diff --git a/go/quickstep/src/com/android/quickstep/views/GoOverviewActionsView.java b/go/quickstep/src/com/android/quickstep/views/GoOverviewActionsView.java
index 046661b..4e0aec3 100644
--- a/go/quickstep/src/com/android/quickstep/views/GoOverviewActionsView.java
+++ b/go/quickstep/src/com/android/quickstep/views/GoOverviewActionsView.java
@@ -35,6 +35,7 @@
  */
 public class GoOverviewActionsView extends OverviewActionsView<OverlayUICallbacksGo> {
 
+    @Nullable
     private ArrowTipView mArrowTipView;
 
     public GoOverviewActionsView(Context context) {
diff --git a/quickstep/src/com/android/quickstep/views/AllAppsEduView.java b/quickstep/src/com/android/quickstep/views/AllAppsEduView.java
index e9d7c3c..d79b318 100644
--- a/quickstep/src/com/android/quickstep/views/AllAppsEduView.java
+++ b/quickstep/src/com/android/quickstep/views/AllAppsEduView.java
@@ -35,6 +35,7 @@
 import android.view.MotionEvent;
 import android.view.View;
 
+import androidx.annotation.Nullable;
 import androidx.core.graphics.ColorUtils;
 
 import com.android.launcher3.AbstractFloatingView;
@@ -58,6 +59,7 @@
     private Launcher mLauncher;
     private AllAppsEduTouchController mTouchController;
 
+    @Nullable
     private AnimatorSet mAnimation;
 
     private GradientDrawable mCircle;
diff --git a/quickstep/src/com/android/quickstep/views/DigitalWellBeingToast.java b/quickstep/src/com/android/quickstep/views/DigitalWellBeingToast.java
index c8a72cd..a770fc6 100644
--- a/quickstep/src/com/android/quickstep/views/DigitalWellBeingToast.java
+++ b/quickstep/src/com/android/quickstep/views/DigitalWellBeingToast.java
@@ -44,6 +44,7 @@
 import android.widget.FrameLayout;
 import android.widget.TextView;
 
+import androidx.annotation.Nullable;
 import androidx.annotation.StringRes;
 
 import com.android.launcher3.BaseActivity;
@@ -69,6 +70,7 @@
     private Task mTask;
     private boolean mHasLimit;
     private long mAppRemainingTimeMs;
+    @Nullable
     private View mBanner;
     private ViewOutlineProvider mOldBannerOutlineProvider;
     private float mBannerOffsetPercentage;
@@ -229,7 +231,7 @@
                 task.titleDescription;
     }
 
-    private void replaceBanner(View view) {
+    private void replaceBanner(@Nullable View view) {
         resetOldBanner();
         setBanner(view);
     }
@@ -243,7 +245,7 @@
         }
     }
 
-    private void setBanner(View view) {
+    private void setBanner(@Nullable View view) {
         mBanner = view;
         if (view != null) {
             setupAndAddBanner();
diff --git a/quickstep/src/com/android/quickstep/views/FloatingWidgetBackgroundView.java b/quickstep/src/com/android/quickstep/views/FloatingWidgetBackgroundView.java
index 1548268..c3b166f 100644
--- a/quickstep/src/com/android/quickstep/views/FloatingWidgetBackgroundView.java
+++ b/quickstep/src/com/android/quickstep/views/FloatingWidgetBackgroundView.java
@@ -27,6 +27,8 @@
 import android.view.ViewOutlineProvider;
 import android.widget.RemoteViews.RemoteViewOutlineProvider;
 
+import androidx.annotation.Nullable;
+
 import com.android.launcher3.widget.LauncherAppWidgetHostView;
 import com.android.launcher3.widget.RoundedCornerEnforcement;
 
@@ -42,7 +44,9 @@
     private final DrawableProperties mForegroundProperties = new DrawableProperties();
     private final DrawableProperties mBackgroundProperties = new DrawableProperties();
 
+    @Nullable
     private Drawable mOriginalForeground;
+    @Nullable
     private Drawable mOriginalBackground;
     private float mFinalRadius;
     private float mInitialOutlineRadius;
@@ -50,7 +54,7 @@
     private boolean mIsUsingFallback;
     private View mSourceView;
 
-    FloatingWidgetBackgroundView(Context context, AttributeSet attrs, int defStyleAttr) {
+    FloatingWidgetBackgroundView(Context context, @Nullable AttributeSet attrs, int defStyleAttr) {
         super(context, attrs, defStyleAttr);
         setOutlineProvider(new ViewOutlineProvider() {
             @Override
@@ -161,8 +165,10 @@
 
     /** Stores and modifies a drawable's properties through an animation. */
     private static class DrawableProperties {
+        @Nullable
         private Drawable mDrawable;
         private float mOriginalRadius;
+        @Nullable
         private float[] mOriginalRadii;
         private final float[] mTmpRadii = new float[8];
 
diff --git a/quickstep/src/com/android/quickstep/views/FloatingWidgetView.java b/quickstep/src/com/android/quickstep/views/FloatingWidgetView.java
index 463ed4b..8a5f42a 100644
--- a/quickstep/src/com/android/quickstep/views/FloatingWidgetView.java
+++ b/quickstep/src/com/android/quickstep/views/FloatingWidgetView.java
@@ -57,10 +57,14 @@
     private LauncherAppWidgetHostView mAppWidgetView;
     private View mAppWidgetBackgroundView;
     private RectF mBackgroundPosition;
+    @Nullable
     private GhostView mForegroundOverlayView;
 
+    @Nullable
     private Runnable mEndRunnable;
+    @Nullable
     private Runnable mFastFinishRunnable;
+    @Nullable
     private Runnable mOnTargetChangeRunnable;
     private boolean mAppTargetIsTranslucent;
 
diff --git a/quickstep/src/com/android/quickstep/views/GroupedTaskView.java b/quickstep/src/com/android/quickstep/views/GroupedTaskView.java
index eace227..d2970bf 100644
--- a/quickstep/src/com/android/quickstep/views/GroupedTaskView.java
+++ b/quickstep/src/com/android/quickstep/views/GroupedTaskView.java
@@ -14,7 +14,6 @@
 import com.android.launcher3.DeviceProfile;
 import com.android.launcher3.R;
 import com.android.launcher3.util.RunnableList;
-import com.android.launcher3.util.SplitConfigurationOptions;
 import com.android.launcher3.util.SplitConfigurationOptions.StagedSplitBounds;
 import com.android.launcher3.util.TransformingTouchDelegate;
 import com.android.quickstep.RecentsModel;
@@ -40,10 +39,13 @@
  */
 public class GroupedTaskView extends TaskView {
 
+    @Nullable
     private Task mSecondaryTask;
     private TaskThumbnailView mSnapshotView2;
     private IconView mIconView2;
+    @Nullable
     private CancellableTask<ThumbnailData> mThumbnailLoadRequest2;
+    @Nullable
     private CancellableTask mIconLoadRequest2;
     private final float[] mIcon2CenterCoords = new float[2];
     private TransformingTouchDelegate mIcon2TouchDelegate;
@@ -154,6 +156,7 @@
         }
     }
 
+    @Nullable
     @Override
     public RunnableList launchTaskAnimated() {
         getRecentsView().getSplitPlaceholder().launchTasks(mTask, mSecondaryTask,
@@ -168,7 +171,7 @@
     }
 
     @Override
-    void refreshThumbnails(HashMap<Integer, ThumbnailData> thumbnailDatas) {
+    void refreshThumbnails(@Nullable HashMap<Integer, ThumbnailData> thumbnailDatas) {
         super.refreshThumbnails(thumbnailDatas);
         if (mSecondaryTask != null && thumbnailDatas != null) {
             final ThumbnailData thumbnailData = thumbnailDatas.get(mSecondaryTask.key.id);
diff --git a/quickstep/src/com/android/quickstep/views/IconView.java b/quickstep/src/com/android/quickstep/views/IconView.java
index 813e653..ccb1a99 100644
--- a/quickstep/src/com/android/quickstep/views/IconView.java
+++ b/quickstep/src/com/android/quickstep/views/IconView.java
@@ -23,6 +23,8 @@
 import android.view.Gravity;
 import android.view.View;
 
+import androidx.annotation.Nullable;
+
 import com.android.launcher3.Utilities;
 
 /**
@@ -31,6 +33,7 @@
  */
 public class IconView extends View {
 
+    @Nullable
     private Drawable mDrawable;
     private int mDrawableWidth, mDrawableHeight;
 
@@ -46,7 +49,10 @@
         super(context, attrs, defStyleAttr);
     }
 
-    public void setDrawable(Drawable d) {
+    /**
+     * Sets a {@link Drawable} to be displayed.
+     */
+    public void setDrawable(@Nullable Drawable d) {
         if (mDrawable != null) {
             mDrawable.setCallback(null);
         }
@@ -76,6 +82,7 @@
         mDrawable.setBounds(drawableRect);
     }
 
+    @Nullable
     public Drawable getDrawable() {
         return mDrawable;
     }
diff --git a/quickstep/src/com/android/quickstep/views/OverviewActionsView.java b/quickstep/src/com/android/quickstep/views/OverviewActionsView.java
index 5c0b50c..f3b6a63 100644
--- a/quickstep/src/com/android/quickstep/views/OverviewActionsView.java
+++ b/quickstep/src/com/android/quickstep/views/OverviewActionsView.java
@@ -90,8 +90,10 @@
     @ActionsDisabledFlags
     protected int mDisabledFlags;
 
+    @Nullable
     protected T mCallbacks;
 
+    @Nullable
     protected DeviceProfile mDp;
 
     public OverviewActionsView(Context context) {
diff --git a/quickstep/src/com/android/quickstep/views/SplitPlaceholderView.java b/quickstep/src/com/android/quickstep/views/SplitPlaceholderView.java
index 845e13e..04a5761 100644
--- a/quickstep/src/com/android/quickstep/views/SplitPlaceholderView.java
+++ b/quickstep/src/com/android/quickstep/views/SplitPlaceholderView.java
@@ -40,6 +40,7 @@
                 }
             };
 
+    @Nullable
     private IconView mIconView;
 
     public SplitPlaceholderView(Context context, AttributeSet attrs) {
diff --git a/quickstep/src/com/android/quickstep/views/TaskMenuView.java b/quickstep/src/com/android/quickstep/views/TaskMenuView.java
index d55b89c..853a023 100644
--- a/quickstep/src/com/android/quickstep/views/TaskMenuView.java
+++ b/quickstep/src/com/android/quickstep/views/TaskMenuView.java
@@ -39,6 +39,8 @@
 import android.widget.LinearLayout;
 import android.widget.TextView;
 
+import androidx.annotation.Nullable;
+
 import com.android.launcher3.AbstractFloatingView;
 import com.android.launcher3.BaseDraggingActivity;
 import com.android.launcher3.DeviceProfile;
@@ -67,6 +69,7 @@
 
     private BaseDraggingActivity mActivity;
     private TextView mTaskName;
+    @Nullable
     private AnimatorSet mOpenCloseAnimator;
     private TaskView mTaskView;
     private TaskIdAttributeContainer mTaskContainer;
diff --git a/quickstep/src/com/android/quickstep/views/TaskThumbnailView.java b/quickstep/src/com/android/quickstep/views/TaskThumbnailView.java
index d498428..c960f88 100644
--- a/quickstep/src/com/android/quickstep/views/TaskThumbnailView.java
+++ b/quickstep/src/com/android/quickstep/views/TaskThumbnailView.java
@@ -78,6 +78,7 @@
             };
 
     private final BaseActivity mActivity;
+    @Nullable
     private TaskOverlay mOverlay;
     private final Paint mPaint = new Paint(Paint.ANTI_ALIAS_FLAG);
     private final Paint mBackgroundPaint = new Paint(Paint.ANTI_ALIAS_FLAG);
@@ -90,8 +91,11 @@
     private final PreviewPositionHelper mPreviewPositionHelper = new PreviewPositionHelper();
     private TaskView.FullscreenDrawParams mFullscreenParams;
 
+    @Nullable
     private Task mTask;
+    @Nullable
     private ThumbnailData mThumbnailData;
+    @Nullable
     protected BitmapShader mBitmapShader;
 
     /** How much this thumbnail is dimmed, 0 not dimmed at all, 1 totally dimmed. */
@@ -141,7 +145,8 @@
      *                   upon swipe up so that a usable screenshot is accessible immediately when
      *                   recents animation needs to be finished / cancelled.
      */
-    public void setThumbnail(Task task, ThumbnailData thumbnailData, boolean refreshNow) {
+    public void setThumbnail(@Nullable Task task, @Nullable ThumbnailData thumbnailData,
+            boolean refreshNow) {
         mTask = task;
         mThumbnailData =
                 (thumbnailData != null && thumbnailData.thumbnail != null) ? thumbnailData : null;
@@ -151,7 +156,7 @@
     }
 
     /** See {@link #setThumbnail(Task, ThumbnailData, boolean)} */
-    public void setThumbnail(Task task, ThumbnailData thumbnailData) {
+    public void setThumbnail(@Nullable Task task, @Nullable ThumbnailData thumbnailData) {
         setThumbnail(task, thumbnailData, true /* refreshNow */);
     }
 
@@ -366,6 +371,10 @@
         return Utilities.makeColorTintingColorFilter(mDimColor, dimAmount);
     }
 
+    /**
+     * Returns current thumbnail or null if none is set.
+     */
+    @Nullable
     public Bitmap getThumbnail() {
         if (mThumbnailData == null) {
             return null;
diff --git a/quickstep/src/com/android/quickstep/views/TaskView.java b/quickstep/src/com/android/quickstep/views/TaskView.java
index 4132006..3a3ec73 100644
--- a/quickstep/src/com/android/quickstep/views/TaskView.java
+++ b/quickstep/src/com/android/quickstep/views/TaskView.java
@@ -92,7 +92,6 @@
 import com.android.quickstep.TaskUtils;
 import com.android.quickstep.TaskViewUtils;
 import com.android.quickstep.util.CancellableTask;
-import com.android.quickstep.util.LauncherSplitScreenListener;
 import com.android.quickstep.util.RecentsOrientedState;
 import com.android.quickstep.util.TaskCornerRadius;
 import com.android.quickstep.util.TransformParams;
@@ -361,6 +360,7 @@
 
     private final TaskOutlineProvider mOutlineProvider;
 
+    @Nullable
     protected Task mTask;
     protected TaskThumbnailView mSnapshotView;
     protected IconView mIconView;
@@ -395,6 +395,7 @@
     private float mSplitSelectTranslationX;
     private float mSplitSelectScrollOffsetPrimary;
 
+    @Nullable
     private ObjectAnimator mIconAndDimAnimator;
     private float mIconScaleAnimStartProgress = 0;
     private float mFocusTransitionProgress = 1;
@@ -412,7 +413,9 @@
     private boolean mShowScreenshot;
 
     // The current background requests to load the task thumbnail and icon
+    @Nullable
     private CancellableTask mThumbnailLoadRequest;
+    @Nullable
     private CancellableTask mIconLoadRequest;
 
     private boolean mEndQuickswitchCuj;
@@ -545,6 +548,7 @@
         return mTaskIdAttributeContainer;
     }
 
+    @Nullable
     public Task getTask() {
         return mTask;
     }
@@ -687,6 +691,7 @@
      * Starts the task associated with this view and animates the startup.
      * @return CompletionStage to indicate the animation completion or null if the launch failed.
      */
+    @Nullable
     public RunnableList launchTaskAnimated() {
         if (mTask != null) {
             TestLogging.recordEvent(
@@ -844,7 +849,7 @@
         }
     }
 
-    protected void setIcon(IconView iconView, Drawable icon) {
+    protected void setIcon(IconView iconView, @Nullable Drawable icon) {
         if (icon != null) {
             iconView.setDrawable(icon);
             iconView.setOnClickListener(v -> {