Fix #3416 Add snackbar on clicking add/remove from bookmarks (#3419)

Author: yashk2000

app/src/main/java/fr/free/nrw/commons/media/MediaDetailPagerFragment.java

@@ -20,6 +20,8 @@
 import androidx.fragment.app.FragmentStatePagerAdapter;
 import androidx.viewpager.widget.ViewPager;
 
+import com.google.android.material.snackbar.Snackbar;
+
 import javax.inject.Inject;
 import javax.inject.Named;
 
@@ -148,7 +150,9 @@ public boolean onOptionsItemSelected(MenuItem item) {
         Media m = provider.getMediaAtPosition(pager.getCurrentItem());
         switch (item.getItemId()) {
             case R.id.menu_bookmark_current_image:
-                bookmarkDao.updateBookmark(bookmark);
+                boolean bookmarkExists = bookmarkDao.updateBookmark(bookmark);
+                Snackbar snackbar = bookmarkExists ? Snackbar.make(getView(), R.string.add_bookmark, Snackbar.LENGTH_LONG) : Snackbar.make(getView(), R.string.remove_bookmark, Snackbar.LENGTH_LONG);
+                snackbar.show();
                 updateBookmarkState(item);
                 return true;
             case R.id.menu_share_current_image:

app/src/main/res/values/strings.xml

@@ -591,4 +591,6 @@ Upload your first media by tapping on the add button.</string>
 
   <string name="upload_nearby_place_found_title">Nearby Place Found</string>
   <string name="upload_nearby_place_found_description">Is this a photo of Place %1$s?</string>
+  <string name="remove_bookmark">Removed from bookmarks</string>
+  <string name="add_bookmark">Added to bookmarks</string>
 </resources>