payment gateway - PayuMoney Integration in Android : Some error occured! Try again -

i'm integrating payumoney (not payu biz) in android application. followed this official documentation of payumoney. have changed merchant key, merchant id , url of hash generation of server in this sample app. taking me payumoney sdk screen can login/signup. showing toast message 'some error occured! try again' once login credentials. there else i'm missing? please guide me.

this happens when server generated hash not equal payumoney generated hash payumoney don't allow payments

also, shows blank screen after login

to fix generate hash formate

string hashsequence=key+"|"+txn+"|"+amount+"|"+productinfo+"|"+firstname+"|"+email+"|"+udf1+"|"+udf2+"|"+udf3+"|"+udf4+"|"+udf5+"|"+salt;