Just a thought, it could be a result of the android gc clearing static
variables.

I noticed this sometimes happens on lower end devices or after a memory
intensive activity.
On Jul 27, 2012 6:16 PM, "Jonathan Pryor" <[email protected]> wrote:

> On Jun 25, 2012, at 6:49 AM, keith <[email protected]> wrote:
> > I have been getting random null reference exceptions in my app when
> running on lower end devices (galaxy ace in this case), but not on a desire
> s or
> > emulators.
>
> There are two things to check.
>
> 1. Check the Android Debug Log for process startup messages:
>
>         http://docs.xamarin.com/android/advanced_topics/android_debug_log
>
> The messages to look for are messages containing "__mono" and your package
> name, and are generated every time a Mono for Android process is started:
>
>         I/ActivityThread(10777): Pub
> Scratch.SreProxy.mono.MonoRuntimeProvider.__mono_init__:
> mono.MonoRuntimeProvider
>
> The above comes from the "Scratch.SreProxy" app (just a random test app).
>
> The question: do you see _two_ (or more) of these messages for a "single"
> app launch?
>
> What could be happening is the Activity lifecycle: if your Activity isn't
> visible, Android is free to kill your process:
>
>
> http://developer.android.com/reference/android/app/Activity.html#ActivityLifecycle
>
> If Android kills your process and then the user navigates back to your
> Activity, Android will re-lauch the process and Activity (thus generating
> another __mono_ message in the debug log).
>
> If you see this, then the solution is to capture the Activity lifecycle
> events and persistently save your singleton data so that you can restore it
> later.
>
> 2. The other thing to check is (of course) various bugs. A "brute force"
> solution is to enable tracing (which WILL spam your logcat, though
> hopefully to useful effect):
>
>         http://docs.xamarin.com/android/advanced_topics/diagnostics
>
> For example:
>
>         adb shell setprop debug.mono.trace all,-N:System.Net
>
>  - Jon
>
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