android - 使用适用于 Android 的 google places api 网络服务搜索附近的特定地点

Question

我正在尝试使用 google places api 网络服务将地点搜索类型限制为医院，但无法实现。

逻辑猫

java.lang.NullPointerException at com.ediode.graphics3d.ClinicFragment.sbMethod(ClinicFragment.java:174) at com.ediode.graphics3d.ClinicFragment.onMapReady(ClinicFragment.java:95)

主 Activity

public class ClinicFragment extends AppCompatActivity implements
    GoogleApiClient.ConnectionCallbacks,GoogleApiClient.OnConnectionFailedListener,
    LocationListener,
    OnMapReadyCallback
    {
     private GoogleMap mGoogleMap;
    SupportMapFragment mapFrag;
    LocationRequest mLocationRequest;
    GoogleApiClient mGoogleApiClient;
    LatLng latLng;
    double mLatitude=0;
    double mLongitude=0;

    @Override
    protected void onCreate(Bundle savedInstanceState)
    {
    super.onCreate(savedInstanceState);

    setContentView(R.layout.clinic_fragment);

    mapFrag = (SupportMapFragment) getSupportFragmentManager().findFragmentById(R.id.map);
    mapFrag.getMapAsync(this);
    }

    @Override
    public void onMapReady(GoogleMap googleMap)
    {

    mGoogleMap = googleMap;
    mGoogleMap.setMyLocationEnabled(true);
    buildGoogleApiClient();
    mGoogleApiClient.connect();
    StringBuilder sbValue = new StringBuilder(sbMethod());
    PlacesTask placesTask = new PlacesTask();
    placesTask.execute(sbValue.toString());
    }

    @Override
    public void onPause()
    {
    super.onPause();
    //Unregister for location callbacks:
    if (mGoogleApiClient != null)
    {
    LocationServices.FusedLocationApi.removeLocationUpdates(mGoogleApiClient, this);
    }
    }

    protected synchronized void buildGoogleApiClient()
    {
    mGoogleApiClient = new GoogleApiClient.Builder(this)
    .addConnectionCallbacks(this)
    .addOnConnectionFailedListener(this)
    .addApi(LocationServices.API)
    .build();
    }

    @Override
    public void onConnected(Bundle bundle) throws SecurityException
    {
    Toast.makeText(this,"Connected",Toast.LENGTH_SHORT).show();
    // Get LocationManager object from System Service LOCATION_SERVICE
    LocationManager locationManager = (LocationManager) getSystemService(Context.LOCATION_SERVICE);
    // Create a criteria object to retrieve provider
    Criteria criteria = new Criteria();
    // Get the name of the best provider
    String provider = locationManager.getBestProvider(criteria, true);
    // Get Current Location
    Location myLocation = locationManager.getLastKnownLocation(provider);
    // Get latitude of the current location
    double latitude = myLocation.getLatitude();
    // Get longitude of the current location
    double longitude = myLocation.getLongitude();
    // Create a LatLng object for the current location
    latLng = new LatLng(latitude, longitude);

    //mGoogleMap.clear();
    //latLng = new LatLng(mLastLocation.getLatitude(), mLastLocation.getLongitude());
    MarkerOptions markerOptions = new MarkerOptions();
    markerOptions.position(latLng);
    markerOptions.title("Current Position");
    markerOptions.icon(BitmapDescriptorFactory.defaultMarker(BitmapDescriptorFactory.HUE_RED));
    Marker m = mGoogleMap.addMarker(markerOptions);
    m.showInfoWindow();
    mGoogleMap.moveCamera(CameraUpdateFactory.newLatLng(latLng));
    mGoogleMap.animateCamera(CameraUpdateFactory.zoomTo(11));
    Toast.makeText(this,"Touch the Pink Markers to View the Details of that Hospital",Toast.LENGTH_LONG).show();
    }

    @Override
    public void onConnectionSuspended(int i) {
    Toast.makeText(this,"onConnectionSuspended",Toast.LENGTH_SHORT).show();
    }

    @Override
    public void onConnectionFailed(ConnectionResult connectionResult) {
    Toast.makeText(this,"onConnectionFailed",Toast.LENGTH_SHORT).show();
    }

    @Override
    public void onLocationChanged(Location location) {

    }


    public StringBuilder sbMethod() throws SecurityException
    {
    LocationManager locationManager = (LocationManager) getSystemService(Context.LOCATION_SERVICE);
    Criteria criteria = new Criteria();
    String provider = locationManager.getBestProvider(criteria, true);
    Location myLocation = locationManager.getLastKnownLocation(provider);
    mLatitude=myLocation.getLatitude();
    mLongitude=myLocation.getLongitude();

    StringBuilder sb = new StringBuilder("https://maps.googleapis.com/maps/api/place/nearbysearch/json?");
    sb.append("location=" + mLatitude + "," + mLongitude);
    sb.append("&radius=20000");
    sb.append("&types=" + "hospital|doctor");
    sb.append("&sensor=true");

    sb.append("&key=***********************");

    Log.d("Map", "url: " + sb.toString());

    return sb;
    }

    private class PlacesTask extends AsyncTask<String, Integer, String>
    {

    String data = null;

// Invoked by execute() method of this object
@Override
protected String doInBackground(String... url) {
    try {
        data = downloadUrl(url[0]);
    } catch (Exception e) {
        Log.d("Background Task", e.toString());
    }
    return data;
}

// Executed after the complete execution of doInBackground() method
@Override
protected void onPostExecute(String result) {
    ParserTask parserTask = new ParserTask();

    // Start parsing the Google places in JSON format
    // Invokes the "doInBackground()" method of the class ParserTask
    parserTask.execute(result);
}
}
private String downloadUrl(String strUrl) throws IOException
{
    String data = "";
    InputStream iStream = null;
    HttpURLConnection urlConnection = null;
    try {
        URL url = new URL(strUrl);

        // Creating an http connection to communicate with url
        urlConnection = (HttpURLConnection) url.openConnection();

        // Connecting to url
        urlConnection.connect();

        // Reading data from url
        iStream = urlConnection.getInputStream();

        BufferedReader br = new BufferedReader(new InputStreamReader(iStream));

        StringBuffer sb = new StringBuffer();

        String line = "";
        while ((line = br.readLine()) != null) {
            sb.append(line);
        }

        data = sb.toString();

        br.close();

    } catch (Exception e) {
        Log.d("Exception", e.toString());
    } finally {
        iStream.close();
        urlConnection.disconnect();
    }
    return data;
}

private class ParserTask extends AsyncTask<String, Integer, List<HashMap<String, String>>> {

JSONObject jObject;

// Invoked by execute() method of this object
@Override
protected List<HashMap<String, String>> doInBackground(String... jsonData) {

    List<HashMap<String, String>> places = null;
    Place_JSON placeJson = new Place_JSON();

    try {
        jObject = new JSONObject(jsonData[0]);

        places = placeJson.parse(jObject);

    } catch (Exception e) {
        Log.d("Exception", e.toString());
    }
    return places;
}

// Executed after the complete execution of doInBackground() method
@Override
protected void onPostExecute(List<HashMap<String, String>> list) {

    Log.d("Map", "list size: " + list.size());
    // Clears all the existing markers;
    //mGoogleMap.clear();

    for (int i = 0; i < list.size(); i++) {

        // Creating a marker
        MarkerOptions markerOptions = new MarkerOptions();

        // Getting a place from the places list
        HashMap<String, String> hmPlace = list.get(i);


        // Getting latitude of the place
        double lat = Double.parseDouble(hmPlace.get("lat"));

        // Getting longitude of the place
        double lng = Double.parseDouble(hmPlace.get("lng"));

        // Getting name
        String name = hmPlace.get("place_name");

        Log.d("Map", "place: " + name);

        // Getting vicinity
        String vicinity = hmPlace.get("vicinity");

        latLng = new LatLng(lat, lng);

        // Setting the position for the marker
        markerOptions.position(latLng);

        markerOptions.title(name + " : " + vicinity);

        markerOptions.icon(BitmapDescriptorFactory.defaultMarker(BitmapDescriptorFactory.HUE_MAGENTA));

        // Placing a marker on the touched position
        Marker m = mGoogleMap.addMarker(markerOptions);
       }
      }
    }
    public class Place_JSON {

/**
 * Receives a JSONObject and returns a list
 */
public List<HashMap<String, String>> parse(JSONObject jObject) {

    JSONArray jPlaces = null;
    try {
        /** Retrieves all the elements in the 'places' array */
        jPlaces = jObject.getJSONArray("results");
    } catch (JSONException e) {
        e.printStackTrace();
    }
    /** Invoking getPlaces with the array of json object
     * where each json object represent a place
     */
    return getPlaces(jPlaces);
}

private List<HashMap<String, String>> getPlaces(JSONArray jPlaces) {
    int placesCount = jPlaces.length();
    List<HashMap<String, String>> placesList = new ArrayList<HashMap<String, String>>();
    HashMap<String, String> place = null;

    /** Taking each place, parses and adds to list object */
    for (int i = 0; i < placesCount; i++) {
        try {
            /** Call getPlace with place JSON object to parse the place */
            place = getPlace((JSONObject) jPlaces.get(i));
            placesList.add(place);
        } catch (JSONException e) {
            e.printStackTrace();
        }
    }
    return placesList;
}

/**
 * Parsing the Place JSON object
 */
private HashMap<String, String> getPlace(JSONObject jPlace)
{

    HashMap<String, String> place = new HashMap<String, String>();
    String placeName = "-NA-";
    String vicinity = "-NA-";
    String latitude = "";
    String longitude = "";
    String reference = "";

    try {
        // Extracting Place name, if available
        if (!jPlace.isNull("name")) {
            placeName = jPlace.getString("name");
        }

        // Extracting Place Vicinity, if available
        if (!jPlace.isNull("vicinity")) {
            vicinity = jPlace.getString("vicinity");
        }

        latitude = jPlace.getJSONObject("geometry").getJSONObject("location").getString("lat");
        longitude = jPlace.getJSONObject("geometry").getJSONObject("location").getString("lng");
        reference = jPlace.getString("reference");

        place.put("place_name", placeName);
        place.put("vicinity", vicinity);
        place.put("lat", latitude);
        place.put("lng", longitude);
        place.put("reference", reference);

    } catch (JSONException e) {
        e.printStackTrace();
    }
    return place;
}
}

Answer 1

首先，您正在连接到 GooglePlayServices，但从未实际使用 GooglePlayServices 获取位置。

取而代之的是:

Location myLocation = locationManager.getLastKnownLocation(provider);

你可能想这样做:

Location mLastLocation = LocationServices.FusedLocationApi.getLastLocation(
                mGoogleApiClient);

但是，这些方法总是有返回null的机会，所以总是对上述方法的结果做一个null检查。在调用 mLatitude=myLocation.getLatitude(); 之前，您缺少对此位置对象的空检查是导致 NullPointerException 的原因。

但是，我也建议不要调用 getLastLocation()，因为它很可能会返回 null。它也不请求新位置，因此即使您返回一个位置，它也可能非常旧，并且不能反射(reflect)设备的当前位置。最好注册一个监听器，即使您只是在获得第一个 onLocationChanged() 回调后取消注册。

看起来你基本上是想结合this answer和 this answer .

我基本上就是这样做的，并且稍微清理了代码。

这是整个类的代码:

import android.location.Location;
import android.os.AsyncTask;
import android.os.Bundle;
import android.support.v7.app.AppCompatActivity;
import android.util.Log;
import com.google.android.gms.common.ConnectionResult;
import com.google.android.gms.common.api.GoogleApiClient;
import com.google.android.gms.location.LocationListener;
import com.google.android.gms.location.LocationRequest;
import com.google.android.gms.location.LocationServices;
import com.google.android.gms.maps.CameraUpdateFactory;
import com.google.android.gms.maps.GoogleMap;
import com.google.android.gms.maps.OnMapReadyCallback;
import com.google.android.gms.maps.SupportMapFragment;
import com.google.android.gms.maps.model.BitmapDescriptorFactory;
import com.google.android.gms.maps.model.LatLng;
import com.google.android.gms.maps.model.Marker;
import com.google.android.gms.maps.model.MarkerOptions;
import org.json.JSONArray;
import org.json.JSONException;
import org.json.JSONObject;
import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.net.HttpURLConnection;
import java.net.URL;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;

public class MapsActivity2 extends AppCompatActivity
        implements OnMapReadyCallback,
        GoogleApiClient.ConnectionCallbacks,
        GoogleApiClient.OnConnectionFailedListener,
        LocationListener {

    GoogleMap mGoogleMap;
    SupportMapFragment mapFrag;
    LocationRequest mLocationRequest;
    GoogleApiClient mGoogleApiClient;
    Location mLastLocation;
    Marker mCurrLocationMarker;
    boolean firstRun = true;

    @Override
    protected void onCreate(Bundle savedInstanceState)
    {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        mapFrag = (SupportMapFragment) getSupportFragmentManager().findFragmentById(R.id.map);
        mapFrag.getMapAsync(this);
    }

    @Override
    public void onPause() {
        super.onPause();

        //stop location updates when Activity is no longer active
        if (mGoogleApiClient != null) {
            LocationServices.FusedLocationApi.removeLocationUpdates(mGoogleApiClient, this);
        }
    }

    @Override
    public void onMapReady(GoogleMap googleMap)
    {
        mGoogleMap=googleMap;
        mGoogleMap.setMyLocationEnabled(true);
        mGoogleMap.setMapType(GoogleMap.MAP_TYPE_HYBRID);

        //Initialize Google Play Services
        buildGoogleApiClient();
        mGoogleApiClient.connect();
    }

    public StringBuilder sbMethod(Location currentLocation) {
        //current location
        double mLatitude = currentLocation.getLatitude();
        double mLongitude = currentLocation.getLongitude();

        StringBuilder sb = new StringBuilder("https://maps.googleapis.com/maps/api/place/nearbysearch/json?");
        sb.append("location=" + mLatitude + "," + mLongitude);
        sb.append("&radius=5000");
        sb.append("&types=" + "restaurant");
        sb.append("&sensor=true");

        sb.append("&key=AIza********************");

        Log.d("Map", "<><>api: " + sb.toString());

        return sb;
    }

    protected synchronized void buildGoogleApiClient() {
        mGoogleApiClient = new GoogleApiClient.Builder(this)
                .addConnectionCallbacks(this)
                .addOnConnectionFailedListener(this)
                .addApi(LocationServices.API)
                .build();
    }

    @Override
    public void onConnected(Bundle bundle) {
        mLocationRequest = new LocationRequest();
        mLocationRequest.setInterval(1000);
        mLocationRequest.setFastestInterval(1000);
        mLocationRequest.setPriority(LocationRequest.PRIORITY_BALANCED_POWER_ACCURACY);
        LocationServices.FusedLocationApi.requestLocationUpdates(mGoogleApiClient, mLocationRequest, this);
    }

    @Override
    public void onConnectionSuspended(int i) {}

    @Override
    public void onConnectionFailed(ConnectionResult connectionResult) {}

    @Override
    public void onLocationChanged(Location location)
    {
        mLastLocation = location;
        if (mCurrLocationMarker != null) {
            mCurrLocationMarker.remove();
        }

        //Place current location marker
        LatLng latLng = new LatLng(location.getLatitude(), location.getLongitude());
        MarkerOptions markerOptions = new MarkerOptions();
        markerOptions.position(latLng);
        markerOptions.title("Current Position");
        markerOptions.icon(BitmapDescriptorFactory.defaultMarker(BitmapDescriptorFactory.HUE_MAGENTA));
        mCurrLocationMarker = mGoogleMap.addMarker(markerOptions);

        //move map camera
        mGoogleMap.moveCamera(CameraUpdateFactory.newLatLng(latLng));
        mGoogleMap.animateCamera(CameraUpdateFactory.zoomTo(11));

        //query places with current location
        StringBuilder sbValue = new StringBuilder(sbMethod(location));
        PlacesTask placesTask = new PlacesTask();
        placesTask.execute(sbValue.toString());

        if (mGoogleApiClient != null) {
            LocationServices.FusedLocationApi.removeLocationUpdates(mGoogleApiClient, this);
        }
    }

    private class PlacesTask extends AsyncTask<String, Integer, String>
    {

        String data = null;

        // Invoked by execute() method of this object
        @Override
        protected String doInBackground(String... url) {
            try {
                data = downloadUrl(url[0]);
            } catch (Exception e) {
                Log.d("Background Task", e.toString());
            }
            return data;
        }

        // Executed after the complete execution of doInBackground() method
        @Override
        protected void onPostExecute(String result) {
            Log.d("result", "<><> result: " + result);
            ParserTask parserTask = new ParserTask();

            // Start parsing the Google places in JSON format
            // Invokes the "doInBackground()" method of the class ParserTask
            parserTask.execute(result);
        }
    }

    private String downloadUrl(String strUrl) throws IOException
    {
        String data = "";
        InputStream iStream = null;
        HttpURLConnection urlConnection = null;
        try {
            URL url = new URL(strUrl);

            // Creating an http connection to communicate with url
            urlConnection = (HttpURLConnection) url.openConnection();

            // Connecting to url
            urlConnection.connect();

            // Reading data from url
            iStream = urlConnection.getInputStream();

            BufferedReader br = new BufferedReader(new InputStreamReader(iStream));

            StringBuffer sb = new StringBuffer();

            String line = "";
            while ((line = br.readLine()) != null) {
                sb.append(line);
            }

            data = sb.toString();

            br.close();

        } catch (Exception e) {
            Log.d("Exception", e.toString());
        } finally {
            iStream.close();
            urlConnection.disconnect();
        }
        return data;
    }

    private class ParserTask extends AsyncTask<String, Integer, List<HashMap<String, String>>> {

        JSONObject jObject;

        // Invoked by execute() method of this object
        @Override
        protected List<HashMap<String, String>> doInBackground(String... jsonData) {

            List<HashMap<String, String>> places = null;
            Place_JSON placeJson = new Place_JSON();

            try {
                jObject = new JSONObject(jsonData[0]);

                places = placeJson.parse(jObject);

            } catch (Exception e) {
                Log.d("Exception", e.toString());
            }
            return places;
        }

        // Executed after the complete execution of doInBackground() method
        @Override
        protected void onPostExecute(List<HashMap<String, String>> list) {

            Log.d("Map", "list size: " + list.size());
            // Clears all the existing markers;
            if (!firstRun) {

                mGoogleMap.clear();
            }
            firstRun = false;

            for (int i = 0; i < list.size(); i++) {

                // Creating a marker
                MarkerOptions markerOptions = new MarkerOptions();

                // Getting a place from the places list
                HashMap<String, String> hmPlace = list.get(i);


                // Getting latitude of the place
                double lat = Double.parseDouble(hmPlace.get("lat"));

                // Getting longitude of the place
                double lng = Double.parseDouble(hmPlace.get("lng"));

                // Getting name
                String name = hmPlace.get("place_name");

                Log.d("Map", "place: " + name);

                // Getting vicinity
                String vicinity = hmPlace.get("vicinity");

                LatLng latLng = new LatLng(lat, lng);

                // Setting the position for the marker
                markerOptions.position(latLng);

                markerOptions.title(name + " : " + vicinity);

                markerOptions.icon(BitmapDescriptorFactory.defaultMarker(BitmapDescriptorFactory.HUE_MAGENTA));

                // Placing a marker on the touched position
                Marker m = mGoogleMap.addMarker(markerOptions);

            }
        }
    }
    public class Place_JSON {

        /**
         * Receives a JSONObject and returns a list
         */
        public List<HashMap<String, String>> parse(JSONObject jObject) {

            JSONArray jPlaces = null;
            try {
                /** Retrieves all the elements in the 'places' array */
                jPlaces = jObject.getJSONArray("results");
            } catch (JSONException e) {
                e.printStackTrace();
            }
            /** Invoking getPlaces with the array of json object
             * where each json object represent a place
             */
            return getPlaces(jPlaces);
        }

        private List<HashMap<String, String>> getPlaces(JSONArray jPlaces) {
            int placesCount = jPlaces.length();
            List<HashMap<String, String>> placesList = new ArrayList<HashMap<String, String>>();
            HashMap<String, String> place = null;

            /** Taking each place, parses and adds to list object */
            for (int i = 0; i < placesCount; i++) {
                try {
                    /** Call getPlace with place JSON object to parse the place */
                    place = getPlace((JSONObject) jPlaces.get(i));
                    placesList.add(place);
                } catch (JSONException e) {
                    e.printStackTrace();
                }
            }
            return placesList;
        }

        /**
         * Parsing the Place JSON object
         */
        private HashMap<String, String> getPlace(JSONObject jPlace)
        {

            HashMap<String, String> place = new HashMap<String, String>();
            String placeName = "-NA-";
            String vicinity = "-NA-";
            String latitude = "";
            String longitude = "";
            String reference = "";

            try {
                // Extracting Place name, if available
                if (!jPlace.isNull("name")) {
                    placeName = jPlace.getString("name");
                }

                // Extracting Place Vicinity, if available
                if (!jPlace.isNull("vicinity")) {
                    vicinity = jPlace.getString("vicinity");
                }

                latitude = jPlace.getJSONObject("geometry").getJSONObject("location").getString("lat");
                longitude = jPlace.getJSONObject("geometry").getJSONObject("location").getString("lng");
                reference = jPlace.getString("reference");

                place.put("place_name", placeName);
                place.put("vicinity", vicinity);
                place.put("lat", latitude);
                place.put("lng", longitude);
                place.put("reference", reference);

            } catch (JSONException e) {
                e.printStackTrace();
            }
            return place;
        }
    }

}

结果: