onLongClickListener in layout with tabs

Question

I followed this tutorial: http://www.android4devs.com/2015/01/how-to-make-material-design-sliding-tabs.html?m=1 to make a layout with 5 tabs. Now I want to put an OnLongClickListener for a button in the first tab to make it share sound1. I have added this code in my MainActivity.java:

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

    button1 = (Button) findViewById(R.id.button1);

    button1.setLongClickable(true);
    button1.setOnLongClickListener(new View.OnLongClickListener() {

        @Override
        public boolean onLongClick(View arg0) {
            Intent share = new Intent(Intent.ACTION_SEND);
            share.setType("audio/ogg");

            Uri uri = Uri.parse("android.resource://" + getPackageName()
                    + "/raw/" + R.raw.sound1);
            share.putExtra(Intent.EXTRA_STREAM, uri);
            startActivity(Intent.createChooser(share, "Share Sound File"));

            return true;
        }

    });

But that makes it crash on startup, and the logcat says this:

Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'void android.view.View.setLongClickable(boolean)' on a null object reference

Answer 1

You are using fragments. You should do that on the Fragment's onCreateView() or onViewCreated() callbacks

public class Tab1 extends Fragment {

    @Override
    public View onCreateView(LayoutInflater inflater, @Nullable ViewGroup container, @Nullable Bundle savedInstanceState) {
        View v =inflater.inflate(R.layout.tab_1,container,false);
        button1 = (Button) v.findViewById(R.id.button1);
        button1.setLongClickable(true);
        ...
        return v;
    }
}