我正在 android studio 中编程,这是我的代码 fragment :
public class settingsView extends Fragment {
public settingsView() {
}
@Nullable
@Override
public View onCreateView(@NonNull LayoutInflater inflater, @Nullable ViewGroup container, @Nullable Bundle savedInstanceState) {
final Spinner citySpinner = (Spinner) getActivity().findViewById(R.id.citySpinner);
FirebaseDatabase.getInstance().getReference("/movies/karnataka").addValueEventListener(new ValueEventListener() {
@Override
public void onDataChange(@NonNull DataSnapshot dataSnapshot) {
ArrayList<String> cityList = new ArrayList<>();
for (DataSnapshot snapshot : dataSnapshot.getChildren()) {
cityList.add(snapshot.getKey());
}
Log.d("firebasedata", cityList.toString());
ArrayAdapter<String> adapter = new ArrayAdapter<String>(getActivity().getApplicationContext(), android.R.layout.simple_spinner_item, cityList );
adapter.setDropDownViewResource(android.R.layout.simple_spinner_item);
citySpinner.setAdapter(adapter);
}
@Override
public void onCancelled(@NonNull DatabaseError databaseError) {
}
});
return inflater.inflate(R.layout.settingsview, container, false);
}
}
我正在获取
java.lang.NullPointerException: Attempt to invoke virtual method 'void android.widget.Spinner.setAdapter(android.widget.SpinnerAdapter) on a null object reference exception
在行:
citySpinner.setAdapter(adapter)
最佳答案
您需要首先在 oncreateview 中填充包含 fragment View 的 xml 文件。
然后使用该 View 执行 findviewbyid:
view = inflater.inflate(R.layout.fragment_xml, container, false);
final Spinner citySpinner = (Spinner) view.findViewById(R.id.citySpinner);
关于java - 为什么我在这里收到微调器的空引用错误?,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/51104938/