System gesture exclusion rects for Views

Allow views to register a list of rects where the device's system UI
should not intercept complex (read: down+move+up) gestures on specific
sub-regions of the view. This should not be used for large-scale,
full-view gesture recognition such as scrolling, but rather for specific
areas such as SeekBar's scroll thumb or DrawerLayout's edge strip for
swiping open a navigation drawer.

Add ability for ViewTreeObserver to observe transformed exclusion rects

Bug: 126360272
Test: atest android.view.cts.SystemGestureExclusionRectsTest
Change-Id: If89b6f66637e40efa12955d6408f6e37b25cb46f

api/current.txt

@@ -50515,6 +50515,7 @@ package android.view {
     method public android.animation.StateListAnimator getStateListAnimator();
     method protected int getSuggestedMinimumHeight();
     method protected int getSuggestedMinimumWidth();
+    method @NonNull public java.util.List<android.graphics.Rect> getSystemGestureExclusionRects();
     method public int getSystemUiVisibility();
     method @android.view.ViewDebug.ExportedProperty public Object getTag();
     method public Object getTag(int);
@@ -50853,6 +50854,7 @@ package android.view {
     method public void setSelected(boolean);
     method public void setSoundEffectsEnabled(boolean);
     method public void setStateListAnimator(android.animation.StateListAnimator);
+    method public void setSystemGestureExclusionRects(@NonNull java.util.List<android.graphics.Rect>);
     method public void setSystemUiVisibility(int);
     method public void setTag(Object);
     method public void setTag(int, Object);
@@ -51681,6 +51683,7 @@ package android.view {
     method public void addOnGlobalLayoutListener(android.view.ViewTreeObserver.OnGlobalLayoutListener);
     method public void addOnPreDrawListener(android.view.ViewTreeObserver.OnPreDrawListener);
     method public void addOnScrollChangedListener(android.view.ViewTreeObserver.OnScrollChangedListener);
+    method public void addOnSystemGestureExclusionRectsChangedListener(java.util.function.Consumer<java.util.List<android.graphics.Rect>>);
     method public void addOnTouchModeChangeListener(android.view.ViewTreeObserver.OnTouchModeChangeListener);
     method public void addOnWindowAttachListener(android.view.ViewTreeObserver.OnWindowAttachListener);
     method public void addOnWindowFocusChangeListener(android.view.ViewTreeObserver.OnWindowFocusChangeListener);
@@ -51695,6 +51698,7 @@ package android.view {
     method public void removeOnGlobalLayoutListener(android.view.ViewTreeObserver.OnGlobalLayoutListener);
     method public void removeOnPreDrawListener(android.view.ViewTreeObserver.OnPreDrawListener);
     method public void removeOnScrollChangedListener(android.view.ViewTreeObserver.OnScrollChangedListener);
+    method public void removeOnSystemGestureExclusionRectsChangedListener(java.util.function.Consumer<java.util.List<android.graphics.Rect>>);
     method public void removeOnTouchModeChangeListener(android.view.ViewTreeObserver.OnTouchModeChangeListener);
     method public void removeOnWindowAttachListener(android.view.ViewTreeObserver.OnWindowAttachListener);
     method public void removeOnWindowFocusChangeListener(android.view.ViewTreeObserver.OnWindowFocusChangeListener);

core/java/android/view/GestureExclusionTracker.java

@@ -0,0 +1,125 @@
+/*
+ * 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 android.view;
+
+import android.annotation.NonNull;
+import android.annotation.Nullable;
+import android.graphics.Rect;
+
+import java.lang.ref.WeakReference;
+import java.util.ArrayList;
+import java.util.Collections;
+import java.util.Iterator;
+import java.util.List;
+
+/**
+ * Used by {@link ViewRootImpl} to track system gesture exclusion rects reported by views.
+ */
+class GestureExclusionTracker {
+    private boolean mGestureExclusionViewsChanged = false;
+    private List<GestureExclusionViewInfo> mGestureExclusionViewInfos = new ArrayList<>();
+    private List<Rect> mGestureExclusionRects = Collections.emptyList();
+
+    public void updateRectsForView(@NonNull View view) {
+        boolean found = false;
+        final Iterator<GestureExclusionViewInfo> i = mGestureExclusionViewInfos.iterator();
+        while (i.hasNext()) {
+            final GestureExclusionViewInfo info = i.next();
+            final View v = info.getView();
+            if (v == null || !v.isAttachedToWindow()) {
+                mGestureExclusionViewsChanged = true;
+                i.remove();
+                continue;
+            }
+            if (v == view) {
+                found = true;
+                info.mDirty = true;
+                break;
+            }
+        }
+        if (!found && view.isAttachedToWindow()) {
+            mGestureExclusionViewInfos.add(new GestureExclusionViewInfo(view));
+            mGestureExclusionViewsChanged = true;
+        }
+    }
+
+    @Nullable
+    public List<Rect> computeChangedRects() {
+        boolean changed = false;
+        final Iterator<GestureExclusionViewInfo> i = mGestureExclusionViewInfos.iterator();
+        final List<Rect> rects = new ArrayList<>();
+        while (i.hasNext()) {
+            final GestureExclusionViewInfo info = i.next();
+            switch (info.update()) {
+                case GestureExclusionViewInfo.CHANGED:
+                    changed = true;
+                    // Deliberate fall-through
+                case GestureExclusionViewInfo.UNCHANGED:
+                    rects.addAll(info.mExclusionRects);
+                    break;
+                case GestureExclusionViewInfo.GONE:
+                    mGestureExclusionViewsChanged = true;
+                    i.remove();
+                    break;
+            }
+        }
+        if (changed || mGestureExclusionViewsChanged) {
+            mGestureExclusionViewsChanged = false;
+            if (!mGestureExclusionRects.equals(rects)) {
+                mGestureExclusionRects = rects;
+                return rects;
+            }
+        }
+        return null;
+    }
+
+    private static class GestureExclusionViewInfo {
+        public static final int CHANGED = 0;
+        public static final int UNCHANGED = 1;
+        public static final int GONE = 2;
+
+        private final WeakReference<View> mView;
+        boolean mDirty = true;
+        List<Rect> mExclusionRects = Collections.emptyList();
+
+        GestureExclusionViewInfo(View view) {
+            mView = new WeakReference<>(view);
+        }
+
+        public View getView() {
+            return mView.get();
+        }
+
+        public int update() {
+            final View excludedView = getView();
+            if (excludedView == null || !excludedView.isAttachedToWindow()) return GONE;
+            final List<Rect> localRects = excludedView.getSystemGestureExclusionRects();
+            final List<Rect> newRects = new ArrayList<>(localRects.size());
+            for (Rect src : localRects) {
+                Rect mappedRect = new Rect(src);
+                ViewParent p = excludedView.getParent();
+                if (p != null && p.getChildVisibleRect(excludedView, mappedRect, null)) {
+                    newRects.add(mappedRect);
+                }
+            }
+
+            if (mExclusionRects.equals(localRects)) return UNCHANGED;
+            mExclusionRects = newRects;
+            return CHANGED;
+        }
+    }
+}

core/java/android/view/SurfaceView.java

@@ -210,7 +210,7 @@ public class SurfaceView extends View implements ViewRootImpl.WindowStoppedCallb
 
     public SurfaceView(Context context, AttributeSet attrs, int defStyleAttr, int defStyleRes) {
         super(context, attrs, defStyleAttr, defStyleRes);
-        mRenderNode.requestPositionUpdates(mPositionListener);
+        mRenderNode.addPositionUpdateListener(mPositionListener);
 
         setWillNotDraw(true);
     }

core/java/android/view/View.java

@@ -4603,6 +4603,16 @@ public class View implements Drawable.Callback, KeyEvent.Callback,
         private ArrayList<OnUnhandledKeyEventListener> mUnhandledKeyListeners;
 
         private WindowInsetsAnimationListener mWindowInsetsAnimationListener;
+
+        /**
+         * This lives here since it's only valid for interactive views.
+         */
+        private List<Rect> mSystemGestureExclusionRects;
+
+        /**
+         * Used to track {@link #mSystemGestureExclusionRects}
+         */
+        public RenderNode.PositionUpdateListener mPositionUpdateListener;
     }
 
     @UnsupportedAppUsage
@@ -10973,6 +10983,95 @@ public class View implements Drawable.Callback, KeyEvent.Callback,
         }
     }
 
+    /**
+     * Sets a list of areas within this view's post-layout coordinate space where the system
+     * should not intercept touch or other pointing device gestures. <em>This method should
+     * be called by {@link #onLayout(boolean, int, int, int, int)} or {@link #onDraw(Canvas)}.</em>
+     *
+     * <p>Use this to tell the system which specific sub-areas of a view need to receive gesture
+     * input in order to function correctly in the presence of global system gestures that may
+     * conflict. For example, if the system wishes to capture swipe-in-from-screen-edge gestures
+     * to provide system-level navigation functionality, a view such as a navigation drawer
+     * container can mark the left (or starting) edge of itself as requiring gesture capture
+     * priority using this API. The system may then choose to relax its own gesture recognition
+     * to allow the app to consume the user's gesture. It is not necessary for an app to register
+     * exclusion rects for broadly spanning regions such as the entirety of a
+     * <code>ScrollView</code> or for simple press and release click targets such as
+     * <code>Button</code>. Mark an exclusion rect when interacting with a view requires
+     * a precision touch gesture in a small area in either the X or Y dimension, such as
+     * an edge swipe or dragging a <code>SeekBar</code> thumb.</p>
+     *
+     * <p>Do not modify the provided list after this method is called.</p>
+     *
+     * @param rects A list of precision gesture regions that this view needs to function correctly
+     */
+    public void setSystemGestureExclusionRects(@NonNull List<Rect> rects) {
+        if (rects.isEmpty() && mListenerInfo == null) return;
+
+        final ListenerInfo info = getListenerInfo();
+        if (rects.isEmpty()) {
+            info.mSystemGestureExclusionRects = null;
+            if (info.mPositionUpdateListener != null) {
+                mRenderNode.removePositionUpdateListener(info.mPositionUpdateListener);
+            }
+        } else {
+            info.mSystemGestureExclusionRects = rects;
+            if (info.mPositionUpdateListener == null) {
+                info.mPositionUpdateListener = new RenderNode.PositionUpdateListener() {
+                    @Override
+                    public void positionChanged(long n, int l, int t, int r, int b) {
+                        postUpdateSystemGestureExclusionRects();
+                    }
+
+                    @Override
+                    public void positionLost(long frameNumber) {
+                        postUpdateSystemGestureExclusionRects();
+                    }
+                };
+                mRenderNode.addPositionUpdateListener(info.mPositionUpdateListener);
+            }
+        }
+        postUpdateSystemGestureExclusionRects();
+    }
+
+    /**
+     * WARNING: this can be called by a hwui worker thread, not just the UI thread!
+     */
+    void postUpdateSystemGestureExclusionRects() {
+        // Potentially racey from a background thread. It's ok if it's not perfect.
+        final Handler h = getHandler();
+        if (h != null) {
+            h.postAtFrontOfQueue(this::updateSystemGestureExclusionRects);
+        }
+    }
+
+    void updateSystemGestureExclusionRects() {
+        final AttachInfo ai = mAttachInfo;
+        if (ai != null) {
+            ai.mViewRootImpl.updateSystemGestureExclusionRectsForView(this);
+        }
+    }
+
+    /**
+     * Retrieve the list of areas within this view's post-layout coordinate space where the system
+     * should not intercept touch or other pointing device gestures.
+     *
+     * <p>Do not modify the returned list.</p>
+     *
+     * @return the list set by {@link #setSystemGestureExclusionRects(List)}
+     */
+    @NonNull
+    public List<Rect> getSystemGestureExclusionRects() {
+        final ListenerInfo info = mListenerInfo;
+        if (info != null) {
+            final List<Rect> list = info.mSystemGestureExclusionRects;
+            if (list != null) {
+                return list;
+            }
+        }
+        return Collections.emptyList();
+    }
+
     /**
      * Compute the view's coordinate within the surface.
      *

core/java/android/view/ViewRootImpl.java

@@ -605,6 +605,8 @@ public final class ViewRootImpl implements ViewParent,
 
     private final InsetsController mInsetsController = new InsetsController(this);
 
+    private final GestureExclusionTracker mGestureExclusionTracker = new GestureExclusionTracker();
+
     static final class SystemUiVisibilityInfo {
         int seq;
         int globalVisibility;
@@ -3977,6 +3979,20 @@ public final class ViewRootImpl implements ViewParent,
         return mAttachInfo.mAccessibilityFocusDrawable;
     }
 
+    void updateSystemGestureExclusionRectsForView(View view) {
+        mGestureExclusionTracker.updateRectsForView(view);
+        mHandler.sendEmptyMessage(MSG_SYSTEM_GESTURE_EXCLUSION_CHANGED);
+    }
+
+    void systemGestureExclusionChanged() {
+        final List<Rect> rectsForWindowManager = mGestureExclusionTracker.computeChangedRects();
+        if (rectsForWindowManager != null) {
+            // TODO Send to WM
+            mAttachInfo.mTreeObserver
+                    .dispatchOnSystemGestureExclusionRectsChanged(rectsForWindowManager);
+        }
+    }
+
     /**
      * Requests that the root render node is invalidated next time we perform a draw, such that
      * {@link WindowCallbacks#onPostDraw} gets called.
@@ -4433,35 +4449,36 @@ public final class ViewRootImpl implements ViewParent,
         }
     }
 
-    private final static int MSG_INVALIDATE = 1;
-    private final static int MSG_INVALIDATE_RECT = 2;
-    private final static int MSG_DIE = 3;
-    private final static int MSG_RESIZED = 4;
-    private final static int MSG_RESIZED_REPORT = 5;
-    private final static int MSG_WINDOW_FOCUS_CHANGED = 6;
-    private final static int MSG_DISPATCH_INPUT_EVENT = 7;
-    private final static int MSG_DISPATCH_APP_VISIBILITY = 8;
-    private final static int MSG_DISPATCH_GET_NEW_SURFACE = 9;
-    private final static int MSG_DISPATCH_KEY_FROM_IME = 11;
-    private final static int MSG_DISPATCH_KEY_FROM_AUTOFILL = 12;
-    private final static int MSG_CHECK_FOCUS = 13;
-    private final static int MSG_CLOSE_SYSTEM_DIALOGS = 14;
-    private final static int MSG_DISPATCH_DRAG_EVENT = 15;
-    private final static int MSG_DISPATCH_DRAG_LOCATION_EVENT = 16;
-    private final static int MSG_DISPATCH_SYSTEM_UI_VISIBILITY = 17;
-    private final static int MSG_UPDATE_CONFIGURATION = 18;
-    private final static int MSG_PROCESS_INPUT_EVENTS = 19;
-    private final static int MSG_CLEAR_ACCESSIBILITY_FOCUS_HOST = 21;
-    private final static int MSG_INVALIDATE_WORLD = 22;
-    private final static int MSG_WINDOW_MOVED = 23;
-    private final static int MSG_SYNTHESIZE_INPUT_EVENT = 24;
-    private final static int MSG_DISPATCH_WINDOW_SHOWN = 25;
-    private final static int MSG_REQUEST_KEYBOARD_SHORTCUTS = 26;
-    private final static int MSG_UPDATE_POINTER_ICON = 27;
-    private final static int MSG_POINTER_CAPTURE_CHANGED = 28;
-    private final static int MSG_DRAW_FINISHED = 29;
-    private final static int MSG_INSETS_CHANGED = 30;
-    private final static int MSG_INSETS_CONTROL_CHANGED = 31;
+    private static final int MSG_INVALIDATE = 1;
+    private static final int MSG_INVALIDATE_RECT = 2;
+    private static final int MSG_DIE = 3;
+    private static final int MSG_RESIZED = 4;
+    private static final int MSG_RESIZED_REPORT = 5;
+    private static final int MSG_WINDOW_FOCUS_CHANGED = 6;
+    private static final int MSG_DISPATCH_INPUT_EVENT = 7;
+    private static final int MSG_DISPATCH_APP_VISIBILITY = 8;
+    private static final int MSG_DISPATCH_GET_NEW_SURFACE = 9;
+    private static final int MSG_DISPATCH_KEY_FROM_IME = 11;
+    private static final int MSG_DISPATCH_KEY_FROM_AUTOFILL = 12;
+    private static final int MSG_CHECK_FOCUS = 13;
+    private static final int MSG_CLOSE_SYSTEM_DIALOGS = 14;
+    private static final int MSG_DISPATCH_DRAG_EVENT = 15;
+    private static final int MSG_DISPATCH_DRAG_LOCATION_EVENT = 16;
+    private static final int MSG_DISPATCH_SYSTEM_UI_VISIBILITY = 17;
+    private static final int MSG_UPDATE_CONFIGURATION = 18;
+    private static final int MSG_PROCESS_INPUT_EVENTS = 19;
+    private static final int MSG_CLEAR_ACCESSIBILITY_FOCUS_HOST = 21;
+    private static final int MSG_INVALIDATE_WORLD = 22;
+    private static final int MSG_WINDOW_MOVED = 23;
+    private static final int MSG_SYNTHESIZE_INPUT_EVENT = 24;
+    private static final int MSG_DISPATCH_WINDOW_SHOWN = 25;
+    private static final int MSG_REQUEST_KEYBOARD_SHORTCUTS = 26;
+    private static final int MSG_UPDATE_POINTER_ICON = 27;
+    private static final int MSG_POINTER_CAPTURE_CHANGED = 28;
+    private static final int MSG_DRAW_FINISHED = 29;
+    private static final int MSG_INSETS_CHANGED = 30;
+    private static final int MSG_INSETS_CONTROL_CHANGED = 31;
+    private static final int MSG_SYSTEM_GESTURE_EXCLUSION_CHANGED = 32;
 
     final class ViewRootHandler extends Handler {
         @Override
@@ -4519,6 +4536,10 @@ public final class ViewRootImpl implements ViewParent,
                     return "MSG_DRAW_FINISHED";
                 case MSG_INSETS_CHANGED:
                     return "MSG_INSETS_CHANGED";
+                case MSG_INSETS_CONTROL_CHANGED:
+                    return "MSG_INSETS_CONTROL_CHANGED";
+                case MSG_SYSTEM_GESTURE_EXCLUSION_CHANGED:
+                    return "MSG_SYSTEM_GESTURE_EXCLUSION_CHANGED";
             }
             return super.getMessageName(message);
         }
@@ -4750,6 +4771,9 @@ public final class ViewRootImpl implements ViewParent,
                 case MSG_DRAW_FINISHED: {
                     pendingDrawFinished();
                 } break;
+                case MSG_SYSTEM_GESTURE_EXCLUSION_CHANGED: {
+                    systemGestureExclusionChanged();
+                } break;
             }
         }
     }

core/java/android/view/ViewTreeObserver.java

@@ -26,7 +26,9 @@ import android.os.Build;
 import android.util.Log;
 
 import java.util.ArrayList;
+import java.util.List;
 import java.util.concurrent.CopyOnWriteArrayList;
+import java.util.function.Consumer;
 
 /**
  * A view tree observer is used to register listeners that can be notified of global
@@ -57,6 +59,7 @@ public final class ViewTreeObserver {
     private CopyOnWriteArray<OnScrollChangedListener> mOnScrollChangedListeners;
     private CopyOnWriteArray<OnPreDrawListener> mOnPreDrawListeners;
     private CopyOnWriteArray<OnWindowShownListener> mOnWindowShownListeners;
+    private CopyOnWriteArray<Consumer<List<Rect>>> mGestureExclusionListeners;
 
     // These listeners cannot be mutated during dispatch
     private boolean mInDispatchOnDraw;
@@ -450,6 +453,14 @@ public final class ViewTreeObserver {
             }
         }
 
+        if (observer.mGestureExclusionListeners != null) {
+            if (mGestureExclusionListeners != null) {
+                mGestureExclusionListeners.addAll(observer.mGestureExclusionListeners);
+            } else {
+                mGestureExclusionListeners = observer.mGestureExclusionListeners;
+            }
+        }
+
         observer.kill();
     }
 
@@ -913,6 +924,35 @@ public final class ViewTreeObserver {
         mOnEnterAnimationCompleteListeners.remove(listener);
     }
 
+    /**
+     * Add a listener to be notified when the tree's <em>transformed</em> gesture exclusion rects
+     * change. This could be the result of an animation or other layout change, or a view calling
+     * {@link View#setSystemGestureExclusionRects(List)}.
+     *
+     * @param listener listener to add
+     * @see View#setSystemGestureExclusionRects(List)
+     */
+    public void addOnSystemGestureExclusionRectsChangedListener(Consumer<List<Rect>> listener) {
+        checkIsAlive();
+        if (mGestureExclusionListeners == null) {
+            mGestureExclusionListeners = new CopyOnWriteArray<>();
+        }
+        mGestureExclusionListeners.add(listener);
+    }
+
+    /**
+     * Unsubscribe the given listener from gesture exclusion rect changes.
+     * @see #addOnSystemGestureExclusionRectsChangedListener(Consumer)
+     * @see View#setSystemGestureExclusionRects(List)
+     */
+    public void removeOnSystemGestureExclusionRectsChangedListener(Consumer<List<Rect>> listener) {
+        checkIsAlive();
+        if (mGestureExclusionListeners == null) {
+            return;
+        }
+        mGestureExclusionListeners.remove(listener);
+    }
+
     private void checkIsAlive() {
         if (!mAlive) {
             throw new IllegalStateException("This ViewTreeObserver is not alive, call "
@@ -1178,6 +1218,21 @@ public final class ViewTreeObserver {
         }
     }
 
+    void dispatchOnSystemGestureExclusionRectsChanged(@NonNull List<Rect> rects) {
+        final CopyOnWriteArray<Consumer<List<Rect>>> listeners = mGestureExclusionListeners;
+        if (listeners != null && listeners.size() > 0) {
+            CopyOnWriteArray.Access<Consumer<List<Rect>>> access = listeners.start();
+            try {
+                final int count = access.size();
+                for (int i = 0; i < count; i++) {
+                    access.get(i).accept(rects);
+                }
+            } finally {
+                listeners.end();
+            }
+        }
+    }
+
     /**
      * Copy on write array. This array is not thread safe, and only one loop can
      * iterate over this array at any given time. This class avoids allocations

graphics/java/android/graphics/RenderNode.java

@@ -27,6 +27,8 @@ import android.view.RenderNodeAnimator;
 import android.view.Surface;
 import android.view.View;
 
+import com.android.internal.util.ArrayUtils;
+
 import dalvik.annotation.optimization.CriticalNative;
 import dalvik.annotation.optimization.FastNative;
 
@@ -179,6 +181,10 @@ public final class RenderNode {
     private final AnimationHost mAnimationHost;
     private RecordingCanvas mCurrentRecordingCanvas;
 
+    // Will be null if not currently registered
+    @Nullable
+    private CompositePositionUpdateListener mCompositePositionUpdateListener;
+
     /**
      * Creates a new RenderNode that can be used to record batches of
      * drawing operations, and store / apply render properties when drawn.
@@ -248,15 +254,70 @@ public final class RenderNode {
 
     }
 
+    private static final class CompositePositionUpdateListener implements PositionUpdateListener {
+        private final PositionUpdateListener[] mListeners;
+
+        CompositePositionUpdateListener(PositionUpdateListener... listeners) {
+            mListeners = listeners;
+        }
+
+        public CompositePositionUpdateListener with(PositionUpdateListener listener) {
+            return new CompositePositionUpdateListener(
+                    ArrayUtils.appendElement(PositionUpdateListener.class, mListeners, listener));
+        }
+
+        public CompositePositionUpdateListener without(PositionUpdateListener listener) {
+            return new CompositePositionUpdateListener(
+                    ArrayUtils.removeElement(PositionUpdateListener.class, mListeners, listener));
+        }
+
+        @Override
+        public void positionChanged(long frameNumber, int left, int top, int right, int bottom) {
+            for (PositionUpdateListener pul : mListeners) {
+                pul.positionChanged(frameNumber, left, top, right, bottom);
+            }
+        }
+
+        @Override
+        public void positionLost(long frameNumber) {
+            for (PositionUpdateListener pul : mListeners) {
+                pul.positionLost(frameNumber);
+            }
+        }
+    }
+
     /**
-     * Enable callbacks for position changes.
+     * Enable callbacks for position changes. Call only from the UI thread or with
+     * external synchronization.
      *
      * @hide
      */
-    public void requestPositionUpdates(PositionUpdateListener listener) {
-        nRequestPositionUpdates(mNativeRenderNode, listener);
+    public void addPositionUpdateListener(@NonNull PositionUpdateListener listener) {
+        CompositePositionUpdateListener comp = mCompositePositionUpdateListener;
+        if (comp == null) {
+            comp = new CompositePositionUpdateListener(listener);
+        } else {
+            comp = comp.with(listener);
+        }
+        mCompositePositionUpdateListener = comp;
+        nRequestPositionUpdates(mNativeRenderNode, comp);
     }
 
+    /**
+     * Disable a callback for position changes. Call only from the UI thread or with
+     * external synchronization.
+     *
+     * @param listener Callback to remove
+     * @hide
+     */
+    public void removePositionUpdateListener(@NonNull PositionUpdateListener listener) {
+        CompositePositionUpdateListener comp = mCompositePositionUpdateListener;
+        if (comp != null) {
+            comp = comp.without(listener);
+            mCompositePositionUpdateListener = comp;
+            nRequestPositionUpdates(mNativeRenderNode, comp);
+        }
+    }
 
     /**
      * Starts recording a display list for the render node. All

tests/HwAccelerationTest/src/com/android/test/hwui/PositionListenerActivity.java

@@ -53,7 +53,7 @@ public class PositionListenerActivity extends Activity {
         MyPositionReporter(Context c) {
             super(c);
             mNode = new RenderNode("positionListener");
-            mNode.requestPositionUpdates(this);
+            mNode.addPositionUpdateListener(this);
             setTextAlignment(TEXT_ALIGNMENT_VIEW_START);
         }