我正在尝试创建并显示设备当前位置和已定义点之间的路由。 我使用这段代码：
public class RoutePath extends MapActivity {
/** Called when the activity is first created. */
MapView mapView;
private RoutePath _activity;
GeoPoint srcGeoPoint,destGeoPoint;
private static List<Overlay> mOverlays;
MapController mc;
Location location;
private MyLocationOverlay myLocationOverlay;
String n;
double longitude;
double latitude;
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
SharedData data = SharedData.getInstance();
mapView = new MapView(this,"apyKey");
mapView.setClickable(true);
setContentView(mapView);
_activity = this;
LocationManager lm = (LocationManager)getSystemService(Context.LOCATION_SERVICE);
Location location =lm.getLastKnownLocation(LocationManager.NETWORK_PROVIDER);
longitude = location.getLongitude();
latitude = location.getLatitude();
double src_lat = latitude;
double src_long = longitude;
double dest_lat = 38.1267303;
double dest_long = 13.3466097;
String n = String.valueOf(src_long);
Log.d("asd",n);
if(src_lat == -1 || src_long == -1 || dest_lat == -1 || dest_long == -1){
showAlert("Please enter source and destination points");
}else{
srcGeoPoint = new GeoPoint((int) (src_lat * 1E6),(int) (src_long * 1E6));
destGeoPoint = new GeoPoint((int) (dest_lat * 1E6),(int) (dest_long * 1E6));
List<Overlay> mapOverlays = mapView.getOverlays();
Drawable srcdrawable = this.getResources().getDrawable(R.drawable.pushpin1);
CustomItemizedOverlay srcitemizedOverlay = new CustomItemizedOverlay(srcdrawable);
//CustomItemizedOverlay srcitemizedOverlay = new CustomItemizedOverlay(getDrawable("com/agarwal/route/pin_green.png"));
OverlayItem srcoverlayitem = new OverlayItem(srcGeoPoint, "Hello!", "This is your Location.");
Drawable destdrawable = this.getResources().getDrawable(R.drawable.pushpin1);
CustomItemizedOverlay destitemizedOverlay = new CustomItemizedOverlay( destdrawable );
// CustomItemizedOverlay destitemizedOverlay = new CustomItemizedOverlay(getDrawable("com/agarwal/route/pin_red.png"));
OverlayItem destoverlayitem = new OverlayItem(destGeoPoint, "Hello!", "This is dest Location.");
srcitemizedOverlay.addOverlay(srcoverlayitem);
destitemizedOverlay.addOverlay(destoverlayitem);
mapOverlays.add(srcitemizedOverlay);
mapOverlays.add(destitemizedOverlay);
connectAsyncTask _connectAsyncTask = new connectAsyncTask();
_connectAsyncTask.execute();
mapView.setBuiltInZoomControls(true);
mapView.displayZoomControls(true);
mOverlays = mapView.getOverlays();
mapView.getController().animateTo(srcGeoPoint);
mapView.getController().setZoom(12);
}
}
@Override
protected boolean isRouteDisplayed() {
// TODO Auto-generated method stub
return false;
}
//era private prima di
private class connectAsyncTask extends AsyncTask<Void, Void, Void>{
private ProgressDialog progressDialog;
@Override
protected void onPreExecute() {
// TODO Auto-generated method stub
super.onPreExecute();
progressDialog = new ProgressDialog(_activity);
progressDialog.setMessage("Caricamento del percorso...");
progressDialog.setIndeterminate(true);
progressDialog.show();
}
@Override
protected Void doInBackground(Void... params) {
// TODO Auto-generated method stub
fetchData();
return null;
}
@Override
protected void onPostExecute(Void result) {
// TODO Auto-generated method stub
super.onPostExecute(result);
if(doc!=null){
Overlay ol = new MyOverlay(_activity,srcGeoPoint,srcGeoPoint,1);
mOverlays.add(ol);
NodeList _nodelist = doc.getElementsByTagName("status");
Node node1 = _nodelist.item(0);
String _status1 = node1.getChildNodes().item(0).getNodeValue();
if(_status1.equalsIgnoreCase("OK")){
NodeList _nodelist_path = doc.getElementsByTagName("overview_polyline");
Node node_path = _nodelist_path.item(0);
Element _status_path = (Element)node_path;
NodeList _nodelist_destination_path = _status_path.getElementsByTagName("points");
Node _nodelist_dest = _nodelist_destination_path.item(0);
String _path = _nodelist_dest.getChildNodes().item(0).getNodeValue();
List<GeoPoint> _geopoints = decodePoly(_path);
GeoPoint gp1;
GeoPoint gp2;
gp2 = _geopoints.get(0);
Log.d("_geopoints","::"+_geopoints.size());
for(int i=1;i<_geopoints.size();i++) // the last one would be crash
{
gp1 = gp2;
gp2 = _geopoints.get(i);
Overlay ol1 = new MyOverlay(gp1,gp2,2,Color.BLUE);
mOverlays.add(ol1);
}
Overlay ol2 = new MyOverlay(_activity,destGeoPoint,destGeoPoint,3);
mOverlays.add(ol2);
progressDialog.dismiss();
}else{
showAlert("Unable to find the route");
}
Overlay ol2 = new MyOverlay(_activity,destGeoPoint,destGeoPoint,3);
mOverlays.add(ol2);
progressDialog.dismiss();
mapView.scrollBy(-1,-1);
mapView.scrollBy(1,1);
}else{
showAlert("Unable to find the route");
}
}
} //end Async
Document doc = null;
private void fetchData()
{
StringBuilder urlString = new StringBuilder();
urlString.append("http://maps.google.com/maps/api/directions/xml?origin=");
urlString.append( Double.toString((double)srcGeoPoint.getLatitudeE6()/1.0E6 ));
urlString.append(",");
urlString.append( Double.toString((double)srcGeoPoint.getLongitudeE6()/1.0E6 ));
urlString.append("&destination=");//to
urlString.append( Double.toString((double)destGeoPoint.getLatitudeE6()/1.0E6 ));
urlString.append(",");
urlString.append( Double.toString((double)destGeoPoint.getLongitudeE6()/1.0E6 ));
urlString.append("&sensor=true&mode=driving");
Log.d("url","::"+urlString.toString());
HttpURLConnection urlConnection= null;
URL url = null;
try
{
url = new URL(urlString.toString());
urlConnection=(HttpURLConnection)url.openConnection();
urlConnection.setRequestMethod("GET");
urlConnection.setDoOutput(true);
urlConnection.setDoInput(true);
urlConnection.connect();
DocumentBuilderFactory dbf = DocumentBuilderFactory.newInstance();
DocumentBuilder db = dbf.newDocumentBuilder();
doc = (Document) db.parse(urlConnection.getInputStream());//Util.XMLfromString(response);
}catch (MalformedURLException e){
e.printStackTrace();
}catch (IOException e){
e.printStackTrace();
}catch (ParserConfigurationException e){
e.printStackTrace();
}
catch (SAXException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
private List<GeoPoint> decodePoly(String encoded) {
List<GeoPoint> poly = new ArrayList<GeoPoint>();
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;
GeoPoint p = new GeoPoint((int) (((double) lat / 1E5) * 1E6),
(int) (((double) lng / 1E5) * 1E6));
poly.add(p);
}
return poly;
}
private void showAlert(String message){
AlertDialog.Builder alert = new AlertDialog.Builder(_activity);
alert.setTitle("Error");
alert.setCancelable(false);
alert.setMessage(message);
alert.setPositiveButton("Ok",new DialogInterface.OnClickListener() {
public void onClick(DialogInterface dialog, int which) {
// TODO Auto-generated method stub
}
});
alert.show();
}
private Drawable getDrawable(String fileName){
return Drawable.createFromStream(_activity.getClass().getClassLoader().getResourceAsStream(fileName), "pin");
}
}
这适用于智能手机Galaxy Nexus，android 4.2。
我在我的平板电脑上测试了它，android 4.0.2，它运行良好。
但是，当我在智能手机上测试它时，它会崩溃。
我尝试使用LocationManager.NETWORK_PROVIDER更改LocationManager.GPS_PROVIDER，但无论如何它都会崩溃。我无法解决这个问题。任何人都可以帮助我吗？
答案 0 :(得分：3)
我在相同的问题上挣扎了好几个小时。同样的代码在我的Android 2.7设备上运行良好，但不适用于我的Android 4.1.1。最后，我发现，由于某些原因，如果不首先调用requestLocationUpdates（），则getLastKnownLocation（）不起作用。 因此，在我将这两行放在后，我的LocationListener开始更新：
locationManager.requestLocationUpdates(provider, 1000, 10, locationListener);
Location location = locationManager.getLastKnownLocation(provider);
希望它有所帮助。
答案 1 :(得分：1)
你有机会获得空指针。
从getLastKnownLocation（）获取位置，然后使用此对象而不检查它是否为null。如果没有已知位置，getLastKnownLocation可以返回null。