来自远程 XML 的 Google Maps v2 上的标记

Question

我设法在我的一个 android 项目中渲染地图、获取位置等

但我正在努力寻找一些关于如何从远程 xml 文件在谷歌地图 v2 上放置标记的基本或高级示例。

那么，如何从远程 xml 中获取标记并使用 Google Maps API v2 显示它们？

以下是 XML 文件格式的示例：

<?xml version="1.0" encoding="UTF-8"?>
<maintag>
   <item>
      <id>1</id>
      <name>Place</name>
      <lat>60.1736245</lat>
      <lng>12.0283267</lng>
      <description>Nice Place</description>
      <type>2</type>
      <spotid>191712</spotid>
      <image>placeimage</image>
   </item>
   <item>
      <id>2</id>
      <name>Place</name>
      <lat>61.1736245</lat>
      <lng>13.0283267</lng>
      <description>Nice Place</description>
      <type>3</type>
      <spotid>291712</spotid>
      <image>placeimage</image>
   </item>
</maintag>

Answer 1

您只需要在后台线程上的网络操作中访问 XML，解析 XML，然后在 UI 线程上相应地显示标记。

我刚刚使用this answer 作为 XML 解析的指南来完成这项工作。

进口：

import android.os.AsyncTask;
import android.os.Bundle;
import android.support.v7.app.AppCompatActivity;
import android.util.Log;

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

import org.w3c.dom.Document;
import org.w3c.dom.Element;
import org.w3c.dom.Node;
import org.w3c.dom.NodeList;
import org.xml.sax.InputSource;
import org.xml.sax.SAXException;

import java.io.IOException;
import java.net.MalformedURLException;
import java.net.URL;
import java.util.ArrayList;
import java.util.List;

import javax.xml.parsers.DocumentBuilder;
import javax.xml.parsers.DocumentBuilderFactory;
import javax.xml.parsers.ParserConfigurationException;

这是完整的 Activity 类，其中包含一个 AsyncTask 作为内部类，它从doInBackground() 中的 URL 下载并解析 XML，然后在 onPostExecute() 中绘制标记：

public class MapFromXML extends AppCompatActivity implements OnMapReadyCallback {

    GoogleMap mMap;

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

    @Override
    public void onResume() {
        super.onResume();

        SupportMapFragment mapFragment = (SupportMapFragment) getSupportFragmentManager().findFragmentById(R.id.map);
        if (mapFragment != null) {
            if (mMap == null) {
                mapFragment.getMapAsync(this);
            } else {
                new GetXmlAsync().execute();
            }
        }
    }

    @Override
    public void onPause() {
        super.onPause();
    }


    @Override
    public void onMapReady(GoogleMap googleMap) {
        mMap = googleMap;
        mMap.setMapType(GoogleMap.MAP_TYPE_HYBRID);

        new GetXmlAsync().execute();
    }


    public class GetXmlAsync extends AsyncTask<URL, Void, List<MarkerInfo>> {

        @Override
        protected List<MarkerInfo> doInBackground(URL... params) {

            List<MarkerInfo> markerInfoList = new ArrayList<>();
            Document doc = null;
            URL url = null;
            try {
                url = new URL("http://www.example.com/GoogleMapXML.xml");

                DocumentBuilderFactory dbf = DocumentBuilderFactory.newInstance();
                DocumentBuilder db = null;
                db = dbf.newDocumentBuilder();
                doc = db.parse(new InputSource(url.openStream()));

            } catch (ParserConfigurationException e1) {
                e1.printStackTrace();
            } catch (MalformedURLException e1) {
                e1.printStackTrace();
            } catch (SAXException e1) {
                e1.printStackTrace();
            } catch (IOException e1) {
                e1.printStackTrace();

            }

            doc.getDocumentElement().normalize();

            NodeList nodeList = doc.getElementsByTagName("item");

            try {
                for (int i = 0; i < nodeList.getLength(); i++) {

                    Node node = nodeList.item(i);
                    Element fstElmnt = (Element) node;

                    NodeList nameList = fstElmnt.getElementsByTagName("name");
                    Element nameElement = (Element) nameList.item(0);
                    nameList = nameElement.getChildNodes();
                    String name = ((Node) nameList.item(0)).getNodeValue();

                    NodeList latList = fstElmnt.getElementsByTagName("lat");
                    Element latElement = (Element) latList.item(0);
                    latList = latElement.getChildNodes();
                    String lat = ((Node) latList.item(0)).getNodeValue();

                    NodeList lonList = fstElmnt.getElementsByTagName("lng");
                    Element lonElement = (Element) lonList.item(0);
                    lonList = lonElement.getChildNodes();
                    String lng = ((Node) lonList.item(0)).getNodeValue();

                    MarkerInfo info = new MarkerInfo(name, Double.parseDouble(lat), Double.parseDouble(lng));
                    markerInfoList.add(info);
                }
            } catch (Exception e) {
                e.printStackTrace();
            }

            return markerInfoList;
        }

        @Override
        protected void onPostExecute(List<MarkerInfo> markerList) {

            for (MarkerInfo info : markerList) {
                mMap.addMarker(new MarkerOptions().position(new LatLng(info.lat, info.lon))
                        .title(info.name)
                        .icon(BitmapDescriptorFactory
                                .defaultMarker(BitmapDescriptorFactory.HUE_BLUE)));
            }

            if (markerList.size() > 0) {
                mMap.moveCamera(CameraUpdateFactory
                        .newLatLng(new LatLng(markerList.get(0).lat, markerList.get(0).lon)));
                mMap.animateCamera(CameraUpdateFactory.zoomTo(5));
            }
        }
    }

    public class MarkerInfo {
        double lat;
        double lon;
        String name;
        public MarkerInfo(String n, double la, double lo) {
            name = n;
            lat = la;
            lon = lo;
        }
    }

}

这是 Activity 的 res/layout/content_map_from_xml.xml 布局文件：

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    app:layout_behavior="@string/appbar_scrolling_view_behavior"
    tools:context=".MapFromXML"
    tools:showIn="@layout/activity_map_from_xml">

    <fragment
        android:id="@+id/map"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        class="com.google.android.gms.maps.SupportMapFragment" />

</RelativeLayout>

结果：