AssistedInject constructor(
         }
     }
 
-    init {
+    override suspend fun onStarted() {
         timeline.start()
         timeline.addListener(this)
         observeRoomSummary()

vector/src/main/java/im/vector/app/features/home/room/list/RoomListFragment.kt

@@ -116,6 +116,8 @@ class RoomListFragment @Inject constructor(
                 .observe()
                 .subscribe { handleQuickActions(it) }
                 .disposeOnDestroyView()
+
+        roomListViewModel.start()
     }
 
     override fun showFailure(throwable: Throwable) {

vector/src/main/java/im/vector/app/features/home/room/list/RoomListViewModel.kt

@@ -55,7 +55,7 @@ class RoomListViewModel @Inject constructor(initialState: RoomListViewState,
     private val displayMode = initialState.displayMode
     private val roomListDisplayModeFilter = RoomListDisplayModeFilter(displayMode)
 
-    init {
+    override suspend fun onStarted() {
         observeRoomSummaries()
         observeMembershipChanges()
     }

vector/src/main/java/im/vector/app/features/widgets/WidgetActivity.kt

@@ -128,6 +128,7 @@ class WidgetActivity : VectorBaseActivity(), ToolbarConfigurable, WidgetViewMode
         viewModel.selectSubscribe(this, WidgetViewState::canManageWidgets) {
             invalidateOptionsMenu()
         }
+        viewModel.start()
     }
 
     override fun create(initialState: WidgetViewState): WidgetViewModel {

vector/src/main/java/im/vector/app/features/widgets/WidgetViewModel.kt

@@ -27,6 +27,10 @@ import com.airbnb.mvrx.Success
 import com.airbnb.mvrx.ViewModelContext
 import com.squareup.inject.assisted.Assisted
 import com.squareup.inject.assisted.AssistedInject
+import im.vector.app.core.platform.VectorViewModel
+import im.vector.app.core.resources.StringProvider
+import im.vector.app.features.widgets.permissions.WidgetPermissionsHelper
+import kotlinx.coroutines.launch
 import org.matrix.android.sdk.api.query.QueryStringValue
 import org.matrix.android.sdk.api.session.Session
 import org.matrix.android.sdk.api.session.events.model.Content
@@ -40,10 +44,6 @@ import org.matrix.android.sdk.internal.util.awaitCallback
 import org.matrix.android.sdk.rx.mapOptional
 import org.matrix.android.sdk.rx.rx
 import org.matrix.android.sdk.rx.unwrap
-import im.vector.app.core.platform.VectorViewModel
-import im.vector.app.core.resources.StringProvider
-import im.vector.app.features.widgets.permissions.WidgetPermissionsHelper
-import kotlinx.coroutines.launch
 import timber.log.Timber
 import javax.net.ssl.HttpsURLConnection
 
@@ -82,7 +82,7 @@ class WidgetViewModel @AssistedInject constructor(@Assisted val initialState: Wi
     // Flag to avoid infinite loop
     private var canRefreshToken = true
 
-    init {
+    override suspend fun onStarted() {
         integrationManagerService.addListener(this)
         if (initialState.widgetKind.isAdmin()) {
             widgetPostAPIHandler = widgetPostAPIHandlerFactory.create(initialState.roomId).apply {

vector/src/main/java/im/vector/app/features/workers/signout/ServerBackupStatusViewModel.kt

@@ -92,7 +92,7 @@ class ServerBackupStatusViewModel @AssistedInject constructor(@Assisted initialS
 
     private val keyBackupPublishSubject: PublishSubject<KeysBackupState> = PublishSubject.create()
 
-    init {
+    override suspend fun onStarted() {
         session.cryptoService().keysBackupService().addListener(this)
 
         keysBackupState.value = session.cryptoService().keysBackupService().state