放置自动完成实施

Question

我已经为我的一个活动获得了此代码，该活动应该在用户开始输入时提供自动填充地址的选项，但在尝试启动活动时会崩溃。

package com.reachmenow;

import java.io.IOException;
import java.io.InputStreamReader;
import java.net.HttpURLConnection;
import java.net.MalformedURLException;
import java.net.URL;
import java.net.URLEncoder;
import java.util.ArrayList;

import org.json.JSONArray;
import org.json.JSONException;
import org.json.JSONObject;

import android.app.Activity;
import android.content.Context;
import android.os.Bundle;
import android.util.Log;
import android.widget.ArrayAdapter;
import android.widget.Filter;
import android.widget.Filterable;
import android.widget.ListView;
import android.widget.TabHost;
import android.widget.TabHost.TabSpec;

public class JoinMeNow extends Activity {
    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 = "AIzaSyAZQpyuuupl4aRHAzfxkaV4jlAmM9nRwxA";

    ListView listView1, listView2;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        // TODO Auto-generated method stub
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_now);

        String[] contacts = { "ex1", "ex2" };
        String[] recent = { "first", "second" };


        TabHost th = (TabHost) findViewById(R.id.tab_host);
        th.setup();

        // tab1
        TabSpec recentLocationsTab = th.newTabSpec("tab1");
        recentLocationsTab.setContent(R.id.recent_locations_tab);
        recentLocationsTab.setIndicator("Recent");
        th.addTab(recentLocationsTab);

        // tab2
        TabSpec allFriendsTab = th.newTabSpec("tab2");
        allFriendsTab.setContent(R.id.all_friends_tab);
        allFriendsTab.setIndicator("All Friends");
        th.addTab(allFriendsTab);

        ArrayAdapter<String> adapter1 = new ArrayAdapter<String>(this,
                android.R.layout.simple_list_item_1, android.R.id.text1,
                contacts);

        listView1 = (ListView) findViewById(R.id.list1);
        // Assign adapter to ListView
        listView1.setAdapter(adapter1);

        ArrayAdapter<String> adapter2 = new ArrayAdapter<String>(this,
                android.R.layout.simple_list_item_1, android.R.id.text1,
                recent);
        listView2 = (ListView) findViewById(R.id.list2);
        // Assign adapter to ListView
        listView2.setAdapter(adapter2);

        PlacesAutoCompleteAdapter autoComplete = new PlacesAutoCompleteAdapter(this, R.layout.list_item);
        int q = autoComplete.getCount();
        System.out.print(q);
    }

    //Autocomplte method
    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;
    }
    private class PlacesAutoCompleteAdapter extends ArrayAdapter<String> implements Filterable {
        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() {
                @Override
                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;
        }
    }
}

活动在清单上声明。

这是logCat上的例外：

    08-31 23:27:54.012: W/dalvikvm(10853): threadid=1: thread exiting with uncaught exception (group=0x414ea2a0)
08-31 23:27:54.032: E/AndroidRuntime(10853): FATAL EXCEPTION: main
08-31 23:27:54.032: E/AndroidRuntime(10853): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.reachmenow/com.reachmenow.JoinMeNow}: java.lang.NullPointerException
08-31 23:27:54.032: E/AndroidRuntime(10853): Caused by: java.lang.NullPointerException