java - Unable to start activity: invalid int -

java - Unable to start activity: invalid int -

please guys writing android app, i'm getting run time error in logcat : java.lang.runtimeexception: unable start activity: java.lang.numberformatexception: invalid int: ""

public class mainactivity extends activity{ edittext et; button guess, randomize; textview tv1, tv2; int num1; int num2; int userans; int answer; final random rand = new random(); @override protected void oncreate(bundle savedinstancestate) { super.oncreate(savedinstancestate); setcontentview(r.layout.main); et = (edittext) findviewbyid(r.id.edittext1); tv1 = (textview) findviewbyid(r.id.textview1); tv2 = (textview) findviewbyid(r.id.textview2); guess = (button) findviewbyid(r.id.btnsubmit); randomize = (button) findviewbyid(r.id.button1); randomize(rand); tv2.settext(num1 + " + " + num2); userans = integer.parseint(et.gettext().tostring()); guess.setonclicklistener(new onclicklistener() { @override public void onclick(view v) { reply = num1 + num2; if (userans == answer) { tv1.settext("correct... reply " +answer); } else { tv1.settext("wrong"); } } }); randomize.setonclicklistener(new onclicklistener() { @override public void onclick(view v) { randomize(rand); } }); } private void randomize(final random rand) { num1 = 1 + rand.nextint(50); num2 = 1 + rand.nextint(50); } }

et empty unless set default value. such, et.gettext homecoming "", not valid number parseint throw exception. need wait text until user has pressed guess button , then.

java android