Have problem that when I press button application crashes. Crash text package com.leftas.vidurkioskaiciavimas;
24367-24367/com.leftas.vidurkioskaiciavimas E/An
try this
mUserOutput = (TextView) findViewById(R.id.textView2); mUserInput = (TextView) findViewById(R.id.textView);
You have already Declared textview's as class member. So initialize them as above.
This
TextView mUserOutput = (TextView) findViewById(R.id.textView2); // makes mUserOutput local