How to retrieve all paints on a canvas ?

[Duc Ta]

Dear all Android developers,
I have an issue that
When I open a canvas application, I draw some paints on this canvas
Then I quit the app. After that, I open the app again
As the result, all paints I drawn before is clear.
So how can I retrieve all the paints I have drawn before?

Thanks all for your helping!

[Tim Moores]

How are you trying do persist the drawings - not at all, I take it?