Referring to localhost from the emulated environment
If you need to refer to your host computer's localhost, such as when you want the emulator client to contact a server running on the same host, use the alias 10.0.2.2 to refer to the host computer's loopback interface. From the emulator's perspective, localhost (127.0.0.1) refers to its own loopback interface.
本地调试时，在模拟器上可以使用 10.0.2.2 ，这个地址对应PC机的 127.0.0.1 ， 本人亲自验证，有效。
