diff --git a/core/java/android/app/MediaRouteButton.java b/core/java/android/app/MediaRouteButton.java
index 181c90758e8e9..70a5e15c6c272 100644
--- a/core/java/android/app/MediaRouteButton.java
+++ b/core/java/android/app/MediaRouteButton.java
@@ -19,6 +19,7 @@ package android.app;
 import com.android.internal.R;
 import com.android.internal.app.MediaRouteDialogPresenter;
 
+import android.annotation.NonNull;
 import android.content.Context;
 import android.content.ContextWrapper;
 import android.content.res.TypedArray;
@@ -279,7 +280,7 @@ public class MediaRouteButton extends View {
     }
 
     @Override
-    protected boolean verifyDrawable(Drawable who) {
+    protected boolean verifyDrawable(@NonNull Drawable who) {
         return super.verifyDrawable(who) || who == mRemoteIndicator;
     }
 
diff --git a/core/java/android/view/View.java b/core/java/android/view/View.java
index 9bd3df0c1a1fe..57ab6d400cd90 100644
--- a/core/java/android/view/View.java
+++ b/core/java/android/view/View.java
@@ -17505,7 +17505,7 @@ public class View implements Drawable.Callback, KeyEvent.Callback,
      *        {@link SystemClock#uptimeMillis} timebase.
      */
     @Override
-    public void scheduleDrawable(Drawable who, Runnable what, long when) {
+    public void scheduleDrawable(@NonNull Drawable who, @NonNull Runnable what, long when) {
         if (verifyDrawable(who) && what != null) {
             final long delay = when - SystemClock.uptimeMillis();
             if (mAttachInfo != null) {
@@ -17527,7 +17527,7 @@ public class View implements Drawable.Callback, KeyEvent.Callback,
      * @param what the action to cancel
      */
     @Override
-    public void unscheduleDrawable(Drawable who, Runnable what) {
+    public void unscheduleDrawable(@NonNull Drawable who, @NonNull Runnable what) {
         if (verifyDrawable(who) && what != null) {
             if (mAttachInfo != null) {
                 mAttachInfo.mViewRootImpl.mChoreographer.removeCallbacks(
@@ -17637,7 +17637,7 @@ public class View implements Drawable.Callback, KeyEvent.Callback,
      * @see #drawableStateChanged()
      */
     @CallSuper
-    protected boolean verifyDrawable(Drawable who) {
+    protected boolean verifyDrawable(@NonNull Drawable who) {
         // Avoid verifying the scroll bar drawable so that we don't end up in
         // an invalidation loop. This effectively prevents the scroll bar
         // drawable from triggering invalidations and scheduling runnables.
diff --git a/core/java/android/view/ViewOverlay.java b/core/java/android/view/ViewOverlay.java
index 0d05c542215dd..69c30bac723a8 100644
--- a/core/java/android/view/ViewOverlay.java
+++ b/core/java/android/view/ViewOverlay.java
@@ -170,7 +170,7 @@ public class ViewOverlay {
         }
 
         @Override
-        protected boolean verifyDrawable(Drawable who) {
+        protected boolean verifyDrawable(@NonNull Drawable who) {
             return super.verifyDrawable(who) || (mDrawables != null && mDrawables.contains(who));
         }
 
@@ -229,7 +229,7 @@ public class ViewOverlay {
         }
 
         @Override
-        public void invalidateDrawable(Drawable drawable) {
+        public void invalidateDrawable(@NonNull Drawable drawable) {
             invalidate(drawable.getBounds());
         }
 
diff --git a/core/java/android/widget/AbsListView.java b/core/java/android/widget/AbsListView.java
index d2aef0ac362c4..7cbe8de674920 100644
--- a/core/java/android/widget/AbsListView.java
+++ b/core/java/android/widget/AbsListView.java
@@ -2864,7 +2864,7 @@ public abstract class AbsListView extends AdapterView<ListAdapter> implements Te
     }
 
     @Override
-    public boolean verifyDrawable(Drawable dr) {
+    public boolean verifyDrawable(@NonNull Drawable dr) {
         return mSelector == dr || super.verifyDrawable(dr);
     }
 
diff --git a/core/java/android/widget/AbsSeekBar.java b/core/java/android/widget/AbsSeekBar.java
index 34f3a47393ba8..878a9eb940cdf 100644
--- a/core/java/android/widget/AbsSeekBar.java
+++ b/core/java/android/widget/AbsSeekBar.java
@@ -18,6 +18,7 @@ package android.widget;
 
 import com.android.internal.R;
 
+import android.annotation.NonNull;
 import android.annotation.Nullable;
 import android.content.Context;
 import android.content.res.ColorStateList;
@@ -485,7 +486,7 @@ public abstract class AbsSeekBar extends ProgressBar {
     }
 
     @Override
-    protected boolean verifyDrawable(Drawable who) {
+    protected boolean verifyDrawable(@NonNull Drawable who) {
         return who == mThumb || who == mTickMark || super.verifyDrawable(who);
     }
 
diff --git a/core/java/android/widget/CheckedTextView.java b/core/java/android/widget/CheckedTextView.java
index 9f94005ff7787..df506ca65da07 100644
--- a/core/java/android/widget/CheckedTextView.java
+++ b/core/java/android/widget/CheckedTextView.java
@@ -308,7 +308,7 @@ public class CheckedTextView extends TextView implements Checkable {
     }
 
     @Override
-    protected boolean verifyDrawable(Drawable who) {
+    protected boolean verifyDrawable(@NonNull Drawable who) {
         return who == mCheckMarkDrawable || super.verifyDrawable(who);
     }
 
diff --git a/core/java/android/widget/CompoundButton.java b/core/java/android/widget/CompoundButton.java
index b19fe17054d70..5d7585f9d9e82 100644
--- a/core/java/android/widget/CompoundButton.java
+++ b/core/java/android/widget/CompoundButton.java
@@ -474,7 +474,7 @@ public abstract class CompoundButton extends Button implements Checkable {
     }
 
     @Override
-    protected boolean verifyDrawable(Drawable who) {
+    protected boolean verifyDrawable(@NonNull Drawable who) {
         return super.verifyDrawable(who) || who == mButtonDrawable;
     }
 
diff --git a/core/java/android/widget/ImageView.java b/core/java/android/widget/ImageView.java
index f601f7df1fa81..3400873896f86 100644
--- a/core/java/android/widget/ImageView.java
+++ b/core/java/android/widget/ImageView.java
@@ -212,7 +212,7 @@ public class ImageView extends View {
     }
 
     @Override
-    protected boolean verifyDrawable(Drawable dr) {
+    protected boolean verifyDrawable(@NonNull Drawable dr) {
         return mDrawable == dr || super.verifyDrawable(dr);
     }
 
@@ -223,7 +223,7 @@ public class ImageView extends View {
     }
 
     @Override
-    public void invalidateDrawable(Drawable dr) {
+    public void invalidateDrawable(@NonNull Drawable dr) {
         if (dr == mDrawable) {
             if (dr != null) {
                 // update cached drawable dimensions if they've changed
diff --git a/core/java/android/widget/ProgressBar.java b/core/java/android/widget/ProgressBar.java
index 72a50ec1af901..ce948706542f6 100644
--- a/core/java/android/widget/ProgressBar.java
+++ b/core/java/android/widget/ProgressBar.java
@@ -1229,7 +1229,7 @@ public class ProgressBar extends View {
     }
 
     @Override
-    protected boolean verifyDrawable(Drawable who) {
+    protected boolean verifyDrawable(@NonNull Drawable who) {
         return who == mProgressDrawable || who == mIndeterminateDrawable
                 || super.verifyDrawable(who);
     }
@@ -1692,7 +1692,7 @@ public class ProgressBar extends View {
     }
 
     @Override
-    public void invalidateDrawable(Drawable dr) {
+    public void invalidateDrawable(@NonNull Drawable dr) {
         if (!mInDrawing) {
             if (verifyDrawable(dr)) {
                 final Rect dirty = dr.getBounds();
diff --git a/core/java/android/widget/ScrollBarDrawable.java b/core/java/android/widget/ScrollBarDrawable.java
index 8880217d94614..11eab2adad301 100644
--- a/core/java/android/widget/ScrollBarDrawable.java
+++ b/core/java/android/widget/ScrollBarDrawable.java
@@ -18,6 +18,7 @@ package android.widget;
 
 import com.android.internal.widget.ScrollBarUtils;
 
+import android.annotation.NonNull;
 import android.graphics.Canvas;
 import android.graphics.ColorFilter;
 import android.graphics.PixelFormat;
@@ -362,17 +363,17 @@ public class ScrollBarDrawable extends Drawable implements Drawable.Callback {
     }
 
     @Override
-    public void invalidateDrawable(Drawable who) {
+    public void invalidateDrawable(@NonNull Drawable who) {
         invalidateSelf();
     }
 
     @Override
-    public void scheduleDrawable(Drawable who, Runnable what, long when) {
+    public void scheduleDrawable(@NonNull Drawable who, @NonNull Runnable what, long when) {
         scheduleSelf(what, when);
     }
 
     @Override
-    public void unscheduleDrawable(Drawable who, Runnable what) {
+    public void unscheduleDrawable(@NonNull Drawable who, @NonNull Runnable what) {
         unscheduleSelf(what);
     }
 
diff --git a/core/java/android/widget/Switch.java b/core/java/android/widget/Switch.java
index 434516da13465..c4a17715896c1 100644
--- a/core/java/android/widget/Switch.java
+++ b/core/java/android/widget/Switch.java
@@ -18,6 +18,7 @@ package android.widget;
 
 import android.animation.ObjectAnimator;
 import android.annotation.DrawableRes;
+import android.annotation.NonNull;
 import android.annotation.Nullable;
 import android.annotation.StyleRes;
 import android.content.Context;
@@ -1371,7 +1372,7 @@ public class Switch extends CompoundButton {
     }
 
     @Override
-    protected boolean verifyDrawable(Drawable who) {
+    protected boolean verifyDrawable(@NonNull Drawable who) {
         return super.verifyDrawable(who) || who == mThumbDrawable || who == mTrackDrawable;
     }
 
diff --git a/core/java/android/widget/TextView.java b/core/java/android/widget/TextView.java
index 0ce4a122d2eeb..e971f865bf455 100644
--- a/core/java/android/widget/TextView.java
+++ b/core/java/android/widget/TextView.java
@@ -5470,7 +5470,7 @@ public class TextView extends View implements ViewTreeObserver.OnPreDrawListener
     }
 
     @Override
-    protected boolean verifyDrawable(Drawable who) {
+    protected boolean verifyDrawable(@NonNull Drawable who) {
         final boolean verified = super.verifyDrawable(who);
         if (!verified && mDrawables != null) {
             for (Drawable dr : mDrawables.mShowing) {
@@ -5495,7 +5495,7 @@ public class TextView extends View implements ViewTreeObserver.OnPreDrawListener
     }
 
     @Override
-    public void invalidateDrawable(Drawable drawable) {
+    public void invalidateDrawable(@NonNull Drawable drawable) {
         boolean handled = false;
 
         if (verifyDrawable(drawable)) {
diff --git a/core/java/com/android/internal/widget/ActionBarContainer.java b/core/java/com/android/internal/widget/ActionBarContainer.java
index 398bbe7af73c8..baf3188fb2358 100644
--- a/core/java/com/android/internal/widget/ActionBarContainer.java
+++ b/core/java/com/android/internal/widget/ActionBarContainer.java
@@ -147,7 +147,7 @@ public class ActionBarContainer extends FrameLayout {
     }
 
     @Override
-    protected boolean verifyDrawable(Drawable who) {
+    protected boolean verifyDrawable(@NonNull Drawable who) {
         return (who == mBackground && !mIsSplit) || (who == mStackedBackground && mIsStacked) ||
                 (who == mSplitBackground && mIsSplit) || super.verifyDrawable(who);
     }
diff --git a/core/java/com/android/internal/widget/ViewPager.java b/core/java/com/android/internal/widget/ViewPager.java
index 948a6bb427443..277fafd4adf72 100644
--- a/core/java/com/android/internal/widget/ViewPager.java
+++ b/core/java/com/android/internal/widget/ViewPager.java
@@ -17,6 +17,7 @@
 package com.android.internal.widget;
 
 import android.annotation.DrawableRes;
+import android.annotation.NonNull;
 import android.content.Context;
 import android.content.res.Resources;
 import android.content.res.TypedArray;
@@ -746,7 +747,7 @@ public class ViewPager extends ViewGroup {
     }
 
     @Override
-    protected boolean verifyDrawable(Drawable who) {
+    protected boolean verifyDrawable(@NonNull Drawable who) {
         return super.verifyDrawable(who) || who == mMarginDrawable;
     }
 
diff --git a/graphics/java/android/graphics/drawable/AnimatedVectorDrawable.java b/graphics/java/android/graphics/drawable/AnimatedVectorDrawable.java
index d354c1f761c1f..39ea2054ce6bf 100644
--- a/graphics/java/android/graphics/drawable/AnimatedVectorDrawable.java
+++ b/graphics/java/android/graphics/drawable/AnimatedVectorDrawable.java
@@ -715,17 +715,17 @@ public class AnimatedVectorDrawable extends Drawable implements Animatable2 {
 
     private final Callback mCallback = new Callback() {
         @Override
-        public void invalidateDrawable(Drawable who) {
+        public void invalidateDrawable(@NonNull Drawable who) {
             invalidateSelf();
         }
 
         @Override
-        public void scheduleDrawable(Drawable who, Runnable what, long when) {
+        public void scheduleDrawable(@NonNull Drawable who, @NonNull Runnable what, long when) {
             scheduleSelf(what, when);
         }
 
         @Override
-        public void unscheduleDrawable(Drawable who, Runnable what) {
+        public void unscheduleDrawable(@NonNull Drawable who, @NonNull Runnable what) {
             unscheduleSelf(what);
         }
     };
diff --git a/graphics/java/android/graphics/drawable/Drawable.java b/graphics/java/android/graphics/drawable/Drawable.java
index 3d8437d668488..f106c680bbc85 100644
--- a/graphics/java/android/graphics/drawable/Drawable.java
+++ b/graphics/java/android/graphics/drawable/Drawable.java
@@ -308,7 +308,7 @@ public abstract class Drawable {
      * to supply your implementation of the interface to the drawable; it uses
      * this interface to schedule and execute animation changes.
      */
-    public static interface Callback {
+    public interface Callback {
         /**
          * Called when the drawable needs to be redrawn.  A view at this point
          * should invalidate itself (or at least the part of itself where the
@@ -316,7 +316,7 @@ public abstract class Drawable {
          *
          * @param who The drawable that is requesting the update.
          */
-        public void invalidateDrawable(Drawable who);
+        void invalidateDrawable(@NonNull Drawable who);
 
         /**
          * A Drawable can call this to schedule the next frame of its
@@ -330,7 +330,7 @@ public abstract class Drawable {
          * @param when The time (in milliseconds) to run.  The timebase is
          *             {@link android.os.SystemClock#uptimeMillis}
          */
-        public void scheduleDrawable(Drawable who, Runnable what, long when);
+        void scheduleDrawable(@NonNull Drawable who, @NonNull Runnable what, long when);
 
         /**
          * A Drawable can call this to unschedule an action previously
@@ -342,7 +342,7 @@ public abstract class Drawable {
          * @param who The drawable being unscheduled.
          * @param what The action being unscheduled.
          */
-        public void unscheduleDrawable(Drawable who, Runnable what);
+        void unscheduleDrawable(@NonNull Drawable who, @NonNull Runnable what);
     }
 
     /**
diff --git a/graphics/java/android/graphics/drawable/DrawableContainer.java b/graphics/java/android/graphics/drawable/DrawableContainer.java
index 3b0e7e8c704e3..f55b6d969b3f1 100644
--- a/graphics/java/android/graphics/drawable/DrawableContainer.java
+++ b/graphics/java/android/graphics/drawable/DrawableContainer.java
@@ -373,21 +373,21 @@ public class DrawableContainer extends Drawable implements Drawable.Callback {
     }
 
     @Override
-    public void invalidateDrawable(Drawable who) {
+    public void invalidateDrawable(@NonNull Drawable who) {
         if (who == mCurrDrawable && getCallback() != null) {
             getCallback().invalidateDrawable(this);
         }
     }
 
     @Override
-    public void scheduleDrawable(Drawable who, Runnable what, long when) {
+    public void scheduleDrawable(@NonNull Drawable who, @NonNull Runnable what, long when) {
         if (who == mCurrDrawable && getCallback() != null) {
             getCallback().scheduleDrawable(this, what, when);
         }
     }
 
     @Override
-    public void unscheduleDrawable(Drawable who, Runnable what) {
+    public void unscheduleDrawable(@NonNull Drawable who, @NonNull Runnable what) {
         if (who == mCurrDrawable && getCallback() != null) {
             getCallback().unscheduleDrawable(this, what);
         }
diff --git a/graphics/java/android/graphics/drawable/DrawableWrapper.java b/graphics/java/android/graphics/drawable/DrawableWrapper.java
index c42787000c49c..4df2d57f25745 100644
--- a/graphics/java/android/graphics/drawable/DrawableWrapper.java
+++ b/graphics/java/android/graphics/drawable/DrawableWrapper.java
@@ -198,7 +198,7 @@ public abstract class DrawableWrapper extends Drawable implements Drawable.Callb
     }
 
     @Override
-    public void invalidateDrawable(Drawable who) {
+    public void invalidateDrawable(@NonNull Drawable who) {
         final Callback callback = getCallback();
         if (callback != null) {
             callback.invalidateDrawable(this);
@@ -206,7 +206,7 @@ public abstract class DrawableWrapper extends Drawable implements Drawable.Callb
     }
 
     @Override
-    public void scheduleDrawable(Drawable who, Runnable what, long when) {
+    public void scheduleDrawable(@NonNull Drawable who, @NonNull Runnable what, long when) {
         final Callback callback = getCallback();
         if (callback != null) {
             callback.scheduleDrawable(this, what, when);
@@ -214,7 +214,7 @@ public abstract class DrawableWrapper extends Drawable implements Drawable.Callb
     }
 
     @Override
-    public void unscheduleDrawable(Drawable who, Runnable what) {
+    public void unscheduleDrawable(@NonNull Drawable who, @NonNull Runnable what) {
         final Callback callback = getCallback();
         if (callback != null) {
             callback.unscheduleDrawable(this, what);
diff --git a/graphics/java/android/graphics/drawable/LayerDrawable.java b/graphics/java/android/graphics/drawable/LayerDrawable.java
index e2150c02c0e6b..d142f9502d913 100644
--- a/graphics/java/android/graphics/drawable/LayerDrawable.java
+++ b/graphics/java/android/graphics/drawable/LayerDrawable.java
@@ -944,17 +944,17 @@ public class LayerDrawable extends Drawable implements Drawable.Callback {
     }
 
     @Override
-    public void invalidateDrawable(Drawable who) {
+    public void invalidateDrawable(@NonNull Drawable who) {
         invalidateSelf();
     }
 
     @Override
-    public void scheduleDrawable(Drawable who, Runnable what, long when) {
+    public void scheduleDrawable(@NonNull Drawable who, @NonNull Runnable what, long when) {
         scheduleSelf(what, when);
     }
 
     @Override
-    public void unscheduleDrawable(Drawable who, Runnable what) {
+    public void unscheduleDrawable(@NonNull Drawable who, @NonNull Runnable what) {
         unscheduleSelf(what);
     }