Android Question How to use the b4a Default to implement Fullscreen with SimpleMediaManager

I found an example of using SimpleMediaManager to play videos for full screen playback, but it was written using B4XPage. I want to use it for programs written in B4A in the past, and I don't want to modify all the programs to B4XPage, as it would require a lot of work.
Here "me" is a class, how should I create my own new class in b4a's default to use it? I don't quite understand this. I have attached the code written by B4XPage and the code I wrote using default. I hope someone can help me modify it. Thank you.