Maintain current scroll position when task moves

app/src/main/java/com/todoroo/astrid/activity/TaskListFragment.java

@@ -248,6 +248,7 @@ public final class TaskListFragment extends InjectingFragment
                 taskListViewModel.getValue())
             : new PagedListRecyclerAdapter(
                 taskAdapter,
+                recyclerView,
                 viewHolderFactory,
                 this,
                 actionModeProvider,

app/src/main/java/org/tasks/tasklist/ManualSortRecyclerAdapter.java

@@ -31,11 +31,12 @@ public class ManualSortRecyclerAdapter extends TaskListRecyclerAdapter {
 
   public ManualSortRecyclerAdapter(
       TaskAdapter adapter,
-      RecyclerView recyclerView, ViewHolderFactory viewHolderFactory,
+      RecyclerView recyclerView,
+      ViewHolderFactory viewHolderFactory,
       TaskListFragment taskList,
       ActionModeProvider actionModeProvider,
       List<TaskContainer> list) {
-    super(adapter, viewHolderFactory, taskList, actionModeProvider);
+    super(adapter, recyclerView, viewHolderFactory, taskList, actionModeProvider);
     this.list = list;
     itemTouchHelperCallback = new ItemTouchHelperCallback(adapter, this, this::drainQueue);
     new ItemTouchHelper(itemTouchHelperCallback).attachToRecyclerView(recyclerView);

app/src/main/java/org/tasks/tasklist/PagedListRecyclerAdapter.java

@@ -3,6 +3,7 @@ package org.tasks.tasklist;
 import androidx.paging.AsyncPagedListDiffer;
 import androidx.paging.PagedList;
 import androidx.recyclerview.widget.AsyncDifferConfig;
+import androidx.recyclerview.widget.RecyclerView;
 import com.todoroo.astrid.activity.TaskListFragment;
 import com.todoroo.astrid.adapter.TaskAdapter;
 import java.util.List;
@@ -14,11 +15,12 @@ public class PagedListRecyclerAdapter extends TaskListRecyclerAdapter {
 
   public PagedListRecyclerAdapter(
       TaskAdapter adapter,
+      RecyclerView recyclerView,
       ViewHolderFactory viewHolderFactory,
       TaskListFragment taskList,
       ActionModeProvider actionModeProvider,
       List<TaskContainer> list) {
-    super(adapter, viewHolderFactory, taskList, actionModeProvider);
+    super(adapter, recyclerView, viewHolderFactory, taskList, actionModeProvider);
 
     differ =
         new AsyncPagedListDiffer<>(

app/src/main/java/org/tasks/tasklist/TaskListRecyclerAdapter.java

@@ -1,11 +1,13 @@
 package org.tasks.tasklist;
 
 import android.os.Bundle;
+import android.view.View;
 import android.view.ViewGroup;
 import androidx.annotation.NonNull;
 import androidx.annotation.Nullable;
 import androidx.appcompat.view.ActionMode;
 import androidx.fragment.app.FragmentActivity;
+import androidx.recyclerview.widget.LinearLayoutManager;
 import androidx.recyclerview.widget.ListUpdateCallback;
 import androidx.recyclerview.widget.RecyclerView;
 import com.google.common.primitives.Longs;
@@ -15,6 +17,7 @@ import com.todoroo.astrid.api.Filter;
 import com.todoroo.astrid.api.GtasksFilter;
 import com.todoroo.astrid.utility.Flags;
 import java.util.List;
+import java.util.Objects;
 import org.tasks.data.TaskContainer;
 import org.tasks.intents.TaskIntents;
 
@@ -25,6 +28,7 @@ public abstract class TaskListRecyclerAdapter extends RecyclerView.Adapter<ViewH
 
   protected final TaskAdapter adapter;
   final TaskListFragment taskList;
+  private final RecyclerView recyclerView;
   private final ViewHolderFactory viewHolderFactory;
   private final ActionModeProvider actionModeProvider;
   private final boolean isGoogleTaskList;
@@ -32,10 +36,12 @@ public abstract class TaskListRecyclerAdapter extends RecyclerView.Adapter<ViewH
 
   TaskListRecyclerAdapter(
       TaskAdapter adapter,
+      RecyclerView recyclerView,
       ViewHolderFactory viewHolderFactory,
       TaskListFragment taskList,
       ActionModeProvider actionModeProvider) {
     this.adapter = adapter;
+    this.recyclerView = recyclerView;
     this.viewHolderFactory = viewHolderFactory;
     this.taskList = taskList;
     this.actionModeProvider = actionModeProvider;
@@ -171,7 +177,18 @@ public abstract class TaskListRecyclerAdapter extends RecyclerView.Adapter<ViewH
 
   @Override
   public void onMoved(int fromPosition, int toPosition) {
+    LinearLayoutManager layoutManager =
+        (LinearLayoutManager) Objects.requireNonNull(recyclerView.getLayoutManager());
+    View firstChild = layoutManager.getChildAt(0);
+    int firstChildPosition = layoutManager.findFirstVisibleItemPosition();
+
     notifyItemMoved(fromPosition, toPosition);
+
+    if (firstChildPosition > 0 && firstChild != null) {
+      layoutManager.scrollToPositionWithOffset(firstChildPosition - 1, firstChild.getTop());
+    } else if (firstChildPosition >= 0) {
+      layoutManager.scrollToPosition(firstChildPosition);
+    }
   }
 
   @Override