SQLite Database in Android: data is does not persist

I posted yesterday about this as my application would crash, but it doesn't anymore so that has been fixed.

However, I am using this person's tutorials on SQLite in Android studio, videos 8-11, ( https://www.youtube.com/watch?v=yfpNgzvpiGI&list=PL_PaSTBkUwk4PXlhZIe4COpwnWeCRnw2F&index=12 ), and I want to make a database in my 'homework' activity, so that data is entered, and after the app is closed and re-opened, it stays there.

I have done everything in these videos, however even when I close the app, the data I entered for 'homework' does not remain, and deletes itself - how do I resolve this?

Here is my Application in GitHub. http://ift.tt/1RCoqvj