You need to make a call to setContentView(your_layout.xml)
before you try making references to views in it for e.g. TextView two = (TextView) findViewById(R.id.one6);
Since you make a call to setContentView later on, the views one
and two
are null. And hence cause an exception when you set the listeners.
EDIT:
Modifying your code a bit
@Override
protected void onCreate(Bundle savedInstanceState)
{
super.onCreate(savedInstanceState);
setContentView(R.layout.quiz);
ImageView one = (ImageView) findViewById(R.id.one5);
TextView two = (TextView) findViewById(R.id.one6);
one.setOnLongClickListener(longlisten);
two.setOnLongClickListener(longlisten);
}