java - AutoCompleteTextView 不显示任何下拉列表

Question

我正在处理一项要求，其中使用自动完成 TextView 来获取匹配的Localities。用户必须输入几个字符，然后从服务器返回与这些字符匹配的 Localities 列表。自动完成 TextView 然后应将此列表显示为下拉列表(或弹出窗口)。出于某种原因，即使我从服务器接收到有效的 Localities，自动完成下拉列表也不会出现。这是我的代码。

位置(模型)

public class Locality {
    private int Id;
    private String name;
    private boolean selected;

    //Getters and Setters
}

DonorSearchFragment.xml(包含AutoCompleteTextView的布局文件)

<AutoCompleteTextView
    android:id="@+id/actLocality"
    android:layout_width="match_parent"
    android:layout_height="wrap_content" />

LocalityListAdapter View (locality_row.xml)

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    ...
    <TextView
        android:id="@+id/txvLocalityName"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        />

</LinearLayout>

LocalityListAdapter.java

public class LocalityListAdapter  extends ArrayAdapter<Locality> {

    List<Locality> localities;
    @Override
    public View getView(int position, View convertView, ViewGroup parent) {
        //The Current View
        View view = convertView;
        if (view == null) {
            LayoutInflater inflater = (LayoutInflater) getContext().getSystemService(Context.LAYOUT_INFLATER_SERVICE);
            view = inflater.inflate(R.layout.locality_row, null);
        }
        Locality currentLocality = localities.get(position);
        if (currentLocality != null) {
            TextView txvLocalityName = (TextView) view.findViewById(R.id.txvLocalityName);
            txvLocalityName.setText(currentLocality.getName());
        }
        return view;
    }
}

DonorSearchFragment.java(显示 AutoCompleteTextView 的 fragment )

public class DonorSearchFragment extends Fragment {
    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container,
                             Bundle savedInstanceState) {
        searchFragmentView = inflater.inflate(R.layout.fragment_donor_search, container, false);

        //Locality AutoComplete
        localityList = new ArrayList<Locality>();
        AutoCompleteTextView actLocality = (AutoCompleteTextView) searchFragmentView.findViewById(R.id.actLocality);
        localityListAdapter = new LocalityListAdapter(this.getActivity(), R.layout.locality_row, localityList);
        actLocality.setAdapter(localityListAdapter);

        actLocality.addTextChangedListener(new TextWatcher() {
        ...
            @Override
            public void afterTextChanged(Editable editable) {
                new LocalitySearchTask().execute();
            }
        });


    private class LocalitySearchTask extends AsyncTask<Void, Void, List<Locality>> {
        ...
        protected List<Locality> doInBackground(Void... voids) {
            List<Locality> localities = null;

            //Call WebService and populate localities

            return localities;
        }

        @Override
        protected void onPostExecute(List<Locality> localities) { 

            //Refresh List backing the Adapter
            //I see valid localities here, but somehow they are not shown by AutoComplete

            localityListAdapter.clear();
            for(Locality locality : localities){
                localityList.add(locality);
            }
            localityListAdapter.notifyDataSetChanged();
        }

    }
}

在 onPostExecute() 中，我检查了我是否收到了有效的地点列表，然后将它们推送到支持适配器的 LocalityList 中，但是下拉列表中没有显示这些地点。实际上没有显示下拉菜单。任何可能错误或遗漏的原因？

Answer 1

我觉得有一种更好的方法可以避免使用 AsyncTask 来处理这种情况.取而代之的是 Filter可以使用，它提供performFiltering()实际上在工作线程中运行的回调。在这里可以决定/准备匹配数据(例如通过服务器调用或类似方式)。当结果准备好时 publishResults在 UI 线程上运行的回调可用于修改支持自定义适配器的列表。我刚刚开始了解 Android 适配器，所以我在这里可能不正确。这是我正在使用的代码

public class LocalityListAdapter  extends ArrayAdapter<Locality> {

    List<Locality> localities;
    @Override
    public View getView(int position, View convertView, ViewGroup parent) {
        View view = convertView;
        if (view == null) {
            LayoutInflater inflater = (LayoutInflater) getContext().getSystemService(Context.LAYOUT_INFLATER_SERVICE);
            view = inflater.inflate(R.layout.locality_row, null);
        }
        Locality currentLocality = localities.get(position);
        if (currentLocality != null) {
            TextView txvLocalityName = (TextView) view.findViewById(R.id.txvLocalityName);
            txvLocalityName.setText(currentLocality.getName());
        }
        return view;
    }

    @Override
    public Filter getFilter() {
        return localityFilter;
    }

    Filter localityFilter = new Filter() {
        @Override
        public CharSequence convertResultToString(Object resultValue) {
            Locality locality = (Locality) resultValue;
            return locality.getName();
        }

        protected FilterResults performFiltering(CharSequence constraint) {
            List<Locality> localityList = new ArrayList<Locality>();
            ...Get Data from Server 
            //Return FilterResults created from response
            FilterResults filterResults = new FilterResults();
            filterResults.values = localityList;
            filterResults.count = localityList.size();
            return filterResults;
        }

        @Override
        protected void publishResults(CharSequence charSequence, FilterResults filterResults) {
            localities.clear();
            List<Locality> filteredList = (List<Locality>) filterResults.values;
            for(Locality locality : filteredList) {
                localities.add(locality);
            }
            notifyDataSetChanged();
        }
    }
}            

DonorSearchFragment.java(来自 MainActivity)

public class DonorSearchFragment extends Fragment {
    ...
    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container,
                             Bundle savedInstanceState) {
        searchFragmentView = inflater.inflate(R.layout.fragment_donor_search, container, false);

        //Locality AutoComplete
        localityList = new ArrayList<Locality>();
        actLocality = (AutoCompleteTextView) searchFragmentView.findViewById(R.id.actLocality);
        localityListAdapter = new LocalityListAdapter(this.getActivity(), R.layout.locality_row, localityList);
        actLocality.setAdapter(localityListAdapter);
        ...
        return searchFragmentView;
    }
}