how to create listener

android_listeners.java

/* 1: listener as Activity's internal object. */
public class ContactsInserter extends Activity {
	View.OnClickListener onInsert=new View.OnClickListener() {
		public void onClick(View v) {

		}
	};
	@Override
	public void onCreate(Bundle savedInstanceState) {
		super.onCreate(savedInstanceState);
		setContentView(R.layout.main);
		Button btn=(Button)findViewById(R.id.insert);
		btn.setOnClickListener(onInsert);
	}
}
/*2:  listener constructed with closure. */
// main_activity.java 
public class main_activity extends FragmentActivity {
    /** Called when the activity is first created. */
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.mainfragment);
    }
}

// main_fragment.java
public class main_fragment extends Fragment
{
    LinearLayout mLayout;
    Button mButton;
    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container,
            Bundle savedInstanceState) {

        mLayout = (LinearLayout) inflater.inflate(R.layout.main_view, null);
        mButton = (Button) mLayout.findViewById(R.id.btn);
        mButton.setOnClickListener(new OnClickListener() {
            @Override
            public void onClick(View v) {
            }
        });
        return mLayout;
    }
}