Say I am developing an Android app. I have the source, I built it myself.
It has a problem where occasionally Android pops up a box saying "[App] isn't responding. * Close app * Wait".
I would like to know what the app is doing when this occurs— stack traces, 1 second of profiling, something.
I expect if I tap "Close app", it should drop something useful in the logcat. I've nabbed a logcat within 120 seconds however and see nothing involving "crash" or "ANR".
Unfortunately I cannot get this to happen on demand, so running with adb connected is not an option. I can only make it happen by using the app regularly for a couple days, if I do this I get the hang once every 12 to 48 hours. So I need something I can do in pure-mobile mode, something like the "Stackshots" from iOS would be perfect.
It seems like since I built the app myself, I ought to have more options than if this were just something I'd downloaded…!
@mcc The most common approach would be to hookup the app to Firebase Crashlytics, and then your ANR traces will end up in the cloud.
I think your odds of getting ADB connected and logcat running before the ANR falls out of the buffer are slim-to-none. Although connecting ADB over wifi and just having your PC continually spool logcat to a file the whole day might work?
@swiftcoder Everything would be perfect if I could just instruct it to copy my ANR traces to a known location on /sdcard! :( I wonder, if Firebase can make that work, whether I could write my own apk to make that work.
@mcc Have you explored the /data/anr/ directory? In theory a copy should be stored there for each ANR (unclear what the timeline for eviction is, however)
@aaryte I was able to list the files in that directory, but shell cat or pull gave me denied permissions when I tried to read them. I was eventually able to get them off with adb bugreport however.
@mcc Would it be possible to connect over adb once you reproduce the issue? Then you could attach a debugger to the running app, pause the app, and look at what each thread is doing. If you can't use adb at all, I'm afraid it's going to be harder
@JosJuice Often it un-wedges itself if I wait 30-60 seconds, so no, my attempts at this have not been successful. It doesn't help that this happens at true random, so sometimes I'm not even at home when it happens.
@JosJuice Wouldn't I need to run in that mode for hours to get the log I need, though? Hm. I guess I could turn it on once the event begins, but the chances of the app being oomkilled while I'm in Settings are high…
@mcc It's not a mode. You press it, and it captures a kind of snapshot of the current state. You do have to go into the settings app to trigger it, but in my experience, modern devices have enough RAM that opening the settings app won't cause a game to have its process killed due to OOM
@JosJuice Thanks. I'll consider it, although at present I am using a $35 phone I got at walmart while my real phone is in repair, so… I dunno if it can be described as a "modern device".
Okay so @swiftcoder has just informed me about Android's /data/anr directory, which sounds like exactly what I'm looking for, and does in fact contain files matching known ANR events. Unfortunately, this phone denies ADB permissions to read those files!
…BUT, adb bugreport does copy, in the FS/data/anr subdirectory, the files, so I now have what I need. Thanks y'all
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