Question

I’d like to know if it is safe to use static variables as a long term storage of business entities in a Mono for Android app.

For instance, if I have this class:

public class Test{
 public static int MyStaticVariable{get;set;}
}

and in my main activity I have this code

 protected override void OnCreate(Bundle bundle)
        {
   ...
   if (Test.MyStaticVariable){
     Test.MyStaticVariable=666;
   }
}

can I always rely on Test.MyStaticVariable==666 or will that value be eventually be reset by the OS when my app goes out of scope and RAM has to be recycled?

Thanks,

Adrian

Answer 1

The variable is scoped to your process, and will not survive a process restart (absent additional code on your part to save/restore the variable).

This is no different than Java. 🙂

If you want to save/restore the value, you should subclass Android.App.Application and override Application.OnLowMemory() and/or Application.OnTrimMemory() and save the value to persistent storage. You can then restore this value within Application.OnCreate().

(There is no way I know of to actually know when the process will be killed — Application.OnTerminate() is only for emulators — but hopefully Android will call the OnLowMemory()/OnTrimMemory() methods before it kills the process…)