[General Questions and Answers] sxlijin:
I've gotten the error message "Unfortunately, System UI has stopped" twice now. The first time, I got around it by re-installing my ROM (something I'd rather not try again, because of how many contacts and data I keep on my phone and how long restoring everything takes). The second time, opening a specific app (Gallery in my case) stopped the errors. I have an SGH-T989 running TWRP 2.6.3.0 and BlackLiquid 2.9.2.

I've found people suggest all of the following as potential fixes:

Force closing specific apps (one that came up frequently was "FaceLock").

Wiping the system UI cache.

Fixing permissions with CWM.

And to add my own personal experience (as mentioned above):

Opening a specific app.

When I encountered the following, I also attempted the following, all of which failed:

Wiping the phone cache in TWRP 2.6.3.0.

Wiping the dalvik-cache in TWRP 2.6.3.0.

Backing up the internal SD, wiping it, restoring the ROM sans cache.

Fixing permissions using TWRP 2.6.3.0.

So, tl;dr - What, if any, consistent, generic reason is there for system UI to crash? (i.e. consistently throw the error message "Unfortunately, System UI has stopped.")

Original post 2013/10/09 08:43PM

Hi, I've been persistently getting the error message "Unfortunately, System UI has stopped" whenever my phone is on. I got annoyed enough with it that I just wiped my phone and re-installed the ROM I had, but that was a rather tedious process that I'd rather not run through again if I encountered it.

I have a Samsung Galaxy S2 T-Mobile (model SGH-T989) with TWRP 2.6.3.0 and BlackLiquid 2.9.2.

I first started having problems with my phone (not the System UI problem) earlier in the day when trying to enter data in fields using Google Chrome - the keyboard would not appear when I selected a text field. In an attempt to fix this, I installed Google Keyboard, which led to no success. From that point on, features would occasionally crash, until at some point later on in the day, as a result of no particular incident that I can recall, I started receiving this error message ("Unfortunately, System UI has stopped"). The notification reappeared within seconds of closing it, and whenever I rebooted my phone, the delay between notifications only increased slightly, and after a minute or so, the notification would refresh almost instantly.

Uninstalling Google Keyboard did not help. I could not clear the System UI cache. Rebooting did nothing except, as mentioned, temporarily increase the time between notification. After dropping my phone once though (not intentionally) and rebooting, it was fine for a few seconds, but then crashed (in all other instances it crashed on startup) - this lasted maybe two reboots.

I ultimately elected to use TWRP to backup my files, perform a system wipe, and then reinstall BlackLiquid. This seems to have fixed my issues, but I'd like to have an idea of any fixes that people are aware of.

Google and searching xda and similar forums told me that:

This error is not isolated to BlackLiquid/LiquidSmooth, but prevalent across all ROMs, including stock ROMs.

Certain apps, e.g. "Face Lock" have a tendency to cause this issue; force closing them will work.

Wiping the System UI cache may work.

Does anyone have any other fixes or reasons this happens? Or possibly for future reference, a set of diagnostics I could run? (I'm new to Android development - I just rooted my phone this past weekend.)

Original follow-up post 2013/10/22 11:43PM

When I first made this thread, I had just reflashed my phone and installed a new ROM to get around the issue as a quick and dirty fix.

Unfortunately, the problem has resurfaced, and in this instance, no app was updated or changed to cause this issue - it just happened spontaneously happened again.

I still have TWRP 2.6.3.0 installed, and none of the following have worked:

- Wiping the cache.

- Wiping the dalvik-cache.

- Fixing permissions.

Research tells me that the "Fix Permissions" option has been since removed from CWM as it is now obsolete.

I would like to note that when I reboot my phone, I will get the "Unfortunately..." error message at the lock screen (the system UI will appear in the background and then crash), but when I use the power/lock button to lock my phone/turn off the screen and turn the screen back on (turning the screen back on can take 5-10s), it does stop the message from occurring at the lock screen (i.e. until I can enter my PIN).

Does anyone have any other solutions?