填充片段中的微调器时出错

Question

I have a Activity with two fragments. One of them hava a spinner. When I populate it the app crashes. I don't know why. In android developers it's confused how do it in fragments, it seems is diferent like normal activity.

Thanks!

public class InstrumentsFrag extends Fragment {

TextView tv1;
Spinner sp;

String[] os = {"Cupcake v1.5", "Donut v1.6", "Éclair v2.0/2.1", "Froyo v2.2",
        "Gingerbread v2.2", "Honeycomb v3.0/3.1"};
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
        Bundle savedInstanceState) {

    return inflater.inflate(R.layout.instruments, container, false);

}
 @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);

        sp = (Spinner) getActivity().findViewById(
                R.id.spinner1);

        ArrayAdapter <CharSequence>adapter = ArrayAdapter.createFromResource( getActivity(), R.array.sections , android.R.layout.simple_spinner_item); 
        adapter.setDropDownViewResource(android.R.layout.simple_spinner_dropdown_item);
        sp.setAdapter(adapter);
 }

Answer 1

I had the same problem where my app crashed when populating a spinner. In my case, the spinner I was populating was defined in the fragment's XML file, so the trick was getting findViewById() to find it. I see in your case you tried to use getActivity():

sp = (Spinner) getActivity().findViewById(R.id.spinner1);

I also tried using both getActivity() and getView(), and both caused crashes (null spinner, and NULL Pointer exception respectively).

I finally got this to work by replacing getActivity() with the fragment's view. I did this by populating the spinner when onCreateView() is called. Here are some snippets from my final code:

private Spinner spinner;
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) 
{
  View view = inflater.inflate(R.layout.myFragmentXmlFile, container, false);
  // Now use the above view to populate the spinner.
  setSpinnerContent( view );
  ...
}

private void setSpinnerContent( View view )
{
  spinner = (Spinner) view.findViewById( R.id.mySpinner );
  ...
  spinner.setAdapter( adapter );
  ...
}

So I passed the fragment view into my function and referenced that view to configure the spinner. That worked perfectly. (And quick disclaimer - I'm new to Android myself, so perhaps some of the above terminology can be corrected or clarified if needed by more experienced people.)

Hope it helps!