Listener to tether state change on Network & internet page.

User can navigates to the page and turn hotspot on or off from the quick
settings. Need to listen to the tether state updates to refresh the
summary for the Hotspot & tethering preference accordingly.

Change-Id: I7c6869b909306b09556e19cf7b7543ce9dcd890e
Fix: 38452559
Test: make RunSettingsRoboTests

src/com/android/settings/network/TetherPreferenceController.java

@@ -18,7 +18,10 @@ package com.android.settings.network;
 import android.bluetooth.BluetoothAdapter;
 import android.bluetooth.BluetoothPan;
 import android.bluetooth.BluetoothProfile;
+import android.content.BroadcastReceiver;
 import android.content.Context;
+import android.content.Intent;
+import android.content.IntentFilter;
 import android.database.ContentObserver;
 import android.net.ConnectivityManager;
 import android.net.Uri;
@@ -67,6 +70,7 @@ public class TetherPreferenceController extends PreferenceController
 
     private SettingObserver mAirplaneModeObserver;
     private Preference mPreference;
+    private TetherBroadcastReceiver mTetherReceiver;
 
     @VisibleForTesting(otherwise = VisibleForTesting.NONE)
     TetherPreferenceController() {
@@ -131,6 +135,11 @@ public class TetherPreferenceController extends PreferenceController
         if (mAirplaneModeObserver == null) {
             mAirplaneModeObserver = new SettingObserver();
         }
+        if (mTetherReceiver == null) {
+            mTetherReceiver = new TetherBroadcastReceiver();
+        }
+        mContext.registerReceiver(
+            mTetherReceiver, new IntentFilter(ConnectivityManager.ACTION_TETHER_STATE_CHANGED));
         mContext.getContentResolver()
                 .registerContentObserver(mAirplaneModeObserver.uri, false, mAirplaneModeObserver);
     }
@@ -140,6 +149,9 @@ public class TetherPreferenceController extends PreferenceController
         if (mAirplaneModeObserver != null) {
             mContext.getContentResolver().unregisterContentObserver(mAirplaneModeObserver);
         }
+        if (mTetherReceiver != null) {
+            mContext.unregisterReceiver(mTetherReceiver);
+        }
     }
 
     @Override
@@ -238,4 +250,14 @@ public class TetherPreferenceController extends PreferenceController
             }
         }
     }
+
+    @VisibleForTesting
+    class TetherBroadcastReceiver extends BroadcastReceiver {
+
+        @Override
+        public void onReceive(Context context, Intent intent) {
+            updateSummary();
+        }
+
+    }
 }