Simplify navigation to the background player activity

[voidc]

In my opinion it should be easier to open the background player activity during background playback.
I suggest to replace the toast, which is shown when starting background playback, with a snackbar allowing to directly open the background player activity.
Additionally a menu item might be added to the top toolbar during playback in the background which opens the background player activity when clicked.
This would also serve as an better indicator that the background player is active besides the notification.

[voidc]

The same could be done for downloading videos. i.e. showing a snackbar allowing to open the downloads activity when starting a new download and showing an icon in the toolbar while downloads are running

[voidc]

Could look like this. (The toast should be removed)

[MuellerSeb]

I miss this feature, too. I always tap on the tray widget of the background player to access its playlist, which feels a bit inconvenient.

[MuellerSeb]

Ping.

[Stypox]

Closing in favour of #2477