fix: cancel potential gallery image generation task

app/src/main/java/com/owncloud/android/datamodel/ThumbnailsCacheManager.java

@@ -325,6 +325,10 @@ public GalleryImageGenerationTask(
             this.backgroundColor = backgroundColor;
         }
 
+        public String getImageKey() {
+            return imageKey;
+        }
+
         public void setListener(GalleryListener listener) {
             this.listener = listener;
         }
@@ -340,11 +344,19 @@ protected Bitmap doInBackground(Object... params) {
 
             file = (OCFile) params[0];
 
+            if (isCancelled()) {
+                return null;
+            }
+
             if (file.getRemoteId() != null || file.isPreviewAvailable()) {
                 // Thumbnail in cache?
                 thumbnail = ThumbnailsCacheManager.getBitmapFromDiskCache(
                     ThumbnailsCacheManager.PREFIX_RESIZED_IMAGE + file.getRemoteId());
 
+                if (isCancelled()) {
+                    return null;
+                }
+
                 if (thumbnail != null && !file.isUpdateThumbnailNeeded())
                     return getThumbnailFromCache(thumbnail);
 
@@ -357,13 +369,21 @@ protected Bitmap doInBackground(Object... params) {
 
         @Nullable
         private Bitmap getThumbnailFromServerAndAddToCache(Bitmap thumbnail) {
+            if (isCancelled()) {
+                return null;
+            }
+
             try {
                 mClient = OwnCloudClientManagerFactory.getDefaultSingleton().getClientFor(user.toOwnCloudAccount(),
                                                                                           MainApp.getAppContext());
 
                 thumbnail = doResizedImageInBackground(file, storageManager);
                 newImage = true;
 
+                if (isCancelled()) {
+                    return null;
+                }
+
                 if (MimeTypeUtil.isVideo(file) && thumbnail != null) {
                     thumbnail = addVideoOverlay(thumbnail, MainApp.getAppContext());
                 }
@@ -416,6 +436,13 @@ private Bitmap getScaledThumbnailAfterSave(Bitmap thumbnail) {
         }
 
         protected void onPostExecute(Bitmap bitmap) {
+            if (isCancelled()) {
+                if (asyncTasks != null) {
+                    asyncTasks.remove(this);
+                }
+                return;
+            }
+
             if (bitmap != null && imageViewReference.get() != null) {
                 final ImageView imageView = imageViewReference.get();
                 final GalleryImageGenerationTask bitmapWorkerTask = getGalleryImageGenerationTask(imageView);
@@ -1164,6 +1191,24 @@ Drawable doAvatarInBackground() {
         }
     }
 
+    public static boolean cancelPotentialGalleryWork(OCFile file, ImageView imageView) {
+        final GalleryImageGenerationTask galleryTask = getGalleryImageGenerationTask(imageView);
+
+        if (galleryTask != null) {
+            final String taskImageKey = galleryTask.imageKey;
+            if (taskImageKey == null || file.getRemoteId() == null ||
+                !taskImageKey.equals(file.getRemoteId())) {
+                // Cancel previous task
+                galleryTask.cancel(true);
+                Log_OC.v(TAG, "Cancelled generation of gallery image for a reused imageView");
+            } else {
+                return false;
+            }
+        }
+
+        return true;
+    }
+
     public static boolean cancelPotentialThumbnailWork(Object file, ImageView imageView) {
         final ThumbnailGenerationTask bitmapWorkerTask = getBitmapWorkerTask(imageView);
 

app/src/main/java/com/owncloud/android/ui/adapter/OCFileListDelegate.kt

@@ -160,14 +160,19 @@ class OCFileListDelegate(
         galleryRowHolder: GalleryRowHolder,
         width: Int
     ) {
-        if (!ThumbnailsCacheManager.cancelPotentialThumbnailWork(file, thumbnailView)) {
-            Log_OC.d(tag, "setGalleryImage.cancelPotentialThumbnailWork()")
+        if (!ThumbnailsCacheManager.cancelPotentialGalleryWork(file, thumbnailView)) {
+            Log_OC.d(tag, "setGalleryImage.cancelPotentialGalleryWork()")
             return
         }
 
-        for (task in asyncTasks) {
-            if (file.remoteId != null && task.imageKey != null && file.remoteId == task.imageKey) {
-                return
+        val iterator = asyncGalleryTasks.iterator()
+        while (iterator.hasNext()) {
+            val task = iterator.next()
+            if (file.remoteId != null && file.remoteId == task.imageKey) {
+                task.cancel(true)
+                iterator.remove()
+                Log_OC.d(tag, "Cancelled duplicate gallery task for: ${file.remoteId}")
+                break
             }
         }
 
@@ -207,7 +212,6 @@ class OCFileListDelegate(
             })
 
             thumbnailView.setImageDrawable(asyncDrawable)
-
             asyncGalleryTasks.add(task)
             task.executeOnExecutor(AsyncTask.THREAD_POOL_EXECUTOR, file)
         } catch (e: IllegalArgumentException) {