private String getMapsApiDirectionsUrl() {
String origin;
String destination=String.valueOf(l.longitude)+","+String.valueOf(l.latitude);
origin=String.valueOf(longitude)+","+String.valueOf(latitude);
// String url = "https://maps.googleapis.com/maps/api/directions/"+ output + "?" + params;
String url="https://maps.googleapis.com/maps/api/directions/json?origin="+origin+"&destination="+destination+"&sensor=false";
return url;
}
我得到了NullPointerException。我知道它是什么但不能确定导致它的原因。假设这个方法之外的一切都是正确的，那么语法上有什么问题呢？
这是我的全部代码：
package autogenie.maptrial;
import android.Manifest;
import android.content.Context;
import android.content.pm.PackageManager;
import android.graphics.Color;
import android.location.Address;
import android.location.Geocoder;
import android.location.Location;
import android.location.LocationListener;
import android.location.LocationManager;
import android.os.AsyncTask;
import android.os.Bundle;
import android.os.Handler;
import android.os.Message;
import android.support.v4.app.ActivityCompat;
import android.support.v4.app.FragmentActivity;
import android.util.Log;
import android.view.View;
import android.widget.Button;
import android.widget.EditText;
import android.widget.Toast;
import com.google.android.gms.common.api.Status;
import com.google.android.gms.location.places.Place;
import com.google.android.gms.location.places.ui.PlaceAutocompleteFragment;
import com.google.android.gms.location.places.ui.PlaceSelectionListener;
import com.google.android.gms.maps.GoogleMap;
import com.google.android.gms.maps.SupportMapFragment;
import com.google.android.gms.maps.model.LatLng;
import com.google.android.gms.maps.model.Marker;
import com.google.android.gms.maps.model.MarkerOptions;
import com.google.android.gms.maps.model.PolylineOptions;
import org.json.JSONObject;
import java.io.IOException;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Locale;
public class MainActivity extends FragmentActivity implements LocationListener,GoogleMap.OnMarkerDragListener {
private double latitude, longitude;
public GoogleMap googleMap,googleMap1;
LocationManager locationManager;
Button addressButton;
PlaceAutocompleteFragment fragment;
LatLng l;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
SupportMapFragment supportMapFragment =
(SupportMapFragment) getSupportFragmentManager().findFragmentById(R.id.map);
googleMap = supportMapFragment.getMap();
googleMap.setMapType(GoogleMap.MAP_TYPE_NORMAL);
googleMap.setMyLocationEnabled(true);
addressButton = (Button) findViewById(R.id.addressButton);
fragment = (PlaceAutocompleteFragment) getFragmentManager().findFragmentById(R.id.place_autocomplete_fragment);
String url = getMapsApiDirectionsUrl();
ReadTask downloadTask = new ReadTask();
downloadTask.execute(url);
locationManager = (LocationManager) getSystemService(Context.LOCATION_SERVICE);
locationManager.requestLocationUpdates(LocationManager.GPS_PROVIDER, 0, 0, this);
if (ActivityCompat.checkSelfPermission(this, Manifest.permission.ACCESS_FINE_LOCATION) != PackageManager.PERMISSION_GRANTED && ActivityCompat.checkSelfPermission(this, Manifest.permission.ACCESS_COARSE_LOCATION) != PackageManager.PERMISSION_GRANTED) {
// TODO: Consider calling
// ActivityCompat#requestPermissions
// here to request the missing permissions, and then overriding
// public void onRequestPermissionsResult(int requestCode, String[] permissions,
// int[] grantResults)
// to handle the case where the user grants the permission. See the documentation
// for ActivityCompat#requestPermissions for more details.
return;
}
addressButton.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View arg0) {
EditText editText = (EditText) findViewById(R.id.enter_place_name);
String address = editText.getText().toString();
GeocodingLocation locationAddress = new GeocodingLocation();
locationAddress.getAddressFromLocation(address,
getApplicationContext(), new GeocoderHandler());
l= getLocationFromAddress(getApplicationContext(), address);
MarkerOptions a=new MarkerOptions().position(l);
Marker m=googleMap.addMarker(a);
m.setPosition(l);
}
});
fragment.setOnPlaceSelectedListener(new PlaceSelectionListener() {
@Override
public void onPlaceSelected(Place place) { // Handle the selected Place
}
@Override
public void onError(Status status) { // Handle the error
}
});
}
public LatLng getLocationFromAddress(Context context,String strAddress) {
Geocoder coder = new Geocoder(context,Locale.getDefault());
List<Address> address;
LatLng p1 = null;
try {
address = coder.getFromLocationName(strAddress, 1);
if (address == null) {
return null;
}
Address location = address.get(0);
location.getLatitude();
location.getLongitude();
p1 = new LatLng(location.getLatitude(), location.getLongitude() );
} catch (Exception ex) {
ex.printStackTrace();
}
return p1;
}
private class GeocoderHandler extends Handler {
@Override
public void handleMessage(Message message) {
String locationAddress;
switch (message.what) {
case 1:
Bundle bundle = message.getData();
locationAddress = bundle.getString("address");
break;
default:
locationAddress = null;
}
Toast.makeText(getApplicationContext(),locationAddress,Toast.LENGTH_LONG).show();
}
}
@Override
public void onLocationChanged(Location location) {
if (location == null) {
latitude = 28.608426;
longitude = 77.225168;
} else {
longitude = location.getLongitude();
latitude = location.getLatitude();
}
String s = "longitude:" + longitude + "latitude:" + latitude;
Log.i("Current location", " latlong value" + s);
googleMap.addMarker(new MarkerOptions()
.position(new LatLng(latitude, longitude))
.title("Hello world"));
/*CameraUpdate center =
CameraUpdateFactory.newLatLng(new LatLng(latitude,
-longitude));
CameraUpdate zoom = CameraUpdateFactory.zoomTo(10);
googleMap.moveCamera(center);
googleMap.animateCamera(zoom);*/
}
@Override
public void onStatusChanged(String provider, int status, Bundle extras) {
}
@Override
public void onProviderEnabled(String provider) {
}
@Override
public void onProviderDisabled(String provider) {
}
@Override
public void onMarkerDragStart(Marker marker) {
}
@Override
public void onMarkerDrag(Marker marker) {
}
@Override
public void onMarkerDragEnd(Marker marker) {
}
//dfg
private String getMapsApiDirectionsUrl() {
// String url = "https://maps.googleapis.com/maps/api/directions/"+ output + "?" + params;
String url="https://maps.googleapis.com/maps/api/directions/json?origin="+l+"&destination="+latitude+","+longitude+"&sensor=false";
return url;
}
private class ReadTask extends AsyncTask<String, Void, String> {
@Override
protected String doInBackground(String... url) {
String data = "";
try {
HttpConnection http = new HttpConnection();
data = http.readUrl(url[0]);
} catch (Exception e) {
Log.d("Background Task", e.toString());
}
return data;
}
@Override
protected void onPostExecute(String result) {
super.onPostExecute(result);
new ParserTask().execute(result);
}
}
private class ParserTask extends
AsyncTask<String, Integer, List<List<HashMap<String, String>>>> {
@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]);
PathJSONParser parser = new PathJSONParser();
routes = parser.parse(jObject);
} catch (Exception e) {
e.printStackTrace();
}
return routes;
}
@Override
protected void onPostExecute(List<List<HashMap<String, String>>> routes) {
ArrayList<LatLng> points = null;
PolylineOptions polyLineOptions = null;
// traversing through routes
for (int i = 0; i < routes.size(); i++) {
points = new ArrayList<LatLng>();
polyLineOptions = new PolylineOptions();
List<HashMap<String, String>> path = routes.get(i);
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);
}
polyLineOptions.addAll(points);
polyLineOptions.width(2);
polyLineOptions.color(Color.BLUE);
}
googleMap.addPolyline(polyLineOptions);
}
}
class GeocodingLocation {
private static final String TAG = "GeocodingLocation";
public String result1,result2;
public void getAddressFromLocation(final String locationAddress,
final Context context, final Handler handler) {
Thread thread = new Thread() {
@Override
public void run() {
Geocoder geocoder = new Geocoder(context, Locale.getDefault());
String result = null;
try {
List
addressList = geocoder.getFromLocationName(locationAddress, 1);
if (addressList != null && addressList.size() > 0) {
Address address = (Address) addressList.get(0);
StringBuilder sb = new StringBuilder();
sb.append(address.getLatitude()).append("\n");
sb.append(address.getLongitude()).append("\n");
result = sb.toString();
}
} catch (IOException e) {
Log.e(TAG, "Unable to connect to Geocoder", e);
} finally {
Message message = Message.obtain();
message.setTarget(handler);
if (result != null) {
message.what = 1;
Bundle bundle = new Bundle();
result = "Address: " + locationAddress +
"\n\nLatitude and Longitude :\n" + result;
bundle.putString("address", result);
message.setData(bundle);
} else {
message.what = 1;
Bundle bundle = new Bundle();
result = "Address: " + locationAddress +
"\n Unable to get Latitude and Longitude for this address location.";
bundle.putString("address", result);
message.setData(bundle);
}
message.sendToTarget();
}
}
};
thread.start();
}
}
}
堆栈追踪：
FATAL EXCEPTION: main
java.lang.NullPointerException
at com.google.maps.api.android.lib6.e.aw.<init>(Unknown Source)
at com.google.maps.api.android.lib6.e.ev.a(Unknown Source)
at com.google.android.gms.maps.internal.j.onTransact(SourceFile:137)
at android.os.Binder.transact(Binder.java:310)
at com.google.android.gms.maps.internal.IGoogleMapDelegate$zza$zza.addPolyline(Unknown Source)
at com.google.android.gms.maps.GoogleMap.addPolyline(Unknown Source)
at autogenie.maptrial.MainActivity$ParserTask.onPostExecute(MainActivity.java:315)
at autogenie.maptrial.MainActivity$ParserTask.onPostExecute(MainActivity.java:267)
at android.os.AsyncTask.finish(AsyncTask.java:631)
at android.os.AsyncTask.access$600(AsyncTask.java:177)
at android.os.AsyncTask$InternalHandler.handleMessage(AsyncTask.java:644)
at android.os.Handler.dispatchMessage(Handler.java:99)
at android.os.Looper.loop(Looper.java:137)
at android.app.ActivityThread.main(ActivityThread.java:5041)
at java.lang.reflect.Method.invokeNative(Native Method)
at java.lang.reflect.Method.invoke(Method.java:511)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:793)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:560)
at dalvik.system.NativeStart.main(Native Method) 01-21 12:24:35.291 3683-3683/autogenie.maptrial I/Process: Sending signal. PID: 3683 SIG: 9
答案 0 :(得分：1)
您的一个变量（l，纬度，经度）为空，因为唯一可能导致异常的地方是valueOf调用。