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Android Android Fragments Introducing Fragments Handling Clicks

in implemeting interface methods there is no syntax error

I put everything right

NewsFragment.java
public class NewsFragment extends Fragment {

  public interface NewsListener{
   public void  onNewsItemSelected(int index);
  }

    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
        View view = inflater.inflate(R.layout.fragment_news, container, false);
        return view;
    }
}
MainActivity.java
public class MainActivity extends AppCompatActivity implements NewsListener {
  public void onNewsItemSelected(int index){

  }

    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        NewsFragment newsFragment = new NewsFragment();
        FragmentManager fragmentManager = getFragmentManager();
        FragmentTransaction fragmentTransaction = fragmentManager.beginTransaction();
        fragmentTransaction.add(R.id.placeholder, newsFragment);
        fragmentTransaction.commit();
    }
}

2 Answers

Seth Kroger
Seth Kroger
56,413 Points

The NewsListener interface is inside NewsFragment, making it an inner interface. Whenever you have an inner class or interface you need to refer to it as OuterClass.InnerClass. So your first line of MainActivity should be:

public class MainActivity extends AppCompatActivity implements NewsFragment.NewsListener {

I'm no Android developer, sadly, but I do notice something that might be causing a Syntax error (I do know some Java). Check this out:

public void  onNewsItemSelected(int index);  //<-------- Sadly this is invalid Java code

public void  onNewsItemSelected(int index) {}  //<-------- This successfully creates a function with no body. Yay!    

I hope this helps :grin:

~Alex

Seth Kroger
Seth Kroger
56,413 Points

Alex, when you're declaring (as opposed to implementing) an interface in Java the first line is valid because you are just declaring an empty method signature.