我再次问这个问题的唯一原因是，因为我已经尝试了所有的答案而且它不适合我，我正在尝试获取当前的用户位置，但它不起作用所以这就是我一直以来尝试做，顺便说一句，我已经设置了所有权限，我继续得到双重android的location.getlatitude空对象引用错误和致命的execption主，pleaaase帮助我 这是我的GPSTRACKER Java类代码：
package com.example.nefissa.androidtest;
import android.*;
import android.Manifest;
import android.app.Service;
import android.content.Context;
import android.content.Intent;
import android.content.pm.PackageManager;
import android.location.Location;
import android.location.LocationListener;
import android.location.LocationManager;
import android.os.Bundle;
import android.os.IBinder;
import android.support.annotation.Nullable;
import android.support.v4.content.ContextCompat;
public class GPSTracker extends Service implements LocationListener{
private final Context context;
boolean isGPSEnabled =false;
boolean isNetworkEnabled =false;
boolean canGetLocation =false;
Location location;
protected LocationManager locationManager;
public GPSTracker(Context context){
this.context=context;
}
// create a GetLocation Method //
public Location getLocation(){
try{
locationManager=(LocationManager) context.getSystemService(LOCATION_SERVICE);
isGPSEnabled = locationManager.isProviderEnabled(locationManager.GPS_PROVIDER);
isNetworkEnabled=locationManager.isProviderEnabled(locationManager.NETWORK_PROVIDER);
if(ContextCompat.checkSelfPermission(context, Manifest.permission.ACCESS_FINE_LOCATION) == PackageManager.PERMISSION_GRANTED
|| ContextCompat.checkSelfPermission(context, Manifest.permission.ACCESS_COARSE_LOCATION) == PackageManager.PERMISSION_GRANTED ){
if(isGPSEnabled){
if(location==null){
locationManager.requestLocationUpdates(LocationManager.GPS_PROVIDER,100000,10,this);
if(locationManager!=null){
location=locationManager.getLastKnownLocation(LocationManager.GPS_PROVIDER);
}
}
}
// if location is not found from GPS then it will found from network //
if(location==null){
if(isNetworkEnabled){
locationManager.requestLocationUpdates(LocationManager.NETWORK_PROVIDER,100000,10,this);
if(locationManager!=null){
location=locationManager.getLastKnownLocation(LocationManager.NETWORK_PROVIDER);
}
}
}
}
}catch(Exception e){
}
return location;
}
@Nullable
@Override
public IBinder onBind(Intent intent) {
return null;
}
@Override
public void onLocationChanged(Location location) {
}
@Override
public void onStatusChanged(String provider, int status, Bundle extras) {
}
@Override
public void onProviderEnabled(String provider) {
}
@Override
public void onProviderDisabled(String provider) {
}
}
和我的主要活动代码：
package com.example.nefissa.androidtest;
import android.location.Location;
import android.support.v4.app.FragmentActivity;
import android.os.Bundle;
import com.google.android.gms.maps.CameraUpdateFactory;
import com.google.android.gms.maps.GoogleMap;
import com.google.android.gms.maps.OnMapReadyCallback;
import com.google.android.gms.maps.SupportMapFragment;
import com.google.android.gms.maps.model.LatLng;
import com.google.android.gms.maps.model.MarkerOptions;
public class MapsActivity extends FragmentActivity implements OnMapReadyCallback {
private GoogleMap mMap;
private GPSTracker gpsTracker;
private Location mLocation;
double latitude;
double longitude;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_maps);
gpsTracker= new GPSTracker(getApplicationContext());
mLocation=gpsTracker.getLocation();
latitude= mLocation.getLatitude();
longitude= mLocation.getLongitude();
// Obtain the SupportMapFragment and get notified when the map is ready to be used.
SupportMapFragment mapFragment = (SupportMapFragment) getSupportFragmentManager()
.findFragmentById(R.id.map);
mapFragment.getMapAsync(this);
}
/**
* Manipulates the map once available.
* This callback is triggered when the map is ready to be used.
* This is where we can add markers or lines, add listeners or move the camera. In this case,
* we just add a marker near Sydney, Australia.
* If Google Play services is not installed on the device, the user will be prompted to install
* it inside the SupportMapFragment. This method will only be triggered once the user has
* installed Google Play services and returned to the app.
*/
@Override
public void onMapReady(GoogleMap googleMap) {
mMap = googleMap;
// Add a marker in Sydney and move the camera
LatLng sydney = new LatLng(latitude,longitude);
mMap.addMarker(new MarkerOptions().position(sydney).title("you are here"));
mMap.moveCamera(CameraUpdateFactory.newLatLng(sydney));
}
}
答案 0 :(得分：0)
调用onMapReady后，最好初始化gpsTracker。
gpsTracker= new GPSTracker(getApplicationContext());
if(gpsTracker!=null){
mLocation=gpsTracker.getLocation();
latitude= mLocation.getLatitude();
longitude= mLocation.getLongitude();
}
我认为gpsTracker.getLocation必须改为逻辑。 请阅读android gps指南。
答案 1 :(得分：-1)
尝试使用
GPS追踪器
//
gps = new GPSTracker(SignUpActivity.this);
if (gps.canGetLocation) {
lat = String.valueOf(gps.getLatitude());
lng = String.valueOf(gps.getLongitude());
}
也来自活动呼叫
的onCreate
class Program
{
static void Main(string[] args)
{
XDocument gbConfig = XDocument.Parse(@"<TradingBlocConfiguration>
<GreatBritain xmlns=""GB"">
<Country/>
<Countries>
<Country/>
<Country/>
</Countries>
</GreatBritain> </TradingBlocConfiguration>");
XDocument euConfig = XDocument.Parse(@"<TradingBlocConfiguration>
<EuropeanUnion xmlns=""EU"">
<Country/>
<Countries>
<Country/>
<Country/>
</Countries>
</EuropeanUnion> </TradingBlocConfiguration>");
var greatBritainConfiguration = BuildConfig<TradingBlocConfiguration>(gbConfig);
// A single 'Country' is always deserialized correctly..
Console.WriteLine("Great Britain Country Type " + greatBritainConfiguration.TradingBlocConfig.MemberCountry.GetType());
// A List of 'Country' is deserialized to the wrong type, depending on what '[XmlElement]' tag is listed first.
Console.WriteLine("Great Britain Countries Type " + greatBritainConfiguration.TradingBlocConfig.MemberCountries[0].GetType());
var euConfiguration = BuildConfig<TradingBlocConfiguration>(euConfig);
Console.WriteLine("EU Country Type " + euConfiguration.TradingBlocConfig.MemberCountry.GetType());
Console.WriteLine("EU Countries Type " + euConfiguration.TradingBlocConfig.MemberCountries[0].GetType());
Console.ReadLine();
}
private static T BuildConfig<T>(XDocument doc) where T : class
{
var stream = new MemoryStream();
doc.Save(stream);
T result;
using (var reader = new StreamReader(stream))
{
stream.Position = 0;
var xs = new XmlSerializer(typeof(T), new Type[] { typeof(GB.GreatBritain.Country) });
result = (T)xs.Deserialize(reader);
}
return result;
}
}
[XmlRoot("TradingBlocConfiguration")]
public sealed class TradingBlocConfiguration
{
[XmlElement("GreatBritain", typeof(GB.GreatBritain), Namespace = "GB")]
[XmlElement("EuropeanUnion", typeof(EU.EuropeanUnion), Namespace = "EU")]
public TradingBloc TradingBlocConfig { get; set; }
}
[XmlRoot]
[XmlInclude(typeof(GB.GreatBritain))]
[XmlInclude(typeof(EU.EuropeanUnion))]
public class BaseCountry { }
public abstract class TradingBloc
{
[XmlIgnore]
public abstract List<BaseCountry> MemberCountries { get; set; }
[XmlIgnore]
public abstract BaseCountry MemberCountry { get; set; }
}
namespace GB
{
[XmlRoot("GreatBritain")]
public class GreatBritain : TradingBloc
{
[XmlElement("Country", typeof(Country))]
public override BaseCountry MemberCountry { get; set; }
[XmlArray("Countries")]
[XmlArrayItem("Country", typeof(Country))]
public override List<BaseCountry> MemberCountries { get; set; }
[XmlRoot(Namespace = "GB")]
public class Country : BaseCountry { }
}
}
namespace EU
{
[XmlRoot("EuropeanUnion")]
public class EuropeanUnion : TradingBloc
{
[XmlElement("Country", typeof(Country))]
public override BaseCountry MemberCountry { get; set; }
[XmlArray("Countries")]
[XmlArrayItem("Country", typeof(Country))]
public override List<BaseCountry> MemberCountries { get; set; }
[XmlRoot(Namespace = "EU")]
public class Country : BaseCountry { }
}
}
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