Merge "Interact with DreamOverlay through distinct clients." into tm-qpr-dev am: b928049681 am: cf8cfa3c23

Original change: https://googleplex-android-review.googlesource.com/c/platform/frameworks/base/+/21109634

Change-Id: I1551c3a299b0dacb01787b57b5ed1c2a06c9c5c7
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>

core/java/android/service/dreams/DreamOverlayService.java

@@ -36,39 +36,101 @@ import android.view.WindowManager;
 public abstract class DreamOverlayService extends Service {
     private static final String TAG = "DreamOverlayService";
     private static final boolean DEBUG = false;
-    private boolean mShowComplications;
-    private ComponentName mDreamComponent;
 
-    private IDreamOverlay mDreamOverlay = new IDreamOverlay.Stub() {
+    // The last client that started dreaming and hasn't ended
+    private OverlayClient mCurrentClient;
+
+    // An {@link IDreamOverlayClient} implementation that identifies itself when forwarding
+    // requests to the {@link DreamOverlayService}
+    private static class OverlayClient extends IDreamOverlayClient.Stub {
+        private final DreamOverlayService mService;
+        private boolean mShowComplications;
+        private ComponentName mDreamComponent;
+        IDreamOverlayCallback mDreamOverlayCallback;
+
+        OverlayClient(DreamOverlayService service) {
+            mService = service;
+        }
+
         @Override
-        public void startDream(WindowManager.LayoutParams layoutParams,
-                IDreamOverlayCallback callback, String dreamComponent,
-                boolean shouldShowComplications) {
-            mDreamOverlayCallback = callback;
+        public void startDream(WindowManager.LayoutParams params, IDreamOverlayCallback callback,
+                String dreamComponent, boolean shouldShowComplications) throws RemoteException {
             mDreamComponent = ComponentName.unflattenFromString(dreamComponent);
             mShowComplications = shouldShowComplications;
-            onStartDream(layoutParams);
+            mDreamOverlayCallback = callback;
+            mService.startDream(this, params);
+        }
+
+
+
+        @Override
+        public void wakeUp() {
+            mService.wakeUp(this, () -> {
+                try {
+                    mDreamOverlayCallback.onWakeUpComplete();
+                } catch (RemoteException e) {
+                    Log.e(TAG, "Could not notify dream of wakeUp", e);
+                }
+            });
         }
 
         @Override
         public void endDream() {
-            onEndDream();
+            mService.endDream(this);
         }
 
+        private void onExitRequested() {
+            try {
+                mDreamOverlayCallback.onExitRequested();
+            } catch (RemoteException e) {
+                Log.e(TAG, "Could not request exit:" + e);
+            }
+        }
+
+        private boolean shouldShowComplications() {
+            return mShowComplications;
+        }
+
+        private ComponentName getComponent() {
+            return mDreamComponent;
+        }
+    }
+
+    private void startDream(OverlayClient client, WindowManager.LayoutParams params) {
+        endDream(mCurrentClient);
+        mCurrentClient = client;
+        onStartDream(params);
+    }
+
+    private void endDream(OverlayClient client) {
+        if (client == null || client != mCurrentClient) {
+            return;
+        }
+
+        onEndDream();
+        mCurrentClient = null;
+    }
+
+    private void wakeUp(OverlayClient client, Runnable callback) {
+        if (mCurrentClient != client) {
+            return;
+        }
+
+        onWakeUp(callback);
+    }
+
+    private IDreamOverlay mDreamOverlay = new IDreamOverlay.Stub() {
         @Override
-        public void wakeUp() {
-            onWakeUp(() -> {
-                try {
-                    mDreamOverlayCallback.onWakeUpComplete();
-                } catch (RemoteException e) {
-                    Log.e(TAG, "Could not notify dream of wakeUp:" + e);
-                }
-            });
+        public void getClient(IDreamOverlayClientCallback callback) {
+            try {
+                callback.onDreamOverlayClient(
+                        new OverlayClient(DreamOverlayService.this));
+            } catch (RemoteException e) {
+                Log.e(TAG, "could not send client to callback", e);
+            }
         }
     };
 
-    IDreamOverlayCallback mDreamOverlayCallback;
-
     public DreamOverlayService() {
     }
 
@@ -110,18 +172,23 @@ public abstract class DreamOverlayService extends Service {
      * This method is invoked to request the dream exit.
      */
     public final void requestExit() {
-        try {
-            mDreamOverlayCallback.onExitRequested();
-        } catch (RemoteException e) {
-            Log.e(TAG, "Could not request exit:" + e);
+        if (mCurrentClient == null) {
+            throw new IllegalStateException("requested exit with no dream present");
         }
+
+        mCurrentClient.onExitRequested();
     }
 
     /**
      * Returns whether to show complications on the dream overlay.
      */
     public final boolean shouldShowComplications() {
-        return mShowComplications;
+        if (mCurrentClient == null) {
+            throw new IllegalStateException(
+                    "requested if should show complication when no dream active");
+        }
+
+        return mCurrentClient.shouldShowComplications();
     }
 
     /**
@@ -129,6 +196,10 @@ public abstract class DreamOverlayService extends Service {
      * @hide
      */
     public final ComponentName getDreamComponent() {
-        return mDreamComponent;
+        if (mCurrentClient == null) {
+            throw new IllegalStateException("requested dream component when no dream active");
+        }
+
+        return mCurrentClient.getComponent();
     }
 }

core/java/android/service/dreams/DreamService.java

@@ -248,25 +248,39 @@ public class DreamService extends Service implements Window.Callback {
     private OverlayConnection mOverlayConnection;
 
     private static class OverlayConnection extends PersistentServiceConnection<IDreamOverlay> {
-        // Overlay set during onBind.
-        private IDreamOverlay mOverlay;
+        // Retrieved Client
+        private IDreamOverlayClient mClient;
+
         // A list of pending requests to execute on the overlay.
-        private final ArrayList<Consumer<IDreamOverlay>> mConsumers = new ArrayList<>();
+        private final ArrayList<Consumer<IDreamOverlayClient>> mConsumers = new ArrayList<>();
+
+        private final IDreamOverlayClientCallback mClientCallback =
+                new IDreamOverlayClientCallback.Stub() {
+            @Override
+            public void onDreamOverlayClient(IDreamOverlayClient client) {
+                mClient = client;
+
+                for (Consumer<IDreamOverlayClient> consumer : mConsumers) {
+                    consumer.accept(mClient);
+                }
+            }
+        };
 
         private final Callback<IDreamOverlay> mCallback = new Callback<IDreamOverlay>() {
             @Override
             public void onConnected(ObservableServiceConnection<IDreamOverlay> connection,
                     IDreamOverlay service) {
-                mOverlay = service;
-                for (Consumer<IDreamOverlay> consumer : mConsumers) {
-                    consumer.accept(mOverlay);
+                try {
+                    service.getClient(mClientCallback);
+                } catch (RemoteException e) {
+                    Log.e(TAG, "could not get DreamOverlayClient", e);
                 }
             }
 
             @Override
             public void onDisconnected(ObservableServiceConnection<IDreamOverlay> connection,
                     int reason) {
-                mOverlay = null;
+                mClient = null;
             }
         };
 
@@ -296,16 +310,16 @@ public class DreamService extends Service implements Window.Callback {
             super.unbind();
         }
 
-        public void addConsumer(Consumer<IDreamOverlay> consumer) {
+        public void addConsumer(Consumer<IDreamOverlayClient> consumer) {
             execute(() -> {
                 mConsumers.add(consumer);
-                if (mOverlay != null) {
-                    consumer.accept(mOverlay);
+                if (mClient != null) {
+                    consumer.accept(mClient);
                 }
             });
         }
 
-        public void removeConsumer(Consumer<IDreamOverlay> consumer) {
+        public void removeConsumer(Consumer<IDreamOverlayClient> consumer) {
             execute(() -> mConsumers.remove(consumer));
         }
 
@@ -1379,7 +1393,7 @@ public class DreamService extends Service implements Window.Callback {
 
         mWindow.getDecorView().addOnAttachStateChangeListener(
                 new View.OnAttachStateChangeListener() {
-                    private Consumer<IDreamOverlay> mDreamStartOverlayConsumer;
+                    private Consumer<IDreamOverlayClient> mDreamStartOverlayConsumer;
 
                     @Override
                     public void onViewAttachedToWindow(View v) {

core/java/android/service/dreams/IDreamOverlay.aidl

@@ -16,8 +16,7 @@
 
 package android.service.dreams;
 
-import android.service.dreams.IDreamOverlayCallback;
-import android.view.WindowManager.LayoutParams;
+import android.service.dreams.IDreamOverlayClientCallback;
 
 /**
 * {@link IDreamOverlay} provides a way for a component to annotate a dream with additional view
@@ -28,20 +27,7 @@ import android.view.WindowManager.LayoutParams;
 */
 interface IDreamOverlay {
     /**
-    * @param params The {@link LayoutParams} for the associated DreamWindow, including the window
-                    token of the Dream Activity.
-    * @param callback The {@link IDreamOverlayCallback} for requesting actions such as exiting the
-    *                dream.
-    * @param dreamComponent The component name of the dream service requesting overlay.
-    * @param shouldShowComplications Whether the dream overlay should show complications, e.g. clock
-    *                and weather.
+    * Retrieves a client the caller can use to interact with the dream overlay.
     */
-    void startDream(in LayoutParams params, in IDreamOverlayCallback callback,
-        in String dreamComponent, in boolean shouldShowComplications);
-
-    /** Called when the dream is waking, to do any exit animations */
-    void wakeUp();
-
-    /** Called when the dream has ended. */
-    void endDream();
+    void getClient(in IDreamOverlayClientCallback callback);
 }

core/java/android/service/dreams/IDreamOverlayClient.aidl

@@ -0,0 +1,45 @@
+/**
+ * Copyright (c) 2023, 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.service.dreams;
+
+import android.service.dreams.IDreamOverlayCallback;
+import android.view.WindowManager.LayoutParams;
+
+/**
+* {@link IDreamOverlayClient} allows {@link DreamService} instances to act upon the dream overlay.
+*
+* @hide
+*/
+interface IDreamOverlayClient {
+    /**
+    * @param params The {@link LayoutParams} for the associated DreamWindow, including the window
+                    token of the Dream Activity.
+    * @param callback The {@link IDreamOverlayCallback} for requesting actions such as exiting the
+    *                dream.
+    * @param dreamComponent The component name of the dream service requesting overlay.
+    * @param shouldShowComplications Whether the dream overlay should show complications, e.g. clock
+    *                and weather.
+    */
+    void startDream(in LayoutParams params, in IDreamOverlayCallback callback,
+        in String dreamComponent, in boolean shouldShowComplications);
+
+    /** Called when the dream is waking, to do any exit animations */
+    void wakeUp();
+
+    /** Called when the dream has ended. */
+    void endDream();
+}

core/java/android/service/dreams/IDreamOverlayClientCallback.aidl

@@ -0,0 +1,30 @@
+/**
+ * Copyright (c) 2023, 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.service.dreams;
+
+import android.service.dreams.IDreamOverlayClient;
+
+/**
+* {@link IDreamOverlayClientCallback} allows receiving a requested {@link IDreamOverlayClient}.
+* @hide
+*/
+interface IDreamOverlayClientCallback {
+    /**
+    * Called with a unique {@link IDreamOverlayClient}.
+    */
+    void onDreamOverlayClient(in IDreamOverlayClient client);
+}

packages/SystemUI/tests/src/com/android/systemui/dreams/DreamOverlayServiceTest.java

@@ -31,6 +31,8 @@ import android.os.IBinder;
 import android.os.RemoteException;
 import android.service.dreams.IDreamOverlay;
 import android.service.dreams.IDreamOverlayCallback;
+import android.service.dreams.IDreamOverlayClient;
+import android.service.dreams.IDreamOverlayClientCallback;
 import android.testing.AndroidTestingRunner;
 import android.view.View;
 import android.view.ViewGroup;
@@ -61,6 +63,7 @@ import org.junit.runner.RunWith;
 import org.mockito.ArgumentCaptor;
 import org.mockito.Captor;
 import org.mockito.Mock;
+import org.mockito.Mockito;
 import org.mockito.MockitoAnnotations;
 
 @SmallTest
@@ -189,13 +192,25 @@ public class DreamOverlayServiceTest extends SysuiTestCase {
                 mDreamOverlayCallbackController);
     }
 
-    @Test
-    public void testOnStartMetricsLogged() throws Exception {
+    public IDreamOverlayClient getClient() throws RemoteException {
         final IBinder proxy = mService.onBind(new Intent());
         final IDreamOverlay overlay = IDreamOverlay.Stub.asInterface(proxy);
+        final IDreamOverlayClientCallback callback =
+                Mockito.mock(IDreamOverlayClientCallback.class);
+        overlay.getClient(callback);
+        final ArgumentCaptor<IDreamOverlayClient> clientCaptor =
+                ArgumentCaptor.forClass(IDreamOverlayClient.class);
+        verify(callback).onDreamOverlayClient(clientCaptor.capture());
+
+        return clientCaptor.getValue();
+    }
+
+    @Test
+    public void testOnStartMetricsLogged() throws Exception {
+        final IDreamOverlayClient client = getClient();
 
         // Inform the overlay service of dream starting.
-        overlay.startDream(mWindowParams, mDreamOverlayCallback, DREAM_COMPONENT,
+        client.startDream(mWindowParams, mDreamOverlayCallback, DREAM_COMPONENT,
                 false /*shouldShowComplication*/);
         mMainExecutor.runAllReady();
 
@@ -206,11 +221,10 @@ public class DreamOverlayServiceTest extends SysuiTestCase {
 
     @Test
     public void testOverlayContainerViewAddedToWindow() throws Exception {
-        final IBinder proxy = mService.onBind(new Intent());
-        final IDreamOverlay overlay = IDreamOverlay.Stub.asInterface(proxy);
+        final IDreamOverlayClient client = getClient();
 
         // Inform the overlay service of dream starting.
-        overlay.startDream(mWindowParams, mDreamOverlayCallback, DREAM_COMPONENT,
+        client.startDream(mWindowParams, mDreamOverlayCallback, DREAM_COMPONENT,
                 false /*shouldShowComplication*/);
         mMainExecutor.runAllReady();
 
@@ -219,11 +233,10 @@ public class DreamOverlayServiceTest extends SysuiTestCase {
 
     @Test
     public void testDreamOverlayContainerViewControllerInitialized() throws Exception {
-        final IBinder proxy = mService.onBind(new Intent());
-        final IDreamOverlay overlay = IDreamOverlay.Stub.asInterface(proxy);
+        final IDreamOverlayClient client = getClient();
 
         // Inform the overlay service of dream starting.
-        overlay.startDream(mWindowParams, mDreamOverlayCallback, DREAM_COMPONENT,
+        client.startDream(mWindowParams, mDreamOverlayCallback, DREAM_COMPONENT,
                 false /*shouldShowComplication*/);
         mMainExecutor.runAllReady();
 
@@ -237,11 +250,10 @@ public class DreamOverlayServiceTest extends SysuiTestCase {
                 .thenReturn(mDreamOverlayContainerViewParent)
                 .thenReturn(null);
 
-        final IBinder proxy = mService.onBind(new Intent());
-        final IDreamOverlay overlay = IDreamOverlay.Stub.asInterface(proxy);
+        final IDreamOverlayClient client = getClient();
 
         // Inform the overlay service of dream starting.
-        overlay.startDream(mWindowParams, mDreamOverlayCallback, DREAM_COMPONENT,
+        client.startDream(mWindowParams, mDreamOverlayCallback, DREAM_COMPONENT,
                 false /*shouldShowComplication*/);
         mMainExecutor.runAllReady();
 
@@ -250,11 +262,10 @@ public class DreamOverlayServiceTest extends SysuiTestCase {
 
     @Test
     public void testShouldShowComplicationsSetByStartDream() throws RemoteException {
-        final IBinder proxy = mService.onBind(new Intent());
-        final IDreamOverlay overlay = IDreamOverlay.Stub.asInterface(proxy);
+        final IDreamOverlayClient client = getClient();
 
         // Inform the overlay service of dream starting.
-        overlay.startDream(mWindowParams, mDreamOverlayCallback, DREAM_COMPONENT,
+        client.startDream(mWindowParams, mDreamOverlayCallback, DREAM_COMPONENT,
                 true /*shouldShowComplication*/);
 
         assertThat(mService.shouldShowComplications()).isTrue();
@@ -262,11 +273,10 @@ public class DreamOverlayServiceTest extends SysuiTestCase {
 
     @Test
     public void testLowLightSetByStartDream() throws RemoteException {
-        final IBinder proxy = mService.onBind(new Intent());
-        final IDreamOverlay overlay = IDreamOverlay.Stub.asInterface(proxy);
+        final IDreamOverlayClient client = getClient();
 
         // Inform the overlay service of dream starting.
-        overlay.startDream(mWindowParams, mDreamOverlayCallback,
+        client.startDream(mWindowParams, mDreamOverlayCallback,
                 LOW_LIGHT_COMPONENT.flattenToString(), false /*shouldShowComplication*/);
         mMainExecutor.runAllReady();
 
@@ -276,11 +286,10 @@ public class DreamOverlayServiceTest extends SysuiTestCase {
 
     @Test
     public void testOnEndDream() throws RemoteException {
-        final IBinder proxy = mService.onBind(new Intent());
-        final IDreamOverlay overlay = IDreamOverlay.Stub.asInterface(proxy);
+        final IDreamOverlayClient client = getClient();
 
         // Inform the overlay service of dream starting.
-        overlay.startDream(mWindowParams, mDreamOverlayCallback,
+        client.startDream(mWindowParams, mDreamOverlayCallback,
                 LOW_LIGHT_COMPONENT.flattenToString(), false /*shouldShowComplication*/);
         mMainExecutor.runAllReady();
 
@@ -302,11 +311,10 @@ public class DreamOverlayServiceTest extends SysuiTestCase {
 
     @Test
     public void testDestroy() throws RemoteException {
-        final IBinder proxy = mService.onBind(new Intent());
-        final IDreamOverlay overlay = IDreamOverlay.Stub.asInterface(proxy);
+        final IDreamOverlayClient client = getClient();
 
         // Inform the overlay service of dream starting.
-        overlay.startDream(mWindowParams, mDreamOverlayCallback,
+        client.startDream(mWindowParams, mDreamOverlayCallback,
                 LOW_LIGHT_COMPONENT.flattenToString(), false /*shouldShowComplication*/);
         mMainExecutor.runAllReady();
 
@@ -346,15 +354,14 @@ public class DreamOverlayServiceTest extends SysuiTestCase {
 
     @Test
     public void testDecorViewNotAddedToWindowAfterDestroy() throws Exception {
-        final IBinder proxy = mService.onBind(new Intent());
-        final IDreamOverlay overlay = IDreamOverlay.Stub.asInterface(proxy);
+        final IDreamOverlayClient client = getClient();
 
         // Destroy the service.
         mService.onDestroy();
         mMainExecutor.runAllReady();
 
         // Inform the overlay service of dream starting.
-        overlay.startDream(mWindowParams, mDreamOverlayCallback, DREAM_COMPONENT,
+        client.startDream(mWindowParams, mDreamOverlayCallback, DREAM_COMPONENT,
                 false /*shouldShowComplication*/);
         mMainExecutor.runAllReady();
 
@@ -372,11 +379,10 @@ public class DreamOverlayServiceTest extends SysuiTestCase {
 
     @Test
     public void testResetCurrentOverlayWhenConnectedToNewDream() throws RemoteException {
-        final IBinder proxy = mService.onBind(new Intent());
-        final IDreamOverlay overlay = IDreamOverlay.Stub.asInterface(proxy);
+        final IDreamOverlayClient client = getClient();
 
         // Inform the overlay service of dream starting. Do not show dream complications.
-        overlay.startDream(mWindowParams, mDreamOverlayCallback, DREAM_COMPONENT,
+        client.startDream(mWindowParams, mDreamOverlayCallback, DREAM_COMPONENT,
                 false /*shouldShowComplication*/);
         mMainExecutor.runAllReady();
 
@@ -393,7 +399,7 @@ public class DreamOverlayServiceTest extends SysuiTestCase {
         // New dream starting with dream complications showing. Note that when a new dream is
         // binding to the dream overlay service, it receives the same instance of IBinder as the
         // first one.
-        overlay.startDream(mWindowParams, mDreamOverlayCallback, DREAM_COMPONENT,
+        client.startDream(mWindowParams, mDreamOverlayCallback, DREAM_COMPONENT,
                 true /*shouldShowComplication*/);
         mMainExecutor.runAllReady();
 
@@ -412,11 +418,10 @@ public class DreamOverlayServiceTest extends SysuiTestCase {
 
     @Test
     public void testWakeUp() throws RemoteException {
-        final IBinder proxy = mService.onBind(new Intent());
-        final IDreamOverlay overlay = IDreamOverlay.Stub.asInterface(proxy);
+        final IDreamOverlayClient client = getClient();
 
         // Inform the overlay service of dream starting.
-        overlay.startDream(mWindowParams, mDreamOverlayCallback, DREAM_COMPONENT,
+        client.startDream(mWindowParams, mDreamOverlayCallback, DREAM_COMPONENT,
                 true /*shouldShowComplication*/);
         mMainExecutor.runAllReady();
 

services/tests/servicestests/src/com/android/server/dreams/DreamOverlayServiceTest.java

@@ -0,0 +1,175 @@
+/*
+ * Copyright (C) 2023 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package com.android.server.dreams;
+
+import static com.google.common.truth.Truth.assertThat;
+
+import static org.mockito.Mockito.never;
+import static org.mockito.Mockito.verify;
+
+import android.content.ComponentName;
+import android.content.Intent;
+import android.os.IBinder;
+import android.os.RemoteException;
+import android.service.dreams.DreamOverlayService;
+import android.service.dreams.IDreamOverlay;
+import android.service.dreams.IDreamOverlayCallback;
+import android.service.dreams.IDreamOverlayClient;
+import android.service.dreams.IDreamOverlayClientCallback;
+import android.view.WindowManager;
+
+import androidx.annotation.NonNull;
+import androidx.test.filters.SmallTest;
+import androidx.test.runner.AndroidJUnit4;
+
+import org.junit.Before;
+import org.junit.Test;
+import org.junit.runner.RunWith;
+import org.mockito.Mock;
+import org.mockito.Mockito;
+import org.mockito.MockitoAnnotations;
+
+/**
+ * A collection of tests to exercise {@link DreamOverlayService}.
+ */
+@SmallTest
+@RunWith(AndroidJUnit4.class)
+public class DreamOverlayServiceTest {
+    private static final ComponentName FIRST_DREAM_COMPONENT =
+            ComponentName.unflattenFromString("com.foo.bar/.DreamService");
+    private static final ComponentName SECOND_DREAM_COMPONENT =
+            ComponentName.unflattenFromString("com.foo.baz/.DreamService");
+
+    @Mock
+    WindowManager.LayoutParams mLayoutParams;
+
+    @Mock
+    IDreamOverlayCallback mOverlayCallback;
+
+    /**
+     * {@link TestDreamOverlayService} is a simple {@link DreamOverlayService} implementation for
+     * tracking interactions across {@link IDreamOverlay} binder interface. The service reports
+     * interactions to a {@link Monitor} instance provided at construction.
+     */
+    private static class TestDreamOverlayService extends DreamOverlayService {
+        /**
+         * An interface implemented to be informed when the corresponding methods in
+         * {@link TestDreamOverlayService} are invoked.
+         */
+        interface Monitor {
+            void onStartDream();
+            void onEndDream();
+            void onWakeUp();
+        }
+
+        private final Monitor mMonitor;
+
+        TestDreamOverlayService(Monitor monitor) {
+            super();
+            mMonitor = monitor;
+        }
+
+        @Override
+        public void onStartDream(@NonNull WindowManager.LayoutParams layoutParams) {
+            mMonitor.onStartDream();
+        }
+
+        @Override
+        public void onEndDream() {
+            mMonitor.onEndDream();
+            super.onEndDream();
+        }
+
+        @Override
+        public void onWakeUp(@NonNull Runnable onCompleteCallback) {
+            mMonitor.onWakeUp();
+            super.onWakeUp(onCompleteCallback);
+        }
+    }
+
+    /**
+     * A {@link IDreamOverlayClientCallback} implementation that captures the requested client.
+     */
+    private static class OverlayClientCallback extends IDreamOverlayClientCallback.Stub {
+        public IDreamOverlayClient retrievedClient;
+        @Override
+        public void onDreamOverlayClient(IDreamOverlayClient client) throws RemoteException {
+            retrievedClient = client;
+        }
+    }
+
+    @Before
+    public void setup() {
+        MockitoAnnotations.initMocks(this);
+    }
+
+    /**
+     * Verifies that only the currently started dream is able to affect the overlay.
+     */
+    @Test
+    public void testOverlayClientInteraction() throws RemoteException {
+        final TestDreamOverlayService.Monitor monitor = Mockito.mock(
+                TestDreamOverlayService.Monitor.class);
+        final TestDreamOverlayService service = new TestDreamOverlayService(monitor);
+        final IBinder binder = service.onBind(new Intent());
+        final IDreamOverlay overlay = IDreamOverlay.Stub.asInterface(binder);
+
+        // Create two overlay clients and ensure they are unique.
+        final IDreamOverlayClient firstClient = getClient(overlay);
+        assertThat(firstClient).isNotNull();
+
+        final IDreamOverlayClient secondClient = getClient(overlay);
+        assertThat(secondClient).isNotNull();
+
+        assertThat(firstClient).isNotEqualTo(secondClient);
+
+        // Start a dream with the first client and ensure the dream is now active from the
+        // overlay's perspective.
+        firstClient.startDream(mLayoutParams, mOverlayCallback,
+                FIRST_DREAM_COMPONENT.flattenToString(), false);
+
+
+        verify(monitor).onStartDream();
+        assertThat(service.getDreamComponent()).isEqualTo(FIRST_DREAM_COMPONENT);
+
+        Mockito.clearInvocations(monitor);
+
+        // Start a dream from the second client and verify that the overlay has both cycled to
+        // the new dream (ended/started).
+        secondClient.startDream(mLayoutParams, mOverlayCallback,
+                SECOND_DREAM_COMPONENT.flattenToString(), false);
+
+        verify(monitor).onEndDream();
+        verify(monitor).onStartDream();
+        assertThat(service.getDreamComponent()).isEqualTo(SECOND_DREAM_COMPONENT);
+
+        Mockito.clearInvocations(monitor);
+
+        // Verify that interactions with the first, now inactive client don't affect the overlay.
+        firstClient.endDream();
+        verify(monitor, never()).onEndDream();
+
+        firstClient.wakeUp();
+        verify(monitor, never()).onWakeUp();
+    }
+
+    private static IDreamOverlayClient getClient(IDreamOverlay overlay) throws RemoteException {
+        final OverlayClientCallback callback = new OverlayClientCallback();
+        overlay.getClient(callback);
+        return callback.retrievedClient;
+    }
+}