Solution :
Bellow line is throwing an Null Pointer Exception, producing an IllegalStateException in the exception chain:
int stopPortRange = Integer.parseInt(stopPort.getText().toString());
As you don't initialize stopPort in your onCreate method.
stopPort = (EditText) findViewById(R.id.stop_port_field);
The statement
EditText stopPort;
simply declares the variable which is null by default. Only instances that have been instantiated can have their methods invoked.
Further Readings:
https://github.com/printdotio/printio-android-sdk/issues/162
