我是谷歌地图V2的新手，我想找到我当前位置和目的地的最短路径。所以，我尝试了一些代码并且它可以工作，但它没有画出最短的路径。我需要帮助：
这是我的代码：
gps = new GPSTracker(ViewOnMap.this);
// check if GPS enabled
if(gps.canGetLocation()){
latitude = gps.getLatitude();
longitude = gps.getLongitude();
}
LatLng origin = new LatLng(latitude,longitude);
LatLng dest = new LatLng(lat,lon);
// 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);
}
@Override
public boolean onCreateOptionsMenu(Menu menu) {
// Inflate the menu; this adds items to the action bar if it is present.
getMenuInflater().inflate(R.menu.view_on_map, menu);
return true;
}
@Override
public void onInfoWindowClick(Marker arg0) {
// TODO Auto-generated method stub
}
@Override
public void onLocationChanged(Location location) {
// TODO Auto-generated method stub
LatLng latLng = new LatLng(location.getLatitude(), location.getLongitude());
CameraUpdate cameraUpdate = CameraUpdateFactory.newLatLngZoom(latLng, 15);
mMap.animateCamera(cameraUpdate);
locationManager.removeUpdates(this);
}
@Override
public void onProviderDisabled(String arg0) {
// TODO Auto-generated method stub
}
@Override
public void onProviderEnabled(String provider) {
// TODO Auto-generated method stub
}
@Override
public void onStatusChanged(String provider, int status, Bundle extras) {
// TODO Auto-generated method stub
}
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";
// Building the parameters to the web service
String parameters = str_origin+"&"+str_dest+"&"+sensor;
// 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;
}
/** A method to download json data from url */
private String downloadUrl(String strUrl) throws IOException{
String data = "";
InputStream iStream = null;
HttpURLConnection urlConnection = null;
try{
URL url = new URL(strUrl);
// Creating an http connection to communicate with url
urlConnection = (HttpURLConnection) url.openConnection();
// Connecting to url
urlConnection.connect();
// Reading data from url
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 while downloading url", e.toString());
}finally{
iStream.close();
urlConnection.disconnect();
}
return data;
}
// Fetches data from url passed
private class DownloadTask extends AsyncTask<String, Void, String>{
// Downloading data in non-ui thread
@Override
protected String doInBackground(String... url) {
// For storing data from web service
String data = "";
try{
// Fetching the data from web service
data = downloadUrl(url[0]);
}catch(Exception e){
Log.d("Background Task",e.toString());
}
return data;
}
// Executes in UI thread, after the execution of
// doInBackground()
@Override
protected void onPostExecute(String result) {
super.onPostExecute(result);
ParserTask parserTask = new ParserTask();
// Invokes the thread for parsing the JSON data
parserTask.execute(result);
}
}
/** A class to parse the Google Places in JSON format */
private class ParserTask extends AsyncTask<String, Integer, List<List<HashMap<String,String>>> >{
// Parsing the data in non-ui thread
@Override
protected List<List<HashMap<String, String>>> doInBackground(String... jsonData) {
JSONObject jObject;
List<List<HashMap<String, String>>> routes = null;
try{
jObject = new JSONObject(jsonData[0]);
DirectionsJSONParser parser = new DirectionsJSONParser();
// Starts parsing data
routes = parser.parse(jObject);
}catch(Exception e){
e.printStackTrace();
}
return routes;
}
// Executes in UI thread, after the parsing process
@Override
protected void onPostExecute(List<List<HashMap<String, String>>> result) {
ArrayList<LatLng> points = null;
PolylineOptions lineOptions = null;
MarkerOptions markerOptions = new MarkerOptions();
// Traversing through all the routes
for(int i=0;i<result.size();i++){
points = new ArrayList<LatLng>();
lineOptions = new PolylineOptions();
// Fetching i-th route
List<HashMap<String, String>> path = result.get(i);
// Fetching all the points in i-th route
for(int j=0;j<path.size();j++){
HashMap<String,String> 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);
}
// Adding all the points in the route to LineOptions
lineOptions.addAll(points);
lineOptions.width(8);
lineOptions.color(Color.BLUE);
}
// Drawing polyline in the Google Map for the i-th route
mMap.addPolyline(lineOptions);
}
}
}
提前谢谢=）
答案 0 :(得分：0)
看here。并使用：
...
DirectonTask dirTask = new DirectonTask(this);
dirTask.execute(md.getUrl(new LatLng(loc1.getLatitude(), loc1.getLongitude()),
new LatLng(loc2.getLatitude(), loc2.getLongitude(),GMapV2Direction.MODE_DRIVING));
...
和任务完成后调用的方法
GMapV2Direction md = new GMapV2Direction();
Document doc;
Polyline currentPath;
public void drawDirection(Document doc) {
this.doc = doc;
ArrayList<LatLng> directionPoint = md.getDirection(doc);
PolylineOptions rectLine = new PolylineOptions().width(3).color(
Color.RED);
for (int i = 0; i < directionPoint.size(); i++)
rectLine.add(directionPoint.get(i));
map.addPolyline(rectLine);
}
GMapV2Direction.java：
public class GMapV2Direction {
public final static String MODE_DRIVING = "driving";
public final static String MODE_WALKING = "walking";
private static final String TAG = "google_map_GMapV2Direction";
public GMapV2Direction() { }
public String getUrl(LatLng start, LatLng end, String mode){
String url = "http://maps.googleapis.com/maps/api/directions/xml?"
+ "origin=" + start.latitude + "," + start.longitude
+ "&destination=" + end.latitude + "," + end.longitude
+ "&sensor=false&mode="+mode;
return url;
}
public Document getDocument(LatLng start, LatLng end, String mode) {
String url = "http://maps.googleapis.com/maps/api/directions/xml?"
+ "origin=" + start.latitude + "," + start.longitude
+ "&destination=" + end.latitude + "," + end.longitude
+ "&sensor=false&mode="+mode;
try {
LOG.d(TAG, "url = "+url);
HttpClient httpClient = new DefaultHttpClient();
HttpGet httpGet = new HttpGet(url);
HttpResponse response = httpClient.execute(httpGet);
InputStream in = response.getEntity().getContent();
DocumentBuilder builder = DocumentBuilderFactory.newInstance().newDocumentBuilder();
Document doc = builder.parse(in);
return doc;
} catch (Exception e) {
e.printStackTrace();
}
return null;
}
public String getDurationText (Document doc) {
NodeList nl1 = doc.getElementsByTagName("duration");
Node node1 = nl1.item(nl1.getLength() - 1);
NodeList nl2 = node1.getChildNodes();
Node node2 = nl2.item(getNodeIndex(nl2, "text"));
LOG.i(TAG,"DurationText: "+ node2.getTextContent());
return node2.getTextContent();
}
public int getDurationValue (Document doc) {
NodeList nl1 = doc.getElementsByTagName("duration");
Node node1 = nl1.item(nl1.getLength() - 1);
NodeList nl2 = node1.getChildNodes();
Node node2 = nl2.item(getNodeIndex(nl2, "value"));
LOG.i(TAG,"DurationValue: "+ node2.getTextContent());
return Integer.parseInt(node2.getTextContent());
}
public String getDistanceText (Document doc) {
NodeList nl1 = doc.getElementsByTagName("distance");
Node node1 = nl1.item(nl1.getLength() - 1);
NodeList nl2 = node1.getChildNodes();
Node node2 = nl2.item(getNodeIndex(nl2, "text"));
LOG.i(TAG,"DistanceText: "+ node2.getTextContent());
return node2.getTextContent();
}
public int getDistanceValue (Document doc) {
NodeList nl1 = doc.getElementsByTagName("distance");
Node node1 = nl1.item(nl1.getLength() - 1);
NodeList nl2 = node1.getChildNodes();
Node node2 = nl2.item(getNodeIndex(nl2, "value"));
LOG.i(TAG,"DistanceValue: " +node2.getTextContent());
return Integer.parseInt(node2.getTextContent());
}
public String getStartAddress (Document doc) {
NodeList nl1 = doc.getElementsByTagName("start_address");
Node node1 = nl1.item(0);
LOG.i(TAG,"StartAddress: "+node1.getTextContent());
return node1.getTextContent();
}
public String getEndAddress (Document doc) {
NodeList nl1 = doc.getElementsByTagName("end_address");
Node node1 = nl1.item(0);
LOG.i(TAG,"StartAddress: "+node1.getTextContent());
return node1.getTextContent();
}
public String getCopyRights (Document doc) {
NodeList nl1 = doc.getElementsByTagName("copyrights");
Node node1 = nl1.item(0);
LOG.i(TAG,"CopyRights: "+node1.getTextContent());
return node1.getTextContent();
}
public ArrayList<LatLng> getDirection (Document doc) {
NodeList nl1, nl2, nl3;
ArrayList<LatLng> listGeopoints = new ArrayList<LatLng>();
nl1 = doc.getElementsByTagName("step");
if (nl1.getLength() > 0) {
for (int i = 0; i < nl1.getLength(); i++) {
Node node1 = nl1.item(i);
nl2 = node1.getChildNodes();
Node locationNode = nl2.item(getNodeIndex(nl2, "start_location"));
nl3 = locationNode.getChildNodes();
Node latNode = nl3.item(getNodeIndex(nl3, "lat"));
double lat = Double.parseDouble(latNode.getTextContent());
Node lngNode = nl3.item(getNodeIndex(nl3, "lng"));
double lng = Double.parseDouble(lngNode.getTextContent());
listGeopoints.add(new LatLng(lat, lng));
locationNode = nl2.item(getNodeIndex(nl2, "polyline"));
nl3 = locationNode.getChildNodes();
latNode = nl3.item(getNodeIndex(nl3, "points"));
ArrayList<LatLng> arr = decodePoly(latNode.getTextContent());
for(int j = 0 ; j < arr.size() ; j++) {
listGeopoints.add(new LatLng(arr.get(j).latitude, arr.get(j).longitude));
}
locationNode = nl2.item(getNodeIndex(nl2, "end_location"));
nl3 = locationNode.getChildNodes();
latNode = nl3.item(getNodeIndex(nl3, "lat"));
lat = Double.parseDouble(latNode.getTextContent());
lngNode = nl3.item(getNodeIndex(nl3, "lng"));
lng = Double.parseDouble(lngNode.getTextContent());
listGeopoints.add(new LatLng(lat, lng));
}
}
return listGeopoints;
}
private int getNodeIndex(NodeList nl, String nodename) {
for(int i = 0 ; i < nl.getLength() ; i++) {
if(nl.item(i).getNodeName().equals(nodename))
return i;
}
return -1;
}
private ArrayList<LatLng> decodePoly(String encoded) {
ArrayList<LatLng> poly = new ArrayList<LatLng>();
int index = 0, len = encoded.length();
int lat = 0, lng = 0;
while (index < len) {
int b, shift = 0, result = 0;
do {
b = encoded.charAt(index++) - 63;
result |= (b & 0x1f) << shift;
shift += 5;
} while (b >= 0x20);
int dlat = ((result & 1) != 0 ? ~(result >> 1) : (result >> 1));
lat += dlat;
shift = 0;
result = 0;
do {
b = encoded.charAt(index++) - 63;
result |= (b & 0x1f) << shift;
shift += 5;
} while (b >= 0x20);
int dlng = ((result & 1) != 0 ? ~(result >> 1) : (result >> 1));
lng += dlng;
LatLng position = new LatLng((double) lat / 1E5, (double) lng / 1E5);
poly.add(position);
}
return poly;
}
}
和DirectionTask：
public class DirectonTask extends AsyncTask<String, Void, Document> {
private static final String TAG = "google_map_DirectonTask";
Context c;
MapGoogle map;
public DirectonTask(MapGoogle map) {
super();
this.map = map;
// this.c = c;
}
@Override
protected void onPreExecute() {
super.onPreExecute();
}
@Override
protected Document doInBackground(String... url) {
// LOG.d(TAG, "url = " + url[0]);
HttpClient httpClient = new DefaultHttpClient();
// HttpContext localContext = new BasicHttpContext();
// HttpPost httpPost = new HttpPost(url);
try {
HttpGet httpGet = new HttpGet(url[0]);
HttpResponse response;
response = httpClient.execute(httpGet);
InputStream in = response.getEntity().getContent();
DocumentBuilder builder = DocumentBuilderFactory.newInstance()
.newDocumentBuilder();
Document doc = builder.parse(in);
return doc;
} catch (ClientProtocolException e) {
// TODO Auto-generated catch block
e.printStackTrace();
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}catch (Exception e) {
e.printStackTrace();
}
return null;
}
@Override
protected void onPostExecute(Document result) {
if (result != null) {
map.drawDirection(result);
} else {
LOG.d("onPostExecute: direction = null");
}
}
}