4G/3G switch
Posted: 08 Oct 2019 14:12
Can this be accomplished without root, or do I have to use Control UI (which will not work with the phone screen off/locked)?
Usually can't be done anymore since Android Lollipop above. But you can try if your phone reflect the secure setting value. Usually mobile data setting is stored at the global category. For network mode, it is usually
[Global] preferred_network_mode1 : 11
This is for LTE only. There are a lot of other modes too, but it is different in each devices, depends on the network support. You have to find it out yourself.
You can try to find the secure setting value using my secure setting logger : viewtopic.php?f=3&t=7931
At my ROM, RR 7.0.2 Pie 9.0, I can turn on/off mobile data, including changing the network mode using this method, without root and can be done in screen off.