Go to the last question in the manual PlayTest and do the following:

  - Click on the Play button
  - Click on the Pause botton
  - Click on the slider and seek to forward
  - Click on the Play button

Notice the slider no longer moves. After calling MediaPlayer.seek(), the MediaPlayer.currentTimeProperty does not get any further notifications. For this reason, the slider does not show the current time as it progresses after you seek, because the sliders position is updated whenever the currentTimeProperty is notified.