diff --git a/quickstep/src/com/android/launcher3/LauncherInitListener.java b/quickstep/src/com/android/launcher3/LauncherLifecycleListener.java
similarity index 78%
rename from quickstep/src/com/android/launcher3/LauncherInitListener.java
rename to quickstep/src/com/android/launcher3/LauncherLifecycleListener.java
index 28bd701..82c646d 100644
--- a/quickstep/src/com/android/launcher3/LauncherInitListener.java
+++ b/quickstep/src/com/android/launcher3/LauncherLifecycleListener.java
@@ -1,5 +1,5 @@
 /*
- * Copyright (C) 2018 The Android Open Source Project
+ * Copyright (C) 2022 The Android Open Source Project
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -16,19 +16,23 @@
 package com.android.launcher3;
 
 import android.animation.AnimatorSet;
+import android.annotation.Nullable;
 import android.annotation.TargetApi;
 import android.os.Build;
 import android.os.CancellationSignal;
 import android.view.RemoteAnimationTarget;
 
 import com.android.launcher3.uioverrides.QuickstepLauncher;
-import com.android.quickstep.util.ActivityInitListener;
+import com.android.quickstep.util.ActivityLifecycleListener;
 import com.android.quickstep.util.RemoteAnimationProvider;
 
 import java.util.function.BiPredicate;
 
+/**
+ * {@link ActivityLifecycleListener} for the in-launcher recents.
+ */
 @TargetApi(Build.VERSION_CODES.P)
-public class LauncherInitListener extends ActivityInitListener<Launcher> {
+public class LauncherLifecycleListener extends ActivityLifecycleListener<Launcher> {
 
     private RemoteAnimationProvider mRemoteAnimationProvider;
 
@@ -36,13 +40,16 @@
      * @param onInitListener a callback made when the activity is initialized. The callback should
      *                       return true to continue receiving callbacks (ie. for if the activity is
      *                       recreated).
+     * @param onDestroyListener a callback made when the activity is destroyed.
      */
-    public LauncherInitListener(BiPredicate<Launcher, Boolean> onInitListener) {
-        super(onInitListener, Launcher.ACTIVITY_TRACKER);
+    public LauncherLifecycleListener(
+            @Nullable BiPredicate<Launcher, Boolean> onInitListener,
+            @Nullable Runnable onDestroyListener) {
+        super(onInitListener, onDestroyListener, Launcher.ACTIVITY_TRACKER);
     }
 
     @Override
-    public boolean handleInit(Launcher launcher, boolean alreadyOnHome) {
+    public boolean handleActivityReady(Launcher launcher, boolean alreadyOnHome) {
         if (mRemoteAnimationProvider != null) {
             QuickstepTransitionManager appTransitionManager =
                     ((QuickstepLauncher) launcher).getAppTransitionManager();
@@ -68,7 +75,7 @@
             }, cancellationSignal);
         }
         launcher.deferOverlayCallbacksUntilNextResumeOrStop();
-        return super.handleInit(launcher, alreadyOnHome);
+        return super.handleActivityReady(launcher, alreadyOnHome);
     }
 
     @Override
diff --git a/quickstep/src/com/android/quickstep/AbsSwipeUpHandler.java b/quickstep/src/com/android/quickstep/AbsSwipeUpHandler.java
index 3d8ffc4..e41841a 100644
--- a/quickstep/src/com/android/quickstep/AbsSwipeUpHandler.java
+++ b/quickstep/src/com/android/quickstep/AbsSwipeUpHandler.java
@@ -50,6 +50,7 @@
 import static com.android.quickstep.MultiStateCallback.DEBUG_STATES;
 import static com.android.quickstep.util.ActiveGestureErrorDetector.GestureEvent.CANCEL_RECENTS_ANIMATION;
 import static com.android.quickstep.util.ActiveGestureErrorDetector.GestureEvent.EXPECTING_TASK_APPEARED;
+import static com.android.quickstep.util.ActiveGestureErrorDetector.GestureEvent.LAUNCHER_DESTROYED;
 import static com.android.quickstep.util.ActiveGestureErrorDetector.GestureEvent.ON_SETTLED_ON_END_TARGET;
 import static com.android.quickstep.util.VibratorWrapper.OVERVIEW_HAPTIC;
 import static com.android.quickstep.views.RecentsView.UPDATE_SYSUI_FLAGS_THRESHOLD;
@@ -113,7 +114,7 @@
 import com.android.quickstep.RemoteTargetGluer.RemoteTargetHandle;
 import com.android.quickstep.util.ActiveGestureErrorDetector;
 import com.android.quickstep.util.ActiveGestureLog;
-import com.android.quickstep.util.ActivityInitListener;
+import com.android.quickstep.util.ActivityLifecycleListener;
 import com.android.quickstep.util.AnimatorControllerWithResistance;
 import com.android.quickstep.util.InputConsumerProxy;
 import com.android.quickstep.util.InputProxyHandlerFactory;
@@ -159,7 +160,7 @@
 
     protected final BaseActivityInterface<S, T> mActivityInterface;
     protected final InputConsumerProxy mInputConsumerProxy;
-    protected final ActivityInitListener mActivityInitListener;
+    protected final ActivityLifecycleListener mActivityInitListener;
     // Callbacks to be made once the recents animation starts
     private final ArrayList<Runnable> mRecentsAnimationStartCallbacks = new ArrayList<>();
     private final OnScrollChangedListener mOnRecentsScrollListener = this::onRecentsViewScroll;
@@ -329,7 +330,8 @@
             InputConsumerController inputConsumer) {
         super(context, deviceState, gestureState);
         mActivityInterface = gestureState.getActivityInterface();
-        mActivityInitListener = mActivityInterface.createActivityInitListener(this::onActivityInit);
+        mActivityInitListener = mActivityInterface.createActivityLifecycleListener(
+                this::onActivityInit, this::onActivityDestroy);
         mInputConsumerProxy =
                 new InputConsumerProxy(context, /* rotationSupplier = */ () -> {
                     if (mRecentsView == null) {
@@ -520,6 +522,11 @@
         return true;
     }
 
+    private void onActivityDestroy() {
+        ActiveGestureLog.INSTANCE.addLog("Launcher activity destroyed", LAUNCHER_DESTROYED);
+        onGestureCancelled();
+    }
+
     /**
      * Return true if the window should be translated horizontally if the recents view scrolls
      */
diff --git a/quickstep/src/com/android/quickstep/BaseActivityInterface.java b/quickstep/src/com/android/quickstep/BaseActivityInterface.java
index 274b686..5523518 100644
--- a/quickstep/src/com/android/quickstep/BaseActivityInterface.java
+++ b/quickstep/src/com/android/quickstep/BaseActivityInterface.java
@@ -60,7 +60,7 @@
 import com.android.launcher3.util.DisplayController;
 import com.android.launcher3.util.NavigationMode;
 import com.android.launcher3.views.ScrimView;
-import com.android.quickstep.util.ActivityInitListener;
+import com.android.quickstep.util.ActivityLifecycleListener;
 import com.android.quickstep.util.AnimatorControllerWithResistance;
 import com.android.quickstep.views.RecentsView;
 import com.android.systemui.shared.recents.model.ThumbnailData;
@@ -123,8 +123,17 @@
     public abstract AnimationFactory prepareRecentsUI(RecentsAnimationDeviceState deviceState,
             boolean activityVisible, Consumer<AnimatorControllerWithResistance> callback);
 
-    public abstract ActivityInitListener createActivityInitListener(
-            Predicate<Boolean> onInitListener);
+    /**
+     * Creates a activity listener for activity initialized and/or destroyed. One or both of these
+     * listeners must be provided.
+     *
+     * @param onInitListener a callback made when the activity is initialized. The callback should
+     *                       return true to continue receiving callbacks (ie. for if the activity is
+     *                       recreated).
+     * @param onDestroyListener a callback made when the activity is destroyed.
+     */
+    public abstract ActivityLifecycleListener createActivityLifecycleListener(
+            @Nullable Predicate<Boolean> onInitListener, @Nullable Runnable onDestroyListener);
 
     /**
      * Sets a callback to be run when an activity launch happens while launcher is not yet resumed.
diff --git a/quickstep/src/com/android/quickstep/FallbackActivityInterface.java b/quickstep/src/com/android/quickstep/FallbackActivityInterface.java
index ae9fb0b..a658566 100644
--- a/quickstep/src/com/android/quickstep/FallbackActivityInterface.java
+++ b/quickstep/src/com/android/quickstep/FallbackActivityInterface.java
@@ -36,7 +36,7 @@
 import com.android.launcher3.util.DisplayController;
 import com.android.quickstep.GestureState.GestureEndTarget;
 import com.android.quickstep.fallback.RecentsState;
-import com.android.quickstep.util.ActivityInitListener;
+import com.android.quickstep.util.ActivityLifecycleListener;
 import com.android.quickstep.util.AnimatorControllerWithResistance;
 import com.android.quickstep.views.RecentsView;
 
@@ -88,10 +88,12 @@
     }
 
     @Override
-    public ActivityInitListener createActivityInitListener(
-            Predicate<Boolean> onInitListener) {
-        return new ActivityInitListener<>((activity, alreadyOnHome) ->
-                onInitListener.test(alreadyOnHome), RecentsActivity.ACTIVITY_TRACKER);
+    public ActivityLifecycleListener createActivityLifecycleListener(
+            @Nullable Predicate<Boolean> onInitListener, @Nullable Runnable onDestroyListener) {
+        return new ActivityLifecycleListener<>(
+                (activity, alreadyOnHome) -> onInitListener.test(alreadyOnHome),
+                onDestroyListener,
+                RecentsActivity.ACTIVITY_TRACKER);
     }
 
     @Nullable
diff --git a/quickstep/src/com/android/quickstep/LauncherActivityInterface.java b/quickstep/src/com/android/quickstep/LauncherActivityInterface.java
index 9ff9416..cb54d2e 100644
--- a/quickstep/src/com/android/quickstep/LauncherActivityInterface.java
+++ b/quickstep/src/com/android/quickstep/LauncherActivityInterface.java
@@ -37,7 +37,7 @@
 import com.android.launcher3.DeviceProfile;
 import com.android.launcher3.Launcher;
 import com.android.launcher3.LauncherAnimUtils;
-import com.android.launcher3.LauncherInitListener;
+import com.android.launcher3.LauncherLifecycleListener;
 import com.android.launcher3.LauncherState;
 import com.android.launcher3.anim.PendingAnimation;
 import com.android.launcher3.statehandlers.DepthController;
@@ -49,7 +49,7 @@
 import com.android.launcher3.util.DisplayController;
 import com.android.launcher3.util.NavigationMode;
 import com.android.quickstep.GestureState.GestureEndTarget;
-import com.android.quickstep.util.ActivityInitListener;
+import com.android.quickstep.util.ActivityLifecycleListener;
 import com.android.quickstep.util.AnimatorControllerWithResistance;
 import com.android.quickstep.util.LayoutUtils;
 import com.android.quickstep.views.RecentsView;
@@ -136,9 +136,10 @@
     }
 
     @Override
-    public ActivityInitListener createActivityInitListener(Predicate<Boolean> onInitListener) {
-        return new LauncherInitListener((activity, alreadyOnHome) ->
-                onInitListener.test(alreadyOnHome));
+    public ActivityLifecycleListener createActivityLifecycleListener(
+            @Nullable Predicate<Boolean> onInitListener, @Nullable Runnable onDestroyListener) {
+        return new LauncherLifecycleListener((activity, alreadyOnHome) ->
+                onInitListener.test(alreadyOnHome), onDestroyListener);
     }
 
     @Override
diff --git a/quickstep/src/com/android/quickstep/util/ActiveGestureErrorDetector.java b/quickstep/src/com/android/quickstep/util/ActiveGestureErrorDetector.java
index 60065fb..0fdd8b5 100644
--- a/quickstep/src/com/android/quickstep/util/ActiveGestureErrorDetector.java
+++ b/quickstep/src/com/android/quickstep/util/ActiveGestureErrorDetector.java
@@ -37,7 +37,7 @@
         ON_SETTLED_ON_END_TARGET, START_RECENTS_ANIMATION, FINISH_RECENTS_ANIMATION,
         CANCEL_RECENTS_ANIMATION, SET_ON_PAGE_TRANSITION_END_CALLBACK, CANCEL_CURRENT_ANIMATION,
         CLEANUP_SCREENSHOT, SCROLLER_ANIMATION_ABORTED, TASK_APPEARED, EXPECTING_TASK_APPEARED,
-        FLAG_USING_OTHER_ACTIVITY_INPUT_CONSUMER,
+        FLAG_USING_OTHER_ACTIVITY_INPUT_CONSUMER, LAUNCHER_DESTROYED,
 
         /**
          * These GestureEvents are specifically associated to state flags that get set in
@@ -162,6 +162,13 @@
                                         + "before/without setting end target to new task",
                                 writer);
                         break;
+                    case LAUNCHER_DESTROYED:
+                        errorDetected |= printErrorIfTrue(
+                                true,
+                                prefix,
+                                /* errorMessage= */ "Launcher destroyed mid-gesture",
+                                writer);
+                        break;
                     case STATE_GESTURE_COMPLETED:
                         errorDetected |= printErrorIfTrue(
                                 !encounteredEvents.contains(GestureEvent.MOTION_UP),
diff --git a/quickstep/src/com/android/quickstep/util/ActivityInitListener.java b/quickstep/src/com/android/quickstep/util/ActivityInitListener.java
deleted file mode 100644
index aeec36f..0000000
--- a/quickstep/src/com/android/quickstep/util/ActivityInitListener.java
+++ /dev/null
@@ -1,73 +0,0 @@
-/*
- * Copyright (C) 2019 The Android Open Source Project
- *
- * Licensed under the Apache License, Version 2.0 (the "License");
- * you may not use this file except in compliance with the License.
- * You may obtain a copy of the License at
- *
- *      http://www.apache.org/licenses/LICENSE-2.0
- *
- * Unless required by applicable law or agreed to in writing, software
- * distributed under the License is distributed on an "AS IS" BASIS,
- * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
- * See the License for the specific language governing permissions and
- * limitations under the License.
- */
-package com.android.quickstep.util;
-
-import com.android.launcher3.BaseActivity;
-import com.android.launcher3.util.ActivityTracker;
-import com.android.launcher3.util.ActivityTracker.SchedulerCallback;
-
-import java.util.function.BiPredicate;
-
-public class ActivityInitListener<T extends BaseActivity> implements
-        SchedulerCallback<T> {
-
-    private BiPredicate<T, Boolean> mOnInitListener;
-    private final ActivityTracker<T> mActivityTracker;
-
-    private boolean mIsRegistered = false;
-
-    /**
-     * @param onInitListener a callback made when the activity is initialized. The callback should
-     *                       return true to continue receiving callbacks (ie. for if the activity is
-     *                       recreated).
-     */
-    public ActivityInitListener(BiPredicate<T, Boolean> onInitListener,
-            ActivityTracker<T> tracker) {
-        mOnInitListener = onInitListener;
-        mActivityTracker = tracker;
-    }
-
-    @Override
-    public final boolean init(T activity, boolean alreadyOnHome) {
-        if (!mIsRegistered) {
-            // Don't receive any more updates
-            return false;
-        }
-        return handleInit(activity, alreadyOnHome);
-    }
-
-    protected boolean handleInit(T activity, boolean alreadyOnHome) {
-        return mOnInitListener.test(activity, alreadyOnHome);
-    }
-
-    /**
-     * Registers the activity-created listener. If the activity is already created, then the
-     * callback provided in the constructor will be called synchronously.
-     */
-    public void register() {
-        mIsRegistered = true;
-        mActivityTracker.registerCallback(this);
-    }
-
-    /**
-     * After calling this, we won't {@link #init} even when the activity is ready.
-     */
-    public void unregister() {
-        mActivityTracker.unregisterCallback(this);
-        mIsRegistered = false;
-        mOnInitListener = null;
-    }
-}
diff --git a/quickstep/src/com/android/quickstep/util/ActivityLifecycleListener.java b/quickstep/src/com/android/quickstep/util/ActivityLifecycleListener.java
new file mode 100644
index 0000000..1edf188
--- /dev/null
+++ b/quickstep/src/com/android/quickstep/util/ActivityLifecycleListener.java
@@ -0,0 +1,113 @@
+/*
+ * Copyright (C) 2022 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package com.android.quickstep.util;
+
+import android.util.Log;
+
+import androidx.annotation.Nullable;
+
+import com.android.launcher3.BaseActivity;
+import com.android.launcher3.util.ActivityTracker;
+import com.android.launcher3.util.ActivityTracker.SchedulerCallback;
+
+import java.util.function.BiPredicate;
+
+/**
+ * Listener for activity initialized and/or destroyed.
+ */
+public class ActivityLifecycleListener<T extends BaseActivity> implements
+        SchedulerCallback<T> {
+
+    private static final String TAG = "ActivityLifecycleListener";
+
+    @Nullable private final BiPredicate<T, Boolean> mOnInitListener;
+    @Nullable private final Runnable mOnDestroyListener;
+    private final ActivityTracker<T> mActivityTracker;
+
+    private boolean mIsRegistered = false;
+
+    /**
+     * One or both of {@code onInitListener} and {@code onInitListener} must be provided, otherwise
+     * the created instance will effectively be a no-op.
+     *
+     * @param onInitListener a callback made when the activity is initialized. The callback should
+     *                       return true to continue receiving callbacks (ie. for if the activity is
+     *                       recreated).
+     * @param onDestroyListener a callback made when the activity is destroyed.
+     */
+    public ActivityLifecycleListener(
+            @Nullable BiPredicate<T, Boolean> onInitListener,
+            @Nullable Runnable onDestroyListener,
+            ActivityTracker<T> tracker) {
+        if (onInitListener == null && onDestroyListener == null) {
+            throw new IllegalArgumentException("Both listeners cannot be null");
+        }
+        mOnInitListener = onInitListener;
+        mOnDestroyListener = onDestroyListener;
+        mActivityTracker = tracker;
+    }
+
+    @Override
+    public final boolean onActivityReady(T activity, boolean alreadyOnHome) {
+        if (!mIsRegistered) {
+            // Don't receive any more updates
+            return false;
+        }
+        return handleActivityReady(activity, alreadyOnHome);
+    }
+
+    protected boolean handleActivityReady(T activity, boolean alreadyOnHome) {
+        if (mOnInitListener == null) {
+            Log.e(TAG, "Cannot handle init: init listener is null", new Exception());
+            return false;
+        }
+        return mOnInitListener.test(activity, alreadyOnHome);
+    }
+
+    @Override
+    public void onActivityDestroyed() {
+        if (mOnDestroyListener == null) {
+            Log.e(TAG, "Cannot clean up: destroy listener is null", new Exception());
+            return;
+        }
+        mOnDestroyListener.run();
+    }
+
+    /**
+     * Registers the activity-created listener. If the activity is already created, then the
+     * callback provided in the constructor will be called synchronously.
+     */
+    public void register() {
+        mIsRegistered = true;
+        mActivityTracker.registerCallback(this, getType());
+    }
+
+    /**
+     * After calling this, we won't call {@link #onActivityReady} even when the activity is ready.
+     */
+    public void unregister() {
+        mActivityTracker.unregisterCallback(this, getType());
+        mIsRegistered = false;
+    }
+
+    private int getType() {
+        return mOnInitListener != null && mOnDestroyListener != null
+                ? ActivityTracker.TYPE_BOTH
+                : (mOnInitListener != null
+                        ? ActivityTracker.TYPE_INIT
+                        : ActivityTracker.TYPE_DESTROY);
+    }
+}
diff --git a/src/com/android/launcher3/dragndrop/BaseItemDragListener.java b/src/com/android/launcher3/dragndrop/BaseItemDragListener.java
index 981e3a6..6d127b3 100644
--- a/src/com/android/launcher3/dragndrop/BaseItemDragListener.java
+++ b/src/com/android/launcher3/dragndrop/BaseItemDragListener.java
@@ -74,7 +74,7 @@
     }
 
     @Override
-    public boolean init(Launcher launcher, boolean alreadyOnHome) {
+    public boolean onActivityReady(Launcher launcher, boolean alreadyOnHome) {
         AbstractFloatingView.closeAllOpenViews(launcher, alreadyOnHome);
         launcher.getStateManager().goToState(NORMAL, alreadyOnHome /* animated */);
         launcher.getDragLayer().setOnDragListener(this);
diff --git a/src/com/android/launcher3/dragndrop/PinItemDragListener.java b/src/com/android/launcher3/dragndrop/PinItemDragListener.java
index af43ae8..fb924c1 100644
--- a/src/com/android/launcher3/dragndrop/PinItemDragListener.java
+++ b/src/com/android/launcher3/dragndrop/PinItemDragListener.java
@@ -72,8 +72,8 @@
     }
 
     @Override
-    public boolean init(Launcher launcher, boolean alreadyOnHome) {
-        super.init(launcher, alreadyOnHome);
+    public boolean onActivityReady(Launcher launcher, boolean alreadyOnHome) {
+        super.onActivityReady(launcher, alreadyOnHome);
         if (!alreadyOnHome) {
             launcher.useFadeOutAnimationForLauncherStart(mCancelSignal);
         }
diff --git a/src/com/android/launcher3/model/GridSizeMigrationUtil.java b/src/com/android/launcher3/model/GridSizeMigrationUtil.java
index d63408b..eded5ea 100644
--- a/src/com/android/launcher3/model/GridSizeMigrationUtil.java
+++ b/src/com/android/launcher3/model/GridSizeMigrationUtil.java
@@ -66,7 +66,7 @@
 public class GridSizeMigrationUtil {
 
     private static final String TAG = "GridSizeMigrationUtil";
-    private static final boolean DEBUG = false;
+    private static final boolean DEBUG = true;
 
     private GridSizeMigrationUtil() {
         // Util class should not be instantiated
@@ -188,27 +188,54 @@
             @NonNull final DeviceGridState srcDeviceState,
             @NonNull final DeviceGridState destDeviceState) {
 
-        final List<DbEntry> hotseatItems = destReader.loadHotseatEntries();
-        final List<DbEntry> workspaceItems = destReader.loadAllWorkspaceEntries();
-        final List<DbEntry> hotseatDiff =
-                calcDiff(srcReader.loadHotseatEntries(), hotseatItems);
-        final List<DbEntry> workspaceDiff =
-                calcDiff(srcReader.loadAllWorkspaceEntries(), workspaceItems);
+        final List<DbEntry> srcHotseatItems = srcReader.loadHotseatEntries();
+        final List<DbEntry> srcWorkspaceItems = srcReader.loadAllWorkspaceEntries();
+        final List<DbEntry> dstHotseatItems = destReader.loadHotseatEntries();
+        final List<DbEntry> dstWorkspaceItems = destReader.loadAllWorkspaceEntries();
+        final List<DbEntry> hotseatToBeAdded = new ArrayList<>(1);
+        final List<DbEntry> workspaceToBeAdded = new ArrayList<>(1);
+        final IntArray toBeRemoved = new IntArray();
+
+        calcDiff(srcHotseatItems, dstHotseatItems, hotseatToBeAdded, toBeRemoved);
+        calcDiff(srcWorkspaceItems, dstWorkspaceItems, workspaceToBeAdded, toBeRemoved);
 
         final int trgX = targetSize.x;
         final int trgY = targetSize.y;
 
-        if (hotseatDiff.isEmpty() && workspaceDiff.isEmpty()) {
+        if (DEBUG) {
+            Log.d(TAG, "Start migration:"
+                    + "\n Source Device:"
+                    + srcWorkspaceItems.stream().map(DbEntry::toString).collect(
+                    Collectors.joining(",\n", "[", "]"))
+                    + "\n Target Device:"
+                    + dstWorkspaceItems.stream().map(DbEntry::toString).collect(
+                    Collectors.joining(",\n", "[", "]"))
+                    + "\n Removing Items:"
+                    + dstWorkspaceItems.stream().filter(entry ->
+                            toBeRemoved.contains(entry.id)).map(DbEntry::toString).collect(
+                    Collectors.joining(",\n", "[", "]"))
+                    + "\n Adding Workspace Items:"
+                    + workspaceToBeAdded.stream().map(DbEntry::toString).collect(
+                    Collectors.joining(",\n", "[", "]"))
+                    + "\n Adding Hotseat Items:"
+                    + hotseatToBeAdded.stream().map(DbEntry::toString).collect(
+                    Collectors.joining(",\n", "[", "]"))
+            );
+        }
+        if (!toBeRemoved.isEmpty()) {
+            removeEntryFromDb(destReader.mDb, destReader.mTableName, toBeRemoved);
+        }
+        if (hotseatToBeAdded.isEmpty() && workspaceToBeAdded.isEmpty()) {
             return false;
         }
 
         // Sort the items by the reading order.
-        Collections.sort(hotseatDiff);
-        Collections.sort(workspaceDiff);
+        Collections.sort(hotseatToBeAdded);
+        Collections.sort(workspaceToBeAdded);
 
         // Migrate hotseat
         solveHotseatPlacement(db, srcReader,
-                destReader, context, destHotseatSize, hotseatItems, hotseatDiff);
+                destReader, context, destHotseatSize, dstHotseatItems, hotseatToBeAdded);
 
         // Migrate workspace.
         // First we create a collection of the screens
@@ -229,8 +256,8 @@
                 Log.d(TAG, "Migrating " + screenId);
             }
             solveGridPlacement(db, srcReader,
-                    destReader, context, screenId, trgX, trgY, workspaceDiff, false);
-            if (workspaceDiff.isEmpty()) {
+                    destReader, context, screenId, trgX, trgY, workspaceToBeAdded, false);
+            if (workspaceToBeAdded.isEmpty()) {
                 break;
             }
         }
@@ -238,42 +265,37 @@
         // In case the new grid is smaller, there might be some leftover items that don't fit on
         // any of the screens, in this case we add them to new screens until all of them are placed.
         int screenId = destReader.mLastScreenId + 1;
-        while (!workspaceDiff.isEmpty()) {
+        while (!workspaceToBeAdded.isEmpty()) {
             solveGridPlacement(db, srcReader,
-                    destReader, context, screenId, trgX, trgY, workspaceDiff, preservePages);
+                    destReader, context, screenId, trgX, trgY, workspaceToBeAdded, preservePages);
             screenId++;
         }
 
         return true;
     }
 
-    /** Return what's in the src but not in the dest */
-    private static List<DbEntry> calcDiff(List<DbEntry> src, List<DbEntry> dest) {
-        Map<String, Integer> destIdSet = new HashMap<>();
-        for (DbEntry entry : dest) {
-            String entryID = entry.getEntryMigrationId();
-            if (destIdSet.containsKey(entryID)) {
-                destIdSet.put(entryID, destIdSet.get(entryID) + 1);
-            } else {
-                destIdSet.put(entryID, 1);
+    /**
+     * Calculate the differences between {@code src} (denoted by A) and {@code dest}
+     * (denoted by B).
+     * All DbEntry in A - B will be added to {@code toBeAdded}
+     * All DbEntry.id in B - A will be added to {@code toBeRemoved}
+     */
+    private static void calcDiff(@NonNull final List<DbEntry> src,
+            @NonNull final List<DbEntry> dest, @NonNull final List<DbEntry> toBeAdded,
+            @NonNull final IntArray toBeRemoved) {
+        src.forEach(entry -> {
+            if (!dest.contains(entry)) {
+                toBeAdded.add(entry);
             }
-        }
-        List<DbEntry> diff = new ArrayList<>();
-        for (DbEntry entry : src) {
-            String entryID = entry.getEntryMigrationId();
-            if (destIdSet.containsKey(entryID)) {
-                Integer count = destIdSet.get(entryID);
-                if (count <= 0) {
-                    diff.add(entry);
-                    destIdSet.remove(entryID);
-                } else {
-                    destIdSet.put(entryID, count - 1);
+        });
+        dest.forEach(entry -> {
+            if (!src.contains(entry)) {
+                toBeRemoved.add(entry.id);
+                if (entry.itemType == LauncherSettings.Favorites.ITEM_TYPE_FOLDER) {
+                    entry.mFolderItems.values().forEach(ids -> ids.forEach(toBeRemoved::add));
                 }
-            } else {
-                diff.add(entry);
             }
-        }
-        return diff;
+        });
     }
 
     private static void insertEntryInDb(SQLiteDatabase db, Context context, DbEntry entry,
@@ -682,12 +704,12 @@
             if (this == o) return true;
             if (o == null || getClass() != o.getClass()) return false;
             DbEntry entry = (DbEntry) o;
-            return Objects.equals(mIntent, entry.mIntent);
+            return Objects.equals(getEntryMigrationId(), entry.getEntryMigrationId());
         }
 
         @Override
         public int hashCode() {
-            return Objects.hash(mIntent);
+            return Objects.hash(getEntryMigrationId());
         }
 
         public void updateContentValues(ContentValues values) {
diff --git a/src/com/android/launcher3/util/ActivityTracker.java b/src/com/android/launcher3/util/ActivityTracker.java
index 7af1a13..5f93a66 100644
--- a/src/com/android/launcher3/util/ActivityTracker.java
+++ b/src/com/android/launcher3/util/ActivityTracker.java
@@ -20,8 +20,6 @@
 import com.android.launcher3.BaseActivity;
 
 import java.lang.ref.WeakReference;
-import java.util.ArrayList;
-import java.util.HashSet;
 import java.util.concurrent.CopyOnWriteArrayList;
 
 /**
@@ -30,8 +28,15 @@
  */
 public final class ActivityTracker<T extends BaseActivity> {
 
+    public static final int TYPE_INIT = 0;
+    public static final int TYPE_DESTROY = 1;
+    public static final int TYPE_BOTH = 2;
+
     private WeakReference<T> mCurrentActivity = new WeakReference<>(null);
-    private CopyOnWriteArrayList<SchedulerCallback<T>> mCallbacks = new CopyOnWriteArrayList<>();
+    private CopyOnWriteArrayList<SchedulerCallback<T>> mActivityReadyCallbacks =
+            new CopyOnWriteArrayList<>();
+    private CopyOnWriteArrayList<SchedulerCallback<T>> mActivityDestroyedCallbacks =
+            new CopyOnWriteArrayList<>();
 
     @Nullable
     public <R extends T> R getCreatedActivity() {
@@ -42,32 +47,74 @@
         if (mCurrentActivity.get() == activity) {
             mCurrentActivity.clear();
         }
+        for (SchedulerCallback<T> cb : mActivityDestroyedCallbacks) {
+            cb.onActivityDestroyed();
+            unregisterCallback(cb, TYPE_DESTROY);
+        }
+    }
+
+    /** Registers an activity create callback. */
+    public void registerCallback(SchedulerCallback<T> callback) {
+        registerCallback(callback, TYPE_INIT);
     }
 
     /**
-     * Call {@link SchedulerCallback#init(BaseActivity, boolean)} when the
-     * activity is ready. If the activity is already created, this is called immediately.
+     * Call {@link SchedulerCallback#onActivityReady(BaseActivity, boolean)} when the
+     * activity is ready and/or {@link SchedulerCallback#onActivityDestroyed()} when the activity
+     * is destroyed.
      *
-     * The tracker maintains a strong ref to the callback, so it is up to the caller to return
-     * {@code false} in the callback OR to unregister the callback explicitly.
+     * If type is {@link ActivityTracker#TYPE_INIT} TYPE_INIT or
+     * {@link ActivityTracker#TYPE_BOTH} and the activity is already created, this
+     * {@link SchedulerCallback#onActivityReady(BaseActivity, boolean)} is called immediately.
      *
-     * @param callback The callback to call init() on when the activity is ready.
+     * If type is {@link ActivityTracker#TYPE_DESTROY} or
+     * {@link ActivityTracker#TYPE_BOTH} and the activity is already destroyed,
+     * {@link SchedulerCallback#onActivityDestroyed()} is called immediately.
+     *
+     * The tracker maintains a strong ref to the callbacks, so it is up to the caller to return
+     * {@code false} in {@link SchedulerCallback#onActivityReady(BaseActivity, boolean)} OR to
+     * unregister the callback explicitly.
+     *
+     * @param callback The callback to call init() or cleanUp() on when the activity is ready or
+     *                 destroyed.
+     * @param type whether to use this callback on activity create, destroy or both.
      */
-    public void registerCallback(SchedulerCallback<T> callback) {
+    public void registerCallback(SchedulerCallback<T> callback, int type) {
         T activity = mCurrentActivity.get();
-        mCallbacks.add(callback);
-        if (activity != null) {
-            if (!callback.init(activity, activity.isStarted())) {
-                unregisterCallback(callback);
+        if (type == TYPE_INIT || type == TYPE_BOTH) {
+            mActivityReadyCallbacks.add(callback);
+            if (activity != null) {
+                if (!callback.onActivityReady(activity, activity.isStarted())) {
+                    unregisterCallback(callback, TYPE_INIT);
+                }
+            }
+        }
+        if (type == TYPE_DESTROY || type == TYPE_BOTH) {
+            mActivityDestroyedCallbacks.add(callback);
+            if (activity == null) {
+                callback.onActivityDestroyed();
+                unregisterCallback(callback, TYPE_DESTROY);
             }
         }
     }
 
     /**
-     * Unregisters a registered callback.
+     * Unregisters a registered activity create callback.
      */
     public void unregisterCallback(SchedulerCallback<T> callback) {
-        mCallbacks.remove(callback);
+        unregisterCallback(callback, TYPE_INIT);
+    }
+
+    /**
+     * Unregisters a registered callback.
+     */
+    public void unregisterCallback(SchedulerCallback<T> callback, int type) {
+        if (type == TYPE_INIT || type == TYPE_BOTH) {
+            mActivityReadyCallbacks.remove(callback);
+        }
+        if (type == TYPE_DESTROY || type == TYPE_BOTH) {
+            mActivityDestroyedCallbacks.remove(callback);
+        }
     }
 
     public boolean handleCreate(T activity) {
@@ -81,8 +128,8 @@
 
     private boolean handleIntent(T activity, boolean alreadyOnHome) {
         boolean handled = false;
-        for (SchedulerCallback<T> cb : mCallbacks) {
-            if (!cb.init(activity, alreadyOnHome)) {
+        for (SchedulerCallback<T> cb : mActivityReadyCallbacks) {
+            if (!cb.onActivityReady(activity, alreadyOnHome)) {
                 // Callback doesn't want any more updates
                 unregisterCallback(cb);
             }
@@ -98,6 +145,11 @@
          * @param alreadyOnHome Whether the activity is already started.
          * @return Whether to continue receiving callbacks (i.e. if the activity is recreated).
          */
-        boolean init(T activity, boolean alreadyOnHome);
+        boolean onActivityReady(T activity, boolean alreadyOnHome);
+
+        /**
+         * Called then the activity gets destroyed.
+         */
+        default void onActivityDestroyed() { }
     }
 }
diff --git a/tests/src/com/android/launcher3/model/GridSizeMigrationUtilTest.kt b/tests/src/com/android/launcher3/model/GridSizeMigrationUtilTest.kt
index 85d7bf9..76a186b 100644
--- a/tests/src/com/android/launcher3/model/GridSizeMigrationUtilTest.kt
+++ b/tests/src/com/android/launcher3/model/GridSizeMigrationUtilTest.kt
@@ -17,6 +17,7 @@
 
 import android.content.Context
 import android.content.Intent
+import android.database.Cursor;
 import android.database.sqlite.SQLiteDatabase
 import android.graphics.Point
 import android.os.Process
@@ -183,15 +184,232 @@
         // Expected dest grid icons
         // _ _ _ _
         // 5 6 7 8
-        // 9 _ 10_
+        // 9 _ _ _
         // _ _ _ _
-        assertThat(locMap.size.toLong()).isEqualTo(6)
+        assertThat(locMap.size.toLong()).isEqualTo(5)
         assertThat(locMap[testPackage5]).isEqualTo(Point(0, 1))
         assertThat(locMap[testPackage6]).isEqualTo(Point(1, 1))
         assertThat(locMap[testPackage7]).isEqualTo(Point(2, 1))
         assertThat(locMap[testPackage8]).isEqualTo(Point(3, 1))
         assertThat(locMap[testPackage9]).isEqualTo(Point(0, 2))
-        assertThat(locMap[testPackage10]).isEqualTo(Point(2, 2))
+    }
+
+    /**
+     * Old migration logic, should be modified once [FeatureFlags.ENABLE_NEW_MIGRATION_LOGIC] is
+     * not needed anymore
+     */
+    @Test
+    @Throws(Exception::class)
+    fun testMigrationBackAndForth() {
+        // Hotseat items in grid A
+        // 1 2 _ 3 4
+        modelHelper.addItem(APP_ICON, 0, HOTSEAT, 0, 0, testPackage1, 1, TMP_CONTENT_URI)
+        modelHelper.addItem(SHORTCUT, 1, HOTSEAT, 0, 0, testPackage2, 2, TMP_CONTENT_URI)
+        modelHelper.addItem(SHORTCUT, 3, HOTSEAT, 0, 0, testPackage3, 3, TMP_CONTENT_URI)
+        modelHelper.addItem(APP_ICON, 4, HOTSEAT, 0, 0, testPackage4, 4, TMP_CONTENT_URI)
+        // Workspace items in grid A
+        // _ _ _ _ _
+        // _ _ _ _ 5
+        // _ _ 6 _ 7
+        // _ _ 8 _ _
+        // _ _ _ _ _
+        modelHelper.addItem(APP_ICON, 0, DESKTOP, 4, 1, testPackage5, 5, TMP_CONTENT_URI)
+        modelHelper.addItem(APP_ICON, 0, DESKTOP, 2, 2, testPackage6, 6, TMP_CONTENT_URI)
+        modelHelper.addItem(APP_ICON, 0, DESKTOP, 4, 2, testPackage7, 7, TMP_CONTENT_URI)
+        modelHelper.addItem(APP_ICON, 0, DESKTOP, 2, 3, testPackage8, 8, TMP_CONTENT_URI)
+
+        // Hotseat items in grid B
+        // 2 _ _ _
+        modelHelper.addItem(SHORTCUT, 0, HOTSEAT, 0, 0, testPackage2)
+        // Workspace items in grid B
+        // _ _ _ _
+        // _ _ _ 10
+        // _ _ _ _
+        // _ _ _ _
+        modelHelper.addItem(APP_ICON, 0, DESKTOP, 1, 3, testPackage10)
+
+        idp.numDatabaseHotseatIcons = 4
+        idp.numColumns = 4
+        idp.numRows = 4
+        val readerGridA = DbReader(db, TMP_TABLE, context, validPackages)
+        val readerGridB = DbReader(db, TABLE_NAME, context, validPackages)
+        // migrate from A -> B
+        GridSizeMigrationUtil.migrate(
+                context,
+                db,
+                readerGridA,
+                readerGridB,
+                idp.numDatabaseHotseatIcons,
+                Point(idp.numColumns, idp.numRows),
+                DeviceGridState(context),
+                DeviceGridState(idp)
+        )
+
+        // Check hotseat items in grid B
+        var c = context.contentResolver.query(
+                CONTENT_URI,
+                arrayOf(SCREEN, INTENT),
+                "container=$CONTAINER_HOTSEAT",
+                null,
+                SCREEN,
+                null
+        ) ?: throw IllegalStateException()
+        // Expected hotseat items in grid B
+        // 2 1 3 4
+        verifyHotseat(c, idp,
+                mutableListOf(testPackage2, testPackage1, testPackage3, testPackage4).toList())
+
+        // Check workspace items in grid B
+        c = context.contentResolver.query(
+                CONTENT_URI,
+                arrayOf(SCREEN, CELLX, CELLY, INTENT),
+                "container=$CONTAINER_DESKTOP",
+                null,
+                null,
+                null
+        ) ?: throw IllegalStateException()
+        var locMap = parseLocMap(context, c)
+        // Expected items in grid B
+        // _ _ _ _
+        // 5 6 7 8
+        // _ _ _ _
+        // _ _ _ _
+        assertThat(locMap.size.toLong()).isEqualTo(4)
+        assertThat(locMap[testPackage5]).isEqualTo(Triple(0, 0, 1))
+        assertThat(locMap[testPackage6]).isEqualTo(Triple(0, 1, 1))
+        assertThat(locMap[testPackage7]).isEqualTo(Triple(0, 2, 1))
+        assertThat(locMap[testPackage8]).isEqualTo(Triple(0, 3, 1))
+
+        // add item in B
+        modelHelper.addItem(APP_ICON, 0, DESKTOP, 0, 2, testPackage9)
+
+        // migrate from B -> A
+        GridSizeMigrationUtil.migrate(
+                context,
+                db,
+                readerGridB,
+                readerGridA,
+                5,
+                Point(5, 5),
+                DeviceGridState(idp),
+                DeviceGridState(context)
+        )
+        // Check hotseat items in grid A
+        c = context.contentResolver.query(
+                TMP_CONTENT_URI,
+                arrayOf(SCREEN, INTENT),
+                "container=$CONTAINER_HOTSEAT",
+                null,
+                SCREEN,
+                null
+        ) ?: throw IllegalStateException()
+        // Expected hotseat items in grid A
+        // 1 2 _ 3 4
+        verifyHotseat(c, idp, mutableListOf(
+                testPackage1, testPackage2, null, testPackage3, testPackage4).toList())
+
+        // Check workspace items in grid A
+        c = context.contentResolver.query(
+                TMP_CONTENT_URI,
+                arrayOf(SCREEN, CELLX, CELLY, INTENT),
+                "container=$CONTAINER_DESKTOP",
+                null,
+                null,
+                null
+        ) ?: throw IllegalStateException()
+        locMap = parseLocMap(context, c)
+        // Expected workspace items in grid A
+        // _ _ _ _ _
+        // _ _ _ _ 5
+        // 9 _ 6 _ 7
+        // _ _ 8 _ _
+        // _ _ _ _ _
+        assertThat(locMap.size.toLong()).isEqualTo(5)
+        // Verify items that existed in grid A remains in same position
+        assertThat(locMap[testPackage5]).isEqualTo(Triple(0, 4, 1))
+        assertThat(locMap[testPackage6]).isEqualTo(Triple(0, 2, 2))
+        assertThat(locMap[testPackage7]).isEqualTo(Triple(0, 4, 2))
+        assertThat(locMap[testPackage8]).isEqualTo(Triple(0, 2, 3))
+        // Verify items that didn't exist in grid A are added in new screen
+        assertThat(locMap[testPackage9]).isEqualTo(Triple(0, 0, 2))
+
+        // remove item from B
+        modelHelper.deleteItem(7, TMP_TABLE)
+
+        // migrate from A -> B
+        GridSizeMigrationUtil.migrate(
+                context,
+                db,
+                readerGridA,
+                readerGridB,
+                idp.numDatabaseHotseatIcons,
+                Point(idp.numColumns, idp.numRows),
+                DeviceGridState(context),
+                DeviceGridState(idp)
+        )
+
+        // Check hotseat items in grid B
+        c = context.contentResolver.query(
+                CONTENT_URI,
+                arrayOf(SCREEN, INTENT),
+                "container=$CONTAINER_HOTSEAT",
+                null,
+                SCREEN,
+                null
+        ) ?: throw IllegalStateException()
+        // Expected hotseat items in grid B
+        // 2 1 3 4
+        verifyHotseat(c, idp,
+                mutableListOf(testPackage2, testPackage1, testPackage3, testPackage4).toList())
+
+        // Check workspace items in grid B
+        c = context.contentResolver.query(
+                CONTENT_URI,
+                arrayOf(SCREEN, CELLX, CELLY, INTENT),
+                "container=$CONTAINER_DESKTOP",
+                null,
+                null,
+                null
+        ) ?: throw IllegalStateException()
+        locMap = parseLocMap(context, c)
+        // Expected workspace items in grid B
+        // _ _ _ _
+        // 5 6 _ 8
+        // 9 _ _ _
+        // _ _ _ _
+        assertThat(locMap.size.toLong()).isEqualTo(4)
+        assertThat(locMap[testPackage5]).isEqualTo(Triple(0, 0, 1))
+        assertThat(locMap[testPackage6]).isEqualTo(Triple(0, 1, 1))
+        assertThat(locMap[testPackage8]).isEqualTo(Triple(0, 3, 1))
+        assertThat(locMap[testPackage9]).isEqualTo(Triple(0, 0, 2))
+    }
+
+    private fun verifyHotseat(c: Cursor, idp: InvariantDeviceProfile, expected: List<String?>) {
+        assertThat(c.count).isEqualTo(idp.numDatabaseHotseatIcons)
+        val screenIndex = c.getColumnIndex(SCREEN)
+        val intentIndex = c.getColumnIndex(INTENT)
+        expected.forEachIndexed { idx, pkg ->
+            if (pkg == null) return@forEachIndexed
+            c.moveToNext()
+            assertThat(c.getInt(screenIndex).toLong()).isEqualTo(idx)
+            assertThat(c.getString(intentIndex)).contains(pkg)
+        }
+        c.close()
+    }
+
+    private fun parseLocMap(context: Context, c: Cursor): Map<String, Triple<Int, Int, Int>> {
+        // Check workspace items
+        val intentIndex = c.getColumnIndex(INTENT)
+        val screenIndex = c.getColumnIndex(SCREEN)
+        val cellXIndex = c.getColumnIndex(CELLX)
+        val cellYIndex = c.getColumnIndex(CELLY)
+        val locMap = mutableMapOf<String, Triple<Int, Int, Int>>()
+        while (c.moveToNext()) {
+            locMap[Intent.parseUri(c.getString(intentIndex), 0).getPackage()] =
+                    Triple(c.getInt(screenIndex), c.getInt(cellXIndex), c.getInt(cellYIndex))
+        }
+        c.close()
+        return locMap.toMap()
     }
 
     @Test
diff --git a/tests/src/com/android/launcher3/util/LauncherModelHelper.java b/tests/src/com/android/launcher3/util/LauncherModelHelper.java
index e7e551f..93bf312 100644
--- a/tests/src/com/android/launcher3/util/LauncherModelHelper.java
+++ b/tests/src/com/android/launcher3/util/LauncherModelHelper.java
@@ -362,6 +362,12 @@
         sandboxContext.getContentResolver().insert(contentUri, values);
     }
 
+    public void deleteItem(int itemId, @NonNull final String tableName) {
+        final Uri uri = Uri.parse("content://"
+                + LauncherProvider.AUTHORITY + "/" + tableName + "/" + itemId);
+        sandboxContext.getContentResolver().delete(uri, null, null);
+    }
+
     public int[][][] createGrid(int[][][] typeArray) {
         return createGrid(typeArray, 1);
     }