安卓谷歌地图 – 绘制两个点之间的路线
在这个教程中，我们将创建一个安卓应用程序，在两个点之间绘制可能的谷歌地图路线。我们将在应用程序中使用谷歌地图方向API。
Android 谷歌地图 – 绘制路线
使用本教程中演示的步骤在API控制台中创建一个新的Google 地图API密钥。创建一个新的Android Studio项目，并选择Google 地图活动模板。将API密钥添加到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，应用程序应该是这样的。
安卓谷歌地图绘制路径的项目结构
DirectionsJSONParser.java文件是用来解析位置并返回路线的文件。然后调用decodePoly()方法来获取后续绘制在地图上的折线数据。
安卓谷歌地图绘制路线的代码
以下是MainActivity.java的代码。
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;
}
}
我们在谷歌地图对象上调用了一个onMapClickListener。它用于在点击的位置上设置一个标记，并将该位置存储在一个ArrayList中。ArrayList仅用于存储起始点和目的地标记。getDirectionsUrl()会调用以下输出和参数的Directions API URL。”https://maps.googleapis.com/maps/api/directions/” + output + “?” + parameters; 输出变量保存一个“json”字符串，而参数字符串的创建方式如下：String parameters = str_origin + “&” + str_dest + “&” + sensor + “&” + mode; 在当前应用程序中我们将mode设置为“driving”（驾车）。其他的交通方式包括：
- driving (default)
- walking
- bicycling
- transit
以下是该应用程序的输出结果：这就结束了本教程。您可以从下面的链接下载最终项目并添加您自己的Google地图API密钥。
下载Android谷歌地图绘制路线项目。
