AutoCompleteTextview下拉列表有时不会出现在Android中

我正在使用GoogleAPI获取位置。当用户在编辑字段中写入时，有时会下拉apear，有时则不会显示。我想知道，当用户写一个单一的字符下拉列表应该出现

atvPlacesFrom = (AutoCompleteTextView) findViewById(R.id.atv_places_from);
    hintList = (ListView) findViewById(R.id.hint_list);

    atvPlacesFrom.setDropDownHorizontalOffset(18);
    atvPlacesFrom.addTextChangedListener(new TextWatcher() {

        @Override
        public void onTextChanged(CharSequence s, int start, int before, int count) {
            placesTask = new PlacesTask();
            placesTask.execute(s.toString());
        }

        @Override
        public void beforeTextChanged(CharSequence s, int start, int count, int after) {
            // TODO Auto-generated method stub
        }

        @Override
        public void afterTextChanged(Editable s) {
            placesTask = new PlacesTask();
            placesTask.execute(s.toString());
        }
    });

---

你有没有试过谷歌提供的例子。如果没有，那么遵循它。还是像下面这样

atvPlacesFrom = (AutoCompleteTextView) findViewById(R.id.atv_places_from);
atvPlacesFrom..setAdapter(new PlacesAutoCompleteAdapter(this, R.layout.list_item));

并创建一个名为PlaceAutoCompleteAdapter的新类，并在其中写下下面的代码

class PlacesAutoCompleteAdapter extends ArrayAdapter<String> implements Filterable {


private static final String LOG_TAG = "ExampleApp";

private static final String PLACES_API_BASE =     "https://maps.googleapis.com/maps/api/place";
private static final String TYPE_AUTOCOMPLETE = "/autocomplete";
private static final String OUT_JSON = "/json";

private static final String API_KEY = "AIzaSyDVrdPvBnkLihvHWZQvSxNgnwTW8lZMHiA";
private ArrayList<String> resultList;

public PlacesAutoCompleteAdapter(Context context, int textViewResourceId) {
    super(context, textViewResourceId);
}

@Override
public int getCount() {
    return resultList.size();
}

@Override
public String getItem(int index) {
    return resultList.get(index);
}

@Override
public Filter getFilter() {
    Filter filter = new Filter() {
        protected FilterResults performFiltering(CharSequence constraint) {
            FilterResults filterResults = new FilterResults();
            if (constraint != null) {
                // Retrieve the autocomplete results.
                resultList = autocomplete(constraint.toString());

                // Assign the data to the FilterResults
                filterResults.values = resultList;
                filterResults.count = resultList.size();
            }
            return filterResults;
        }

        @Override
        protected void publishResults(CharSequence constraint, FilterResults results) {
            if (results != null && results.count > 0) {
                notifyDataSetChanged();
            }
            else {
                notifyDataSetInvalidated();
            }
        }};
    return filter;
}




private ArrayList<String> autocomplete(String input) {
    ArrayList<String> resultList = null;

    HttpURLConnection conn = null;
    StringBuilder jsonResults = new StringBuilder();
    try {
        StringBuilder sb = new StringBuilder(PLACES_API_BASE + TYPE_AUTOCOMPLETE + OUT_JSON);
        sb.append("?key=" + API_KEY);
       // sb.append("&components=country:uk");
        sb.append("&input=" + URLEncoder.encode(input, "utf8"));

        URL url = new URL(sb.toString());
        conn = (HttpURLConnection) url.openConnection();
        InputStreamReader in = new InputStreamReader(conn.getInputStream());

        // Load the results into a StringBuilder
        int read;
        char[] buff = new char[1024];
        while ((read = in.read(buff)) != -1) {
            jsonResults.append(buff, 0, read);
        }
    } catch (MalformedURLException e) {
        Log.e(LOG_TAG, "Error processing Places API URL", e);
        return resultList;
    } catch (IOException e) {
        Log.e(LOG_TAG, "Error connecting to Places API", e);
        return resultList;
    } finally {
        if (conn != null) {
            conn.disconnect();
        }
    }

    try {
        // Create a JSON object hierarchy from the results
        JSONObject jsonObj = new JSONObject(jsonResults.toString());
        JSONArray predsJsonArray = jsonObj.getJSONArray("predictions");

        // Extract the Place descriptions from the results
        resultList = new ArrayList<String>(predsJsonArray.length());
        for (int i = 0; i < predsJsonArray.length(); i++) {
            resultList.add(predsJsonArray.getJSONObject(i).getString("description"));
        }
    } catch (JSONException e) {
        Log.e(LOG_TAG, "Cannot process JSON results", e);
    }

    return resultList;
}
}

请不要在PlaceAutoCompleteAdapter类中更改任何内容