使用JSON在Android中的地图上立即更新标记

Question

您好我发现此代码使用来自JSON网络服务和Google Maps Android API v2的数据在Android地图上绘制标记 任何人都可以帮我如何立即更新标记而无需刷新视图以跟踪地图上的位置

    package com.example.google.maps.demo;

import com.google.android.gms.maps.GoogleMap;
import com.google.android.gms.maps.SupportMapFragment;
import com.google.android.gms.maps.model.LatLng;
import com.google.android.gms.maps.model.MarkerOptions;

import org.json.JSONArray;
import org.json.JSONException;
import org.json.JSONObject;

import android.os.Bundle;
import android.support.v4.app.FragmentActivity;
import android.util.Log;

import java.io.IOException;
import java.io.InputStreamReader;
import java.net.HttpURLConnection;
import java.net.URL;

/**
 * @author saxman
 */
public class MainActivity extends FragmentActivity {
    private static final String LOG_TAG = "taxitag";

    private static final String SERVICE_URL = "http://192.168.1.3/taxi.php";

    protected GoogleMap map;

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

    @Override
    protected void onResume() {
        super.onResume();
        setUpMapIfNeeded();
    }

    private void setUpMapIfNeeded() {
        if (map == null) {
            map = ((SupportMapFragment) getSupportFragmentManager().findFragmentById(R.id.map))
                    .getMap();
            if (map != null) {
                setUpMap();
            }
        }
    }

    private void setUpMap() {
        // Retrieve the city data from the web service
        // In a worker thread since it's a network operation.
        new Thread(new Runnable() {
            public void run() {
                try {
                    retrieveAndAddCities();
                } catch (IOException e) {
                    Log.e(LOG_TAG, "Cannot retrive cities", e);
                    return;
                }
            }
        }).start();
    }

    protected void retrieveAndAddCities() throws IOException {
        HttpURLConnection conn = null;
        final StringBuilder json = new StringBuilder();
        try {
            // Connect to the web service
            URL url = new URL(SERVICE_URL);
            conn = (HttpURLConnection) url.openConnection();
            InputStreamReader in = new InputStreamReader(conn.getInputStream());

            // Read the JSON data into the StringBuilder
            int read;
            char[] buff = new char[1024];
            while ((read = in.read(buff)) != -1) {
                json.append(buff, 0, read);
            }
        } catch (IOException e) {
            Log.e(LOG_TAG, "Error connecting to service", e);
            throw new IOException("Error connecting to service", e);
        } finally {
            if (conn != null) {
                conn.disconnect();
            }
        }

        // Create markers for the city data.
        // Must run this on the UI thread since it's a UI operation.
        runOnUiThread(new Runnable() {
            public void run() {
                try {
                    createMarkersFromJson(json.toString());
                } catch (JSONException e) {
                    Log.e(LOG_TAG, "Error processing JSON", e);
                }
            }
        });
    }

    void createMarkersFromJson(String json) throws JSONException {
        // De-serialize the JSON string into an array of city objects
        JSONArray jsonArray = new JSONArray(json);
        for (int i = 0; i < jsonArray.length(); i++) {
            // Create a marker for each city in the JSON data.
            JSONObject jsonObj = jsonArray.getJSONObject(i);
            map.addMarker(new MarkerOptions()
                .title(jsonObj.getString("name"))
                .snippet(Integer.toString(jsonObj.getInt("population")))
                .position(new LatLng(
                        jsonObj.getJSONArray("latlng").getDouble(0),
                        jsonObj.getJSONArray("latlng").getDouble(1)
                 ))
            );
        }
    }
}

谢谢

Answer 1

你可以使用它，她将获得更新标记的解决方案。

link