android fragment listener

activitySecunder.java

public class activitySecunder extends ActionBarActivity {

    OnMukaUpdateListener onMukaUpdateListener;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_activity_secunder);


        activitySecunderFragment firstFragment = new activitySecunderFragment();
        getSupportFragmentManager().beginTransaction()
                .add(R.id.fragmentContainer,firstFragment)
                .commit();

        onMukaUpdateListener = (OnMukaUpdateListener) firstFragment;

        Button btn = (Button) findViewById(R.id.btn);
        btn.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                onMukaUpdateListener.onMukaUpdate("hi");
            }
        });
    }

activitySecunderFragment.java

public class activitySecunderFragment extends Fragment implements OnMukaUpdateListener {

    TextView tv2;
    
    public activitySecunderFragment(){
    }

    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
        return inflater.inflate(R.layout.fragment_activity_secunder, container, false);
    }

    @Override
    public void onViewCreated(View view, Bundle savedInstanceState) {
        tv2 = (TextView)view.findViewById(R.id.tv2);
        super.onViewCreated(view, savedInstanceState);
    }

    @Override
    public void onMukaUpdate(String text) {
        tv2.setText(text);
    }
}

OnMukaUpdateListener.java

public interface OnMukaUpdateListener {
    public void onMukaUpdate(String text);
}