Monday, 2 June 2014

Pitfalls of adding WP8.1 support to a universal app (Part 1 of N)

As part of our continuing port from Windows 8.1 to WP8.1 of Surface Level, I’ve just recently tracked down a problem thrown during suspension.

We’d already written quite a few classes that would act as a base class, and as a result, I implemented a partial method which I could call for certain tasks.  One of these tasks was registering our Suspension handler.

The bug I was seeing was an end of file reached while reading back our state file, which we use when we resume.  But there were two problems

1.  I kept getting odd suspension manager exceptions in my crash logs.
2.  The suspended handler never seemed to be called anyway.

Item 2 was the first to solve.  It appears that like W8.1, apps aren’t suspended when run in the debugger.  The only problem was, I couldn’t find the UI to shut it off.

Well, eventually I found it here on the Debug Location toolbar:


Clicking Suspend actually caused my suspension to run (twice in fact)

The first crash was caused by the state file being read only (a side effect of running suspension twice).  It turns out that when I added the WP8.1 project, the wizard had added a second call wiring up the suspension code, which I hadn’t spotted.  Removing the duplicate wiring allowed me to get suspension working properly.

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