我在将新对象从 util 类实例化为片段类时遇到问题。实例化需要传递上下文，但我无法获取上下文。
我尝试通过 getActivity() 但仍然收到 GpsAssist.getLatitude 的 NULL POINTER EXCEPTION（因为这是第一个被调用的）错误。
我正在尝试从 GpsAssist 调用方法 getLatitude() 和 getLongitude()
下面是我的代码。可以使用所有的帮助。
谢谢
MapsActivity 类：
public class MapsActivity extends Fragment {
GoogleMap map;
private View view;
GpsAssist gAssist = new GpsAssist(getActivity());
double lat = gAssist.getLatitude();
double lng = gAssist.getLongitude();
private final LatLng MOUNTAIN_VIEW = new LatLng(lat, lng);
private LatLngBounds loc = new LatLngBounds(new LatLng(37, -121), new LatLng(37,-121));
public void get(){
}
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
View view = inflater.inflate(R.layout.map_test, container, false);
if(map == null){
map = ((SupportMapFragment) getFragmentManager().findFragmentById(R.id.map)).getMap();
map.addMarker(new MarkerOptions().position(MOUNTAIN_VIEW).title("Marker"));
map.animateCamera(CameraUpdateFactory.newCameraPosition(posi()));
}else{
//map.moveCamera(CameraUpdateFactory.newLatLngBounds(loc, 15));
}
return view;
}
public CameraPosition posi(){
CameraPosition posi = new CameraPosition.Builder()
.target(MOUNTAIN_VIEW)
.zoom(17)
.build();
return posi;
}
@Override
public void onDestroyView() {
try{
SupportMapFragment fragment = ((SupportMapFragment) getFragmentManager().findFragmentById(R.id.map));
FragmentTransaction ft = getActivity().getSupportFragmentManager().beginTransaction();
ft.remove(fragment);
ft.commit();
//map.addMarker(new MarkerOptions().position(new LatLng(0, 0)).title("Marker"));
}catch(Exception e){
}
super.onDestroyView();
}
}
我的 GpsAssist 课程：
public class GpsAssist extends Service {
//Primitive declarations
private double lat;
private double lng;
private String provider;
//Class instances
private Context context;
private Geocoder gCoder;
Location location;
public GpsAssist(Context context){
this.context = context;
}
//Checking if GPS is enabled
LocationManager lManager;
public Location gpsConnected(){
lManager = (LocationManager) context.getSystemService(Context.LOCATION_SERVICE);
boolean gpsEnabled = lManager.isProviderEnabled(LocationManager.GPS_PROVIDER);
boolean networkEnabled = lManager.isProviderEnabled(LocationManager.NETWORK_PROVIDER);
if(! gpsEnabled && ! networkEnabled ){
Intent i = new Intent(Settings.ACTION_LOCATION_SOURCE_SETTINGS);
startActivity(i);
}else {
location = lManager.getLastKnownLocation(LocationManager.NETWORK_PROVIDER);
if(location != null){
lat = getLatitude();
lng = getLongitude();
Toast t = Toast.makeText(context, "Your location" + lat + " " + lng, Toast.LENGTH_SHORT);
t.show();
String addresses = getAddress(lat, lng, 2);
Toast address = Toast.makeText(context, addresses, Toast.LENGTH_LONG);
address.show();
}else{
Toast t = Toast.makeText(context, "Cannot get your location", Toast.LENGTH_SHORT);
t.show();
}
}
return location;
}
//Method to find the best possible provider
public String getProvider(){
Criteria criteria = new Criteria();
//true means that only enabled providers will be returned
provider = lManager.getBestProvider(criteria, true);
return provider;
}
public double getLatitude(){
lat = location.getLatitude();
return lat;
}
public double getLongitude(){
lng = location.getLongitude();
return lng;
}
public String getAddress(double lat, double lng, int maxR){
String addres = "";
gCoder = new Geocoder(context, Locale.getDefault());
try {
List<Address> address = gCoder.getFromLocation(lat, lng, maxR);
if(address != null){
Address adName = address.get(0);
StringBuilder str = new StringBuilder("Address: \n");
for(int i=0; i<adName.getMaxAddressLineIndex(); i++){
str.append(adName.getAddressLine(i)).append("\n");
}
addres = str.toString();
System.out.println(addres);
}else{
addres = "Address is null";
}
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}