php - 如何能够显示标记的地名而不是从mysql数据库检索的经度、纬度？

Question

我一直在关注此网站的教程:' http://wptrafficanalyzer.in/blog/storing-google-maps-android-api-v2-marker-locations-in-mysql/ '并被这些代码困扰了几天。我的问题是我无法显示标记的标题与地名而不是经度、纬度，如教程所述。我已经添加了字符串名称，但是当我尝试运行应用程序时，标记不显示标题。请帮助我......

MainActivity.java

public class MainActivity extends FragmentActivity implements LocationListener {

    GoogleMap mGoogleMap;

    double mLatitude=0;
    double mLongitude=0;

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




        // Getting Google Play availability status
        int status = GooglePlayServicesUtil.isGooglePlayServicesAvailable(getBaseContext());
        if(status!= ConnectionResult.SUCCESS){ // Google Play Services are not available

            int requestCode = 10;
            Dialog dialog = GooglePlayServicesUtil.getErrorDialog(status, this, requestCode);
            dialog.show();
        }else { // Google Play Services are available


            // Getting reference to SupportMapFragment
            SupportMapFragment fragment = (SupportMapFragment) getSupportFragmentManager()
                    .findFragmentById(R.id.map);

            // Creating GoogleMap from SupportMapFragment
            mGoogleMap = fragment.getMap();


            // Enabling MyLocation button for the Google Map
            mGoogleMap.setMyLocationEnabled(true);

            // Getting LocationManager object from System Service LOCATION_SERVICE
            LocationManager locationManager = (LocationManager) getSystemService(LOCATION_SERVICE);

            // Creating a criteria object to retrieve provider
            Criteria criteria = new Criteria();

            // Getting the name of the best provider
            String provider = locationManager.getBestProvider(criteria, true);

            // Getting Current Location From GPS
            Location location = locationManager.getLastKnownLocation(provider);

            if(location!=null){
                onLocationChanged(location);
            }

            locationManager.requestLocationUpdates(provider, 20000, 0, this);


            // Setting OnClickEvent listener for the GoogleMap
      /*  mGoogleMap.setOnMapClickListener(new OnMapClickListener() {
            @Override
            public void onMapClick(LatLng latlng) {
                addMarker(latlng);
                sendToServer(latlng);
            }
        }); */

            // Starting locations retrieve task
            new RetrieveTask().execute();


        }
    }


    // Adding marker on the GoogleMaps

    private void addMarker(LatLng latlng) {
        MarkerOptions markerOptions = new MarkerOptions();
        markerOptions.position(latlng);
        markerOptions.title(name);
        String name ="place_name";
        //markerOptions.title(latlng.latitude + "," + latlng.longitude);

        markerOptions.icon(BitmapDescriptorFactory.fromResource(R.drawable.restoicon));
        mGoogleMap.addMarker(markerOptions);
    }

    // Invoking background thread to store the touched location in Remove MySQL server
    /*private void sendToServer(LatLng latlng) {
        new SaveTask().execute(latlng);
    }
    // Background thread to save the location in remove MySQL server
    private class SaveTask extends AsyncTask<LatLng, Void, Void> {
        @Override
        protected Void doInBackground(LatLng... params) {
            String lat = Double.toString(params[0].latitude);
            String lng = Double.toString(params[0].longitude);
            String strUrl = "http://my-url/save.php"; //http://192.168.0.105/location_marker_mysql/save.php
            URL url = null;
            try {
                url = new URL(strUrl);

                HttpURLConnection connection = (HttpURLConnection) url
                        .openConnection();
                connection.setRequestMethod("POST");
                connection.setDoOutput(true);
                OutputStreamWriter outputStreamWriter = new OutputStreamWriter(
                        connection.getOutputStream());

                outputStreamWriter.write("lat=" + lat + "&lng="+lng);
                outputStreamWriter.flush();
                outputStreamWriter.close();

                InputStream iStream = connection.getInputStream();
                BufferedReader reader = new BufferedReader(new
                        InputStreamReader(iStream));

                StringBuffer sb = new StringBuffer();

                String line = "";

                while( (line = reader.readLine()) != null){
                    sb.append(line);
                }

                reader.close();
                iStream.close();

            } catch (MalformedURLException e) {
                e.printStackTrace();
            } catch (IOException e) {
                e.printStackTrace();
            }

            return null;
        }
    } */

    // Background task to retrieve locations from remote mysql server
    private class RetrieveTask extends AsyncTask<Void, Void, String>{

        @Override
        protected String doInBackground(Void... params) {
            String strUrl = "http://my-url/retrieve.php"; //http://192.168.0.105/location_marker_mysql/retrieve.php
            URL url = null;
            StringBuffer sb = new StringBuffer();
            try {
                url = new URL(strUrl);
                HttpURLConnection connection = (HttpURLConnection) url.openConnection();
                connection.connect();
                InputStream iStream = connection.getInputStream();
                BufferedReader reader = new BufferedReader(new InputStreamReader(iStream));
                String line = "";
                while( (line = reader.readLine()) != null){
                    sb.append(line);
                }

                reader.close();
                iStream.close();

            } catch (MalformedURLException e) {
                e.printStackTrace();
            } catch (IOException e) {
                e.printStackTrace();
            }
            return sb.toString();
        }

        @Override
        protected void onPostExecute(String result) {
            super.onPostExecute(result);
            new ParserTask().execute(result);
        }
    }

    // Background thread to parse the JSON data retrieved from MySQL server
    private class ParserTask extends AsyncTask<String, Void, List<HashMap<String, String>>>{
        @Override
        protected List<HashMap<String,String>> doInBackground(String... params) {
            MarkerJSONParser markerParser = new MarkerJSONParser();
            JSONObject json = null;
            try {
                json = new JSONObject(params[0]);
            } catch (JSONException e) {
                e.printStackTrace();
            }
            List<HashMap<String, String>> markersList = markerParser.parse(json);
            return markersList;
        }

        @Override
        protected void onPostExecute(List<HashMap<String, String>> result) {
            for(int i=0; i<result.size();i++){
                //Creating a marker
                MarkerOptions markerOptions = new MarkerOptions();
                HashMap<String, String> marker = result.get(i);
                //LatLng latlng = new LatLng(Double.parseDouble(marker.get("lat")), Double.parseDouble(marker.get("lng")));

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

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

                LatLng latlng= new LatLng(lat, lng);

                markerOptions.position(latlng);


                //addMarker(latlng);


                 //Setting the position for the marker


                // Setting the title for the marker.
                //This will be displayed on taping the marker


                //use custom marker icon
                markerOptions.icon(BitmapDescriptorFactory.fromResource(R.drawable.restoicon));
                mGoogleMap.addMarker(markerOptions);
            }
        }
    }

    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        // Inflate the menu; this adds items to the action bar if it is present.
        getMenuInflater().inflate(R.menu.menu_main, menu);
        return true;
    }

    @Override
    public void onLocationChanged(Location location) {
        mLatitude = location.getLatitude();
        mLongitude = location.getLongitude();
        LatLng latLng = new LatLng(mLatitude, mLongitude);

        mGoogleMap.moveCamera(CameraUpdateFactory.newLatLng(latLng));
        mGoogleMap.animateCamera(CameraUpdateFactory.zoomTo(12));
    }

    @Override
    public void onProviderDisabled(String provider) {
        // TODO Auto-generated method stub
    }

    @Override
    public void onProviderEnabled(String provider) {
        // TODO Auto-generated method stub
    }

    @Override
    public void onStatusChanged(String provider, int status, Bundle extras) {
        // TODO Auto-generated method stub
    }

}

MarkerJSONParser.java

public class MarkerJSONParser {

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

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

    private List<HashMap<String, String>> getMarkers(JSONArray jMarkers){
        int markersCount = jMarkers.length();
        List<HashMap<String, String>> markersList = new ArrayList<HashMap<String,String>>();
        HashMap<String, String> marker = null;

        /** Taking each marker, parses and adds to list object */
        for(int i=0; i<markersCount;i++){
            try {
                /** Call getMarker with marker JSON object to parse the marker */
                marker = getMarker((JSONObject)jMarkers.get(i));
                markersList.add(marker);
            }catch (JSONException e){
                e.printStackTrace();
            }
        }
        return markersList;
    }

    /** Parsing the Marker JSON object */
    private HashMap<String, String> getMarker(JSONObject jMarker){

        HashMap<String, String> marker = new HashMap<String, String>();
        String lat = "-NA-";
        String lng ="-NA-";

        try {
            // Extracting latitude, if available
            if(!jMarker.isNull("lat")){
                lat = jMarker.getString("lat");
            }

            // Extracting longitude, if available
            if(!jMarker.isNull("lng")){
                lng = jMarker.getString("lng");
            }

            marker.put("lat", lat);
            marker.put("lng", lng);

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

我还编辑了这个 php 文件，以便能够从远程 mysql 数据库读取“place_name”:

检索.php

<?php


require_once("config.php"); 

$markers = array();
$sql = "select place_name,lat,lng from markers";
$mysqli = new mysqli($host, $username, $password, $db_name);

if($res = $mysqli->query($sql)){
    while($row=$res->fetch_assoc()){
                $place_name = $row['place_name'];
                $lat = $row['lat'];
            $lng = $row['lng'];
                $data= array("place_name"=>$place_name,"lat"=>$lat,"lng"=>$lng);
                $marker[] = $data;
    }

        $markers = array("markers"=>$marker);

        echo json_encode($markers);
}

?>

Answer 1

在 MarkerJSONParser 类中，您必须添加:

   private HashMap<String, String> getMarker(JSONObject jMarker){

    HashMap<String, String> marker = new HashMap<String, String>();
    String lat = "-NA-";
    String lng ="-NA-";
    String place_name ="-NA-";

    try {
        // Extracting latitude, if available
        if(!jMarker.isNull("lat")){
            lat = jMarker.getString("lat");
        }

        // Extracting longitude, if available
        if(!jMarker.isNull("lng")){
            lng = jMarker.getString("lng");
        }

         if(!jMarker.isNull("place_name"){
            place_name = jMarker.getString("place_name");
        }
        marker.put("lat", lat);
        marker.put("lng", lng);
        marker.put("place_name",place_name);

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

在PostExecute中的MainActivity中添加:

String place_name=marker.get("place_name");