Added a IntentService to receive Broadcast-Intents to remotely control / configure the app.

MainActivity: Moved binding-functions to onPause() and onResume() so that the SyncThingService is only bound to the activity if the activity is active.

New class AppConfigReceiver:
Support start and stop of the SyncThingService
- restarting a running service again should not be an issue
- stop service only if "always run in background"-mode is disabled. Otherwise show a notification indicating this.

Instrumentation-tests:
- Added tests for AppConfigReceiver
- Extended MockContext to also consume stopService commands.
- testGetReadableTransferRate: Apparently the return-values have changed a bit. Adjusted the asserts to the current return-values.

SycthingService:
Added code for thread-safety in case the service still starting when it should be stopped. Then PollWebGuiAvailableTaskImpl is active and waits for the Synthing-API to become active. So that and onDestroy have to be synchronized.
Added a stopSelf() in PollWebGuiAvailableTaskImpl.onPostExecute() in case mStopScheduled was active.

Commented my change in the javadoc at onDestroy. Put a reference to that comment to .onPostExecution()

src/androidTest/java/com/nutomic/syncthingandroid/test/MockContext.java

@@ -16,6 +16,7 @@ import java.util.List;
 public class MockContext extends ContextWrapper {
 
     private ArrayList<Intent> mReceivedIntents = new ArrayList<>();
+    private ArrayList<Intent> mStopServiceIntents = new ArrayList<>();
 
     /**
      * Use the actual context for calls that aren't easily mocked. May be null if those
@@ -36,10 +37,20 @@ public class MockContext extends ContextWrapper {
         return null;
     }
 
+    @Override
+    public boolean stopService(Intent intent) {
+        mStopServiceIntents.add(intent);
+        return true;
+    }
+
     public List<Intent> getReceivedIntents() {
         return mReceivedIntents;
     }
 
+    public List<Intent> getStopServiceIntents() {
+        return mStopServiceIntents;
+    }
+
     public void clearReceivedIntents() {
         mReceivedIntents.clear();
     }

src/androidTest/java/com/nutomic/syncthingandroid/test/syncthing/AppConfigReceiverTest.java

@@ -0,0 +1,108 @@
+package com.nutomic.syncthingandroid.test.syncthing;
+
+import android.content.Intent;
+import android.preference.PreferenceManager;
+import android.test.AndroidTestCase;
+
+import com.nutomic.syncthingandroid.syncthing.AppConfigReceiver;
+import com.nutomic.syncthingandroid.syncthing.SyncthingService;
+import com.nutomic.syncthingandroid.test.MockContext;
+
+/**
+ * Test the correct behaviour of the AppConfigReceiver
+ *
+ * Created by sqrt-1674 on 27.03.16.
+ */
+public class AppConfigReceiverTest extends AndroidTestCase {
+    private AppConfigReceiver mReceiver;
+    private MockContext mContext;
+
+    @Override
+    protected void setUp() throws Exception {
+        super.setUp();
+        mReceiver = new AppConfigReceiver();
+        mContext = new MockContext(getContext());
+    }
+
+    @Override
+    protected void tearDown() throws Exception {
+        PreferenceManager.getDefaultSharedPreferences(mContext).edit().clear().commit();
+        super.tearDown();
+    }
+
+
+    /**
+     * Test starting the Syncthing-Service if "always run in background" is enabled
+     * In this case starting the service is allowed
+     */
+    public void testStartSyncthingServiceBackground() {
+        PreferenceManager.getDefaultSharedPreferences(mContext)
+                .edit()
+                .putBoolean(SyncthingService.PREF_ALWAYS_RUN_IN_BACKGROUND, true)
+                .commit();
+
+        Intent intent = new Intent(new Intent(mContext, AppConfigReceiver.class));
+        intent.setAction(AppConfigReceiver.ACTION_START);
+
+        mReceiver.onReceive(mContext, intent);
+        assertEquals("Start SyncthingService Background", 1, mContext.getReceivedIntents().size());
+        assertEquals("Start SyncthingService Background", SyncthingService.class.getName(),
+                        mContext.getReceivedIntents().get(0).getComponent().getClassName());
+    }
+
+    /**
+     * Test stopping the service if "alway run in background" is enabled.
+     * Stopping the service in this mode is not allowed, so no stopService-intent may be issued.
+     */
+    public void testStopSyncthingServiceBackground() {
+        PreferenceManager.getDefaultSharedPreferences(mContext)
+                .edit()
+                .putBoolean(SyncthingService.PREF_ALWAYS_RUN_IN_BACKGROUND, true)
+                .commit();
+
+        Intent intent = new Intent(new Intent(mContext, AppConfigReceiver.class));
+        intent.setAction(AppConfigReceiver.ACTION_STOP);
+
+        mReceiver.onReceive(mContext, intent);
+        assertEquals("Stop SyncthingService Background", 0, mContext.getStopServiceIntents().size());
+    }
+
+    /**
+     * Test starting the Syncthing-Service if "always run in background" is disabled
+     * In this case starting the service is allowed
+     */
+    public void testStartSyncthingServiceForeground() {
+        PreferenceManager.getDefaultSharedPreferences(mContext)
+                .edit()
+                .putBoolean(SyncthingService.PREF_ALWAYS_RUN_IN_BACKGROUND, false)
+                .commit();
+
+        Intent intent = new Intent(new Intent(mContext, AppConfigReceiver.class));
+        intent.setAction(AppConfigReceiver.ACTION_START);
+
+        mReceiver.onReceive(mContext, intent);
+        assertEquals("Start SyncthingService Foreround", 1, mContext.getReceivedIntents().size());
+        assertEquals("Start SyncthingService Foreround", SyncthingService.class.getName(),
+                            mContext.getReceivedIntents().get(0).getComponent().getClassName());
+    }
+
+    /**
+     * Test stopping the Syncthing-Service if "always run in background" is disabled
+     * In this case stopping the service is allowed
+     */
+    public void testStopSyncthingServiceForeground() {
+        PreferenceManager.getDefaultSharedPreferences(mContext)
+                .edit()
+                .putBoolean(SyncthingService.PREF_ALWAYS_RUN_IN_BACKGROUND, false)
+                .commit();
+
+        Intent intent = new Intent(new Intent(mContext, AppConfigReceiver.class));
+        intent.setAction(AppConfigReceiver.ACTION_STOP);
+
+        mReceiver.onReceive(mContext, intent);
+        assertEquals("Stop SyncthingService Foreround", 1, mContext.getStopServiceIntents().size());
+        Intent receivedIntent = mContext.getStopServiceIntents().get(0);
+        assertEquals("Stop SyncthingService Foreround", SyncthingService.class.getName(),
+                                                receivedIntent.getComponent().getClassName());
+    }
+}

src/main/AndroidManifest.xml

@@ -91,6 +91,12 @@
                 <action android:name="android.intent.action.BOOT_COMPLETED" />
             </intent-filter>
         </receiver>
+        <receiver android:name=".syncthing.AppConfigReceiver">
+            <intent-filter>
+                <action android:name="com.nutomic.syncthingandroid.action.START" />
+                <action android:name="com.nutomic.syncthingandroid.action.STOP" />
+            </intent-filter>
+        </receiver>
     </application>
 
 </manifest>

src/main/java/com/nutomic/syncthingandroid/activities/SyncthingActivity.java

@@ -33,14 +33,20 @@ public abstract class SyncthingActivity extends ToolbarBindingActivity implement
     protected void onCreate(Bundle savedInstanceState) {
         super.onCreate(savedInstanceState);
         startService(new Intent(this, SyncthingService.class));
-        bindService(new Intent(this, SyncthingService.class),
-                this, Context.BIND_AUTO_CREATE);
     }
 
     @Override
-    protected void onDestroy() {
-        super.onDestroy();
+    protected void onPause() {
         unbindService(this);
+
+        super.onPause();
+    }
+
+    @Override
+    protected void onResume() {
+        super.onResume();
+
+        bindService(new Intent(this, SyncthingService.class), this, Context.BIND_AUTO_CREATE);
     }
 
     @Override

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

@@ -0,0 +1,75 @@
+package com.nutomic.syncthingandroid.syncthing;
+
+import android.app.Notification;
+import android.app.NotificationManager;
+import android.app.PendingIntent;
+import android.content.BroadcastReceiver;
+import android.content.Context;
+import android.content.Intent;
+import android.os.Build;
+import android.support.v4.app.NotificationCompat;
+
+import com.nutomic.syncthingandroid.R;
+import com.nutomic.syncthingandroid.activities.MainActivity;
+
+/**
+ * Broadcast-receiver to control and configure SyncThing remotely
+ *
+ * Created by sqrt-1764 on 25.03.16.
+ */
+public class AppConfigReceiver extends BroadcastReceiver {
+    private static final int ID_NOTIFICATION_BACKGROUND_ACTIVE = 3;
+
+    /**
+     * Start the Syncthing-Service
+     */
+    public static final String ACTION_START = "com.nutomic.syncthingandroid.action.START";
+
+    /**
+     * Stop the Syncthing-Service
+     * If alwaysRunInBackground is enabled the service must not be stopped. Instead a
+     * notification is presented to the user.
+     */
+    public static final String ACTION_STOP  = "com.nutomic.syncthingandroid.action.STOP";
+
+    @Override
+    public void onReceive(Context context, Intent intent) {
+        switch (intent.getAction()) {
+            case ACTION_START:
+                context.startService(new Intent(context, SyncthingService.class));
+                break;
+
+            case ACTION_STOP:
+                if (SyncthingService.alwaysRunInBackground(context)) {
+                    final String msg = context.getString(R.string.appconfig_receiver_background_enabled);
+
+                    Context appContext = context.getApplicationContext();
+
+                    NotificationCompat.Builder nb = new NotificationCompat.Builder(context)
+                            .setContentText(msg)
+                            .setTicker(msg)
+                            .setStyle(new NotificationCompat.BigTextStyle().bigText(msg))
+                            .setContentTitle(context.getText(context.getApplicationInfo().labelRes))
+                            .setSmallIcon(R.drawable.ic_stat_notify)
+                            .setAutoCancel(true)
+                            .setContentIntent(PendingIntent.getActivity(appContext,
+                                                        0,
+                                                        new Intent(appContext, MainActivity.class),
+                                                        PendingIntent.FLAG_UPDATE_CURRENT));
+
+                    if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.LOLLIPOP) {
+                        nb.setCategory(Notification.CATEGORY_ERROR);        // Only supported in API 21 or better
+                    }
+
+                    NotificationManager nm =
+                            (NotificationManager)context.getSystemService(Context.NOTIFICATION_SERVICE);
+
+                    nm.notify(ID_NOTIFICATION_BACKGROUND_ACTIVE, nb.build());
+
+                } else {
+                    context.stopService(new Intent(context, SyncthingService.class));
+                }
+                break;
+        }
+    }
+}

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

@@ -59,7 +59,6 @@ public class SyncthingService extends Service implements
     public static final String ACTION_RESET =
             "com.nutomic.syncthingandroid.service.SyncthingService.RESET";
 
-
     /**
      * Interval in ms at which the GUI is updated (eg {@link com.nutomic.syncthingandroid.fragments.DrawerFragment}).
      */
@@ -144,6 +143,12 @@ public class SyncthingService extends Service implements
 
     private State mCurrentState = State.INIT;
 
+    /**
+     * Object that can be locked upon when accessing mCurrentState
+     * Currently used to male onDestroy() and PollWebGuiAvailableTaskImpl.onPostExcecute() tread-safe
+     */
+    private final Object stateLock = new Object();
+
     /**
      * True if a stop was requested while syncthing is starting, in that case, perform stop in
      * {@link PollWebGuiAvailableTaskImpl}.
@@ -227,10 +232,8 @@ public class SyncthingService extends Service implements
             if (mConfig != null) {
                 mCurrentState = State.STARTING;
 
-                if (mApi != null) {
+                if (mApi != null)
                     registerOnWebGuiAvailableListener(mApi);
-                    mApi.setWebGuiUrl(mConfig.getWebGuiUrl());
-                }
                 if (mEventProcessor != null)
                     registerOnWebGuiAvailableListener(mEventProcessor);
                 new PollWebGuiAvailableTaskImpl(getFilesDir() + "/" + HTTPS_CERT_FILE)
@@ -426,12 +429,25 @@ public class SyncthingService extends Service implements
 
     /**
      * Stops the native binary.
+     *
+     * The native binary crashes if stopped before it is fully active. In that case signal the
+     * stop request to PollWebGuiAvailableTaskImpl that is active in that situation and terminate
+     * the service there.
      */
     @Override
     public void onDestroy() {
-        super.onDestroy();
-        Log.i(TAG, "Shutting down service");
-        shutdown();
+
+        synchronized (stateLock) {
+            if (mCurrentState == State.INIT || mCurrentState == State.STARTING) {
+                Log.i(TAG, "Delay shutting down service until initialisation of Syncthing finished");
+                mStopScheduled = true;
+
+            } else {
+                Log.i(TAG, "Shutting down service immediately");
+                shutdown();
+            }
+        }
+
         SharedPreferences sp = PreferenceManager.getDefaultSharedPreferences(this);
         sp.unregisterOnSharedPreferenceChangeListener(this);
     }
@@ -512,14 +528,24 @@ public class SyncthingService extends Service implements
             super(httpsCertPath);
         }
 
+        /**
+         * Wait for the web-gui of the native syncthing binary to come online.
+         *
+         * In case the binary is to be stopped, also be aware that another thread could request
+         * to stop the binary in the time while waiting for the GUI to become active. See the comment
+         * for SyncthingService.onDestroy for details.
+         */
         @Override
         protected void onPostExecute(Void aVoid) {
-            if (mStopScheduled) {
-                mCurrentState = State.DISABLED;
-                onApiChange();
-                shutdown();
-                mStopScheduled = false;
-                return;
+            synchronized (stateLock) {
+                if (mStopScheduled) {
+                    mCurrentState = State.DISABLED;
+                    onApiChange();
+                    shutdown();
+                    mStopScheduled = false;
+                    stopSelf();
+                    return;
+                }
             }
             Log.i(TAG, "Web GUI has come online at " + mConfig.getWebGuiUrl());
             mCurrentState = State.STARTING;

src/main/res/values/strings.xml

@@ -468,4 +468,5 @@ Please report any problems you encounter via Github.</string>
     <!-- Format string for folder size, eg "500 MiB / 1 GiB" -->
     <string name="folder_size_format">%1$s / %2$s</string>
 
+    <string name="appconfig_receiver_background_enabled">Stopping Syncthing is not supported when running in background is enabled.</string>
 </resources>