smsManager不在java类中工作

Question

public class ExpandableListAdapter extends BaseExpandableListAdapter {

----
--SOME SET OF CODE--
----

@Override
    public View getChildView(int groupPosition, final int childPosition,
            boolean isLastChild, View convertView, ViewGroup parent) {

        final String childText = (String) getChild(groupPosition, childPosition);

        if (convertView == null) {
            LayoutInflater infalInflater = (LayoutInflater) this._context
                    .getSystemService(Context.LAYOUT_INFLATER_SERVICE);
            convertView = infalInflater.inflate(R.layout.list_item, null);
        }

        TextView txtListChild = (TextView) convertView.findViewById(R.id.lblListItem);

        txtListChild.setText(childText);

         Button btn_submit = (Button)convertView.findViewById(R.id.button1);
         btn_submit.setOnClickListener(new View.OnClickListener() {

                @Override
                public void onClick(View v) {
                    String myConst = null;
                    TextView txtListChild = (TextView) v.findViewById(R.id.lblListItem);
                    TextView PhoneNo = (TextView) v.findViewById(R.id.editText1);
                    // TODO Auto-generated method stub
                    Log.v(myConst, "Read string"+childText);

           -------
           ---SMS MANAGER NOT WORKING ----
           -------


                    try {
                        SmsManager smsManager = SmsManager.getDefault();
                        smsManager.sendTextMessage(PhoneNo.toString(),null,childText,null,null);    
     -------
     ---SMS MANAGER NOT WORKING ----
     -------

                    } catch (Exception ex) {
                        Log.v(myConst, "Read string"+ex.getStackTrace());
                        ex.printStackTrace();
                    }

                    //Log.v(myConst, "Message sent"+PhoneNo.toString());

                }
         });
        return convertView;
    }

-----
--SOME SET OF CODE---
-----
}

短信管理员不在JAVA CLASS中工作，但这个相同的代码在活动类中工作正常。

  

SmsManager smsManager = SmsManager.getDefault（）;

请告知。