This is the third tutorial note to be published from a collection I created in support of a schools IT programme. It covers preserving state between screens, refactoring of code, and passing of values between screens. It is rather a long article as it goes into some detail.
As a reminder, the notes here address one or more specific problems that the students had while writing their own application.
The app has some buttons to represent a Tic-Tac-Toe game – each button in a 3×3 array can show nothing, a X or a 0. Each tap of the button changes the state to the next one. (This game is also known as Noughts and Crosses.)
It looks something like this:
The problem to solve is that the app needs to remember the state of the buttons when switching to a different screen and then coming back.
This is the second of my tutorials created as part of my contribution to mentoring teams of school children in an IT challenge here in New Zealand – see earlier article for details of that.
These notes were prepared in answer to a question from a student “How do you make something happen when a sprite collides with a barrier”. The following describes one way you can detect when one sprite hits a barrier.
There are in fact two types of collision detection:
- Colliding with other sprites
- Colliding with the edge of the screen (or, more accurately, the edge of the canvas that the sprite moves across).
These notes describe the first case – the second one is really easy.
By the way, “collision detection” is fundamental to pretty much any computer game, and understanding the basics of it is really useful.