Sometimes we encounter some devices which have two or more SIM cards. So my question is:
How can I determine the number of SIM cards on the device?
Actually, I am developing a field test app and for example, if I have 2 SIM cards on the device, the user can choose between them to launch measurements.
There is currently no Android API for handling multiple SIM cards; any device support is entirely down to the handset manufacturer having modified the Android source. You could see if the particular manufacturer offers any kind of SDK or published API to help you, but it will be on a case by case basis.