I have a China Unicom in my phone currently (as a second SIM, but I might now take it out) and haven't had any problems with Google Maps. When I was in China in June I was using Google Maps via VPN. This doesn't mean much of course as things can move pretty quickly. I also didn't realise a SIM card's capabilities.
One of the bug commenters said that "neither reviews nor photos" could be seen and believes that it was because "I once used this app in China" but does not explicitly mention swapping out the SIM card.
my question: does a visitor to China have to swap out the SIM card in their phone in order to use it there?
Yes, I heard that the Great Fire Wall in China treats network traffic differently when one is on T-mobile data roaming...A friend of mine could use her T-mobile phone to access google, gmail and instagram in china directly, without using a VPN...But you can only access 2G or 3G network (not 4G) in most of the areas there...
Somewhat related: I was in China recently, and bought a SIM at the airport. You know those arrows on the mobile data icon in the notification bar on Android that tell you whether your device is actively transferring data? The upload arrow was on non-stop, the entire time I was there. I still have no clue what it was doing.
That's basically what I assumed, but I wasn't aware that SIM cards had that kind of access to the device storage. I thought at minimum it was sending out my location constantly though.
I know next to nothing about telecoms technology, but in my head always assumed that SIMs were basically just read-only chips containing keys to authorise the phone to use the network. Clearly my assumption was wrong in some way.
SIM cards can contain applets that execute on the baseband.
The baseband often uses the same system memory as the application cpu (where android runs), and might even be in the same package or on the same silicon. In theory devices shipped with an MMU to prevent the baseband from fucking with the application processor. In reality, even Qualcomm ships broken MMU configs, and don't bother to ship a fix until the device is near EOL. I can't even imagine the horror show of Mediatek's MMU.
Of course it's also possible that this is Google playing nice with Chinese legislation...
The most likely explanation is that you had applications that were trying to connect to censored servers, so it was just always retrying, but never getting any data back (so the download arrow wouldn’t show).
