无法在安卓工作室中获取位置

Question

它给了我这个错误(double android.location.Location.getLatitude()' on a null object reference)

我尝试了许多不同的解决方案，但都是一样的，我知道fusedLocationClient。lastLocation它只给出其他应用的最后位置，但我不想要这个，我想在没有它的情况下获得当前位置，因为它给出了空值?那么如何修复这个并获得当前位置??

import android.Manifest
import android.content.ContentValues.TAG
import android.content.Context
import android.content.pm.PackageManager
import android.location.LocationManager
import android.os.Bundle
import android.util.Log
import android.view.LayoutInflater
import android.view.View
import android.view.ViewGroup
import androidx.core.app.ActivityCompat
import androidx.core.content.ContextCompat
import androidx.fragment.app.Fragment
import com.firebase.geofire.GeoFire
import com.firebase.geofire.GeoLocation
import com.firebase.geofire.GeoQueryEventListener
import com.google.android.gms.location.FusedLocationProviderClient
import com.google.android.gms.location.LocationServices
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
import com.google.firebase.database.DatabaseError
import com.google.firebase.database.FirebaseDatabase
import com.moapp.guardaroundd.R
import com.moapp.guardaroundd.databinding.FragmentMapBinding
import com.moapp.guardaroundd.utils.Constants.DEFAULT_ZOOM
import com.moapp.guardaroundd.utils.Constants.LOCATION_PERMISSION_REQUEST_CODE
import com.moapp.guardaroundd.utils.createAlertEnableLocation

class MapFragment : Fragment(), OnMapReadyCallback {
private lateinit var mMap: GoogleMap
private lateinit var binding: FragmentMapBinding
private lateinit var fusedLocationClient: FusedLocationProviderClient
private var mLocationPermissionsGranted = false

override fun onCreateView(
inflater: LayoutInflater, container: ViewGroup?,
savedInstanceState: Bundle?
): View {
// Inflate the layout for this fragment
binding = FragmentMapBinding.inflate(layoutInflater)
val mapFragment = childFragmentManager.findFragmentById(R.id.map) as SupportMapFragment
mapFragment.getMapAsync(this)
fusedLocationClient = LocationServices.getFusedLocationProviderClient(requireActivity())

return binding.root
}
override fun onMapReady(googleMap: GoogleMap) {
mMap = googleMap
getLocationPermission()
}
private fun isLocationEnabled(): Boolean {
val locationManager =
activity?.getSystemService(Context.LOCATION_SERVICE) as LocationManager?
return locationManager!!.isProviderEnabled(LocationManager.GPS_PROVIDER) || locationManager.isProviderEnabled(
LocationManager.NETWORK_PROVIDER
)
}
private fun moveCamera(latLng: LatLng) {
mMap.moveCamera(CameraUpdateFactory.newLatLngZoom(latLng, DEFAULT_ZOOM))
}
private fun getLocation() {
if (isLocationEnabled()) {
try {
fusedLocationClient.lastLocation.addOnSuccessListener {
moveCamera(LatLng(it.latitude, it.longitude))
mMap.isMyLocationEnabled = true
}
} catch (ex: SecurityException) {
}
} else {
//Custom alert
createAlertEnableLocation(requireContext())
}
}
private fun getLocationPermission() {
if (ContextCompat.checkSelfPermission(
requireContext(),
Manifest.permission.ACCESS_FINE_LOCATION
)
== PackageManager.PERMISSION_GRANTED
) {
mLocationPermissionsGranted = true
getLocation()
} else {
ActivityCompat.requestPermissions(
requireActivity(), arrayOf(Manifest.permission.ACCESS_FINE_LOCATION),
LOCATION_PERMISSION_REQUEST_CODE
)
}
}

override fun onRequestPermissionsResult(
requestCode: Int,
permissions: Array<String>,
grantResults: IntArray
) {
mLocationPermissionsGranted = false
when (requestCode) {
LOCATION_PERMISSION_REQUEST_CODE -> {
// If request is cancelled, the result arrays are empty.
if (grantResults.isNotEmpty() &&
grantResults[0] == PackageManager.PERMISSION_GRANTED
) {
mLocationPermissionsGranted = true
}
}
}
}

Answer 1

避免null location的最简单方法是启动Google Maps App并按我的定位按钮。然后你回到你的应用程序，fusedLocationClient.lastLocation这次会给你非空设备的最后位置。

既然你显然不喜欢这个，那么你需要使用位置更新。

为此，我会稍微调整一下getLocation()代码。

private fun getLocation() {
// last known location from fusedLocationProviderClient returned as a task
fusedLocationProviderClient.lastLocation
//check if the last location is null
.addOnSuccessListener { lastLoc ->
if (lastLoc != null) {
// initialize lastKnownLocation from fusedLocationProviderClient
lastKnownLocation = lastLoc
moveCamera(LatLng(lastLoc.latitude, lastLoc.longitude))
} else {
//if null trigger location update to get location
fusedLocationProviderClient.requestLocationUpdates(
locationRequest, locationCallback, Looper.getMainLooper()
)
}
// in case of error Toast the error in a short Toast message
}
.addOnFailureListener {
Toast.makeText(requireActivity(), "${it.message}", Toast.LENGTH_SHORT).show()
}
}

我还需要把LocationRequest和Location Callback带到游戏中。

class MapFragment : Fragment(), OnMapReadyCallback { .......
// LOCATION COMPONENTS
private lateinit var lastKnownLocation: Location
private lateinit var fusedLocationProviderClient: FusedLocationProviderClient
private val locationRequest =
LocationRequest().apply {
priority = LocationRequest.PRIORITY_HIGH_ACCURACY
interval = TimeUnit.SECONDS.toMillis(10)
fastestInterval = TimeUnit.SECONDS.toMillis(1)
}

private val locationCallback =
object : LocationCallback() {
override fun onLocationResult(locationResult: LocationResult?) {
super.onLocationResult(locationResult)
if (locationResult != null) {
lastKnownLocation = locationResult.lastLocation
//call the above getLocation() again to move camera
getLocation()
}
}
}

因此，每当来自fusedClient的最后一个已知位置为空时，就会触发更新并移动相机位置。