android intent activity turning back with id

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http://stackoverflow.com – I have 2 different activities connected with their id #'s . When I started my activity 1 Its working however when I try to back I've get Null Pointer Exception cause of I cannot retrieve my id # in turning back activity. These are my button and activity codes , can you give any suggestion ? Where can I add my existing id ? backButton = (Button) findViewById(R.id.backButton); backButton.setOnClickListener(new View.OnClickListener() { public void onClick(View v) { Intent back = new Intent(getApplicationContext(), ITStaffPage.class); back.addFlags(Intent.FLAG_ (HowTos)