Fix the ANR in panel when changing volume continuously

When users open volume panel and keep on changing the volume slider for
a while, the panel starts to defer the slider updating, and finally gets
stuck and causes an ANR.

Root cause:
Volume panel has four volume adjusting slices. Each of them registers
a broadcast receiver to listen to the volume changed and muted events.
However, when the media volume changes, AudioManager will send four
broadcasts (music, assistant, accessibility, tts) to every receiver, and
each of them will reload slice four times. Thus, one media volume
changed event will lead to 16 (4*4) UI updates. Consequently, keeping on
sliding the volume bar will trigger hundreds of broadcasts and UI
updates, which makes the system busy and getting stuck.

Solution:
Introduce a VolumeSliceHelper to integrate the broadcasts of the volume
slices specifically.
1. Only register one broadcast receiver to reduce the broadcast loading
   since the four slices are listening to the same signal.
2. Filter the only one eligible broadcast among the multiple concurrent
   ones, and then relay it to the registered slice.
3. Listen to one more action STREAM_DEVICES_CHANGED_ACTION to update the
   volume panel when audio output device changes.

Test: robotest, visual
Bug: 144134209
Bug: 160489394
Change-Id: I780b9eee35802b19a5f0ab0a7d07bd3e081f5556

src/com/android/settings/slices/CustomSliceRegistry.java

@@ -216,6 +216,16 @@ public class CustomSliceRegistry {
             .appendPath("ring_volume")
             .build();
 
+    /**
+     * Full {@link Uri} for the all volume Slices.
+     */
+    public static final Uri VOLUME_SLICES_URI = new Uri.Builder()
+            .scheme(ContentResolver.SCHEME_CONTENT)
+            .authority(SettingsSliceProvider.SLICE_AUTHORITY)
+            .appendPath(SettingsSlicesContract.PATH_SETTING_ACTION)
+            .appendPath("volume_slices")
+            .build();
+
     /**
      * Full {@link Uri} for the Wifi Calling Slice.
      */

src/com/android/settings/slices/SettingsSliceProvider.java

@@ -47,6 +47,7 @@ import com.android.settings.R;
 import com.android.settings.Utils;
 import com.android.settings.bluetooth.BluetoothSliceBuilder;
 import com.android.settings.core.BasePreferenceController;
+import com.android.settings.notification.VolumeSeekBarPreferenceController;
 import com.android.settings.notification.zen.ZenModeSliceBuilder;
 import com.android.settings.overlay.FeatureFactory;
 import com.android.settingslib.SliceBroadcastRelay;
@@ -184,7 +185,10 @@ public class SettingsSliceProvider extends SliceProvider {
 
     @Override
     public void onSliceUnpinned(Uri sliceUri) {
-        SliceBroadcastRelay.unregisterReceivers(getContext(), sliceUri);
+        final Context context = getContext();
+        if (!VolumeSliceHelper.unregisterUri(context, sliceUri)) {
+            SliceBroadcastRelay.unregisterReceivers(context, sliceUri);
+        }
         ThreadUtils.postOnMainThread(() -> stopBackgroundWorker(sliceUri));
     }
 
@@ -390,7 +394,13 @@ public class SettingsSliceProvider extends SliceProvider {
 
         final IntentFilter filter = controller.getIntentFilter();
         if (filter != null) {
-            registerIntentToUri(filter, uri);
+            if (controller instanceof VolumeSeekBarPreferenceController) {
+                // Register volume slices to a broadcast relay to reduce unnecessary UI updates
+                VolumeSliceHelper.registerIntentToUri(getContext(), filter, uri,
+                        ((VolumeSeekBarPreferenceController) controller).getAudioStream());
+            } else {
+                registerIntentToUri(filter, uri);
+            }
         }
 
         ThreadUtils.postOnMainThread(() -> startBackgroundWorker(controller, uri));

src/com/android/settings/slices/VolumeSliceHelper.java

@@ -0,0 +1,127 @@
+/*
+ * Copyright (C) 2020 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.settings.slices;
+
+import static com.android.settings.slices.CustomSliceRegistry.VOLUME_SLICES_URI;
+
+import android.content.ContentProvider;
+import android.content.Context;
+import android.content.Intent;
+import android.content.IntentFilter;
+import android.media.AudioManager;
+import android.net.Uri;
+import android.util.ArrayMap;
+import android.util.Log;
+
+import androidx.annotation.VisibleForTesting;
+
+import com.android.settingslib.SliceBroadcastRelay;
+
+import java.util.Map;
+
+/**
+ * This helper is to handle the broadcasts of volume slices
+ */
+public class VolumeSliceHelper {
+
+    private static final String TAG = "VolumeSliceHelper";
+
+    @VisibleForTesting
+    static Map<Uri, Integer> sRegisteredUri = new ArrayMap<>();
+    @VisibleForTesting
+    static IntentFilter sIntentFilter;
+
+    static void registerIntentToUri(Context context, IntentFilter intentFilter, Uri sliceUri,
+            int audioStream) {
+        Log.d(TAG, "Registering uri for broadcast relay: " + sliceUri);
+        synchronized (sRegisteredUri) {
+            if (sRegisteredUri.isEmpty()) {
+                SliceBroadcastRelay.registerReceiver(context, VOLUME_SLICES_URI,
+                        VolumeSliceRelayReceiver.class, intentFilter);
+                sIntentFilter = intentFilter;
+            }
+            sRegisteredUri.put(sliceUri, audioStream);
+        }
+    }
+
+    static boolean unregisterUri(Context context, Uri sliceUri) {
+        if (!sRegisteredUri.containsKey(sliceUri)) {
+            return false;
+        }
+
+        Log.d(TAG, "Unregistering uri broadcast relay: " + sliceUri);
+        synchronized (sRegisteredUri) {
+            sRegisteredUri.remove(sliceUri);
+            if (sRegisteredUri.isEmpty()) {
+                sIntentFilter = null;
+                SliceBroadcastRelay.unregisterReceivers(context, VOLUME_SLICES_URI);
+            }
+        }
+        return true;
+    }
+
+    static void onReceive(Context context, Intent intent) {
+        final String action = intent.getAction();
+        if (sIntentFilter == null || action == null || !sIntentFilter.hasAction(action)) {
+            return;
+        }
+
+        final String uriString = intent.getStringExtra(SliceBroadcastRelay.EXTRA_URI);
+        if (uriString == null) {
+            return;
+        }
+
+        final Uri uri = Uri.parse(uriString);
+        if (!VOLUME_SLICES_URI.equals(ContentProvider.getUriWithoutUserId(uri))) {
+            Log.w(TAG, "Invalid uri: " + uriString);
+            return;
+        }
+
+        if (AudioManager.VOLUME_CHANGED_ACTION.equals(action)) {
+            handleVolumeChanged(context, intent);
+        } else if (AudioManager.STREAM_MUTE_CHANGED_ACTION.equals(action)
+                || AudioManager.STREAM_DEVICES_CHANGED_ACTION.equals(action)) {
+            handleStreamChanged(context, intent);
+        } else {
+            notifyAllStreamsChanged(context);
+        }
+    }
+
+    private static void handleVolumeChanged(Context context, Intent intent) {
+        final int vol = intent.getIntExtra(AudioManager.EXTRA_VOLUME_STREAM_VALUE, -1);
+        final int prevVol = intent.getIntExtra(AudioManager.EXTRA_PREV_VOLUME_STREAM_VALUE, -1);
+        if (vol != prevVol) {
+            handleStreamChanged(context, intent);
+        }
+    }
+
+    private static void handleStreamChanged(Context context, Intent intent) {
+        final int inputType = intent.getIntExtra(AudioManager.EXTRA_VOLUME_STREAM_TYPE, -1);
+        for (Map.Entry<Uri, Integer> entry : sRegisteredUri.entrySet()) {
+            if (entry.getValue() == inputType) {
+                context.getContentResolver().notifyChange(entry.getKey(), null /* observer */);
+                break;
+            }
+        }
+    }
+
+    private static void notifyAllStreamsChanged(Context context) {
+        sRegisteredUri.forEach((uri, audioStream) -> {
+            context.getContentResolver().notifyChange(uri, null /* observer */);
+        });
+    }
+}

src/com/android/settings/slices/VolumeSliceRelayReceiver.java

@@ -0,0 +1,32 @@
+/*
+ * Copyright (C) 2020 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.settings.slices;
+
+import android.content.BroadcastReceiver;
+import android.content.Context;
+import android.content.Intent;
+
+/**
+ * Receives broadcasts to notify that Settings volume Slices are potentially stale.
+ */
+public class VolumeSliceRelayReceiver extends BroadcastReceiver {
+
+    @Override
+    public void onReceive(Context context, Intent intent) {
+        VolumeSliceHelper.onReceive(context, intent);
+    }
+}