Return an empty observable rather than null if local image is absent

This would not be a problem given the fact that we will always reference
existing local images, but returning an empty observable is more
consistent with the existing behaviour.

Part of implementation of #3438.

1 files changed, 4 insertions, 5 deletions

diff --git a/main/src/cgeo/geocaching/network/HtmlImage.java b/main/src/cgeo/geocaching/network/HtmlImage.java
index ae9821b..36ce9c1 100644
--- a/main/src/cgeo/geocaching/network/HtmlImage.java
+++ b/main/src/cgeo/geocaching/network/HtmlImage.java
@@ -30,7 +30,6 @@ import rx.functions.Func1;
 import rx.schedulers.Schedulers;
 import rx.subjects.PublishSubject;
 import rx.subscriptions.CompositeSubscription;
-import rx.util.async.Async;
 
 import android.content.res.Resources;
 import android.graphics.Bitmap;
@@ -137,13 +136,13 @@ public class HtmlImage implements Html.ImageGetter {
         // Explicit local file URLs are loaded from the filesystem regardless of their age. The IO part is short
         // enough to make the whole operation on the computation scheduler.
         if (url.startsWith("file://")) {
-            return Async.fromCallable(new Func0<BitmapDrawable>() {
+            return Observable.defer(new Func0<Observable<? extends BitmapDrawable>>() {
                 @Override
-                public BitmapDrawable call() {
+                public Observable<? extends BitmapDrawable> call() {
                     final Bitmap bitmap = loadCachedImage(new File(url.substring(7)), true).getLeft();
-                    return bitmap != null ? ImageUtils.scaleBitmapToFitDisplay(bitmap) : null;
+                    return bitmap != null ? Observable.from(ImageUtils.scaleBitmapToFitDisplay(bitmap)) : Observable.<BitmapDrawable>empty();
                 }
-            }, RxUtils.computationScheduler);
+            }).subscribeOn(RxUtils.computationScheduler);
         }
 
         final boolean shared = url.contains("/images/icons/icon_");