在本教程中，我们将创建一个Android应用程序，该应用程序在两点之间绘制一条可能的Google地图路线。
我们将在应用程序中使用Google Maps Directions API。

Android Google Map –绘图路线

使用本教程中演示的步骤，从API控制台创建一个新的Google Map API密钥。

创建一个新的Android Studio项目，然后选择模板作为Google Maps Activity。
将API密钥添加到位于debug-> res-> values文件夹中的google_maps_api.xml文件中

如果您使用的是最新的Android Studio，则该应用程序应为这样。

Android Google Maps绘图路径项目结构

DirectionsJSONParser.java文件是解析位置并返回路线的文件。
然后调用decodePoly()方法来获取折线数据，该折线数据稍后会在地图上绘制。

Android Google Maps绘图路线代码

MainActivity.java代码如下。

public class MapsActivity extends FragmentActivity implements OnMapReadyCallback {

  private GoogleMap mMap;
  ArrayList markerPoints= new ArrayList();

  @Override
  protected void onCreate(Bundle savedInstanceState) {
      super.onCreate(savedInstanceState);
      setContentView(R.layout.activity_maps);
      //Obtain the SupportMapFragment and get notified when the map is ready to be used.
      SupportMapFragment mapFragment = (SupportMapFragment) getSupportFragmentManager()
              .findFragmentById(R.id.map);
      mapFragment.getMapAsync(this);
  }

  @Override
  public void onMapReady(GoogleMap googleMap) {
      mMap = googleMap;
      LatLng sydney = new LatLng(-34, 151);
      //mMap.addMarker(new MarkerOptions().position(sydney).title("Marker in Sydney"));
      mMap.moveCamera(CameraUpdateFactory.newLatLngZoom(sydney, 16));

      mMap.setOnMapClickListener(new GoogleMap.OnMapClickListener() {
          @Override
          public void onMapClick(LatLng latLng) {

              if (markerPoints.size() > 1) {
                  markerPoints.clear();
                  mMap.clear();
              }

              //Adding new item to the ArrayList
              markerPoints.add(latLng);

              //Creating MarkerOptions
              MarkerOptions options = new MarkerOptions();

              //Setting the position of the marker
              options.position(latLng);

              if (markerPoints.size() == 1) {
                  options.icon(BitmapDescriptorFactory.defaultMarker(BitmapDescriptorFactory.HUE_GREEN));
              } else if (markerPoints.size() == 2) {
                  options.icon(BitmapDescriptorFactory.defaultMarker(BitmapDescriptorFactory.HUE_RED));
              }

              //Add new marker to the Google Map Android API V2
              mMap.addMarker(options);

              //Checks, whether start and end locations are captured
              if (markerPoints.size() >= 2) {
                  LatLng origin = (LatLng) markerPoints.get(0);
                  LatLng dest = (LatLng) markerPoints.get(1);

                  //Getting URL to the Google Directions API
                  String url = getDirectionsUrl(origin, dest);

                  DownloadTask downloadTask = new DownloadTask();

                  //Start downloading json data from Google Directions API
                  downloadTask.execute(url);
              }

          }
      });

  }

  private class DownloadTask extends AsyncTask {

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

          String data = "";

          try {
              data = downloadUrl(url[0]);
          } catch (Exception e) {
              Log.d("Background Task", e.toString());
          }
          return data;
      }

      @Override
      protected void onPostExecute(String result) {
          super.onPostExecute(result);

          ParserTask parserTask = new ParserTask();

          parserTask.execute(result);

      }
  }

  private class ParserTask extends AsyncTask<String, Integer, List<List<HashMap>>> {

      //Parsing the data in non-ui thread
      @Override
      protected List<List<HashMap>> doInBackground(String... jsonData) {

          JSONObject jObject;
          List<List<HashMap>> routes = null;

          try {
              jObject = new JSONObject(jsonData[0]);
              DirectionsJSONParser parser = new DirectionsJSONParser();

              routes = parser.parse(jObject);
          } catch (Exception e) {
              e.printStackTrace();
          }
          return routes;
      }

      @Override
      protected void onPostExecute(List<List<HashMap>> result) {
          ArrayList points = null;
          PolylineOptions lineOptions = null;
          MarkerOptions markerOptions = new MarkerOptions();

          for (int i = 0; i < result.size(); i++) {
              points = new ArrayList();
              lineOptions = new PolylineOptions();

              List<HashMap> path = result.get(i);

              for (int j = 0; j < path.size(); j++) {
                  HashMap point = path.get(j);

                  double lat = Double.parseDouble(point.get("lat"));
                  double lng = Double.parseDouble(point.get("lng"));
                  LatLng position = new LatLng(lat, lng);

                  points.add(position);
              }

              lineOptions.addAll(points);
              lineOptions.width(12);
              lineOptions.color(Color.RED);
              lineOptions.geodesic(true);

          }

//Drawing polyline in the Google Map for the i-th route
          mMap.addPolyline(lineOptions);
      }
  }

  private String getDirectionsUrl(LatLng origin, LatLng dest) {

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

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

      //Sensor enabled
      String sensor = "sensor=false";
      String mode = "mode=driving";

      //Building the parameters to the web service
      String parameters = str_origin + "&" + str_dest + "&" + sensor + "&" + mode;

      //Output format
      String output = "json";

      //Building the url to the web service
      String url = "https://maps.googleapis.com/maps/api/directions/" + output + "?" + parameters;
      

      return url;
  }

  private String downloadUrl(String strUrl) throws IOException {
      String data = "";
      InputStream iStream = null;
      HttpURLConnection urlConnection = null;
      try {
          URL url = new URL(strUrl);

          urlConnection = (HttpURLConnection) url.openConnection();

          urlConnection.connect();

          iStream = urlConnection.getInputStream();

          BufferedReader br = new BufferedReader(new InputStreamReader(iStream));

          StringBuffer sb = new StringBuffer();

          String line = "";
          while ((line = br.readLine()) != null) {
              sb.append(line);
          }

          data = sb.toString();

          br.close();

      } catch (Exception e) {
          Log.d("Exception", e.toString());
      } finally {
          iStream.close();
          urlConnection.disconnect();
      }
      return data;
  }
}

我们在Google地图对象上称为" onMapClickListener"。
它用于在点击的位置上设置标记，并将该位置存储在ArrayList中。
ArrayList仅用于存储源标记和目标标记。
" getDirectionsUrl()"称为Directions API URL，其输出和参数如下所示。

" https://maps.googleapis.com/maps/api/directions/" +输出+"？" +参数;

输出变量包含一个" json"字符串，参数字符串创建为：String parameters = str_origin +"&" + str_dest +"&" + sensor +"&" + mode;

我们在当前应用程序中将模式设置为"驾驶"。
其他运输方式是：

• 驾驶(默认)
• 步行
• 单车
• 过境