Merge "Manage scan requests in MediaRouter2Manager"

media/java/android/media/MediaRouter2.java

@@ -48,6 +48,7 @@ import java.util.Objects;
 import java.util.Set;
 import java.util.concurrent.CopyOnWriteArrayList;
 import java.util.concurrent.Executor;
+import java.util.concurrent.atomic.AtomicBoolean;
 import java.util.concurrent.atomic.AtomicInteger;
 import java.util.stream.Collectors;
 
@@ -124,6 +125,7 @@ public final class MediaRouter2 {
     private final Map<String, RoutingController> mNonSystemRoutingControllers = new ArrayMap<>();
 
     private final AtomicInteger mNextRequestId = new AtomicInteger(1);
+    private final AtomicBoolean mIsScanning = new AtomicBoolean(/* initialValue= */ false);
 
     final Handler mHandler;
 
@@ -255,7 +257,9 @@ public final class MediaRouter2 {
     @RequiresPermission(Manifest.permission.MEDIA_CONTENT_CONTROL)
     public void startScan() {
         if (isSystemRouter()) {
-            sManager.startScan();
+            if (!mIsScanning.getAndSet(true)) {
+                sManager.registerScanRequest();
+            }
         }
     }
 
@@ -281,7 +285,9 @@ public final class MediaRouter2 {
     @RequiresPermission(Manifest.permission.MEDIA_CONTENT_CONTROL)
     public void stopScan() {
         if (isSystemRouter()) {
-            sManager.stopScan();
+            if (mIsScanning.getAndSet(false)) {
+                sManager.unregisterScanRequest();
+            }
         }
     }
 

media/java/android/media/MediaRouter2Manager.java

@@ -82,6 +82,7 @@ public final class MediaRouter2Manager {
     @GuardedBy("sLock")
     private Client mClient;
     private final IMediaRouterService mMediaRouterService;
+    private final AtomicInteger mScanRequestCount = new AtomicInteger(/* initialValue= */ 0);
     final Handler mHandler;
     final CopyOnWriteArrayList<CallbackRecord> mCallbackRecords = new CopyOnWriteArrayList<>();
 
@@ -155,20 +156,17 @@ public final class MediaRouter2Manager {
     }
 
     /**
-     * Starts scanning remote routes.
-     * <p>
-     * Route discovery can happen even when the {@link #startScan()} is not called.
-     * This is because the scanning could be started before by other apps.
-     * Therefore, calling this method after calling {@link #stopScan()} does not necessarily mean
-     * that the routes found before are removed and added again.
-     * <p>
-     * Use {@link Callback} to get the route related events.
-     * <p>
-     * @see #stopScan()
+     * Registers a request to scan for remote routes.
+     *
+     * <p>Increases the count of active scanning requests. When the count transitions from zero to
+     * one, sends a request to the system server to start scanning.
+     *
+     * <p>Clients must {@link #unregisterScanRequest() unregister their scan requests} when scanning
+     * is no longer needed, to avoid unnecessary resource usage.
      */
-    public void startScan() {
-        Client client = getOrCreateClient();
-        if (client != null) {
+    public void registerScanRequest() {
+        if (mScanRequestCount.getAndIncrement() == 0) {
+            Client client = getOrCreateClient();
             try {
                 mMediaRouterService.startScan(client);
             } catch (RemoteException ex) {
@@ -178,21 +176,25 @@ public final class MediaRouter2Manager {
     }
 
     /**
-     * Stops scanning remote routes to reduce resource consumption.
-     * <p>
-     * Route discovery can be continued even after this method is called.
-     * This is because the scanning is only turned off when all the apps stop scanning.
-     * Therefore, calling this method does not necessarily mean the routes are removed.
-     * Also, for the same reason it does not mean that {@link Callback#onRoutesAdded(List)}
-     * is not called afterwards.
-     * <p>
-     * Use {@link Callback} to get the route related events.
+     * Unregisters a scan request made by {@link #registerScanRequest()}.
      *
-     * @see #startScan()
+     * <p>Decreases the count of active scanning requests. When the count transitions from one to
+     * zero, sends a request to the system server to stop scanning.
+     *
+     * @throws IllegalStateException If called while there are no active scan requests.
      */
-    public void stopScan() {
-        Client client = getOrCreateClient();
-        if (client != null) {
+    public void unregisterScanRequest() {
+        if (mScanRequestCount.updateAndGet(
+                count -> {
+                    if (count == 0) {
+                        throw new IllegalStateException(
+                                "No active scan requests to unregister.");
+                    } else {
+                        return --count;
+                    }
+                })
+                == 0) {
+            Client client = getOrCreateClient();
             try {
                 mMediaRouterService.stopScan(client);
             } catch (RemoteException ex) {

media/tests/MediaRouter/src/com/android/mediaroutertest/MediaRouter2ManagerTest.java

@@ -39,6 +39,7 @@ import static org.junit.Assert.assertEquals;
 import static org.junit.Assert.assertFalse;
 import static org.junit.Assert.assertNotNull;
 import static org.junit.Assert.assertNull;
+import static org.junit.Assert.assertThrows;
 import static org.junit.Assert.assertTrue;
 
 import android.Manifest;
@@ -121,7 +122,7 @@ public class MediaRouter2ManagerTest {
         MediaRouter2ManagerTestActivity.startActivity(mContext);
 
         mManager = MediaRouter2Manager.getInstance(mContext);
-        mManager.startScan();
+        mManager.registerScanRequest();
         mRouter2 = MediaRouter2.getInstance(mContext);
 
         // If we need to support thread pool executors, change this to thread pool executor.
@@ -152,7 +153,7 @@ public class MediaRouter2ManagerTest {
 
     @After
     public void tearDown() {
-        mManager.stopScan();
+        mManager.unregisterScanRequest();
 
         // order matters (callbacks should be cleared at the last)
         releaseAllSessions();
@@ -818,6 +819,13 @@ public class MediaRouter2ManagerTest {
         assertFalse(failureLatch.await(WAIT_TIME_MS, TimeUnit.MILLISECONDS));
     }
 
+    @Test
+    public void unregisterScanRequest_enforcesANonNegativeCount() {
+        mManager.unregisterScanRequest(); // One request was made in the test setup.
+        assertThrows(IllegalStateException.class, () -> mManager.unregisterScanRequest());
+        mManager.registerScanRequest(); // So that the cleanup doesn't fail.
+    }
+
     /**
      * Tests if getSelectableRoutes and getDeselectableRoutes filter routes based on
      * selected routes

packages/SettingsLib/src/com/android/settingslib/media/InfoMediaManager.java

@@ -92,14 +92,14 @@ public class InfoMediaManager extends MediaManager {
     public void startScan() {
         mMediaDevices.clear();
         mRouterManager.registerCallback(mExecutor, mMediaRouterCallback);
-        mRouterManager.startScan();
+        mRouterManager.registerScanRequest();
         refreshDevices();
     }
 
     @Override
     public void stopScan() {
         mRouterManager.unregisterCallback(mMediaRouterCallback);
-        mRouterManager.stopScan();
+        mRouterManager.unregisterScanRequest();
     }
 
     /**