添加具有实时更新功能的GeoJson（无跟踪）

Question

我正在尝试将以下示例用于自己的应用。要添加Geojson文件，我已经用其他代码进行了管理，但是我无法使其与实时数据一起使用。我只想根据接受实时信息点的情况显示不同的颜色。代码的第一个问题是它没有运行示例，存在许多错误。将其用于我的应用程序的第二次尝试显示了一些额外的错误。故障之一是被getmapAync代替的getmap（），但没有解决问题。 有关代码错误的任何建议。是添加实时空间数据的更好的方法，没有跟踪信息只是其属性的状态。

GeoJSON — displays and styles GeoJSON data

package com.example.testnavbar;

import android.content.Context;
import android.net.Uri;
import android.os.AsyncTask;
import android.os.Bundle;
import android.support.annotation.NonNull;
import android.support.annotation.Nullable;
import android.support.v4.app.Fragment;
import android.util.Log;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.Toast;

import com.google.android.gms.maps.CameraUpdateFactory;
import com.google.android.gms.maps.GoogleMap;
import com.google.android.gms.maps.MapView;
import com.google.android.gms.maps.MapsInitializer;
import com.google.android.gms.maps.OnMapReadyCallback;
import com.google.android.gms.maps.model.BitmapDescriptor;
import com.google.android.gms.maps.model.BitmapDescriptorFactory;
import com.google.android.gms.maps.model.CameraPosition;
import com.google.android.gms.maps.model.LatLng;
import com.google.android.gms.maps.model.MarkerOptions;
import com.google.android.gms.maps.model.PolylineOptions;
import com.google.maps.android.data.Feature;
import com.google.maps.android.data.geojson.GeoJsonFeature;
import com.google.maps.android.data.geojson.GeoJsonLayer;
import com.google.maps.android.data.geojson.GeoJsonLineString;
import com.google.maps.android.data.geojson.GeoJsonPointStyle;

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.URL;
import java.util.List;

import static com.mapbox.mapboxsdk.Mapbox.getApplicationContext;


public class HomeFragment extends Fragment {

    private final static String mLogTag = "GeoJson";

    GoogleMap mGoogleMap;
    MapView mMapView;
    View mView;

    /**
     * Assigns a color based on the given magnitude
     */
    private static float magnitudeToColor(double status) {
        if (status == 1) {
            return BitmapDescriptorFactory.HUE_GREEN;
        } else if (status == 2) {
            return BitmapDescriptorFactory.HUE_YELLOW;
        } else {
            return BitmapDescriptorFactory.HUE_RED;
        }
    }

    protected int getLayoutId() {
        return R.layout.activity_maps;
    }


    protected void startDemo() {
        // Download the GeoJSON file.
        retrieveFileFromUrl();
        // Alternate approach of loading a local GeoJSON file.
        //retrieveFileFromResource();
    }

    private void retrieveFileFromUrl() {
        new DownloadGeoJsonFile().execute(getString(R.string.geojson_url));
    }

    private void retrieveFileFromResource() {
        try {
            GeoJsonLayer layer = new GeoJsonLayer(getMap(), R.raw.picnicsites, this);
            addGeoJsonLayerToMap(layer);
        } catch (IOException e) {
            Log.e(mLogTag, "GeoJSON file could not be read");
        } catch (JSONException e) {
            Log.e(mLogTag, "GeoJSON file could not be converted to a JSONObject");
        }
    }

    /**
     * Adds a point style to all features to change the color of the marker based on its magnitude
     * property
     */
    private void addColorsToMarkers(GeoJsonLayer layer) {
        // Iterate over all the features stored in the layer
        for (GeoJsonFeature feature : layer.getFeatures()) {
            // Check if the magnitude property exists
            if (feature.getProperty("mag") != null && feature.hasProperty("place")) {
                double magnitude = Double.parseDouble(feature.getProperty("mag"));

                // Get the icon for the feature
                BitmapDescriptor pointIcon = BitmapDescriptorFactory
                        .defaultMarker(magnitudeToColor(magnitude));

                // Create a new point style
                GeoJsonPointStyle pointStyle = new GeoJsonPointStyle();

                // Set options for the point style
                pointStyle.setIcon(pointIcon);
                pointStyle.setTitle("Magnitude of " + magnitude);
                pointStyle.setSnippet("Earthquake occured " + feature.getProperty("place"));

                // Assign the point style to the feature
                feature.setPointStyle(pointStyle);
            }
        }
    }

    private class DownloadGeoJsonFile extends AsyncTask<String, Void, GeoJsonLayer> {

        @Override
        protected GeoJsonLayer doInBackground(String... params) {
            try {
                // Open a stream from the URL
                InputStream stream = new URL(params[0]).openStream();

                String line;
                StringBuilder result = new StringBuilder();
                BufferedReader reader = new BufferedReader(new InputStreamReader(stream));

                while ((line = reader.readLine()) != null) {
                    // Read and save each line of the stream
                    result.append(line);
                }

                // Close the stream
                reader.close();
                stream.close();

                return new GeoJsonLayer(getMap(), new JSONObject(result.toString()));
            } catch (IOException e) {
                Log.e(mLogTag, "GeoJSON file could not be read");
            } catch (JSONException e) {
                Log.e(mLogTag, "GeoJSON file could not be converted to a JSONObject");
            }
            return null;
        }

        @Override
        protected void onPostExecute(GeoJsonLayer layer) {
            if (layer != null) {
                addGeoJsonLayerToMap(layer);
            }
        }

    }


    private void addGeoJsonLayerToMap(GeoJsonLayer layer) {

        addColorsToMarkers(layer);
        layer.addLayerToMap();
        getMap().moveCamera(CameraUpdateFactory.newLatLng(new LatLng(35.126411,33.429859)));
        // Demonstrate receiving features via GeoJsonLayer clicks.
        layer.setOnFeatureClickListener(new GeoJsonLayer.GeoJsonOnFeatureClickListener() {
            @Override
            public void onFeatureClick(Feature feature) {
                Toast.makeText(HomeFragment.this,
                        "Feature clicked: " + feature.getProperty("title"),
                        Toast.LENGTH_SHORT).show();
            }

        });

    }
}