open date picker on button click event
 btn.setOnClickListener(new OnClickListener() {          @TargetApi(Build.VERSION_CODES.HONEYCOMB)         @Override         public void onClick(View v) {          // TODO Auto-generated method stub           final Calendar c = Calendar.getInstance();          int mYear = c.get(Calendar.YEAR);          int mMonth = c.get(Calendar.MONTH);          int mDay = c.get(Calendar.DAY_OF_MONTH);           // Launch Date Picker Dialog          DatePickerDialog dpd = new DatePickerDialog(            SurveyMain.this,            new DatePickerDialog.OnDateSetListener() {             @TargetApi(Build.VERSION_CODES.HONEYCOMB)             @Override             public void onDateSet(               DatePicker view, int year,               int monthOfYear,               int dayOfMonth) {              GregorianCalendar gc = new GregorianCalendar();              gc.add(Calendar.DATE, 1);              datetomoroow = gc.getTime();               c.set(Calendar.YEAR, year);              c.set(Calendar.MONTH,  ...