Create a default channel and display the notification in it

As part of the move to API 26, create a default channel and display
the notification in it
e-mission/e-mission-docs#325 (comment)

Bonus fix:
- support pending intents that come from a resolution + pending intents that
  the activity knows how to handle directly

src/android/NotificationHelper.java

@@ -1,5 +1,6 @@
 package edu.berkeley.eecs.emission.cordova.unifiedlogger;
 
+import android.annotation.TargetApi;
 import android.app.Notification;
 import android.app.NotificationChannel;
 import android.app.NotificationManager;
@@ -16,11 +17,15 @@
 
 import edu.berkeley.eecs.emission.MainActivity;
 import edu.berkeley.eecs.emission.R;
+
 import java.util.List;
 
 
 public class NotificationHelper {
 	private static String TAG = "NotificationHelper";
+	private static String DEFAULT_CHANNEL_ID = "emissionPluginChannel";
+	private static String DEFAULT_CHANNEL_DESCRIPTION = "common channel used by all e-mission native plugins";
+	public static final String DISPLAY_RESOLUTION_ACTION = "DISPLAY_RESOLUTION";
 	public static final String RESOLUTION_PENDING_INTENT_KEY = "rpIntentKey";
 
 	public static void createNotification(Context context, int id, String message) {
@@ -48,25 +53,29 @@ public static void createNotification(Context context, int id, String message) {
 		nMgr.notify(id, builder.build());
 	}
 
-	/*
-	 * Used to show a pending intent - e.g. to turn on location services
-	 */
 	public static void createNotification(Context context, int id, String message, PendingIntent intent) {
 		NotificationManager nMgr =
 				(NotificationManager)context.getSystemService(Context.NOTIFICATION_SERVICE);
 
 		Notification.Builder builder = getNotificationBuilderForApp(context, nMgr, message);
+		builder.setContentIntent(intent);
+
+		Log.d(context, TAG, "Generating notify with id " + id + ", message " + message
+				+ " and pending intent " + intent);
+		nMgr.notify(id, builder.build());
+	}
 
 		/*
-		 * This is a bit of magic voodoo. The tutorial on launching the activity actually uses a stackbuilder
-		 * to create a fake stack for the new activity. However, it looks like the stackbuilder
-		 * is only available in more recent versions of the API. So I use the version for a special activity PendingIntent
-		 * (since our app currently has only one activity) which resolves that issue.
-		 * This also appears to work, at least in the emulator.
-		 *
-		 * TODO: Decide what level API we want to support, and whether we want a more comprehensive activity.
+	 * Used to show a resolution - e.g. to turn on location services
 		 */
+	public static void createResolveNotification(Context context, int id, String message, PendingIntent intent) {
+		NotificationManager nMgr =
+				(NotificationManager)context.getSystemService(Context.NOTIFICATION_SERVICE);
+
+		Notification.Builder builder = getNotificationBuilderForApp(context, nMgr, message);
+
 		Intent activityIntent = new Intent(context, MainActivity.class);
+		activityIntent.setAction(DISPLAY_RESOLUTION_ACTION);
 		activityIntent.setFlags(Intent.FLAG_ACTIVITY_NEW_TASK);
 		activityIntent.putExtra(NotificationHelper.RESOLUTION_PENDING_INTENT_KEY, intent);
 
@@ -93,13 +102,8 @@ public static Notification.Builder getNotificationBuilderForApp(Context context,
 																	String message) {
 		Notification.Builder builder = null;
 		if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.O) {
-			List<NotificationChannel> channels = nMgr.getNotificationChannels();
-			String channelID;
-			if (channels.size() < 1) {
-				throw new AssertionError("Did not find any channels, no notifications will be generated");
-			}
-			channelID = channels.get(0).getId();
-			builder = new Notification.Builder(context, channelID);
+			createDefaultNotificationChannelIfNeeded(context);
+			builder = new Notification.Builder(context, DEFAULT_CHANNEL_ID);
 		} else {
 			builder = new Notification.Builder(context);
 		}
@@ -111,4 +115,28 @@ public static Notification.Builder getNotificationBuilderForApp(Context context,
 
 		return builder;
 	}
+
+	@TargetApi(26)
+	private static void createDefaultNotificationChannelIfNeeded(final Context ctxt) {
+		// only call on Android O and above
+		if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.O) {
+			final NotificationManager notificationManager = (NotificationManager) ctxt.getSystemService(Context.NOTIFICATION_SERVICE);
+			List<NotificationChannel> channels = notificationManager.getNotificationChannels();
+
+			for (int i = 0; i < channels.size(); i++) {
+				String id = channels.get(i).getId();
+				Log.d(ctxt, TAG, "Checking channel with id = "+id);
+				if (DEFAULT_CHANNEL_ID.equals(id)) {
+					Log.d(ctxt, TAG, "Default channel found, returning");
+					return;
+				}
+			}
+
+			Log.d(ctxt, TAG, "Default channel not found, creating a new one");
+			NotificationChannel dChannel = new NotificationChannel(DEFAULT_CHANNEL_ID,
+					DEFAULT_CHANNEL_DESCRIPTION, NotificationManager.IMPORTANCE_DEFAULT);
+			dChannel.enableVibration(true);
+			notificationManager.createNotificationChannel(dChannel);
+		}
+	}
 }