Save the user's reading position in the home timeline (#3614)

- Add a field to AccountEntity to hold the reading position
- Provide a method to save in the viewmodel to save the position
- Save the position when TimelineFragment pauses

Does not restore the position yet.

app/src/main/java/com/keylesspalace/tusky/components/timeline/TimelineFragment.kt

@@ -77,7 +77,6 @@ import com.mikepenz.iconics.utils.colorInt
 import com.mikepenz.iconics.utils.sizeDp
 import io.reactivex.rxjava3.android.schedulers.AndroidSchedulers
 import io.reactivex.rxjava3.core.Observable
-import kotlinx.coroutines.flow.collect
 import kotlinx.coroutines.flow.collectLatest
 import kotlinx.coroutines.launch
 import java.io.IOException
@@ -578,6 +577,17 @@ class TimelineFragment :
 
     private var talkBackWasEnabled = false
 
+    override fun onPause() {
+        super.onPause()
+        (binding.recyclerView.layoutManager as? LinearLayoutManager)?.findFirstVisibleItemPosition()?.let { position ->
+            if (position != RecyclerView.NO_POSITION) {
+                adapter.snapshot().getOrNull(position)?.id?.let { statusId ->
+                    viewModel.saveReadingPosition(statusId)
+                }
+            }
+        }
+    }
+
     override fun onResume() {
         super.onResume()
         val a11yManager =

app/src/main/java/com/keylesspalace/tusky/components/timeline/viewmodel/CachedTimelineViewModel.kt

@@ -289,6 +289,14 @@ class CachedTimelineViewModel @Inject constructor(
         }
     }
 
+    override fun saveReadingPosition(statusId: String) {
+        accountManager.activeAccount?.let { account ->
+            Log.d(TAG, "Saving position at: $statusId")
+            account.lastVisibleHomeTimelineStatusId = statusId
+            accountManager.saveAccount(account)
+        }
+    }
+
     override suspend fun invalidate() {
         // invalidating when we don't have statuses yet can cause empty timelines because it cancels the network load
         if (db.timelineDao().getStatusCount(accountManager.activeAccount!!.id) > 0) {
@@ -297,6 +305,7 @@ class CachedTimelineViewModel @Inject constructor(
     }
 
     companion object {
+        private const val TAG = "CachedTimelineViewModel"
         private const val MAX_STATUSES_IN_CACHE = 1000
     }
 }

app/src/main/java/com/keylesspalace/tusky/components/timeline/viewmodel/NetworkTimelineViewModel.kt

@@ -255,6 +255,10 @@ class NetworkTimelineViewModel @Inject constructor(
         }
     }
 
+    override fun saveReadingPosition(statusId: String) {
+        /** Does nothing for non-cached timelines */
+    }
+
     override suspend fun invalidate() {
         currentSource?.invalidate()
     }

app/src/main/java/com/keylesspalace/tusky/components/timeline/viewmodel/TimelineViewModel.kt

@@ -182,6 +182,9 @@ abstract class TimelineViewModel(
 
     abstract fun clearWarning(status: StatusViewData.Concrete)
 
+    /** Saves the user's reading position so it can be restored later */
+    abstract fun saveReadingPosition(statusId: String)
+
     /** Triggered when currently displayed data must be reloaded. */
     protected abstract suspend fun invalidate()
 

app/src/main/java/com/keylesspalace/tusky/db/AccountEntity.kt

@@ -82,7 +82,13 @@ data class AccountEntity(
     var pushPubKey: String = "",
     var pushPrivKey: String = "",
     var pushAuth: String = "",
-    var pushServerKey: String = ""
+    var pushServerKey: String = "",
+
+    /**
+     * ID of the status at the top of the visible list in the home timeline when the
+     * user navigated away.
+     */
+    var lastVisibleHomeTimelineStatusId: String? = null
 ) {
 
     val identifier: String

app/src/main/java/com/keylesspalace/tusky/db/AppDatabase.java

@@ -16,6 +16,7 @@
 package com.keylesspalace.tusky.db;
 
 import androidx.annotation.NonNull;
+import androidx.room.AutoMigration;
 import androidx.room.Database;
 import androidx.room.RoomDatabase;
 import androidx.room.migration.Migration;
@@ -29,9 +30,20 @@ import java.io.File;
 /**
  * DB version & declare DAO
  */
-@Database(entities = { DraftEntity.class, AccountEntity.class, InstanceEntity.class, TimelineStatusEntity.class,
-                TimelineAccountEntity.class,  ConversationEntity.class
-        }, version = 48)
+@Database(
+    entities = {
+        DraftEntity.class,
+        AccountEntity.class,
+        InstanceEntity.class,
+        TimelineStatusEntity.class,
+        TimelineAccountEntity.class,
+        ConversationEntity.class
+    },
+    version = 49,
+    autoMigrations = {
+        @AutoMigration(from = 48, to = 49)
+    }
+)
 public abstract class AppDatabase extends RoomDatabase {
 
     public abstract AccountDao accountDao();