[TIMOB-3040] Android: If image stored directly in Resources/images, referencing it causes too many unnecessary exceptions

"Failcase" is, for example, the Table View Layout 2 test in KitchenSink. It's not really a "failure" since the test actually works. But behind the scenes a bunch of exceptions -- handled exceptions -- are happening, very likely affecting performance.

You can see it happening if you run KS with <property type="bool" name="ti.android.debug">true</property> in tiapp.xml. Run adb logcat at the command line, then -- with KS running in your emulator -- go to the Views -> Table Views -> Layout 2 test. As the test loads, watch logcat scrolling by -- you'll end up seeing a ton of exceptions. If you then scroll up and down on the table view in the test, you'll see a ton more exceptions being logged in logcat.

Alternatively, you can watch me doing it here:

http://screencast.com/t/FD9E6klYe">http://screencast.com/t/FD9E6klYe

What's happening is this: Because the image path begins with Resources/images -- which is one of our standard locations to check for density-specific images -- we do the density image name mangling and check to see if the image exists as an Android resource. The checking to see if it's a resource uses reflection (see TiRHelper.locateResource), and has to accept the fact that an exception will be raised if the resource doesn't exist. It handles that fine (and sends it to logcat if debug is turned on -- which is what we're seeing in that video) and the result is that our loadDrawable method ends up successfully finding the image file in the standard file system. But I imagine those exceptions are expensive. The problem is that -- unlike successful finds of a resource image -- we do not cache the failures. So it tries every time to load the same image as a resource that doesn't exist.

I think putting images into the Resources/images folder is probably a fairly common pattern for app developers. So we could perhaps improvement performance for these people by caching resource lookup failures to avoid going through the series of exceptions over and over again.