如何获取当前位置并将纬度和经度作为字符串？

Posted 2023-04-14

【中文标题】如何获取当前位置并将纬度和经度作为字符串？

【英文标题】：How do I get my current location and get latitude and longitude as string?

【发布时间】：2020-08-14 04:28:20

【问题描述】：

我正在学习一个教程并尝试使用 Google 地图获取我的当前位置，但我在 LatLng 处遇到错误，它说“尝试调用虚拟方法和空对象引用”。我想获取我当前的位置，并以字符串形式获取纬度和经度。我想使用这些纬度和经度进行实时位置跟踪。

public class DriverCurrentLocationActivity extends FragmentActivity implements OnMapReadyCallback 

    private GoogleMap mMap;
    LocationManager locationManager;
    LocationListener locationListener;

    @Override
    public void onRequestPermissionsResult(int requestCode, String[] permissions, int[] grantResults) 
        super.onRequestPermissionsResult(requestCode, permissions, grantResults);

        if (requestCode == 1) 
            if (grantResults.length > 0 && grantResults[0] == PackageManager.PERMISSION_GRANTED) 

                if (ContextCompat.checkSelfPermission(this, Manifest.permission.ACCESS_FINE_LOCATION) == PackageManager.PERMISSION_GRANTED) 

                    locationManager.requestLocationUpdates(LocationManager.GPS_PROVIDER, 0, 0, locationListener);
                    Location lastKnownLocation = locationManager.getLastKnownLocation(LocationManager.GPS_PROVIDER);
                    updateMap(lastKnownLocation);

                

            
        
    

    public void updateMap(Location location) 
        try 

            LatLng userLocation = new LatLng(location.getLatitude(), location.getLongitude());
            mMap.clear();
            mMap.moveCamera(CameraUpdateFactory.newLatLng(userLocation));
            mMap.addMarker(new MarkerOptions().position(userLocation).title("Your Location"));
        catch (Exception e)
            Toast.makeText(this, e.getMessage(), Toast.LENGTH_SHORT).show();
        

        


    @Override
    protected void onCreate(Bundle savedInstanceState) 
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_driver_current_location);
        // 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);
    


    @Override
    public void onMapReady(GoogleMap googleMap) 
        mMap = googleMap;


        locationManager = (LocationManager) this.getSystemService(Context.LOCATION_SERVICE);
        locationListener = new LocationListener() 
            @Override
            public void onLocationChanged(Location location) 
                updateMap(location);
            

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

            

            @Override
            public void onProviderEnabled(String provider) 

            

            @Override
            public void onProviderDisabled(String provider) 

            
        ;

        if (Build.VERSION.SDK_INT < 23) 
            locationManager.requestLocationUpdates(LocationManager.GPS_PROVIDER, 0, 0, locationListener);



        else 
            if (ContextCompat.checkSelfPermission(this, Manifest.permission.ACCESS_FINE_LOCATION) != PackageManager.PERMISSION_GRANTED)
                ActivityCompat.requestPermissions(this,new String[]Manifest.permission.ACCESS_FINE_LOCATION,1);
             else 
                locationManager.requestLocationUpdates(LocationManager.GPS_PROVIDER,0,0,locationListener);
                Location lastKnownLocation = locationManager.getLastKnownLocation(LocationManager.GPS_PROVIDER);

                if (lastKnownLocation != null)
                    updateMap(lastKnownLocation);
                
            
        
    

【参考方案1】：

在 onCreate 中创建 someMethod()

        fusedLocationProviderClient = LocationServices.getFusedLocationProviderClient(getActivity());
        fetchLastLocation();

 private void someMethod() 

        if (ActivityCompat.checkSelfPermission(this, Manifest.permission.ACCESS_FINE_LOCATION) != PackageManager.PERMISSION_GRANTED) 
            ActivityCompat.requestPermissions(this, new String[]Manifest.permission.ACCESS_FINE_LOCATION, REQUEST_CODE);
            return;
        
    Task<Location> task = fusedLocationProviderClient.getLastLocation();
    task.addOnSuccessListener(new OnSuccessListener<Location>() 
        @Override
        public void onSuccess(Location location) 

            if (location != null)
                currentLocation = location;
                Toast.makeText(this,currentLocation.getLatitude() +""+ currentLocation.getLongitude(),Toast.LENGTH_LONG).show();
                SupportMapFragment mapFragment = (SupportMapFragment) getChildFragmentManager().findFragmentById(R.id.map);
                mapFragment.getMapAsync(MapFragment.this);
            
        
    );

然后在您的 onMapReady() 方法中使用以下代码：

 LatLng center = new LatLng(currentLocation.getLatitude(), currentLocation.getLongitude());
    MarkerOptions markerOptions = new MarkerOptions().position(center).title(center.latitude + ":" + center.longitude);
    mMap.clear();
    googleMap.animateCamera(CameraUpdateFactory.newLatLng(center));
    googleMap.animateCamera(CameraUpdateFactory.newLatLngZoom(center, 18));
    googleMap.addMarker(markerOptions);

将 LatLng 转换为字符串：

String string_latlng = center.toString();

希望对你有帮助:)

【参考方案2】：

检查您的 updateMap 函数是否为 null，因为 getLastKnownLocation 有时可能会返回 null，这样您就不会遇到崩溃或异常。也可以试试this。