Disable sync if Android sync setting is disabled (fixes #588).

src/main/AndroidManifest.xml

@@ -12,6 +12,7 @@
     <uses-permission android:name="android.permission.ACCESS_WIFI_STATE" />
     <uses-permission android:name="android.permission.RECEIVE_BOOT_COMPLETED" />
     <uses-permission android:name="android.permission.WAKE_LOCK" />
+    <uses-permission android:name="android.permission.READ_SYNC_SETTINGS" />
 
     <application
         android:allowBackup="false"

src/main/java/com/nutomic/syncthingandroid/syncthing/DeviceStateHolder.java

@@ -2,6 +2,7 @@ package com.nutomic.syncthingandroid.syncthing;
 
 import android.annotation.TargetApi;
 import android.content.BroadcastReceiver;
+import android.content.ContentResolver;
 import android.content.Context;
 import android.content.Intent;
 import android.content.SharedPreferences;
@@ -103,9 +104,14 @@ public class DeviceStateHolder extends BroadcastReceiver {
         return mWifiSsid;
     }
 
+    /**
+     * Determines if Syncthing should currently run.
+     */
     public boolean shouldRun() {
-        if (SyncthingService.alwaysRunInBackground(mContext)) {
+        if (!ContentResolver.getMasterSyncAutomatically()) {
-            // Always run, ignoring wifi/charging state.
+            return false;
+        }
+        else if (SyncthingService.alwaysRunInBackground(mContext)) {
             return true;
         }
         else {

src/main/java/com/nutomic/syncthingandroid/syncthing/SyncthingService.java

@@ -3,10 +3,12 @@ package com.nutomic.syncthingandroid.syncthing;
 import android.app.NotificationManager;
 import android.app.PendingIntent;
 import android.app.Service;
+import android.content.ContentResolver;
 import android.content.Context;
 import android.content.Intent;
 import android.content.IntentFilter;
 import android.content.SharedPreferences;
+import android.content.SyncStatusObserver;
 import android.os.AsyncTask;
 import android.os.Build;
 import android.os.Environment;
@@ -124,6 +126,13 @@ public class SyncthingService extends Service implements
     private final HashSet<OnApiChangeListener> mOnApiChangeListeners =
             new HashSet<>();
 
+    private final SyncStatusObserver mSyncStatusObserver = new SyncStatusObserver() {
+        @Override
+        public void onStatusChanged(int i) {
+            updateState();
+        }
+    };
+
     /**
      * INIT: Service is starting up and initializing.
      * STARTING: Syncthing binary is starting (but the API is not yet ready).
@@ -314,6 +323,8 @@ public class SyncthingService extends Service implements
         registerReceiver(mDeviceStateHolder, new IntentFilter(Intent.ACTION_BATTERY_CHANGED));
         new StartupTask(sp.getString("gui_user",""), sp.getString("gui_password","")).execute();
         sp.registerOnSharedPreferenceChangeListener(this);
+        ContentResolver.addStatusChangeListener(ContentResolver.SYNC_OBSERVER_TYPE_SETTINGS,
+                                                mSyncStatusObserver);
     }
 
     /**
@@ -420,6 +431,7 @@ public class SyncthingService extends Service implements
 
         SharedPreferences sp = PreferenceManager.getDefaultSharedPreferences(this);
         sp.unregisterOnSharedPreferenceChangeListener(this);
+        ContentResolver.removeStatusChangeListener(mSyncStatusObserver);
     }
 
     private void shutdown() {