Ensure that the Notification listener service gets restarted if crashed.

This change adds an additional service that checks the status of the NotificationListenerService, and restarts it if it's stale/crashed.
Crashes happen mostly during development, but were reported also by users.

app/src/main/AndroidManifest.xml

@@ -251,6 +251,7 @@
                 <action android:name="android.service.notification.NotificationListenerService" />
             </intent-filter>
         </service>
+        <service android:name=".service.NotificationCollectorMonitorService" />
         <service android:name=".service.DeviceCommunicationService" />
 
         <receiver

app/src/main/java/nodomain/freeyourgadget/gadgetbridge/GBApplication.java

@@ -53,6 +53,7 @@ import nodomain.freeyourgadget.gadgetbridge.impl.GBDevice;
 import nodomain.freeyourgadget.gadgetbridge.impl.GBDeviceService;
 import nodomain.freeyourgadget.gadgetbridge.model.ActivityUser;
 import nodomain.freeyourgadget.gadgetbridge.model.DeviceService;
+import nodomain.freeyourgadget.gadgetbridge.service.NotificationCollectorMonitorService;
 import nodomain.freeyourgadget.gadgetbridge.util.FileUtils;
 import nodomain.freeyourgadget.gadgetbridge.util.GB;
 import nodomain.freeyourgadget.gadgetbridge.util.GBPrefs;
@@ -146,6 +147,8 @@ public class GBApplication extends Application {
 
         if (isRunningMarshmallowOrLater()) {
             notificationManager = (NotificationManager) context.getSystemService(Context.NOTIFICATION_SERVICE);
+            //the following will ensure the notification manager is kept alive
+            startService(new Intent(this, NotificationCollectorMonitorService.class));
         }
     }
 

app/src/main/java/nodomain/freeyourgadget/gadgetbridge/service/NotificationCollectorMonitorService.java

@@ -0,0 +1,79 @@
+package nodomain.freeyourgadget.gadgetbridge.service;
+
+import android.app.ActivityManager;
+import android.app.Service;
+import android.content.ComponentName;
+import android.content.Context;
+import android.content.Intent;
+import android.content.pm.PackageManager;
+import android.os.IBinder;
+import android.os.Process;
+
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+import java.util.List;
+
+import nodomain.freeyourgadget.gadgetbridge.externalevents.NotificationListener;
+
+/**
+ * Original source by xinghui - see https://gist.github.com/xinghui/b2ddd8cffe55c4b62f5d8846d5545bf9
+ * NB: no license specified in the source code as of 2017-04-19
+ */
+public class NotificationCollectorMonitorService extends Service {
+
+    private static final Logger LOG = LoggerFactory.getLogger(NotificationCollectorMonitorService.class);
+
+
+    @Override
+    public void onCreate() {
+        super.onCreate();
+        ensureCollectorRunning();
+    }
+
+    @Override
+    public int onStartCommand(Intent intent, int flags, int startId) {
+        return START_STICKY;
+    }
+
+    private void ensureCollectorRunning() {
+        ComponentName collectorComponent = new ComponentName(this, NotificationListener.class);
+        LOG.info("ensureCollectorRunning collectorComponent: " + collectorComponent);
+        ActivityManager manager = (ActivityManager) getSystemService(Context.ACTIVITY_SERVICE);
+        boolean collectorRunning = false;
+        List<ActivityManager.RunningServiceInfo> runningServices = manager.getRunningServices(Integer.MAX_VALUE);
+        if (runningServices == null) {
+            LOG.info("ensureCollectorRunning() runningServices is NULL");
+            return;
+        }
+        for (ActivityManager.RunningServiceInfo service : runningServices) {
+            if (service.service.equals(collectorComponent)) {
+                LOG.warn("ensureCollectorRunning service - pid: " + service.pid + ", currentPID: " + Process.myPid() + ", clientPackage: " + service.clientPackage + ", clientCount: " + service.clientCount
+                        + ", clientLabel: " + ((service.clientLabel == 0) ? "0" : "(" + getResources().getString(service.clientLabel) + ")"));
+                if (service.pid == Process.myPid() /*&& service.clientCount > 0 && !TextUtils.isEmpty(service.clientPackage)*/) {
+                    collectorRunning = true;
+                }
+            }
+        }
+        if (collectorRunning) {
+            LOG.debug("ensureCollectorRunning: collector is running");
+            return;
+        }
+        LOG.debug("ensureCollectorRunning: collector not running, reviving...");
+        toggleNotificationListenerService();
+    }
+
+    private void toggleNotificationListenerService() {
+        LOG.debug("toggleNotificationListenerService() called");
+        ComponentName thisComponent = new ComponentName(this, NotificationListener.class);
+        PackageManager pm = getPackageManager();
+        pm.setComponentEnabledSetting(thisComponent, PackageManager.COMPONENT_ENABLED_STATE_DISABLED, PackageManager.DONT_KILL_APP);
+        pm.setComponentEnabledSetting(thisComponent, PackageManager.COMPONENT_ENABLED_STATE_ENABLED, PackageManager.DONT_KILL_APP);
+
+    }
+
+    @Override
+    public IBinder onBind(Intent intent) {
+        return null;
+    }
+}