Question

您正在开发一个应用程序，即显示具有当前位置和经度和纬度值的地图并更改该位置。每隔5分钟将这些纬度和经度值存储在sqlitedatabase中，并使这些数据库值正常工作。但是，如何使用存储的数据库值绘制路径。请有人告诉我解决方案。

代码：

    PolylineOptions polylineOptions = new PolylineOptions();
    polylineOptions.color(Color.RED);
    polylineOptions.width(5);
    double latitude=Double.parseDouble(c.getString(0));
    double longitude=Double.parseDouble(c.getString(1));

    LatLng latlngval=new LatLng(latitude, longitude);
    Log.e("path", ""+latlngval);
    ArrayList<LatLng> latlnglist=new ArrayList<LatLng>();
    latlnglist.add(latlngval);

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

        polylineOptions.add(latlnglist.get(i));

    }

Answer 1

您可以使用Polyline

PolylineOptions polylineOptions = new PolylineOptions();
polylineOptions.color(Color.RED);
polylineOptions.width(5);
Cursor c = database.query( ... ); //select the latitude and longitude column
while (c.moveToNext()) {
    polylineOptions.add(new LatLng(Double.parseDouble(c.getString(0)), Double.parseDouble(c.getString(1))));
}
googleMap.addPolyline(polylineOptions);

Answer 2

public class DrawrootTask extends AsyncTask<String, String, String> {
private Context context;
public static boolean flagCompleted = false;
private GoogleMap googleMap;
private double source_lat = 0.0;
private double source_long = 0.0;
private double dest_lat = 0.0;
private double dest_long = 0.0;
Userdata userdata;
String tag = "DrawRootTask";
private ProgressDialog progressDialog;
public static double dist, time;
private Polyline line;
String distanceText = "";
String durationText = "";

public DrawrootTask(Context context, LatLng source, LatLng destination,
        GoogleMap googleMap) {
    source_lat = source.latitude;
    source_long = source.longitude;
    dest_lat = destination.latitude;
    dest_long = destination.longitude;

    this.googleMap = googleMap;
    this.context = context;
    userdata = Userdata.getinstance(context);

}

protected void onPreExecute() {
    // // TODO Auto-generated method stub
    super.onPreExecute();
    progressDialog = new ProgressDialog(context);
    progressDialog.setMessage(context.getResources().getString(
            R.string.please_wait));
    progressDialog.setIndeterminate(true);
    progressDialog.show();

}

@Override
protected String doInBackground(String... params) {

    String json = "";

    // constructor
    StringBuilder urlString = new StringBuilder();
    urlString.append("http://maps.googleapis.com/maps/api/directions/json");
    HashMap<String, String> keyValue = new HashMap<String, String>();
    urlString.append("?origin=");// from
    urlString.append(Double.toString(source_lat));
    urlString.append(",");
    urlString.append(Double.toString(source_long));
    urlString.append("&destination=");// to
    urlString.append(Double.toString(dest_lat));
    urlString.append(",");
    urlString.append(Double.toString(dest_long));
    urlString.append("&sensor=false&mode=driving&alternatives=true");

    // defaultHttpClient
    String url = urlString.toString();
    FetchUrl fetchurl = new FetchUrl();
    json = fetchurl.fetchUrl(url, keyValue);

    Log.e("Buffer Error", json);
    return json;

}

@Override
protected void onPostExecute(String result) {
    // TODO Auto-generated method stub
    super.onPostExecute(result);
    try {
        progressDialog.dismiss();
        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);

        for (int z = 0; z < list.size() - 1; z++) {
            LatLng src = list.get(z);
            LatLng dest = list.get(z + 1);
            line = googleMap.addPolyline(new PolylineOptions()
                    .add(new LatLng(src.latitude, src.longitude),
                            new LatLng(dest.latitude, dest.longitude))
                    // .width(8).color(Color.BLUE).geodesic(true));
                    .width(8)
                    .color(context.getResources().getColor(
                            R.color.actionbar_color)).geodesic(true));
            Log.i("draw root", "" + "" + line.toString());
        }
        JSONArray legs = routes.getJSONArray("legs");
        JSONObject steps = legs.getJSONObject(0);
        JSONObject duration = steps.getJSONObject("duration");
        JSONObject distance = steps.getJSONObject("distance");
        distanceText = distance.getString("text");
        durationText = duration.getString("text");
        Log.i("draw root", "" + distance.toString());
        dist = Double.parseDouble(distance.getString("text").replaceAll(
                "[^\\.0123456789]", ""));
        time = Double.parseDouble(duration.getString("text").replaceAll(
                "[^\\.0123456789]", ""));
        userdata.setDistance(dist);
        userdata.setTime(time);
        Log.d(tag, "distace is " + dist + " time is " + time);
        flagCompleted = true;
    } catch (JSONException e) {
        Log.d("draw root", "" + 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;
}

}

Answer 3

可能会帮助你..

http://javapapers.com/android/draw-lines-on-google-maps-android-api/

而不是采用硬编码值（如示例中所示）从数据库中检索值

如何在android中的map中从数据库中绘制路径纬度和经度值

3 个答案: