My phone started popping up with "Unfortunately, Google App has stopped." notification non stop. The keyboard wouldn't come up on my phone. I decided to restart my phone, which I guess was a bad idea because now I'm stuck on the lock screen. The keyboard won't come up, so I can't type in my password to get into the phone. I've tried restarting, taking the battery out, leaving it off for a while. Nothing has worked. I tried going into Safe Mode but the keyboard still won't come up. I also tried going into recovery mode and clearing the cache, that didn't help either. I would really like to avoid a factory reset. Help??
I have a possible solution. But I don't think it works most of the time.
When you are at the lock screen and your keyboard doesn't pop-up, connect the phone to the charger or your laptop/desktop. It resets the processes and your phone will come back to normal. Disconnect the cable if connected previously. After the lock-screen is opened, take a gap of 20 - 30 seconds and connect it and try opening it.
This is an old regulation for many android phones and worked a lot of times in my case with Sony Xperia SP C5302. Hope it works in your case also.