How to execute the code before the user sees the activity?

Question

Android

You need to execute code that will change the ImageView's bitmap before the user sees the activity. The code needs to be executed once when the application starts. The application has one single activity.
PS New to android.
PPS Google - all attempts led to the crash of the application.

Answer 1

Execute it in onCreate of your activity. In order for the code to be executed once at startup (but at the same time every startup) - keep the flag whether the conversion was performed somewhere in your Application implementation, for example. If you need to do it once at all, then you can write it to a file, or somewhere else.
You can of course try to execute the code in onCreate of the Application itself.