Fix sometimes seeing outdated thumbnail in notification

Before the thumbnail finishes loading for the new video the player is now playing, the old thumbnail was being used, leading to wrong thumbnails set in the media session and the notification.

Author: Stypox

app/src/main/java/org/schabi/newpipe/player/Player.java

@@ -748,11 +748,15 @@ private void unregisterBroadcastReceiver() {
     //////////////////////////////////////////////////////////////////////////*/
     //region Thumbnail loading
 
-    private void initThumbnail(final String url) {
+    private void loadCurrentThumbnail(final String url) {
         if (DEBUG) {
-            Log.d(TAG, "Thumbnail - initThumbnail() called with url = ["
+            Log.d(TAG, "Thumbnail - loadCurrentThumbnail() called with url = ["
                     + (url == null ? "null" : url) + "]");
         }
+
+        // Unset currentThumbnail, since it is now outdated. This ensures it is not used in media
+        // session metadata while the new thumbnail is being loaded by Picasso.
+        currentThumbnail = null;
         if (isNullOrEmpty(url)) {
             return;
         }
@@ -762,8 +766,8 @@ private void initThumbnail(final String url) {
             @Override
             public void onBitmapLoaded(final Bitmap bitmap, final Picasso.LoadedFrom from) {
                 if (DEBUG) {
-                    Log.d(TAG, "Thumbnail - onLoadingComplete() called with: url = [" + url
-                            + "], " + "loadedImage = [" + bitmap + " -> " + bitmap.getWidth() + "x"
+                    Log.d(TAG, "Thumbnail - onBitmapLoaded() called with: url = [" + url
+                            + "], " + "bitmap = [" + bitmap + " -> " + bitmap.getWidth() + "x"
                             + bitmap.getHeight() + "], from = [" + from + "]");
                 }
 
@@ -1727,7 +1731,7 @@ private void updateMetadataWith(@NonNull final StreamInfo info) {
 
         maybeAutoQueueNextStream(info);
 
-        initThumbnail(info.getThumbnailUrl());
+        loadCurrentThumbnail(info.getThumbnailUrl());
         registerStreamViewed();
 
         notifyMetadataUpdateToListeners();

app/src/main/java/org/schabi/newpipe/util/PicassoHelper.java

@@ -1,11 +1,13 @@
 package org.schabi.newpipe.util;
 
+import static org.schabi.newpipe.MainActivity.DEBUG;
 import static org.schabi.newpipe.extractor.utils.Utils.isBlank;
 
 import android.annotation.SuppressLint;
 import android.content.Context;
 import android.graphics.Bitmap;
 import android.graphics.drawable.Drawable;
+import android.util.Log;
 
 import androidx.annotation.Nullable;
 
@@ -27,6 +29,7 @@
 import okhttp3.OkHttpClient;
 
 public final class PicassoHelper {
+    private static final String TAG = PicassoHelper.class.getSimpleName();
     public static final String PLAYER_THUMBNAIL_TAG = "PICASSO_PLAYER_THUMBNAIL_TAG";
     private static final String PLAYER_THUMBNAIL_TRANSFORMATION_KEY =
             "PICASSO_PLAYER_THUMBNAIL_TRANSFORMATION_KEY";
@@ -128,6 +131,10 @@ public static RequestCreator loadScaledDownThumbnail(final Context context, fina
                 .transform(new Transformation() {
                     @Override
                     public Bitmap transform(final Bitmap source) {
+                        if (DEBUG) {
+                            Log.d(TAG, "Thumbnail - transform() called");
+                        }
+
                         final float notificationThumbnailWidth = Math.min(
                                 context.getResources()
                                         .getDimension(R.dimen.player_notification_thumbnail_width),