Draw canvas like Pattern

I need to write code for my android app. Basic concept: I need to Draw canvas like pattern. it will be 3x3, when user touch and draw b/w two points Line may appears permanently. i.e. as is happen in pattern.

Functionality:-

1. When app open draw pattern Dots
2. User can draw line b/w two pattern dots. Line draw appears permanently 3.User can draw another line with same method , but cannot override the previously drawled line.

For details see attached image.

==================================== Can somebody advise me code. it will be incubation for user like me.