How do I fix system ui on android?

Here's how to fix unfortunately system UI has stopped working in Android:
Step 1 - Launch Settings
Step 2 - Go to Application Manager
Step 3 - Choose Installed App
Step 4 - Search for the Google application you want to uninstall
Step 5 - Press Uninstall App Step
6 - Reboot your Android device and check if this works to fix the said problem

reset it. per manual.

and pray

Unfortunately system UI has stopped and System UI is not responding do you want to close both are common error in android phone. Sometimes phone can not handle the user interface request at that time it show this error and it can be solved very easily. ... please restart your phone

if your have faced this issue while using your computer. Then you need to follow these steps to fix UI Failed to Load on windows

https://www.mygeekshelp.com/avast-ui-failed-to-load-after-windows-10-update

If you mean it shuts down then the battery is most likely failing, if you mean the programs stop running then try doing a memory dump, get rid of all the old data files you can. Transferring as much data to a SD memory card helps as well

That sounds like a hardware problem not software.

Check the attached links,
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How to Fix Unfortunately System UI has Stopped Messages on Android...
Android operating system How can solve Unfortunately System UI has stopped...

Android System UI has stopped working Explained

If it's an iPhone, there is a setting you can turn off and on to show the percentage of charge your battery has left. You can also get an app to tell you that and more.

This probably caused by an feature called 'Face Unlock'; either uninstall or disable it. Usually this done by Settings --> Apps --> (All -->) Face Unlock --> disable / uninstall.

Or when you actually really like that feature, make sure you've updated your phone and that Face Unlock app to the latest version.

PS: What it actually means is the Android System UI component has crashed (and will automatically restarted afterwards). You might see the statusbar at the top disappear and reappear after a few seconds as well ... (symptom).