如何获取当前位置并将纬度和经度作为字符串

Question

我遵循了一个教程，试图使用谷歌地图获取我的当前位置，但我在LatLng遇到了一个错误，它说"试图调用虚拟方法和空对象引用"。我想得到我的当前位置，也得到纬度和经度作为字符串。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);
}
}
}
}
}

Answer 1

检查updateMap函数是否为null，因为getLastKnownLocation有时可能返回null，这样就不会出现崩溃或异常。也可以试试这个。

Answer 2

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();

希望这能帮助你：(