From e436804466a5d5beb62b4df688c56c19ffeff65c Mon Sep 17 00:00:00 2001
From: Aaron Huang <huangaaron@google.com>
Date: Wed, 20 May 2020 15:21:28 +0800
Subject: [PATCH] Dynamically enable/disable watch for RAT type changes

Add ContentObserver to observe the status of
NETSTATS_COMBINE_SUBTYPE_ENABLED to determine that
NetworkStatsSubscriptionsMonitor start or stop
monitoring data usage per RAT type changes.

Bug: 154080515
Test: atest NetworkStatsServiceTest#testDynamicWatchForNetworkRatTypeChanges
Change-Id: I272d589633c9186b45753228b05aa0b40b7c7b89
---
 .../server/net/NetworkStatsService.java       | 42 ++++++++++++++++---
 1 file changed, 37 insertions(+), 5 deletions(-)

diff --git a/services/core/java/com/android/server/net/NetworkStatsService.java b/services/core/java/com/android/server/net/NetworkStatsService.java
index ba538e1cd8..6e01592c51 100644
--- a/services/core/java/com/android/server/net/NetworkStatsService.java
+++ b/services/core/java/com/android/server/net/NetworkStatsService.java
@@ -87,6 +87,7 @@ import android.content.Intent;
 import android.content.IntentFilter;
 import android.content.pm.ApplicationInfo;
 import android.content.pm.PackageManager;
+import android.database.ContentObserver;
 import android.net.DataUsageRequest;
 import android.net.INetworkManagementEventObserver;
 import android.net.INetworkStatsService;
@@ -103,6 +104,7 @@ import android.net.NetworkStats.NonMonotonicObserver;
 import android.net.NetworkStatsHistory;
 import android.net.NetworkTemplate;
 import android.net.TrafficStats;
+import android.net.Uri;
 import android.net.netstats.provider.INetworkStatsProvider;
 import android.net.netstats.provider.INetworkStatsProviderCallback;
 import android.net.netstats.provider.NetworkStatsProvider;
@@ -213,6 +215,9 @@ public class NetworkStatsService extends INetworkStatsService.Stub {
 
     private final boolean mUseBpfTrafficStats;
 
+    private final ContentObserver mContentObserver;
+    private final ContentResolver mContentResolver;
+
     @VisibleForTesting
     public static final String ACTION_NETWORK_STATS_POLL =
             "com.android.server.action.NETWORK_STATS_POLL";
@@ -438,6 +443,9 @@ public class NetworkStatsService extends INetworkStatsService.Stub {
         mHandler = new NetworkStatsHandler(handlerThread.getLooper());
         mNetworkStatsSubscriptionsMonitor = deps.makeSubscriptionsMonitor(mContext,
                 new HandlerExecutor(mHandler), this);
+        mContentResolver = mContext.getContentResolver();
+        mContentObserver = mDeps.makeContentObserver(mHandler, mSettings,
+                mNetworkStatsSubscriptionsMonitor);
     }
 
     /**
@@ -466,6 +474,25 @@ public class NetworkStatsService extends INetworkStatsService.Stub {
             return new NetworkStatsSubscriptionsMonitor(context, executor, (subscriberId, type) ->
                     service.handleOnCollapsedRatTypeChanged());
         }
+
+        /**
+         * Create a ContentObserver instance which is used to observe settings changes,
+         * and dispatch onChange events on handler thread.
+         */
+        public @NonNull ContentObserver makeContentObserver(@NonNull Handler handler,
+                @NonNull NetworkStatsSettings settings,
+                @NonNull NetworkStatsSubscriptionsMonitor monitor) {
+            return new ContentObserver(handler) {
+                @Override
+                public void onChange(boolean selfChange, @NonNull Uri uri) {
+                    if (!settings.getCombineSubtypeEnabled()) {
+                        monitor.start();
+                    } else {
+                        monitor.stop();
+                    }
+                }
+            };
+        }
     }
 
     private void registerLocalService() {
@@ -530,11 +557,14 @@ public class NetworkStatsService extends INetworkStatsService.Stub {
         mAlarmManager.setInexactRepeating(AlarmManager.ELAPSED_REALTIME, currentRealtime,
                 mSettings.getPollInterval(), pollIntent);
 
-        // TODO: listen to settings changed to support dynamically enable/disable.
-        // watch for networkType changes
-        if (!mSettings.getCombineSubtypeEnabled()) {
-            mNetworkStatsSubscriptionsMonitor.start();
-        }
+        mContentResolver.registerContentObserver(Settings.Global
+                .getUriFor(Settings.Global.NETSTATS_COMBINE_SUBTYPE_ENABLED),
+                        false /* notifyForDescendants */, mContentObserver);
+
+        // Post a runnable on handler thread to call onChange(). It's for getting current value of
+        // NETSTATS_COMBINE_SUBTYPE_ENABLED to decide start or stop monitoring RAT type changes.
+        mHandler.post(() -> mContentObserver.onChange(false, Settings.Global
+                .getUriFor(Settings.Global.NETSTATS_COMBINE_SUBTYPE_ENABLED)));
 
         registerGlobalAlert();
     }
@@ -560,6 +590,8 @@ public class NetworkStatsService extends INetworkStatsService.Stub {
             mNetworkStatsSubscriptionsMonitor.stop();
         }
 
+        mContentResolver.unregisterContentObserver(mContentObserver);
+
         final long currentTime = mClock.millis();
 
         // persist any pending stats