Beijing Transportation Card / subway ticket

Foreigners need to go to the service center to get a Yikatong card. Actually you can use Alipay to WeChat pay for public transportation and notably there is the payment service center for foreigners at the two airports in Beijing which help foreign tourist to get access to the transportation QR code. Just go there for help after landing in.
Xi'an metro has one day pass and three day pass you can buy it on the machines.
Shanghai also has one day, three day and seven day pass sold on the machines.

Another news is released today. Both airports and major railway stations are to handle special Yikatong called "Beijing Pass" for foreign visitors.

Beijing City wants more foreign tourists for sure.

There are so much confusion here. You need to find out for yourself.

The news also mentioned that foreigners will be able to buy subway tickets with visa or MasterCard at vending machines. Very very confusing it is.