Start VideoPlayer and rewind a few seconds ago

MIT App Inventor Help
1

Wish everyone luck!

  1. When Button1 is clicked, the video does not play, and it plays normally when the play_btn is clicked.
    What went wrong?

    1
    1720×195 45.7 KB

  2. When using the extension called VideoLayout, the following text appears.
    What went wrong?

“Runtime Error
attempt to invoke virtual method 'void androad.widget.VideoView.setVideoPath(java.lang.String)' on a null object reference“

2
2720×127 33.1 KB

  1. What I want is to go back a few seconds and play the video.
    Please let me know the way.
2

/abcde.mp4

Where does the MP4 file come from?