我正在尝试使用osmdroid api进行简单的地理编码测试，但我总是遇到错误，但我试图从网址（nominatim）获得json响应。我在AsyncTask中执行它但似乎gps坐标仅在try / catch中可用，但是在其余代码中它们被设置为null，因此我得到一个nullpointer异常...我该如何解决这个问题？
我的最终目的是设法在地图上显示EditText中用户所写的2个地址之间的道路
这是我的代码：
class OsmRoadTask extends AsyncTask<String, String, Void> {
MapView mapView;
MapController mapController;
Context context;
GeoPoint geostartpoint = null;
GeoPoint geoendpoint = null;
ArrayList<GeoPoint> points = new ArrayList<GeoPoint>();
Polyline roadOverlay;
ProgressDialog pd = new ProgressDialog(OsmRoadTaskActivity.this);
InputStream isdepart = null;
InputStream isarrivee = null;
String resultdepart = "";
String resultarrivee = "";
RoadManager roadmanager = null;
Road road = null;
public OsmRoadTask(Context ctx) {
// TODO Auto-generated constructor stub
}
protected void onPreExecute() {
pd.setMessage("Recherche d'itineraire en cours, merci de patienter");
pd.show();
pd.setOnCancelListener(new OnCancelListener() {
public void onCancel(DialogInterface arg0) {
OsmRoadTask.this.cancel(true);
}
});
}
protected Void doInBackground(String... arg0) {
String adresseDepart = OsmRoadTaskActivity.Estartpoint.getText()
.toString();
String adresseDepartFormate = adresseDepart.replaceAll(" ", "+");
String urldepart = "http://nominatim.openstreetmap.org/search?q="
+ adresseDepartFormate + "&format=json&polygon_svg=1";
try {
HttpGet httpgetdepart = new HttpGet(urldepart);
HttpClient httpclientdepart = new DefaultHttpClient();
HttpResponse responsedepart = httpclientdepart
.execute(httpgetdepart);
HttpEntity httpentitydepart = responsedepart.getEntity();
isdepart = httpentitydepart.getContent();
} catch (ClientProtocolException e) {
e.printStackTrace();
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
try {
StringBuilder sbdepart = new StringBuilder();
BufferedReader reader = new BufferedReader(
new InputStreamReader(isdepart, "iso-8859-1"), 8);
String line = null;
while ((line = reader.readLine()) != null) {
sbdepart.append(line + "\n");
}
isdepart.close();
resultdepart = sbdepart.toString();
} catch (ClientProtocolException e) {
e.printStackTrace();
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
try {
JSONArray jArray = new JSONArray(resultdepart);
for (int i = 0; i < jArray.length(); i++) {
JSONObject jobject = jArray.getJSONObject(i);
double latdepart = jobject.getDouble("lat");
double lngarrivee = jobject.getDouble("lon");
geostartpoint = new GeoPoint(latdepart, lngarrivee);
// i think geostartpoint is not null here...
}
} catch (JSONException e) {
e.printStackTrace();
}
points.add(geostartpoint); //but here it's null
roadmanager = new OSRMRoadManager();
return null;
}
protected void onPostExecute(Void result) {
mapView = (MapView) findViewById(R.id.mapview);
mapController = (MapController) mapView.getController();
mapView.setTileSource(TileSourceFactory.MAPNIK);
mapView.setBuiltInZoomControls(false);
mapView.setMultiTouchControls(true);
mapView.getOverlays().add(roadOverlay);
Marker startmarker = new Marker(mapView);
Marker endmarker = new Marker(mapView);
startmarker.setPosition(geostartpoint);
startmarker.setAnchor(Marker.ANCHOR_BOTTOM, Marker.ANCHOR_CENTER);
// endmarker.setPosition(geoendpoint);
// endmarker.setAnchor(Marker.ANCHOR_BOTTOM, Marker.ANCHOR_CENTER);
mapView.getOverlays().add(startmarker);
// mapView.getOverlays().add(endmarker);
mapController.setCenter(geostartpoint);
mapController.animateTo(geostartpoint);
mapController.setZoom(13);
mapView.invalidate();
}
}
日志显示
04-20 14:14:23.593: E/AndroidRuntime(564): FATAL EXCEPTION: main
04-20 14:14:23.593: E/AndroidRuntime(564): java.lang.NullPointerException
04-20 14:14:23.593: E/AndroidRuntime(564): at org.osmdroid.bonuspack.overlays.Marker.setPosition(Marker.java:123)
04-20 14:14:23.593: E/AndroidRuntime(564): at toutel.testcarte.OsmRoadTaskActivity$OsmRoadTask.onPostExecute(OsmRoadTaskActivity.java:278)
04-20 14:14:23.593: E/AndroidRuntime(564): at toutel.testcarte.OsmRoadTaskActivity$OsmRoadTask.onPostExecute(OsmRoadTaskActivity.java:1)
04-20 14:14:23.593: E/AndroidRuntime(564): at android.os.AsyncTask.finish(AsyncTask.java:631)
04-20 14:14:23.593: E/AndroidRuntime(564): at android.os.AsyncTask.access$600(AsyncTask.java:177)
04-20 14:14:23.593: E/AndroidRuntime(564): at android.os.AsyncTask$InternalHandler.handleMessage(AsyncTask.java:644)
04-20 14:14:23.593: E/AndroidRuntime(564): at android.os.Handler.dispatchMessage(Handler.java:99)
04-20 14:14:23.593: E/AndroidRuntime(564): at android.os.Looper.loop(Looper.java:137)
04-20 14:14:23.593: E/AndroidRuntime(564): at android.app.ActivityThread.main(ActivityThread.java:4921)
04-20 14:14:23.593: E/AndroidRuntime(564): at java.lang.reflect.Method.invokeNative(Native Method)
04-20 14:14:23.593: E/AndroidRuntime(564): at java.lang.reflect.Method.invoke(Method.java:511)
04-20 14:14:23.593: E/AndroidRuntime(564): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1038)
04-20 14:14:23.593: E/AndroidRuntime(564): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:805)
04-20 14:14:23.593: E/AndroidRuntime(564): at dalvik.system.NativeStart.main(Native Method)