Firestore旋转器在检索数据后传递列表时出错

Question

我正试图填充一个旋转器，但由于某些原因，当试图通过对象列表时，我得到了一个错误。请看一下：

public class AddFacultyFragment extends Fragment {

@BindView(R.id.spinner_search_UniFac)
Spinner spinner_search_UniFac;
ArrayList<University> list = new ArrayList<>();
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
                         Bundle savedInstanceState) {
    View view = inflater.inflate(R.layout.fragment_add_faculty,
            container,
            false);
    ButterKnife.bind(this, view);
    FirebaseFirestore db = FirebaseFirestore.getInstance();
    CollectionReference docRef = db.collection("university");
    docRef.get().addOnCompleteListener((OnCompleteListener<QuerySnapshot>) task -> {
        if (task.isSuccessful()) {
            for(DocumentSnapshot a : task.getResult()){
                University u = new University();
                u.setID(a.getId());
                u.setDesc(a.get("Desc").toString());
                list.add(u);
            }
        }
    });
    ArrayAdapter<University> spinnerArrayAdapter = new ArrayAdapter<University>
            (this, android.R.layout.simple_spinner_item,
                    list);
    spinnerArrayAdapter.setDropDownViewResource(android.R.layout
            .simple_spinner_dropdown_item);
    spinner_search_UniFac.setAdapter(spinnerArrayAdapter);
    return view;
}

public AddFacultyFragment() {
    // Required empty public constructor
}

}

Answer 1

我想你错过的只是正确的上下文。不能在片段上使用this，必须使用getcontext()才能工作。像这样：

公共类AddFacultyFragment扩展Fragment{

@BindView(R.id.spinner_search_UniFac)
Spinner spinner_search_UniFac;
ArrayList<University> list = new ArrayList<>();
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
                         Bundle savedInstanceState) {
    View view = inflater.inflate(R.layout.fragment_add_faculty,
            container,
            false);
    ButterKnife.bind(this, view);
    FirebaseFirestore db = FirebaseFirestore.getInstance();
    CollectionReference docRef = db.collection("university");
    docRef.get().addOnCompleteListener((OnCompleteListener<QuerySnapshot>) task -> {
        if (task.isSuccessful()) {
            for(DocumentSnapshot a : task.getResult()){
                University u = new University();
                u.setID(a.getId());
                u.setDesc(a.get("Desc").toString());
                list.add(u);
            }
        }
    });
    ArrayAdapter<University> spinnerArrayAdapter = new ArrayAdapter<University>
            (getContext(), android.R.layout.simple_spinner_item,
                    list);
    spinnerArrayAdapter.setDropDownViewResource(android.R.layout
            .simple_spinner_dropdown_item);
    spinner_search_UniFac.setAdapter(spinnerArrayAdapter);
    return view;
}

public AddFacultyFragment() {
    // Required empty public constructor
}

}