How to add codes in Tabbed Activity,android project

[AC Question]

I have created an tabbed Activity and Java class file for every tab and I want to put this code but I do not know where, please help me? what is the right way to add this thing!!
public class MainActivity extends ListActivity {
ArrayList<String> list = new ArrayList<String>();
ArrayAdapter<String> adapter;
@override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
Button btn = (Button) findViewById(R.id.btnAdd);
Button btnDel = (Button) findViewById(R.id.btnDel);
adapter = new ArrayAdapter<String>(this, android.R.layout.simple_list_item_multiple_choice, list);
OnClickListener listener = new OnClickListener() {
@override
public void onClick(View v) {
EditText edit = (EditText) findViewById(R.id.txtItem);
list.add(edit.getText().toString());
edit.setText("");
adapter.notifyDataSetChanged();
}
};
OnClickListener listenerDel = new OnClickListener() {
@override
public void onClick(View v) {
SparseBooleanArray checkedItemPositions = getListView().getCheckedItemPositions();
int itemCount = getListView().getCount();

for(int i=itemCount-1; i >= 0; i--){
if(checkedItemPositions.get(i)){
adapter.remove(list.get(i));
}
}
checkedItemPositions.clear();
adapter.notifyDataSetChanged();
}
};
btn.setOnClickListener(listener);
btnDel.setOnClickListener(listenerDel);
setListAdapter(adapter);
}

 

[B. Diddy]

Moved to the Software Development forum.