diff --git a/src/com/android/launcher3/LauncherModel.java b/src/com/android/launcher3/LauncherModel.java
index 68b7701..20df897 100644
--- a/src/com/android/launcher3/LauncherModel.java
+++ b/src/com/android/launcher3/LauncherModel.java
@@ -33,6 +33,7 @@
 import android.util.Log;
 import android.util.Pair;
 
+import androidx.annotation.NonNull;
 import androidx.annotation.Nullable;
 import androidx.annotation.WorkerThread;
 
@@ -89,9 +90,11 @@
 
     static final String TAG = "Launcher.Model";
 
+    @NonNull
     private final LauncherAppState mApp;
+    @NonNull
     private final Object mLock = new Object();
-
+    @Nullable
     private LoaderTask mLoaderTask;
     private boolean mIsLoaderTaskRunning;
 
@@ -107,20 +110,25 @@
         }
     }
 
+    @NonNull
     private final ArrayList<Callbacks> mCallbacksList = new ArrayList<>(1);
 
     // < only access in worker thread >
+    @NonNull
     private final AllAppsList mBgAllAppsList;
 
     /**
      * All the static data should be accessed on the background thread, A lock should be acquired
      * on this object when accessing any data from this model.
      */
+    @NonNull
     private final BgDataModel mBgDataModel = new BgDataModel();
 
+    @NonNull
     private final ModelDelegate mModelDelegate;
 
     // Runnable to check if the shortcuts permission has changed.
+    @NonNull
     private final Runnable mDataValidationCheck = new Runnable() {
         @Override
         public void run() {
@@ -130,14 +138,16 @@
         }
     };
 
-    LauncherModel(Context context, LauncherAppState app, IconCache iconCache, AppFilter appFilter,
-            boolean isPrimaryInstance) {
+    LauncherModel(@NonNull final Context context, @NonNull final LauncherAppState app,
+            @NonNull final IconCache iconCache, @NonNull final AppFilter appFilter,
+            final boolean isPrimaryInstance) {
         mApp = app;
         mBgAllAppsList = new AllAppsList(iconCache, appFilter);
         mModelDelegate = ModelDelegate.newInstance(context, app, mBgAllAppsList, mBgDataModel,
                 isPrimaryInstance);
     }
 
+    @NonNull
     public ModelDelegate getModelDelegate() {
         return mModelDelegate;
     }
@@ -145,52 +155,57 @@
     /**
      * Adds the provided items to the workspace.
      */
-    public void addAndBindAddedWorkspaceItems(List<Pair<ItemInfo, Object>> itemList) {
+    public void addAndBindAddedWorkspaceItems(
+            @NonNull final List<Pair<ItemInfo, Object>> itemList) {
         for (Callbacks cb : getCallbacks()) {
             cb.preAddApps();
         }
         enqueueModelUpdateTask(new AddWorkspaceItemsTask(itemList));
     }
 
-    public ModelWriter getWriter(boolean hasVerticalHotseat, boolean verifyChanges,
-            @Nullable Callbacks owner) {
+    @NonNull
+    public ModelWriter getWriter(final boolean hasVerticalHotseat, final boolean verifyChanges,
+            @Nullable final Callbacks owner) {
         return new ModelWriter(mApp.getContext(), this, mBgDataModel,
                 hasVerticalHotseat, verifyChanges, owner);
     }
 
     @Override
-    public void onPackageChanged(String packageName, UserHandle user) {
+    public void onPackageChanged(
+            @NonNull final String packageName, @NonNull final UserHandle user) {
         int op = PackageUpdatedTask.OP_UPDATE;
         enqueueModelUpdateTask(new PackageUpdatedTask(op, user, packageName));
     }
 
     @Override
-    public void onPackageRemoved(String packageName, UserHandle user) {
+    public void onPackageRemoved(
+            @NonNull final String packageName, @NonNull final UserHandle user) {
         onPackagesRemoved(user, packageName);
     }
 
-    public void onPackagesRemoved(UserHandle user, String... packages) {
+    public void onPackagesRemoved(
+            @NonNull final UserHandle user, @NonNull final String... packages) {
         int op = PackageUpdatedTask.OP_REMOVE;
         FileLog.d(TAG, "package removed received " + TextUtils.join(",", packages));
         enqueueModelUpdateTask(new PackageUpdatedTask(op, user, packages));
     }
 
     @Override
-    public void onPackageAdded(String packageName, UserHandle user) {
+    public void onPackageAdded(@NonNull final String packageName, @NonNull final UserHandle user) {
         int op = PackageUpdatedTask.OP_ADD;
         enqueueModelUpdateTask(new PackageUpdatedTask(op, user, packageName));
     }
 
     @Override
-    public void onPackagesAvailable(String[] packageNames, UserHandle user,
-            boolean replacing) {
+    public void onPackagesAvailable(@NonNull final String[] packageNames,
+            @NonNull final UserHandle user, final boolean replacing) {
         enqueueModelUpdateTask(
                 new PackageUpdatedTask(PackageUpdatedTask.OP_UPDATE, user, packageNames));
     }
 
     @Override
-    public void onPackagesUnavailable(String[] packageNames, UserHandle user,
-            boolean replacing) {
+    public void onPackagesUnavailable(@NonNull final String[] packageNames,
+            @NonNull final UserHandle user, final boolean replacing) {
         if (!replacing) {
             enqueueModelUpdateTask(new PackageUpdatedTask(
                     PackageUpdatedTask.OP_UNAVAILABLE, user, packageNames));
@@ -198,20 +213,22 @@
     }
 
     @Override
-    public void onPackagesSuspended(String[] packageNames, UserHandle user) {
+    public void onPackagesSuspended(
+            @NonNull final String[] packageNames, @NonNull final UserHandle user) {
         enqueueModelUpdateTask(new PackageUpdatedTask(
                 PackageUpdatedTask.OP_SUSPEND, user, packageNames));
     }
 
     @Override
-    public void onPackagesUnsuspended(String[] packageNames, UserHandle user) {
+    public void onPackagesUnsuspended(
+            @NonNull final String[] packageNames, @NonNull final UserHandle user) {
         enqueueModelUpdateTask(new PackageUpdatedTask(
                 PackageUpdatedTask.OP_UNSUSPEND, user, packageNames));
     }
 
     @Override
-    public void onPackageLoadingProgressChanged(
-                String packageName, UserHandle user, float progress) {
+    public void onPackageLoadingProgressChanged(@NonNull final String packageName,
+            @NonNull final UserHandle user, final float progress) {
         if (Utilities.ATLEAST_S) {
             enqueueModelUpdateTask(new PackageIncrementalDownloadUpdatedTask(
                     packageName, user, progress));
@@ -219,8 +236,8 @@
     }
 
     @Override
-    public void onShortcutsChanged(String packageName, List<ShortcutInfo> shortcuts,
-            UserHandle user) {
+    public void onShortcutsChanged(@NonNull final String packageName,
+            @NonNull final List<ShortcutInfo> shortcuts, @NonNull final UserHandle user) {
         enqueueModelUpdateTask(new ShortcutsChangedTask(packageName, shortcuts, user, true));
     }
 
@@ -228,7 +245,8 @@
      * Called when the icon for an app changes, outside of package event
      */
     @WorkerThread
-    public void onAppIconChanged(String packageName, UserHandle user) {
+    public void onAppIconChanged(@NonNull final String packageName,
+            @NonNull final UserHandle user) {
         // Update the icon for the calendar package
         Context context = mApp.getContext();
         onPackageChanged(packageName, user);
@@ -256,7 +274,7 @@
         MODEL_EXECUTOR.execute(mModelDelegate::destroy);
     }
 
-    public void onBroadcastIntent(Intent intent) {
+    public void onBroadcastIntent(@NonNull final Intent intent) {
         if (DEBUG_RECEIVER) Log.d(TAG, "onReceive intent=" + intent);
         final String action = intent.getAction();
         if (Intent.ACTION_LOCALE_CHANGED.equals(action)) {
@@ -322,7 +340,7 @@
     /**
      * Removes an existing callback
      */
-    public void removeCallbacks(Callbacks callbacks) {
+    public void removeCallbacks(@NonNull final Callbacks callbacks) {
         synchronized (mCallbacksList) {
             Preconditions.assertUIThread();
             if (mCallbacksList.remove(callbacks)) {
@@ -338,7 +356,7 @@
      * Adds a callbacks to receive model updates
      * @return true if workspace load was performed synchronously
      */
-    public boolean addCallbacksAndLoad(Callbacks callbacks) {
+    public boolean addCallbacksAndLoad(@NonNull final Callbacks callbacks) {
         synchronized (mLock) {
             addCallbacks(callbacks);
             return startLoader(new Callbacks[] { callbacks });
@@ -349,7 +367,7 @@
     /**
      * Adds a callbacks to receive model updates
      */
-    public void addCallbacks(Callbacks callbacks) {
+    public void addCallbacks(@NonNull final Callbacks callbacks) {
         Preconditions.assertUIThread();
         synchronized (mCallbacksList) {
             if (TestProtocol.sDebugTracing) {
@@ -370,7 +388,7 @@
         return startLoader(new Callbacks[0]);
     }
 
-    private boolean startLoader(Callbacks[] newCallbacks) {
+    private boolean startLoader(@NonNull final Callbacks[] newCallbacks) {
         // Enable queue before starting loader. It will get disabled in Launcher#finishBindingItems
         ItemInstallQueue.INSTANCE.get(mApp.getContext())
                 .pauseModelPush(ItemInstallQueue.FLAG_LOADER_RUNNING);
@@ -433,7 +451,7 @@
      * Loads the model if not loaded
      * @param callback called with the data model upon successful load or null on model thread.
      */
-    public void loadAsync(Consumer<BgDataModel> callback) {
+    public void loadAsync(@NonNull final Consumer<BgDataModel> callback) {
         synchronized (mLock) {
             if (!mModelLoaded && !mIsLoaderTaskRunning) {
                 startLoader();
@@ -443,11 +461,12 @@
     }
 
     @Override
-    public void onInstallSessionCreated(final PackageInstallInfo sessionInfo) {
+    public void onInstallSessionCreated(@NonNull final PackageInstallInfo sessionInfo) {
         if (FeatureFlags.PROMISE_APPS_IN_ALL_APPS.get()) {
             enqueueModelUpdateTask(new BaseModelUpdateTask() {
                 @Override
-                public void execute(LauncherAppState app, BgDataModel dataModel, AllAppsList apps) {
+                public void execute(@NonNull final LauncherAppState app,
+                        @NonNull final BgDataModel dataModel, @NonNull final AllAppsList apps) {
                     apps.addPromiseApp(app.getContext(), sessionInfo);
                     bindApplicationsIfNeeded();
                 }
@@ -456,10 +475,12 @@
     }
 
     @Override
-    public void onSessionFailure(String packageName, UserHandle user) {
+    public void onSessionFailure(@NonNull final String packageName,
+            @NonNull final UserHandle user) {
         enqueueModelUpdateTask(new BaseModelUpdateTask() {
             @Override
-            public void execute(LauncherAppState app, BgDataModel dataModel, AllAppsList apps) {
+            public void execute(@NonNull final LauncherAppState app,
+                    @NonNull final BgDataModel dataModel, @NonNull final AllAppsList apps) {
                 final IntSet removedIds = new IntSet();
                 synchronized (dataModel) {
                     for (ItemInfo info : dataModel.itemsIdMap) {
@@ -483,7 +504,7 @@
     }
 
     @Override
-    public void onPackageStateChanged(PackageInstallInfo installInfo) {
+    public void onPackageStateChanged(@NonNull final PackageInstallInfo installInfo) {
         enqueueModelUpdateTask(new PackageInstallStateChangedTask(installInfo));
     }
 
@@ -491,7 +512,8 @@
      * Updates the icons and label of all pending icons for the provided package name.
      */
     @Override
-    public void onUpdateSessionDisplay(PackageUserKey key, PackageInstaller.SessionInfo info) {
+    public void onUpdateSessionDisplay(@NonNull final PackageUserKey key,
+            @NonNull final PackageInstaller.SessionInfo info) {
         mApp.getIconCache().updateSessionCache(key, info);
 
         HashSet<String> packages = new HashSet<>();
@@ -502,9 +524,10 @@
 
     public class LoaderTransaction implements AutoCloseable {
 
+        @NonNull
         private final LoaderTask mTask;
 
-        private LoaderTransaction(LoaderTask task) throws CancellationException {
+        private LoaderTransaction(@NonNull final LoaderTask task) throws CancellationException {
             synchronized (mLock) {
                 if (mLoaderTask != task) {
                     throw new CancellationException("Loader already stopped");
@@ -534,7 +557,8 @@
         }
     }
 
-    public LoaderTransaction beginLoader(LoaderTask task) throws CancellationException {
+    public LoaderTransaction beginLoader(@NonNull final LoaderTask task)
+            throws CancellationException {
         return new LoaderTransaction(task);
     }
 
@@ -551,7 +575,8 @@
     /**
      * Called when the icons for packages have been updated in the icon cache.
      */
-    public void onPackageIconsUpdated(HashSet<String> updatedPackages, UserHandle user) {
+    public void onPackageIconsUpdated(@NonNull final HashSet<String> updatedPackages,
+            @NonNull final UserHandle user) {
         // If any package icon has changed (app was updated while launcher was dead),
         // update the corresponding shortcuts.
         enqueueModelUpdateTask(new CacheDataUpdatedTask(
@@ -561,17 +586,19 @@
     /**
      * Called when the labels for the widgets has updated in the icon cache.
      */
-    public void onWidgetLabelsUpdated(HashSet<String> updatedPackages, UserHandle user) {
+    public void onWidgetLabelsUpdated(@NonNull final HashSet<String> updatedPackages,
+            @NonNull final UserHandle user) {
         enqueueModelUpdateTask(new BaseModelUpdateTask() {
             @Override
-            public void execute(LauncherAppState app, BgDataModel dataModel, AllAppsList apps) {
+            public void execute(@NonNull final LauncherAppState app,
+                    @NonNull final BgDataModel dataModel, @NonNull final AllAppsList apps) {
                 dataModel.widgetsModel.onPackageIconsUpdated(updatedPackages, user, app);
                 bindUpdatedWidgets(dataModel);
             }
         });
     }
 
-    public void enqueueModelUpdateTask(ModelUpdateTask task) {
+    public void enqueueModelUpdateTask(@NonNull final ModelUpdateTask task) {
         if (mModelDestroyed) {
             return;
         }
@@ -585,7 +612,7 @@
      */
     public interface CallbackTask {
 
-        void execute(Callbacks callbacks);
+        void execute(@NonNull Callbacks callbacks);
     }
 
     /**
@@ -596,12 +623,14 @@
         /**
          * Called before the task is posted to initialize the internal state.
          */
-        void init(LauncherAppState app, LauncherModel model,
-                BgDataModel dataModel, AllAppsList allAppsList, Executor uiExecutor);
+        void init(@NonNull LauncherAppState app, @NonNull LauncherModel model,
+                @NonNull BgDataModel dataModel, @NonNull AllAppsList allAppsList,
+                @NonNull Executor uiExecutor);
 
     }
 
-    public void updateAndBindWorkspaceItem(WorkspaceItemInfo si, ShortcutInfo info) {
+    public void updateAndBindWorkspaceItem(@NonNull final WorkspaceItemInfo si,
+            @NonNull final ShortcutInfo info) {
         updateAndBindWorkspaceItem(() -> {
             si.updateFromDeepShortcutInfo(info, mApp.getContext());
             mApp.getIconCache().getShortcutIcon(si, info);
@@ -612,10 +641,12 @@
     /**
      * Utility method to update a shortcut on the background thread.
      */
-    public void updateAndBindWorkspaceItem(final Supplier<WorkspaceItemInfo> itemProvider) {
+    public void updateAndBindWorkspaceItem(
+            @NonNull final Supplier<WorkspaceItemInfo> itemProvider) {
         enqueueModelUpdateTask(new BaseModelUpdateTask() {
             @Override
-            public void execute(LauncherAppState app, BgDataModel dataModel, AllAppsList apps) {
+            public void execute(@NonNull final LauncherAppState app,
+                    @NonNull final BgDataModel dataModel, @NonNull final AllAppsList apps) {
                 WorkspaceItemInfo info = itemProvider.get();
                 getModelWriter().updateItemInDatabase(info);
                 ArrayList<WorkspaceItemInfo> update = new ArrayList<>();
@@ -628,14 +659,16 @@
     public void refreshAndBindWidgetsAndShortcuts(@Nullable final PackageUserKey packageUser) {
         enqueueModelUpdateTask(new BaseModelUpdateTask() {
             @Override
-            public void execute(LauncherAppState app, BgDataModel dataModel, AllAppsList apps) {
+            public void execute(@NonNull final LauncherAppState app,
+                    @NonNull final BgDataModel dataModel, @NonNull final AllAppsList apps) {
                 dataModel.widgetsModel.update(app, packageUser);
                 bindUpdatedWidgets(dataModel);
             }
         });
     }
 
-    public void dumpState(String prefix, FileDescriptor fd, PrintWriter writer, String[] args) {
+    public void dumpState(@Nullable final String prefix, @Nullable final FileDescriptor fd,
+            @NonNull final PrintWriter writer, @NonNull final String[] args) {
         if (args.length > 0 && TextUtils.equals(args[0], "--all")) {
             writer.println(prefix + "All apps list: size=" + mBgAllAppsList.data.size());
             for (AppInfo info : mBgAllAppsList.data) {
@@ -661,6 +694,7 @@
     /**
      * Returns an array of currently attached callbacks
      */
+    @NonNull
     public Callbacks[] getCallbacks() {
         synchronized (mCallbacksList) {
             return mCallbacksList.toArray(new Callbacks[mCallbacksList.size()]);
diff --git a/src/com/android/launcher3/allapps/search/DefaultAppSearchAlgorithm.java b/src/com/android/launcher3/allapps/search/DefaultAppSearchAlgorithm.java
index d2d7a6c..ab47097 100644
--- a/src/com/android/launcher3/allapps/search/DefaultAppSearchAlgorithm.java
+++ b/src/com/android/launcher3/allapps/search/DefaultAppSearchAlgorithm.java
@@ -22,6 +22,7 @@
 import android.os.Handler;
 
 import androidx.annotation.AnyThread;
+import androidx.annotation.NonNull;
 
 import com.android.launcher3.LauncherAppState;
 import com.android.launcher3.allapps.BaseAllAppsAdapter.AdapterItem;
@@ -68,7 +69,8 @@
     public void doSearch(String query, SearchCallback<AdapterItem> callback) {
         mAppState.getModel().enqueueModelUpdateTask(new BaseModelUpdateTask() {
             @Override
-            public void execute(LauncherAppState app, BgDataModel dataModel, AllAppsList apps) {
+            public void execute(@NonNull final LauncherAppState app,
+                    @NonNull final BgDataModel dataModel, @NonNull final AllAppsList apps) {
                 ArrayList<AdapterItem> result = getTitleMatchResult(apps.data, query);
                 if (mAddNoResultsMessage && result.isEmpty()) {
                     result.add(getEmptyMessageAdapterItem(query));
diff --git a/src/com/android/launcher3/folder/FolderNameProvider.java b/src/com/android/launcher3/folder/FolderNameProvider.java
index 5021644..bf59594 100644
--- a/src/com/android/launcher3/folder/FolderNameProvider.java
+++ b/src/com/android/launcher3/folder/FolderNameProvider.java
@@ -24,6 +24,7 @@
 import android.text.TextUtils;
 import android.util.Log;
 
+import androidx.annotation.NonNull;
 import androidx.annotation.WorkerThread;
 
 import com.android.launcher3.LauncherAppState;
@@ -192,7 +193,8 @@
 
     private class FolderNameWorker extends BaseModelUpdateTask {
         @Override
-        public void execute(LauncherAppState app, BgDataModel dataModel, AllAppsList apps) {
+        public void execute(@NonNull final LauncherAppState app,
+                @NonNull final BgDataModel dataModel, @NonNull final AllAppsList apps) {
             mFolderInfos = dataModel.folders.clone();
             mAppInfos = Arrays.asList(apps.copyData());
         }
diff --git a/src/com/android/launcher3/model/AddWorkspaceItemsTask.java b/src/com/android/launcher3/model/AddWorkspaceItemsTask.java
index 4c0f1ae..0d978e1 100644
--- a/src/com/android/launcher3/model/AddWorkspaceItemsTask.java
+++ b/src/com/android/launcher3/model/AddWorkspaceItemsTask.java
@@ -23,6 +23,9 @@
 import android.util.Log;
 import android.util.Pair;
 
+import androidx.annotation.NonNull;
+import androidx.annotation.Nullable;
+
 import com.android.launcher3.LauncherAppState;
 import com.android.launcher3.LauncherModel.CallbackTask;
 import com.android.launcher3.LauncherSettings;
@@ -42,6 +45,7 @@
 
 import java.util.ArrayList;
 import java.util.List;
+import java.util.Objects;
 
 /**
  * Task to add auto-created workspace items.
@@ -50,14 +54,16 @@
 
     private static final String LOG = "AddWorkspaceItemsTask";
 
+    @NonNull
     private final List<Pair<ItemInfo, Object>> mItemList;
 
+    @NonNull
     private final WorkspaceItemSpaceFinder mItemSpaceFinder;
 
     /**
      * @param itemList items to add on the workspace
      */
-    public AddWorkspaceItemsTask(List<Pair<ItemInfo, Object>> itemList) {
+    public AddWorkspaceItemsTask(@NonNull final List<Pair<ItemInfo, Object>> itemList) {
         this(itemList, new WorkspaceItemSpaceFinder());
     }
 
@@ -65,14 +71,15 @@
      * @param itemList items to add on the workspace
      * @param itemSpaceFinder inject WorkspaceItemSpaceFinder dependency for testing
      */
-    public AddWorkspaceItemsTask(List<Pair<ItemInfo, Object>> itemList,
-            WorkspaceItemSpaceFinder itemSpaceFinder) {
+    public AddWorkspaceItemsTask(@NonNull final List<Pair<ItemInfo, Object>> itemList,
+            @NonNull final WorkspaceItemSpaceFinder itemSpaceFinder) {
         mItemList = itemList;
         mItemSpaceFinder = itemSpaceFinder;
     }
 
     @Override
-    public void execute(LauncherAppState app, BgDataModel dataModel, AllAppsList apps) {
+    public void execute(@NonNull final LauncherAppState app, @NonNull final BgDataModel dataModel,
+            @NonNull final AllAppsList apps) {
         if (mItemList.isEmpty()) {
             return;
         }
@@ -98,7 +105,8 @@
                     }
 
                     // b/139663018 Short-circuit this logic if the icon is a system app
-                    if (PackageManagerHelper.isSystemApp(app.getContext(), item.getIntent())) {
+                    if (PackageManagerHelper.isSystemApp(app.getContext(),
+                            Objects.requireNonNull(item.getIntent()))) {
                         if (TestProtocol.sDebugTracing) {
                             Log.d(TestProtocol.MISSING_PROMISE_ICON,
                                     LOG + " Item is a system app.");
@@ -159,7 +167,7 @@
                         continue;
                     }
 
-                    List<LauncherActivityInfo> activities = launcherApps
+                    List<LauncherActivityInfo> activities = Objects.requireNonNull(launcherApps)
                             .getActivityList(packageName, item.user);
                     boolean hasActivity = activities != null && !activities.isEmpty();
 
@@ -218,7 +226,7 @@
         if (!addedItemsFinal.isEmpty()) {
             scheduleCallbackTask(new CallbackTask() {
                 @Override
-                public void execute(Callbacks callbacks) {
+                public void execute(@NonNull Callbacks callbacks) {
                     final ArrayList<ItemInfo> addAnimated = new ArrayList<>();
                     final ArrayList<ItemInfo> addNotAnimated = new ArrayList<>();
                     if (!addedItemsFinal.isEmpty()) {
@@ -243,7 +251,8 @@
      * Returns true if the shortcuts already exists on the workspace. This must be called after
      * the workspace has been loaded. We identify a shortcut by its intent.
      */
-    protected boolean shortcutExists(BgDataModel dataModel, Intent intent, UserHandle user) {
+    protected boolean shortcutExists(@NonNull final BgDataModel dataModel,
+            @Nullable final Intent intent, @NonNull final UserHandle user) {
         final String compPkgName, intentWithPkg, intentWithoutPkg;
         if (intent == null) {
             // Skip items with null intents
diff --git a/src/com/android/launcher3/model/AllAppsList.java b/src/com/android/launcher3/model/AllAppsList.java
index 95150dc..6da948c 100644
--- a/src/com/android/launcher3/model/AllAppsList.java
+++ b/src/com/android/launcher3/model/AllAppsList.java
@@ -66,7 +66,10 @@
     /** The list off all apps. */
     public final ArrayList<AppInfo> data = new ArrayList<>(DEFAULT_APPLICATIONS_NUMBER);
 
+    @NonNull
     private IconCache mIconCache;
+
+    @NonNull
     private AppFilter mAppFilter;
 
     private boolean mDataChanged = false;
diff --git a/src/com/android/launcher3/model/BaseModelUpdateTask.java b/src/com/android/launcher3/model/BaseModelUpdateTask.java
index 2a6a691..5b6f9f6 100644
--- a/src/com/android/launcher3/model/BaseModelUpdateTask.java
+++ b/src/com/android/launcher3/model/BaseModelUpdateTask.java
@@ -17,6 +17,7 @@
 
 import android.util.Log;
 
+import androidx.annotation.NonNull;
 import androidx.annotation.Nullable;
 
 import com.android.launcher3.LauncherAppState;
@@ -47,14 +48,17 @@
     private static final boolean DEBUG_TASKS = false;
     private static final String TAG = "BaseModelUpdateTask";
 
+    // Nullabilities are explicitly omitted here because these are late-init fields,
+    // They will be non-null after init(), which is always the case in enqueueModelUpdateTask().
     private LauncherAppState mApp;
     private LauncherModel mModel;
     private BgDataModel mDataModel;
     private AllAppsList mAllAppsList;
     private Executor mUiExecutor;
 
-    public void init(LauncherAppState app, LauncherModel model,
-            BgDataModel dataModel, AllAppsList allAppsList, Executor uiExecutor) {
+    public void init(@NonNull final LauncherAppState app, @NonNull final LauncherModel model,
+            @NonNull final BgDataModel dataModel, @NonNull final AllAppsList allAppsList,
+            @NonNull final Executor uiExecutor) {
         mApp = app;
         mModel = model;
         mDataModel = dataModel;
@@ -64,7 +68,7 @@
 
     @Override
     public final void run() {
-        if (!mModel.isModelLoaded()) {
+        if (!Objects.requireNonNull(mModel).isModelLoaded()) {
             if (DEBUG_TASKS) {
                 Log.d(TAG, "Ignoring model task since loader is pending=" + this);
             }
@@ -77,13 +81,13 @@
     /**
      * Execute the actual task. Called on the worker thread.
      */
-    public abstract void execute(
-            LauncherAppState app, BgDataModel dataModel, AllAppsList apps);
+    public abstract void execute(@NonNull LauncherAppState app,
+            @NonNull BgDataModel dataModel, @NonNull AllAppsList apps);
 
     /**
      * Schedules a {@param task} to be executed on the current callbacks.
      */
-    public final void scheduleCallbackTask(final CallbackTask task) {
+    public final void scheduleCallbackTask(@NonNull final CallbackTask task) {
         for (final Callbacks cb : mModel.getCallbacks()) {
             mUiExecutor.execute(() -> task.execute(cb));
         }
@@ -95,7 +99,7 @@
         return mModel.getWriter(false /* hasVerticalHotseat */, false /* verifyChanges */, null);
     }
 
-    public void bindUpdatedWorkspaceItems(List<WorkspaceItemInfo> allUpdates) {
+    public void bindUpdatedWorkspaceItems(@NonNull final List<WorkspaceItemInfo> allUpdates) {
         // Bind workspace items
         List<WorkspaceItemInfo> workspaceUpdates = allUpdates.stream()
                 .filter(info -> info.id != ItemInfo.NO_ID)
@@ -113,18 +117,18 @@
                 .forEach(this::bindExtraContainerItems);
     }
 
-    public void bindExtraContainerItems(FixedContainerItems item) {
+    public void bindExtraContainerItems(@NonNull final FixedContainerItems item) {
         FixedContainerItems copy = item.clone();
         scheduleCallbackTask(c -> c.bindExtraContainerItems(copy));
     }
 
-    public void bindDeepShortcuts(BgDataModel dataModel) {
+    public void bindDeepShortcuts(@NonNull final BgDataModel dataModel) {
         final HashMap<ComponentKey, Integer> shortcutMapCopy =
                 new HashMap<>(dataModel.deepShortcutMap);
         scheduleCallbackTask(callbacks -> callbacks.bindDeepShortcutMap(shortcutMapCopy));
     }
 
-    public void bindUpdatedWidgets(BgDataModel dataModel) {
+    public void bindUpdatedWidgets(@NonNull final BgDataModel dataModel) {
         final ArrayList<WidgetsListBaseEntry> widgets =
                 dataModel.widgetsModel.getWidgetsListForPicker(mApp.getContext());
         scheduleCallbackTask(c -> c.bindAllWidgets(widgets));
diff --git a/src/com/android/launcher3/model/CacheDataUpdatedTask.java b/src/com/android/launcher3/model/CacheDataUpdatedTask.java
index f644d49..57fefaa 100644
--- a/src/com/android/launcher3/model/CacheDataUpdatedTask.java
+++ b/src/com/android/launcher3/model/CacheDataUpdatedTask.java
@@ -18,6 +18,8 @@
 import android.content.ComponentName;
 import android.os.UserHandle;
 
+import androidx.annotation.NonNull;
+
 import com.android.launcher3.LauncherAppState;
 import com.android.launcher3.LauncherSettings;
 import com.android.launcher3.icons.IconCache;
@@ -35,17 +37,23 @@
     public static final int OP_SESSION_UPDATE = 2;
 
     private final int mOp;
+
+    @NonNull
     private final UserHandle mUser;
+
+    @NonNull
     private final HashSet<String> mPackages;
 
-    public CacheDataUpdatedTask(int op, UserHandle user, HashSet<String> packages) {
+    public CacheDataUpdatedTask(final int op, @NonNull final UserHandle user,
+            @NonNull final HashSet<String> packages) {
         mOp = op;
         mUser = user;
         mPackages = packages;
     }
 
     @Override
-    public void execute(LauncherAppState app, BgDataModel dataModel, AllAppsList apps) {
+    public void execute(@NonNull final LauncherAppState app, @NonNull final BgDataModel dataModel,
+            @NonNull final AllAppsList apps) {
         IconCache iconCache = app.getIconCache();
         ArrayList<WorkspaceItemInfo> updatedShortcuts = new ArrayList<>();
 
@@ -65,7 +73,7 @@
         bindApplicationsIfNeeded();
     }
 
-    public boolean isValidShortcut(WorkspaceItemInfo si) {
+    public boolean isValidShortcut(@NonNull final WorkspaceItemInfo si) {
         switch (mOp) {
             case OP_CACHE_UPDATE:
                 return true;
diff --git a/src/com/android/launcher3/model/PackageIncrementalDownloadUpdatedTask.java b/src/com/android/launcher3/model/PackageIncrementalDownloadUpdatedTask.java
index c0dc34a..b9fba9d 100644
--- a/src/com/android/launcher3/model/PackageIncrementalDownloadUpdatedTask.java
+++ b/src/com/android/launcher3/model/PackageIncrementalDownloadUpdatedTask.java
@@ -17,6 +17,8 @@
 
 import android.os.UserHandle;
 
+import androidx.annotation.NonNull;
+
 import com.android.launcher3.LauncherAppState;
 import com.android.launcher3.model.data.AppInfo;
 import com.android.launcher3.model.data.ItemInfoWithIcon;
@@ -31,19 +33,24 @@
  */
 public class PackageIncrementalDownloadUpdatedTask extends BaseModelUpdateTask {
 
+    @NonNull
     private final UserHandle mUser;
+
     private final int mProgress;
+
+    @NonNull
     private final String mPackageName;
 
-    public PackageIncrementalDownloadUpdatedTask(
-            String packageName, UserHandle user, float progress) {
+    public PackageIncrementalDownloadUpdatedTask(@NonNull final String packageName,
+            @NonNull final UserHandle user, final float progress) {
         mUser = user;
         mProgress = 1 - progress > 0.001 ? (int) (100 * progress) : 100;
         mPackageName = packageName;
     }
 
     @Override
-    public void execute(LauncherAppState app, BgDataModel dataModel, AllAppsList appsList) {
+    public void execute(@NonNull LauncherAppState app, @NonNull final BgDataModel dataModel,
+            @NonNull final AllAppsList appsList) {
         PackageInstallInfo downloadInfo = new PackageInstallInfo(
                 mPackageName,
                 PackageInstallInfo.STATUS_INSTALLED_DOWNLOADING,
diff --git a/src/com/android/launcher3/model/PackageInstallStateChangedTask.java b/src/com/android/launcher3/model/PackageInstallStateChangedTask.java
index b74d0fc..76a87ed 100644
--- a/src/com/android/launcher3/model/PackageInstallStateChangedTask.java
+++ b/src/com/android/launcher3/model/PackageInstallStateChangedTask.java
@@ -18,6 +18,8 @@
 import android.content.pm.ApplicationInfo;
 import android.content.pm.PackageManager;
 
+import androidx.annotation.NonNull;
+
 import com.android.launcher3.LauncherAppState;
 import com.android.launcher3.model.data.AppInfo;
 import com.android.launcher3.model.data.ItemInfo;
@@ -33,14 +35,16 @@
  */
 public class PackageInstallStateChangedTask extends BaseModelUpdateTask {
 
+    @NonNull
     private final PackageInstallInfo mInstallInfo;
 
-    public PackageInstallStateChangedTask(PackageInstallInfo installInfo) {
+    public PackageInstallStateChangedTask(@NonNull final PackageInstallInfo installInfo) {
         mInstallInfo = installInfo;
     }
 
     @Override
-    public void execute(LauncherAppState app, BgDataModel dataModel, AllAppsList apps) {
+    public void execute(@NonNull final LauncherAppState app, @NonNull final BgDataModel dataModel,
+            @NonNull final AllAppsList apps) {
         if (mInstallInfo.state == PackageInstallInfo.STATUS_INSTALLED) {
             try {
                 // For instant apps we do not get package-add. Use setting events to update
diff --git a/src/com/android/launcher3/model/PackageUpdatedTask.java b/src/com/android/launcher3/model/PackageUpdatedTask.java
index a9d272e..3d9d81f 100644
--- a/src/com/android/launcher3/model/PackageUpdatedTask.java
+++ b/src/com/android/launcher3/model/PackageUpdatedTask.java
@@ -29,6 +29,8 @@
 import android.os.UserManager;
 import android.util.Log;
 
+import androidx.annotation.NonNull;
+
 import com.android.launcher3.Launcher;
 import com.android.launcher3.LauncherAppState;
 import com.android.launcher3.LauncherSettings;
@@ -80,17 +82,23 @@
     public static final int OP_USER_AVAILABILITY_CHANGE = 7; // user available/unavailable
 
     private final int mOp;
+
+    @NonNull
     private final UserHandle mUser;
+
+    @NonNull
     private final String[] mPackages;
 
-    public PackageUpdatedTask(int op, UserHandle user, String... packages) {
+    public PackageUpdatedTask(final int op, @NonNull final UserHandle user,
+            @NonNull final String... packages) {
         mOp = op;
         mUser = user;
         mPackages = packages;
     }
 
     @Override
-    public void execute(LauncherAppState app, BgDataModel dataModel, AllAppsList appsList) {
+    public void execute(@NonNull final LauncherAppState app, @NonNull final BgDataModel dataModel,
+            @NonNull final AllAppsList appsList) {
         final Context context = app.getContext();
         final IconCache iconCache = app.getIconCache();
 
diff --git a/src/com/android/launcher3/model/ReloadStringCacheTask.java b/src/com/android/launcher3/model/ReloadStringCacheTask.java
index f4d4298..34f7057 100644
--- a/src/com/android/launcher3/model/ReloadStringCacheTask.java
+++ b/src/com/android/launcher3/model/ReloadStringCacheTask.java
@@ -15,6 +15,8 @@
  */
 package com.android.launcher3.model;
 
+import androidx.annotation.NonNull;
+
 import com.android.launcher3.LauncherAppState;
 
 /**
@@ -22,14 +24,17 @@
  * {@link android.app.admin.DevicePolicyManager#ACTION_DEVICE_POLICY_RESOURCE_UPDATED}.
  */
 public class ReloadStringCacheTask extends BaseModelUpdateTask {
+
+    @NonNull
     private ModelDelegate mModelDelegate;
 
-    public ReloadStringCacheTask(ModelDelegate modelDelegate) {
+    public ReloadStringCacheTask(@NonNull final ModelDelegate modelDelegate) {
         mModelDelegate = modelDelegate;
     }
 
     @Override
-    public void execute(LauncherAppState app, BgDataModel dataModel, AllAppsList appsList) {
+    public void execute(@NonNull final LauncherAppState app, @NonNull final BgDataModel dataModel,
+            @NonNull final AllAppsList appsList) {
         synchronized (dataModel) {
             mModelDelegate.loadStringCache(dataModel.stringCache);
             StringCache cloneSC = dataModel.stringCache.clone();
diff --git a/src/com/android/launcher3/model/ShortcutsChangedTask.java b/src/com/android/launcher3/model/ShortcutsChangedTask.java
index 1026e0b..a6a04a7 100644
--- a/src/com/android/launcher3/model/ShortcutsChangedTask.java
+++ b/src/com/android/launcher3/model/ShortcutsChangedTask.java
@@ -19,6 +19,8 @@
 import android.content.pm.ShortcutInfo;
 import android.os.UserHandle;
 
+import androidx.annotation.NonNull;
+
 import com.android.launcher3.LauncherAppState;
 import com.android.launcher3.LauncherSettings;
 import com.android.launcher3.model.data.WorkspaceItemInfo;
@@ -38,13 +40,20 @@
  */
 public class ShortcutsChangedTask extends BaseModelUpdateTask {
 
+    @NonNull
     private final String mPackageName;
+
+    @NonNull
     private final List<ShortcutInfo> mShortcuts;
+
+    @NonNull
     private final UserHandle mUser;
+
     private final boolean mUpdateIdMap;
 
-    public ShortcutsChangedTask(String packageName, List<ShortcutInfo> shortcuts,
-            UserHandle user, boolean updateIdMap) {
+    public ShortcutsChangedTask(@NonNull final String packageName,
+            @NonNull final List<ShortcutInfo> shortcuts, @NonNull final UserHandle user,
+            final boolean updateIdMap) {
         mPackageName = packageName;
         mShortcuts = shortcuts;
         mUser = user;
@@ -52,7 +61,8 @@
     }
 
     @Override
-    public void execute(LauncherAppState app, BgDataModel dataModel, AllAppsList apps) {
+    public void execute(@NonNull final LauncherAppState app, @NonNull final BgDataModel dataModel,
+            @NonNull final AllAppsList apps) {
         final Context context = app.getContext();
         // Find WorkspaceItemInfo's that have changed on the workspace.
         ArrayList<WorkspaceItemInfo> matchingWorkspaceItems = new ArrayList<>();
diff --git a/src/com/android/launcher3/model/UserLockStateChangedTask.java b/src/com/android/launcher3/model/UserLockStateChangedTask.java
index 1565b19..63ca35b 100644
--- a/src/com/android/launcher3/model/UserLockStateChangedTask.java
+++ b/src/com/android/launcher3/model/UserLockStateChangedTask.java
@@ -21,6 +21,8 @@
 import android.content.pm.ShortcutInfo;
 import android.os.UserHandle;
 
+import androidx.annotation.NonNull;
+
 import com.android.launcher3.LauncherAppState;
 import com.android.launcher3.LauncherSettings;
 import com.android.launcher3.model.data.WorkspaceItemInfo;
@@ -40,16 +42,18 @@
  */
 public class UserLockStateChangedTask extends BaseModelUpdateTask {
 
+    @NonNull
     private final UserHandle mUser;
     private boolean mIsUserUnlocked;
 
-    public UserLockStateChangedTask(UserHandle user, boolean isUserUnlocked) {
+    public UserLockStateChangedTask(@NonNull final UserHandle user, final boolean isUserUnlocked) {
         mUser = user;
         mIsUserUnlocked = isUserUnlocked;
     }
 
     @Override
-    public void execute(LauncherAppState app, BgDataModel dataModel, AllAppsList apps) {
+    public void execute(@NonNull final LauncherAppState app, @NonNull final BgDataModel dataModel,
+            @NonNull final AllAppsList apps) {
         Context context = app.getContext();
 
         HashMap<ShortcutKey, ShortcutInfo> pinnedShortcuts = new HashMap<>();
diff --git a/src/com/android/launcher3/model/data/WorkspaceItemInfo.java b/src/com/android/launcher3/model/data/WorkspaceItemInfo.java
index 1f16474..59ef320 100644
--- a/src/com/android/launcher3/model/data/WorkspaceItemInfo.java
+++ b/src/com/android/launcher3/model/data/WorkspaceItemInfo.java
@@ -24,7 +24,6 @@
 import android.text.TextUtils;
 
 import androidx.annotation.NonNull;
-import androidx.annotation.Nullable;
 
 import com.android.launcher3.LauncherSettings;
 import com.android.launcher3.LauncherSettings.Favorites;
@@ -76,6 +75,7 @@
     /**
      * The intent used to start the application.
      */
+    @NonNull
     public Intent intent;
 
     /**
@@ -148,7 +148,7 @@
     }
 
     @Override
-    @Nullable
+    @NonNull
     public Intent getIntent() {
         return intent;
     }
@@ -166,7 +166,8 @@
         return isPromise() && !hasStatusFlag(FLAG_SUPPORTS_WEB_UI);
     }
 
-    public void updateFromDeepShortcutInfo(ShortcutInfo shortcutInfo, Context context) {
+    public void updateFromDeepShortcutInfo(@NonNull final ShortcutInfo shortcutInfo,
+            @NonNull final Context context) {
         // {@link ShortcutInfo#getActivity} can change during an update. Recreate the intent
         intent = ShortcutKey.makeIntent(shortcutInfo);
         title = shortcutInfo.getShortLabel();
diff --git a/src/com/android/launcher3/pm/InstallSessionHelper.java b/src/com/android/launcher3/pm/InstallSessionHelper.java
index b695194..16bb868 100644
--- a/src/com/android/launcher3/pm/InstallSessionHelper.java
+++ b/src/com/android/launcher3/pm/InstallSessionHelper.java
@@ -30,6 +30,7 @@
 import android.util.Log;
 
 import androidx.annotation.NonNull;
+import androidx.annotation.Nullable;
 import androidx.annotation.RequiresApi;
 import androidx.annotation.WorkerThread;
 
@@ -51,38 +52,50 @@
 import java.util.HashMap;
 import java.util.Iterator;
 import java.util.List;
+import java.util.Objects;
 
 /**
  * Utility class to tracking install sessions
  */
 public class InstallSessionHelper {
 
+    @NonNull
     private static final String LOG = "InstallSessionHelper";
 
     // Set<String> of session ids of promise icons that have been added to the home screen
     // as FLAG_PROMISE_NEW_INSTALLS.
+    @NonNull
     protected static final String PROMISE_ICON_IDS = "promise_icon_ids";
 
     private static final boolean DEBUG = false;
 
+    @NonNull
     public static final MainThreadInitializedObject<InstallSessionHelper> INSTANCE =
             new MainThreadInitializedObject<>(InstallSessionHelper::new);
 
+    @Nullable
     private final LauncherApps mLauncherApps;
+
+    @NonNull
     private final Context mAppContext;
 
+    @NonNull
     private final PackageInstaller mInstaller;
+
+    @NonNull
     private final HashMap<String, Boolean> mSessionVerifiedMap = new HashMap<>();
 
+    @Nullable
     private IntSet mPromiseIconIds;
 
-    public InstallSessionHelper(Context context) {
+    public InstallSessionHelper(@NonNull final Context context) {
         mInstaller = context.getPackageManager().getPackageInstaller();
         mAppContext = context.getApplicationContext();
         mLauncherApps = context.getSystemService(LauncherApps.class);
     }
 
     @WorkerThread
+    @NonNull
     private IntSet getPromiseIconIds() {
         Preconditions.assertWorkerThread();
         if (mPromiseIconIds != null) {
@@ -108,6 +121,7 @@
         return mPromiseIconIds;
     }
 
+    @NonNull
     public HashMap<PackageUserKey, SessionInfo> getActiveSessions() {
         HashMap<PackageUserKey, SessionInfo> activePackages = new HashMap<>();
         for (SessionInfo info : getAllVerifiedSessions()) {
@@ -117,6 +131,7 @@
         return activePackages;
     }
 
+    @Nullable
     public SessionInfo getActiveSessionInfo(UserHandle user, String pkg) {
         for (SessionInfo info : getAllVerifiedSessions()) {
             boolean match = pkg.equals(info.getAppPackageName());
@@ -136,11 +151,13 @@
                 .apply();
     }
 
-    SessionInfo getVerifiedSessionInfo(int sessionId) {
+    @Nullable
+    SessionInfo getVerifiedSessionInfo(final int sessionId) {
         return verify(mInstaller.getSessionInfo(sessionId));
     }
 
-    private SessionInfo verify(SessionInfo sessionInfo) {
+    @Nullable
+    private SessionInfo verify(@Nullable final SessionInfo sessionInfo) {
         if (sessionInfo == null
                 || sessionInfo.getInstallerPackageName() == null
                 || TextUtils.isEmpty(sessionInfo.getAppPackageName())) {
@@ -167,9 +184,10 @@
         return mSessionVerifiedMap.get(pkg) ? sessionInfo : null;
     }
 
+    @NonNull
     public List<SessionInfo> getAllVerifiedSessions() {
         List<SessionInfo> list = new ArrayList<>(Utilities.ATLEAST_Q
-                ? mLauncherApps.getAllPackageInstallerSessions()
+                ? Objects.requireNonNull(mLauncherApps).getAllPackageInstallerSessions()
                 : mInstaller.getAllSessions());
         Iterator<SessionInfo> it = list.iterator();
         while (it.hasNext()) {
@@ -201,12 +219,12 @@
     }
 
     @WorkerThread
-    public boolean promiseIconAddedForId(int sessionId) {
+    public boolean promiseIconAddedForId(final int sessionId) {
         return getPromiseIconIds().contains(sessionId);
     }
 
     @WorkerThread
-    public void removePromiseIconId(int sessionId) {
+    public void removePromiseIconId(final int sessionId) {
         if (promiseIconAddedForId(sessionId)) {
             getPromiseIconIds().getArray().removeValue(sessionId);
             updatePromiseIconPrefs();
@@ -222,7 +240,7 @@
      * - A promise icon for the session has not already been created
      */
     @WorkerThread
-    void tryQueuePromiseAppIcon(PackageInstaller.SessionInfo sessionInfo) {
+    void tryQueuePromiseAppIcon(@Nullable final PackageInstaller.SessionInfo sessionInfo) {
         if (TestProtocol.sDebugTracing) {
             Log.d(TestProtocol.MISSING_PROMISE_ICON, LOG + " tryQueuePromiseAppIcon"
                     + ", SessionCommitReceiveEnabled" + SessionCommitReceiver.isEnabled(mAppContext)
@@ -244,7 +262,7 @@
         }
     }
 
-    public boolean verifySessionInfo(PackageInstaller.SessionInfo sessionInfo) {
+    public boolean verifySessionInfo(@Nullable final PackageInstaller.SessionInfo sessionInfo) {
         if (TestProtocol.sDebugTracing) {
             boolean appNotInstalled = sessionInfo == null
                     || !new PackageManagerHelper(mAppContext)
@@ -267,14 +285,15 @@
                         sessionInfo.getAppPackageName(), getUserHandle(sessionInfo));
     }
 
-    public InstallSessionTracker registerInstallTracker(InstallSessionTracker.Callback callback) {
+    public InstallSessionTracker registerInstallTracker(
+            @Nullable final InstallSessionTracker.Callback callback) {
         InstallSessionTracker tracker = new InstallSessionTracker(
                 this, callback, mInstaller, mLauncherApps);
         tracker.register();
         return tracker;
     }
 
-    public static UserHandle getUserHandle(SessionInfo info) {
+    public static UserHandle getUserHandle(@NonNull final SessionInfo info) {
         return Utilities.ATLEAST_Q ? info.getUser() : Process.myUserHandle();
     }
 }
diff --git a/src/com/android/launcher3/pm/InstallSessionTracker.java b/src/com/android/launcher3/pm/InstallSessionTracker.java
index b16aaa2..aeaa320 100644
--- a/src/com/android/launcher3/pm/InstallSessionTracker.java
+++ b/src/com/android/launcher3/pm/InstallSessionTracker.java
@@ -28,12 +28,15 @@
 import android.util.Log;
 import android.util.SparseArray;
 
+import androidx.annotation.NonNull;
+import androidx.annotation.Nullable;
 import androidx.annotation.WorkerThread;
 
 import com.android.launcher3.testing.shared.TestProtocol;
 import com.android.launcher3.util.PackageUserKey;
 
 import java.lang.ref.WeakReference;
+import java.util.Objects;
 
 @WorkerThread
 public class InstallSessionTracker extends PackageInstaller.SessionCallback {
@@ -41,14 +44,22 @@
     // Lazily initialized
     private SparseArray<PackageUserKey> mActiveSessions = null;
 
+    @NonNull
     private final WeakReference<InstallSessionHelper> mWeakHelper;
+
+    @NonNull
     private final WeakReference<Callback> mWeakCallback;
+
+    @NonNull
     private final PackageInstaller mInstaller;
+
+    @Nullable
     private final LauncherApps mLauncherApps;
 
 
-    InstallSessionTracker(InstallSessionHelper installerCompat, Callback callback,
-            PackageInstaller installer, LauncherApps launcherApps) {
+    InstallSessionTracker(@Nullable final InstallSessionHelper installerCompat,
+            @Nullable final Callback callback, @NonNull final PackageInstaller installer,
+            @Nullable LauncherApps launcherApps) {
         mWeakHelper = new WeakReference<>(installerCompat);
         mWeakCallback = new WeakReference<>(callback);
         mInstaller = installer;
@@ -56,7 +67,7 @@
     }
 
     @Override
-    public void onCreated(int sessionId) {
+    public void onCreated(final int sessionId) {
         InstallSessionHelper helper = mWeakHelper.get();
         Callback callback = mWeakCallback.get();
         if (TestProtocol.sDebugTracing) {
@@ -80,7 +91,7 @@
     }
 
     @Override
-    public void onFinished(int sessionId, boolean success) {
+    public void onFinished(final int sessionId, final boolean success) {
         InstallSessionHelper helper = mWeakHelper.get();
         Callback callback = mWeakCallback.get();
         if (callback == null || helper == null) {
@@ -108,7 +119,7 @@
     }
 
     @Override
-    public void onProgressChanged(int sessionId, float progress) {
+    public void onProgressChanged(final int sessionId, final float progress) {
         InstallSessionHelper helper = mWeakHelper.get();
         Callback callback = mWeakCallback.get();
         if (callback == null || helper == null) {
@@ -121,10 +132,10 @@
     }
 
     @Override
-    public void onActiveChanged(int sessionId, boolean active) { }
+    public void onActiveChanged(final int sessionId, final boolean active) { }
 
     @Override
-    public void onBadgingChanged(int sessionId) {
+    public void onBadgingChanged(final int sessionId) {
         InstallSessionHelper helper = mWeakHelper.get();
         Callback callback = mWeakCallback.get();
         if (callback == null || helper == null) {
@@ -136,8 +147,9 @@
         }
     }
 
-    private SessionInfo pushSessionDisplayToLauncher(
-            int sessionId, InstallSessionHelper helper, Callback callback) {
+    @Nullable
+    private SessionInfo pushSessionDisplayToLauncher(final int sessionId,
+            @NonNull final InstallSessionHelper helper, @NonNull final Callback callback) {
         SessionInfo session = helper.getVerifiedSessionInfo(sessionId);
         if (session != null && session.getAppPackageName() != null) {
             PackageUserKey key =
@@ -149,7 +161,9 @@
         return null;
     }
 
-    private SparseArray<PackageUserKey> getActiveSessionMap(InstallSessionHelper helper) {
+    @NonNull
+    private SparseArray<PackageUserKey> getActiveSessionMap(
+            @NonNull final InstallSessionHelper helper) {
         if (mActiveSessions == null) {
             mActiveSessions = new SparseArray<>();
             helper.getActiveSessions().forEach(
@@ -162,7 +176,8 @@
         if (Build.VERSION.SDK_INT < Build.VERSION_CODES.Q) {
             mInstaller.registerSessionCallback(this, MODEL_EXECUTOR.getHandler());
         } else {
-            mLauncherApps.registerPackageInstallerSessionCallback(MODEL_EXECUTOR, this);
+            Objects.requireNonNull(mLauncherApps).registerPackageInstallerSessionCallback(
+                    MODEL_EXECUTOR, this);
         }
     }
 
@@ -170,18 +185,18 @@
         if (Build.VERSION.SDK_INT < Build.VERSION_CODES.Q) {
             mInstaller.unregisterSessionCallback(this);
         } else {
-            mLauncherApps.unregisterPackageInstallerSessionCallback(this);
+            Objects.requireNonNull(mLauncherApps).unregisterPackageInstallerSessionCallback(this);
         }
     }
 
     public interface Callback {
 
-        void onSessionFailure(String packageName, UserHandle user);
+        void onSessionFailure(@NonNull String packageName, @NonNull UserHandle user);
 
-        void onUpdateSessionDisplay(PackageUserKey key, SessionInfo info);
+        void onUpdateSessionDisplay(@NonNull PackageUserKey key, @NonNull SessionInfo info);
 
-        void onPackageStateChanged(PackageInstallInfo info);
+        void onPackageStateChanged(@NonNull PackageInstallInfo info);
 
-        void onInstallSessionCreated(PackageInstallInfo info);
+        void onInstallSessionCreated(@NonNull PackageInstallInfo info);
     }
 }
diff --git a/src/com/android/launcher3/util/PackageManagerHelper.java b/src/com/android/launcher3/util/PackageManagerHelper.java
index f42d304..12e8b54 100644
--- a/src/com/android/launcher3/util/PackageManagerHelper.java
+++ b/src/com/android/launcher3/util/PackageManagerHelper.java
@@ -43,6 +43,9 @@
 import android.util.Pair;
 import android.widget.Toast;
 
+import androidx.annotation.NonNull;
+import androidx.annotation.Nullable;
+
 import com.android.launcher3.PendingAddItemInfo;
 import com.android.launcher3.R;
 import com.android.launcher3.Utilities;
@@ -54,6 +57,7 @@
 
 import java.net.URISyntaxException;
 import java.util.List;
+import java.util.Objects;
 
 /**
  * Utility methods using package manager
@@ -62,22 +66,28 @@
 
     private static final String TAG = "PackageManagerHelper";
 
+    @NonNull
     private final Context mContext;
+
+    @NonNull
     private final PackageManager mPm;
+
+    @NonNull
     private final LauncherApps mLauncherApps;
 
-    public PackageManagerHelper(Context context) {
+    public PackageManagerHelper(@NonNull final Context context) {
         mContext = context;
         mPm = context.getPackageManager();
-        mLauncherApps = context.getSystemService(LauncherApps.class);
+        mLauncherApps = Objects.requireNonNull(context.getSystemService(LauncherApps.class));
     }
 
     /**
      * Returns true if the app can possibly be on the SDCard. This is just a workaround and doesn't
      * guarantee that the app is on SD card.
      */
-    public boolean isAppOnSdcard(String packageName, UserHandle user) {
-        ApplicationInfo info = getApplicationInfo(
+    public boolean isAppOnSdcard(@NonNull final String packageName,
+            @NonNull final UserHandle user) {
+        final ApplicationInfo info = getApplicationInfo(
                 packageName, user, PackageManager.MATCH_UNINSTALLED_PACKAGES);
         return info != null && (info.flags & ApplicationInfo.FLAG_EXTERNAL_STORAGE) != 0;
     }
@@ -86,23 +96,27 @@
      * Returns whether the target app is suspended for a given user as per
      * {@link android.app.admin.DevicePolicyManager#isPackageSuspended}.
      */
-    public boolean isAppSuspended(String packageName, UserHandle user) {
-        ApplicationInfo info = getApplicationInfo(packageName, user, 0);
+    public boolean isAppSuspended(@NonNull final String packageName,
+            @NonNull final UserHandle user) {
+        final ApplicationInfo info = getApplicationInfo(packageName, user, 0);
         return info != null && isAppSuspended(info);
     }
 
     /**
      * Returns whether the target app is installed for a given user
      */
-    public boolean isAppInstalled(String packageName, UserHandle user) {
-        ApplicationInfo info = getApplicationInfo(packageName, user, 0);
+    public boolean isAppInstalled(@NonNull final String packageName,
+            @NonNull final UserHandle user) {
+        final ApplicationInfo info = getApplicationInfo(packageName, user, 0);
         return info != null;
     }
 
     /**
      * Returns the application info for the provided package or null
      */
-    public ApplicationInfo getApplicationInfo(String packageName, UserHandle user, int flags) {
+    @Nullable
+    public ApplicationInfo getApplicationInfo(@NonNull final String packageName,
+            @NonNull final UserHandle user, final int flags) {
         try {
             ApplicationInfo info = mLauncherApps.getApplicationInfo(packageName, flags, user);
             return (info.flags & ApplicationInfo.FLAG_INSTALLED) == 0 || !info.enabled
@@ -116,7 +130,8 @@
         return mPm.isSafeMode();
     }
 
-    public Intent getAppLaunchIntent(String pkg, UserHandle user) {
+    @Nullable
+    public Intent getAppLaunchIntent(@Nullable final String pkg, @NonNull final UserHandle user) {
         List<LauncherActivityInfo> activities = mLauncherApps.getActivityList(pkg, user);
         return activities.isEmpty() ? null :
                 AppInfo.makeLaunchIntent(activities.get(0));
@@ -251,7 +266,8 @@
         return packageFilter;
     }
 
-    public static boolean isSystemApp(Context context, Intent intent) {
+    public static boolean isSystemApp(@NonNull final Context context,
+            @NonNull final Intent intent) {
         PackageManager pm = context.getPackageManager();
         ComponentName cn = intent.getComponent();
         String packageName = null;