Android Spinner onItemSelected 未在 Fragment 内部调用

Question

我有一个调用多个 fragment 的 Activity 。在其中一个 fragment 中，我试图以编程方式创建一个对话框微调器并将其添加到菜单选项(在工具栏中)。我设法让它工作(至少显示了 View )，但是没有调用它的 onItemSelected。

我的代码:

public class NewsFeed extends Fragment {
private static final String TAG = "tag";
private String tag;
private ArrayAdapter<New> newsadapter;
private ArrayAdapter<Tag> tagsadapter;
private Spinner spinner;

public NewsFeed() {
    setHasOptionsMenu(true);
}

public static NewsFeed newInstance(String tag) {
    NewsFeed fragment = new NewsFeed();
    Bundle args = new Bundle();
    args.putString(TAG, tag);
    fragment.setArguments(args);
    return fragment;
}

@Override
public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    if (getArguments() != null) {
        tag = getArguments().getString(TAG);
    }
    setHasOptionsMenu(true);

}

@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
                         Bundle savedInstanceState) {
    getActivity().setTitle(tag);
    NavigationView activitynav = (NavigationView) getActivity().findViewById(R.id.nav_view);
    BottomNavigationView activitybuttomnav = (BottomNavigationView) getActivity().findViewById(R.id.navigation);
    activitynav.setCheckedItem(R.id.nav_news);
    activitybuttomnav.getMenu().getItem(1).setChecked(true);
    View v = inflater.inflate(R.layout.fragment_news_feed, container, false);

    //Spinner related code      
    tagsadapter = new TagsAdapter(getActivity(), android.R.layout.simple_spinner_item, (ArrayList<Tag>) ApplicationData.tags);
    spinner = new Spinner(getActivity(), Spinner.MODE_DIALOG);
    tagsadapter.setDropDownViewResource(android.R.layout.simple_spinner_dropdown_item);
    spinner.setPrompt("Filtrar por categoria:");
    spinner.setAdapter(tagsadapter);
    spinner.setOnItemSelectedListener(new AdapterView.OnItemSelectedListener() {
        @Override
        public void onItemSelected(AdapterView<?> parent, View view, int position, long id) {

        }

        @Override
        public void onNothingSelected(AdapterView<?> parent) {

        }
    });

    newsadapter = new NewsAdapter(getActivity().getApplicationContext(), 0, (ArrayList<New>) ApplicationData.news);
    ListView listview = (ListView) v.findViewById(R.id.listview);
    listview.setOnItemClickListener(new AdapterView.OnItemClickListener() {
        @Override
        public void onItemClick(AdapterView<?> adapter, View view, int position, long id) {
            FragmentTransaction ft = getActivity().getSupportFragmentManager().beginTransaction();
            NewsDisplay nd = NewsDisplay.newInstance(tag, ApplicationData.news.get(position).getNewsUrl());
            ft.addToBackStack(null);
            ft.replace(R.id.fragmentcontent, nd).commit();
        }
    });
    listview.setAdapter(newsadapter);
    return v;
}

@Override
public void onCreateOptionsMenu(Menu menu, MenuInflater inflater) {
    inflater.inflate(R.menu.main, menu);
    super.onCreateOptionsMenu(menu, inflater);
}

@Override
public boolean onOptionsItemSelected(MenuItem item) {
    int id = item.getItemId();

    if (id == R.id.filter_category) {
         //For showing the spinner
        spinner.performClick();
        return true;
    }
    return super.onOptionsItemSelected(item);
}

已经尝试过:

使 NewsFeed 实现 OnItemSelectedListener。

在 SetOnItemSelectedListener 中创建 OnItemSelectedListener 对象。

你能帮我一些忙吗？这可能与这是一个 fragment 有关，并且工具栏在 Activity 中。

Answer 1

Spinner 是动态创建的(private val popupSpinner: Spinner by lazy { Spinner(this, Spinner.MODE_DIALOG) })，需要分配父 View 。如果没有，则 OnItemSelected 不会因为某种原因被调用。

我写了这个 hack 来缓解这个问题。添加到父 View 并将其隐藏。确保不要在 onResume() 方法和类似方法中运行它。

findViewById<ViewGroup>(android.R.id.content).addView(popupSpinner)
popupSpinner.visibility = View.INVISIBLE

附言。有些人可能认为这个问题没有答案。但是在评论中作者自己找到了解决办法。