android - 根据我自己在 android Google maps v2 中的标记绘制路线路径

Question

我在 Uni 校园里做关于公交车跟踪器的 android 项目。我需要绘制一条从一个巴士站到另一个巴士站的路线，直到回到起点巴士站。(我的 Uni 大约有 20 个巴士站，需要绘制路线让第一个用户知道巴士的路线)。

我按照本教程设法绘制了一条路径 here

在另一个教程中，我发现了一个博客，该博客教授在 3 个位置的谷歌地图上绘制路径。示例代码为

private static final LatLng LOWER_MANHATTAN = new LatLng(40.722543,-73.998585);
private static final LatLng BROOKLYN_BRIDGE = new LatLng(40.7057, -73.9964);
private static final LatLng WALL_STREET = new LatLng(40.7064, -74.0094);

private String getMapsApiDirectionsUrl() {
    String waypoints = "waypoints=optimize:true|"
            + LOWER_MANHATTAN.latitude + "," + LOWER_MANHATTAN.longitude
            + "|" + "|" + BROOKLYN_BRIDGE.latitude + ","
            + BROOKLYN_BRIDGE.longitude + "|" + WALL_STREET.latitude + ","
            + WALL_STREET.longitude;

    String sensor = "sensor=false";
    String params = waypoints + "&" + sensor;
    String output = "json";
    String url = "https://maps.googleapis.com/maps/api/directions/"
            + output + "?" + params;
    return url;
}

但是我得到了一个错误:

java.io.FileNotFoundException: https://maps.googleapis.com/maps/api/directions/json?waypoints=optimize:true|2.920114,101.775244||2.919726,101.771172|2.92234,101.769628&sensor=false
E/Background Task: java.lang.NullPointerException
E/ParserTask: errororg.json.JSONException: End of input at character 0 of

博客的教程与链接相同。只是不一样

String waypoints = "waypoints=optimize:true|"
            + LOWER_MANHATTAN.latitude + "," + LOWER_MANHATTAN.longitude
            + "|" + "|" + BROOKLYN_BRIDGE.latitude + ","
            + BROOKLYN_BRIDGE.longitude + "|" + WALL_STREET.latitude + ","
            + WALL_STREET.longitude;

和

/ Origin of route
String str_origin = "origin="+origin.latitude+","+origin.longitude;

// Destination of route
String str_dest = "destination="+dest.latitude+","+dest.longitude;

任何人都可以给我一些关于在多个标记中绘制路径的教程或指导吗？提前致谢!

Answer 1

首先你需要修正你的方法

private static final LatLng LOWER_MANHATTAN = new LatLng(40.722543,-73.998585);
private static final LatLng BROOKLYN_BRIDGE = new LatLng(40.7057, -73.9964);
private static final LatLng WALL_STREET = new LatLng(40.7064, -74.0094);

private String getMapsApiDirectionsUrl() {
    String origin = "origin=" + LOWER_MANHATTAN.latitude + "," + LOWER_MANHATTAN.longitude;
    String waypoints = "waypoints=optimize:true|" + BROOKLYN_BRIDGE.latitude + "," + BROOKLYN_BRIDGE.longitude + "|";
    String destination = "destination=" + WALL_STREET.latitude + "," + WALL_STREET.longitude;

    String sensor = "sensor=false";
    String params = origin + "&" + waypoints + "&"  + destination + "&" + sensor;
    String output = "json";
    String url = "https://maps.googleapis.com/maps/api/directions/"
            + output + "?" + params;
    return url;
}

为了获得绘图路径，我遵循了这个答案 https://stackoverflow.com/a/14702636/2697368

一旦你得到JSON，就去做

public void drawPath(String result) {

    try {
        //Tranform the string into a json object
        final JSONObject json = new JSONObject(result);
        JSONArray routeArray = json.getJSONArray("routes");
        JSONObject routes = routeArray.getJSONObject(0);
        JSONObject overviewPolylines = routes.getJSONObject("overview_polyline");
        String encodedString = overviewPolylines.getString("points");
        List<LatLng> list = decodePoly(encodedString);

        Polyline line = mMap.addPolyline(new PolylineOptions()
                .addAll(list)
                .width(12)
                .color(Color.parseColor("#05b1fb"))//Google maps blue color
                .geodesic(true)
        );

    } catch (JSONException e) {

    }
}

private List<LatLng> decodePoly(String encoded) {

    List<LatLng> poly = new ArrayList<LatLng>();
    int index = 0, len = encoded.length();
    int lat = 0, lng = 0;

    while (index < len) {
        int b, shift = 0, result = 0;
        do {
            b = encoded.charAt(index++) - 63;
            result |= (b & 0x1f) << shift;
            shift += 5;
        } while (b >= 0x20);
        int dlat = ((result & 1) != 0 ? ~(result >> 1) : (result >> 1));
        lat += dlat;

        shift = 0;
        result = 0;
        do {
            b = encoded.charAt(index++) - 63;
            result |= (b & 0x1f) << shift;
            shift += 5;
        } while (b >= 0x20);
        int dlng = ((result & 1) != 0 ? ~(result >> 1) : (result >> 1));
        lng += dlng;

        LatLng p = new LatLng((((double) lat / 1E5)),
                (((double) lng / 1E5)));
        poly.add(p);
    }

    return poly;
}