本地化返回 null。代码有什么问题？

Question

double longitude = 0;
double latitude = 0;


try {
    LocationManager lm = (LocationManager) getSystemService(Context.LOCATION_SERVICE);
    Location location = lm.getLastKnownLocation(LocationManager.GPS_PROVIDER);

    longitude = location.getLongitude();
    latitude = location.getLatitude();

} catch (Exception e1) {
    // TODO Auto-generated catch block
    e1.printStackTrace();
}

在这段代码中，纬度和经度返回null。我想在不使用互联网的情况下获取位置。

Answer 1

您的代码没有任何问题，您正在使用 GPS_PROVIDER，它需要开放的天空场来获取 GPS 信息。如果您还想在房间内获取 GPS 详细信息，我建议您使用 NETWORK_PROVIDER。

try 
{
    LocationManager lm = (LocationManager) getSystemService(Context.LOCATION_SERVICE);
    Location location = lm.getLastKnownLocation(LocationManager.NETWORK_PROVIDER);

    longitude = location.getLongitude();
    latitude = location.getLatitude();

} catch (Exception e1) {
    // TODO Auto-generated catch block
    e1.printStackTrace();
}

Answer 2

public class LocationHandler extends Service implements LocationListener {

private final Context mContext;

boolean isGPSEnabled = false;

boolean isNetworkEnabled = false;

boolean canGetLocation = false;

Location location; // location
double latitude; // latitude
double longitude; // longitude


private static final long MIN_DISTANCE_CHANGE_FOR_UPDATES = 0; 


private static final long MIN_TIME_BW_UPDATES = 1000 * 1; 


protected LocationManager locationManager;

public LocationHandler(Context context) {
    this.mContext = context;
    getLocation();
}

public Location getLocation() {
    try {
        locationManager = (LocationManager) mContext
                .getSystemService(LOCATION_SERVICE);

        // getting GPS status
        isGPSEnabled = locationManager
                .isProviderEnabled(LocationManager.GPS_PROVIDER);

        // getting network status
        isNetworkEnabled = locationManager
                .isProviderEnabled(LocationManager.NETWORK_PROVIDER);

        if (!isGPSEnabled && !isNetworkEnabled) {
            // no network provider is enabled
        } else {
            this.canGetLocation = true;
            if (isNetworkEnabled) {
                locationManager.requestLocationUpdates(
                        LocationManager.NETWORK_PROVIDER,
                        MIN_TIME_BW_UPDATES,
                        MIN_DISTANCE_CHANGE_FOR_UPDATES, this);
                if (locationManager != null) {
                    location = locationManager
                            .getLastKnownLocation(LocationManager.NETWORK_PROVIDER);
                    if (location != null) {
                        latitude = location.getLatitude();
                        longitude = location.getLongitude();
                    }
                }
            }
            // if GPS Enabled get lat/long using GPS Services
            if (isGPSEnabled) {
                if (location == null) {
                    locationManager.requestLocationUpdates(
                            LocationManager.GPS_PROVIDER,
                            MIN_TIME_BW_UPDATES,
                            MIN_DISTANCE_CHANGE_FOR_UPDATES, this);
                    if (locationManager != null) {
                        location = locationManager
                                .getLastKnownLocation(LocationManager.GPS_PROVIDER);
                        if (location != null) {
                            latitude = location.getLatitude();
                            longitude = location.getLongitude();
                        }
                    }
                }
            }
        }

    } catch (Exception e) {
        e.printStackTrace();
    }

    return location;
}
public void stopUsingGPS() {
    if (locationManager != null) {
        locationManager.removeUpdates(LocationHandler.this);
    }
}

public double getLatitude() {
    if (location != null) {
        latitude = location.getLatitude();
    }

    // return latitude
    return latitude;
}

public double getLongitude() {
    if (location != null) {
        longitude = location.getLongitude();
    }

    // return longitude
    return longitude;
}

public boolean canGetLocation() {
    return this.canGetLocation;
}


public void showSettingsAlert() {
    try {
        AlertDialog.Builder alertDialog = new AlertDialog.Builder(mContext);


        alertDialog.setTitle("GPS is settings");


        alertDialog
                .setMessage("GPS is not enabled. Do you want to go to settings menu?");


        alertDialog.setPositiveButton("Settings",
                new DialogInterface.OnClickListener() {
                    public void onClick(DialogInterface dialog, int which) {
                        Intent intent = new Intent(
                                Settings.ACTION_LOCATION_SOURCE_SETTINGS);
                        mContext.startActivity(intent);
                    }
                });


        alertDialog.setNegativeButton("Cancel",
                new DialogInterface.OnClickListener() {
                    public void onClick(DialogInterface dialog, int which) {
                        dialog.cancel();
                    }
                });


        alertDialog.show();
    } catch (Exception e) {
        Log.e("", e.getMessage());
    }
}

@Override
public void onLocationChanged(Location location) {
    if (location != null) {
        this.latitude = location.getLatitude();
        this.longitude = location.getLongitude();
        Log.e("onLocationChanged", "YES");
    }

}

@Override
public void onProviderDisabled(String provider) {
    if (!TextUtils.isEmpty(provider)) {
        if (provider.equalsIgnoreCase(LocationManager.GPS_PROVIDER)
                && provider
                        .equalsIgnoreCase(LocationManager.NETWORK_PROVIDER)) {
            showSettingsAlert();
        }
    }
}

@Override
public void onProviderEnabled(String provider) {
}

@Override
public void onStatusChanged(String provider, int status, Bundle extras) {
}

@Override
public IBinder onBind(Intent arg0) {
    return null;
}

}

.....

LocationHandler gps = new LocationHandler(this);
                if (gps.canGetLocation) {
                    Log.e(" Latitude", String.valueOf(gps.getLatitude()));
                    Log.e(" Longitude", String.valueOf(gps.getLongitude()));
                }

........权限

<uses-permission android:name="android.permission.ACCESS_FINE_LOCATION" />
    <uses-permission android:name="android.permission.ACCESS_COARSE_LOCATION" />