标记之间的 Google Maps API 和自定义折线路线

Google Maps API and custom polyline route between Markers(标记之间的 Google Maps API 和自定义折线路线)

问题描述

我想为一个安卓应用创建一个自定义路由，我不确定我应该使用哪个 API 以及它是否与 Java 兼容.

据我所知，我需要使用航路点来制定路线(我不需要知道两点之间的距离，只是为了制定路线).

目标是从地图一侧的菜单中选择一个选项，并显示两个标记之间的自定义路线之一.

您可以使用

I'd like to make a custom route for an android app, I'm not sure which API should I use and if it is compatible with Java.

As far as I know I need to use waypoints to make a route (I don't need to know the distance between the two points, just to make a route).

The objective is to choose an option from a menu on the side of the map and show one of the custom routes between two Markers.

You can do this using the Google Maps API v2 for Android, and the Google Maps Directions webservice API

For getting started with the Google Maps API, there are plenty of other good answers already. See here for a complete working example of a simple map Activity. Note that you'll also need to get an API key set up to work with your project.

As for using the Google Maps Directions webservice API, you should first read the documentation. You can use an API key and enable the API in your developer console, but it still works currently without using an API key.

Here is the basic code you'll need in order to use the Google Maps API to draw a Polyline between two points, note that the points returned from the API are encoded in a base 64 encoded String that needs to be decoded.

First, ensure that your project includes the Google Maps Utility library, which will be used to decode the base64 encoded polyline:

dependencies {
    compile 'com.google.maps.android:android-maps-utils:0.5+'
    //.......
}

Here is the AsyncTask, that you should give two LatLng points to when calling it.

You would call the AsyncTask with two LatLng objects, for example between two Markers:

new GetDirectionsAsync().execute(markerOne.getPosition(), markerTwo.getPosition());

Here is the AsyncTask code:

class GetDirectionsAsync extends AsyncTask<LatLng, Void, List<LatLng>> {

    JSONParser jsonParser;
    String DIRECTIONS_URL = "https://maps.googleapis.com/maps/api/directions/json";


    @Override
    protected void onPreExecute() {
        super.onPreExecute();
    }

    @Override
    protected List<LatLng> doInBackground(LatLng... params) {
        LatLng start = params[0];
        LatLng end = params[1];

        HashMap<String, String> points = new HashMap<>();
        points.put("origin", start.latitude + "," + start.longitude);
        points.put("destination", end.latitude + "," + end.longitude);

        jsonParser = new JSONParser();

        JSONObject obj = jsonParser.makeHttpRequest(DIRECTIONS_URL, "GET", points, true);

        if (obj == null) return null;

        try {
            List<LatLng> list = null;

            JSONArray routeArray = obj.getJSONArray("routes");
            JSONObject routes = routeArray.getJSONObject(0);
            JSONObject overviewPolylines = routes.getJSONObject("overview_polyline");
            String encodedString = overviewPolylines.getString("points");
            list = PolyUtil.decode(encodedString);

            return list;

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

        return null;
    }

    @Override
    protected void onPostExecute(List<LatLng> pointsList) {

        if (pointsList == null) return;

        if (line != null){
            line.remove();
        }

        PolylineOptions options = new PolylineOptions().width(5).color(Color.MAGENTA).geodesic(true);
        for (int i = 0; i < pointsList.size(); i++) {
            LatLng point = pointsList.get(i);
            options.add(point);
        }
        line = mMap.addPolyline(options);

    }
}

The AsyncTask references some member variables of the Activity, namely the Polyline and the GoogleMap, the Activity definition would look like this:

public class MapsActivity extends AppCompatActivity implements OnMapReadyCallback{

    GoogleMap mMap;
    Polyline line;
    //.....

Here's the JSONParser class used in this example, note that this is a modified version updated for android-23 that I wrote a blog post about:

public class JSONParser {

    String charset = "UTF-8";
    HttpURLConnection conn;
    DataOutputStream wr;
    StringBuilder result;
    URL urlObj;
    JSONObject jObj = null;
    StringBuilder sbParams;
    String paramsString;

    public JSONObject makeHttpRequest(String url, String method,
                                      HashMap<String, String> params, boolean encode) {

        sbParams = new StringBuilder();
        int i = 0;
        for (String key : params.keySet()) {
            try {
                if (i != 0){
                    sbParams.append("&");
                }
                if (encode) {
                    sbParams.append(key).append("=")
                            .append(URLEncoder.encode(params.get(key), charset));
                }
                else{
                    sbParams.append(key).append("=")
                            .append(params.get(key));
                }

            } catch (UnsupportedEncodingException e) {
                e.printStackTrace();
            }
            i++;
        }

        if (method.equals("POST")) {
            // request method is POST
            try {
                urlObj = new URL(url);

                conn = (HttpURLConnection) urlObj.openConnection();

                conn.setDoOutput(true);

                conn.setRequestMethod("POST");

                conn.setRequestProperty("Accept-Charset", charset);

                conn.setReadTimeout(10000);
                conn.setConnectTimeout(15000);

                conn.connect();

                paramsString = sbParams.toString();

                wr = new DataOutputStream(conn.getOutputStream());
                wr.writeBytes(paramsString);
                wr.flush();
                wr.close();

            } catch (IOException e) {
                e.printStackTrace();
            }
        }
        else if(method.equals("GET")){
            // request method is GET

            if (sbParams.length() != 0) {
                url += "?" + sbParams.toString();
            }

            Log.d("JSONParser", "full GET url: " + url);

            try {
                urlObj = new URL(url);

                conn = (HttpURLConnection) urlObj.openConnection();

                conn.setDoOutput(false);

                conn.setRequestMethod("GET");

                conn.setRequestProperty("Accept-Charset", charset);

                conn.setConnectTimeout(15000);

                conn.connect();

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

        }

        try {
            //Receive the response from the server
            InputStream in = new BufferedInputStream(conn.getInputStream());
            BufferedReader reader = new BufferedReader(new InputStreamReader(in));

            String line;
            result = new StringBuilder();
            while ((line = reader.readLine()) != null) {
                result.append(line);
            }

            Log.d("JSON Parser", "result: " + result.toString());

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

        conn.disconnect();

        // try parse the string to a JSON object
        try {
            jObj = new JSONObject(result.toString());
        } catch (JSONException e) {
            Log.e("JSON Parser", "Error parsing data " + e.toString());
        }

        // return JSON Object
        return jObj;
    }
}

Result of drawing a route between two Markers:

这篇关于标记之间的 Google Maps API 和自定义折线路线的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持编程学习网！