callAsync AndroidStudio XMLRPC

I'm making an asynchronous connection in an android app, but when I put the credentials and login, the app closes. However if I make a synchronous connection it works perfect.

Error:

E/AndroidRuntime: FATAL EXCEPTION: Thread-4148
              Process: com.example.pargibay.androidphprpcxml, PID: 20553
              java.lang.RuntimeException: Can't create handler inside thread that has not called Looper.prepare()
                  at android.os.Handler.<init>(Handler.java:209)
                  at android.os.Handler.<init>(Handler.java:123)
                  at android.widget.Toast$TN.<init>(Toast.java:349)
                  at android.widget.Toast.<init>(Toast.java:105)
                  at android.widget.Toast.makeText(Toast.java:263)
                  at com.example.pargibay.androidphprpcxml.MainActivity$3.onResponse(MainActivity.java:112)
                  at de.timroes.axmlrpc.XMLRPCClient$Caller.run(XMLRPCClient.java:588)

Asynchronous Call (does not work) - >

client.callAsync(listener,"examples.login", new Object[]{users,
passw});