Add Stub implementation for DreamOverlayService.

This changelist introduces a stub implementation for
DreamOverlayService for test purposes. It also allows
DreamManager to set the DreamOverlay.

Bug: 204890435
Test: atest DreamOverlayTest
Change-Id: Ia59e70d08f76d5928e72e815c990195934292ad5

core/api/test-current.txt

@@ -257,7 +257,8 @@ package android.app {
 
   public class DreamManager {
     method @RequiresPermission(android.Manifest.permission.READ_DREAM_STATE) public boolean isDreaming();
-    method @RequiresPermission(android.Manifest.permission.WRITE_DREAM_STATE) public void setActiveDream(@NonNull android.content.ComponentName);
+    method @RequiresPermission(android.Manifest.permission.WRITE_DREAM_STATE) public void setActiveDream(@Nullable android.content.ComponentName);
+    method @RequiresPermission(android.Manifest.permission.WRITE_DREAM_STATE) public void setDreamOverlay(@Nullable android.content.ComponentName);
     method @RequiresPermission(android.Manifest.permission.WRITE_DREAM_STATE) public void startDream(@NonNull android.content.ComponentName);
     method @RequiresPermission(android.Manifest.permission.WRITE_DREAM_STATE) public void stopDream();
   }
@@ -2364,6 +2365,17 @@ package android.service.autofill.augmented {
 
 }
 
+package android.service.dreams {
+
+  public abstract class DreamOverlayService extends android.app.Service {
+    ctor public DreamOverlayService();
+    method @Nullable public final android.os.IBinder onBind(@NonNull android.content.Intent);
+    method public abstract void onStartDream(@NonNull android.view.WindowManager.LayoutParams);
+    method public final void requestExit();
+  }
+
+}
+
 package android.service.notification {
 
   @Deprecated public abstract class ConditionProviderService extends android.app.Service {

core/java/android/app/DreamManager.java

@@ -17,6 +17,7 @@
 package android.app;
 
 import android.annotation.NonNull;
+import android.annotation.Nullable;
 import android.annotation.RequiresPermission;
 import android.annotation.SystemService;
 import android.annotation.TestApi;
@@ -91,10 +92,30 @@ public class DreamManager {
     @TestApi
     @UserHandleAware
     @RequiresPermission(android.Manifest.permission.WRITE_DREAM_STATE)
-    public void setActiveDream(@NonNull ComponentName dreamComponent) {
+    public void setActiveDream(@Nullable ComponentName dreamComponent) {
         ComponentName[] dreams = {dreamComponent};
+
         try {
-            mService.setDreamComponentsForUser(mContext.getUserId(), dreams);
+            mService.setDreamComponentsForUser(mContext.getUserId(),
+                    dreamComponent != null ? dreams : null);
+        } catch (RemoteException e) {
+            e.rethrowFromSystemServer();
+        }
+    }
+
+    /**
+     * Sets the active dream on the device to be "dreamComponent".
+     *
+     * <p>This is only used for testing the dream service APIs.
+     *
+     * @hide
+     */
+    @TestApi
+    @UserHandleAware
+    @RequiresPermission(android.Manifest.permission.WRITE_DREAM_STATE)
+    public void setDreamOverlay(@Nullable ComponentName dreamOverlayComponent) {
+        try {
+            mService.registerDreamOverlayService(dreamOverlayComponent);
         } catch (RemoteException e) {
             e.rethrowFromSystemServer();
         }

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

@@ -0,0 +1,77 @@
+/*
+ * Copyright (C) 2021 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.annotation.NonNull;
+import android.annotation.Nullable;
+import android.annotation.TestApi;
+import android.app.Service;
+import android.content.Intent;
+import android.os.IBinder;
+import android.os.RemoteException;
+import android.util.Log;
+import android.view.WindowManager;
+
+
+/**
+ * Basic implementation of for {@link IDreamOverlay} for testing.
+ * @hide
+ */
+@TestApi
+public abstract class DreamOverlayService extends Service {
+    private static final String TAG = "DreamOverlayService";
+    private static final boolean DEBUG = false;
+
+    private IDreamOverlay mDreamOverlay = new IDreamOverlay.Stub() {
+        @Override
+        public void startDream(WindowManager.LayoutParams layoutParams,
+                IDreamOverlayCallback callback) {
+            mDreamOverlayCallback = callback;
+            onStartDream(layoutParams);
+        }
+    };
+
+    IDreamOverlayCallback mDreamOverlayCallback;
+
+    public DreamOverlayService() {
+    }
+
+    @Nullable
+    @Override
+    public final IBinder onBind(@NonNull Intent intent) {
+        return mDreamOverlay.asBinder();
+    }
+
+    /**
+     * This method is overridden by implementations to handle when the dream has started and the
+     * window is ready to be interacted with.
+     * @param layoutParams The {@link android.view.WindowManager.LayoutParams} associated with the
+     *                     dream window.
+     */
+    public abstract void onStartDream(@NonNull WindowManager.LayoutParams layoutParams);
+
+    /**
+     * 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);
+        }
+    }
+}