问题
I recently added get location function. When I try to show longitude and latitude, it returns zero.
This my LocationListener class:
inner class MylocationListener: LocationListener {
constructor():super(){
mylocation= Location("me")
mylocation!!.longitude
mylocation!!.latitude
}
override fun onLocationChanged(location: Location?) {
mylocation=location
}
override fun onStatusChanged(p0: String?, p1: Int, p2: Bundle?) {}
override fun onProviderEnabled(p0: String?) {}
override fun onProviderDisabled(p0: String?) {}
}
And this my GetUserLocation function:
fun GetUserLocation(){
var mylocation= MylocationListener()
var locationManager=getSystemService(Context.LOCATION_SERVICE) as LocationManager
locationManager.requestLocationUpdates(LocationManager.GPS_PROVIDER,0,0.1f,mylocation)
}
And this my function to return my longitude and latitude:
fun getLoction (view: View){
prgDialog!!.show();
GetUserLocation()
button.setTextColor(getResources().getColor(R.color.green));
textView.text = mylocation!!.latitude.toFloat().toString()
Toast.makeText(this, mylocation!!.latitude.toFloat().toString(), Toast.LENGTH_LONG).show()
Toast.makeText(this, mylocation!!.longitude.toFloat().toString(), Toast.LENGTH_LONG).show()
prgDialog!!.hide()
}
回答1:
When GetUserLocation returns, locationManager goes out of scope and presumably is destroyed, preventing onLocationChanged from being called and providing updates.
Also, you've defined mylocation inside of GetUserLocation so it also goes out of scope and further kills any chance or your getting an update.
You have not shown where and how the outer mylocation is declared (outside of GetUserLocation), but how ever it is declared, it is being shadowed by the one inside of GetUserLocation. So you aren't getting much.
Here is an example of how you might do it. (The variable thetext is defined within the layout xml and accessed with Kotlin extensions.)
// in the android manifest
<uses-permission android:name="android.permission.ACCESS_COARSE_LOCATION"/>
<uses-permission android:name="android.permission.ACCESS_FINE_LOCATION"/>
// allow these through Appliation Manager if necessary
// inside a basic activity
private var locationManager : LocationManager? = null
override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
setContentView(R.layout.activity_main)
setSupportActionBar(toolbar)
// Create persistent LocationManager reference
locationManager = getSystemService(LOCATION_SERVICE) as LocationManager?;
fab.setOnClickListener { view ->
try {
// Request location updates
locationManager?.requestLocationUpdates(LocationManager.NETWORK_PROVIDER, 0L, 0f, locationListener);
} catch(ex: SecurityException) {
Log.d("myTag", "Security Exception, no location available");
}
}
}
//define the listener
private val locationListener: LocationListener = object : LocationListener {
override fun onLocationChanged(location: Location) {
thetext.setText("" + location.longitude + ":" + location.latitude);
}
override fun onStatusChanged(provider: String, status: Int, extras: Bundle) {}
override fun onProviderEnabled(provider: String) {}
override fun onProviderDisabled(provider: String) {}
}
回答2:
I know it's late, but now Google has made it simpler to use. In the developer site, it says that you need to create a Client:
private lateinit var fusedLocationClient: FusedLocationProviderClient
Then onCreate get the provider:
override fun onCreate(savedInstanceState: Bundle?) {
// ...
fusedLocationClient = LocationServices.getFusedLocationProviderClient(this)
}
And finally, to get your last location just call:
//Don't forget to ask for permissions for ACCESS_COARSE_LOCATION
//and ACCESS_FINE_LOCATION
@SuppressLint("MissingPermission")
private fun obtieneLocalizacion(){
fusedLocationClient.lastLocation
.addOnSuccessListener { location: Location? ->
latitude = location?.latitude
longitude = location?.longitude
}
}
*Tested with this implementation for location (Setup in your app gradle file)
implementation 'com.google.android.gms:play-services-location:15.0.1'
For more info, check this link:
Obtain last location
回答3:
I would like to help someone who is trying to get location from scratch. Here is the reference: Kotlin Get Current Location
Code will first check whether location is on or off in device and then will fetch latitude and longitudes and will update it constantly.
In build.gradle(Module:app) file put this
compile 'com.google.android.gms:play-services:11.8.0'
activity_main.xml code
<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout
xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:layout_marginTop="10dp"
android:layout_marginLeft="10dp"
android:layout_width="match_parent"
android:layout_height="match_parent"
tools:context=".MainActivity">
<TextView
android:id="@+id/latitude"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_alignParentLeft="true"
android:layout_alignParentTop="true"
android:text="Latitude:"
android:textSize="18sp" />
<TextView
android:id="@+id/latitude_textview"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_alignBaseline="@+id/latitude"
android:layout_marginLeft="10dp"
android:layout_toRightOf="@+id/latitude"
android:textSize="16sp" />
<TextView
android:id="@+id/longitude"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_alignParentLeft="true"
android:layout_alignParentTop="true"
android:text="Longitude:"
android:layout_marginTop="24dp"
android:textSize="18sp" />
<TextView
android:id="@+id/longitude_textview"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_alignBaseline="@+id/longitude"
android:layout_marginLeft="10dp"
android:layout_toRightOf="@+id/longitude"
android:textSize="16sp"/>
</RelativeLayout>
MainActivity.kt
import android.Manifest
import android.annotation.SuppressLint
import android.content.Context
import android.content.Intent
import android.content.pm.PackageManager
import android.location.Location
import android.location.LocationManager
import android.provider.Settings
import android.support.v4.app.ActivityCompat
import android.support.v7.app.AlertDialog
import android.support.v7.app.AppCompatActivity
import android.os.Bundle
import android.util.Log
import android.widget.TextView
import android.widget.Toast
import com.google.android.gms.common.ConnectionResult
import com.google.android.gms.common.api.GoogleApiClient
import com.google.android.gms.location.LocationRequest
import com.google.android.gms.location.LocationServices
import com.google.android.gms.maps.model.LatLng
class MainActivity : AppCompatActivity(), GoogleApiClient.ConnectionCallbacks, GoogleApiClient.OnConnectionFailedListener, com.google.android.gms.location.LocationListener {
private var mLatitudeTextView: TextView? = null
private var mLongitudeTextView: TextView? = null
private var mGoogleApiClient: GoogleApiClient? = null
private var mLocation: Location? = null
private var mLocationManager: LocationManager? = null
private var mLocationRequest: LocationRequest? = null
private val listener: com.google.android.gms.location.LocationListener? = null
private val UPDATE_INTERVAL = (2 * 1000).toLong() /* 10 secs */
private val FASTEST_INTERVAL: Long = 2000 /* 2 sec */
private var locationManager: LocationManager? = null
private val isLocationEnabled: Boolean
get() {
locationManager = getSystemService(Context.LOCATION_SERVICE) as LocationManager
return locationManager!!.isProviderEnabled(LocationManager.GPS_PROVIDER) || locationManager!!.isProviderEnabled(LocationManager.NETWORK_PROVIDER)
}
override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
setContentView(R.layout.activity_main)
mLatitudeTextView = findViewById(R.id.latitude_textview) as TextView
mLongitudeTextView = findViewById(R.id.longitude_textview) as TextView
mGoogleApiClient = GoogleApiClient.Builder(this)
.addConnectionCallbacks(this)
.addOnConnectionFailedListener(this)
.addApi(LocationServices.API)
.build()
mLocationManager = this.getSystemService(Context.LOCATION_SERVICE) as LocationManager
Log.d("gggg","uooo");
checkLocation() //check whether location service is enable or not in your phone
}
@SuppressLint("MissingPermission")
override fun onConnected(p0: Bundle?) {
if (ActivityCompat.checkSelfPermission(this, Manifest.permission.ACCESS_FINE_LOCATION) != PackageManager.PERMISSION_GRANTED && ActivityCompat.checkSelfPermission(this, Manifest.permission.ACCESS_COARSE_LOCATION) != PackageManager.PERMISSION_GRANTED) {
// TODO: Consider calling
// ActivityCompat#requestPermissions
// here to request the missing permissions, and then overriding
// public void onRequestPermissionsResult(int requestCode, String[] permissions,
// int[] grantResults)
// to handle the case where the user grants the permission. See the documentation
// for ActivityCompat#requestPermissions for more details.
return
}
startLocationUpdates()
mLocation = LocationServices.FusedLocationApi.getLastLocation(mGoogleApiClient)
if (mLocation == null) {
startLocationUpdates()
}
if (mLocation != null) {
// mLatitudeTextView.setText(String.valueOf(mLocation.getLatitude()));
//mLongitudeTextView.setText(String.valueOf(mLocation.getLongitude()));
} else {
Toast.makeText(this, "Location not Detected", Toast.LENGTH_SHORT).show()
}
}
override fun onConnectionSuspended(i: Int) {
Log.i(TAG, "Connection Suspended")
mGoogleApiClient!!.connect()
}
override fun onConnectionFailed(connectionResult: ConnectionResult) {
Log.i(TAG, "Connection failed. Error: " + connectionResult.getErrorCode())
}
override fun onStart() {
super.onStart()
if (mGoogleApiClient != null) {
mGoogleApiClient!!.connect()
}
}
override fun onStop() {
super.onStop()
if (mGoogleApiClient!!.isConnected()) {
mGoogleApiClient!!.disconnect()
}
}
@SuppressLint("MissingPermission")
protected fun startLocationUpdates() {
// Create the location request
mLocationRequest = LocationRequest.create()
.setPriority(LocationRequest.PRIORITY_HIGH_ACCURACY)
.setInterval(UPDATE_INTERVAL)
.setFastestInterval(FASTEST_INTERVAL)
// Request location updates
if (ActivityCompat.checkSelfPermission(this, Manifest.permission.ACCESS_FINE_LOCATION) != PackageManager.PERMISSION_GRANTED && ActivityCompat.checkSelfPermission(this, Manifest.permission.ACCESS_COARSE_LOCATION) != PackageManager.PERMISSION_GRANTED) {
// TODO: Consider calling
// ActivityCompat#requestPermissions
// here to request the missing permissions, and then overriding
// public void onRequestPermissionsResult(int requestCode, String[] permissions,
// int[] grantResults)
// to handle the case where the user grants the permission. See the documentation
// for ActivityCompat#requestPermissions for more details.
return
}
LocationServices.FusedLocationApi.requestLocationUpdates(mGoogleApiClient,
mLocationRequest, this)
Log.d("reque", "--->>>>")
}
override fun onLocationChanged(location: Location) {
val msg = "Updated Location: " +
java.lang.Double.toString(location.latitude) + "," +
java.lang.Double.toString(location.longitude)
mLatitudeTextView!!.text = location.latitude.toString()
mLongitudeTextView!!.text = location.longitude.toString()
Toast.makeText(this, msg, Toast.LENGTH_SHORT).show()
// You can now create a LatLng Object for use with maps
val latLng = LatLng(location.latitude, location.longitude)
}
private fun checkLocation(): Boolean {
if (!isLocationEnabled)
showAlert()
return isLocationEnabled
}
private fun showAlert() {
val dialog = AlertDialog.Builder(this)
dialog.setTitle("Enable Location")
.setMessage("Your Locations Settings is set to 'Off'.\nPlease Enable Location to " + "use this app")
.setPositiveButton("Location Settings") { paramDialogInterface, paramInt ->
val myIntent = Intent(Settings.ACTION_LOCATION_SOURCE_SETTINGS)
startActivity(myIntent)
}
.setNegativeButton("Cancel") { paramDialogInterface, paramInt -> }
dialog.show()
}
companion object {
private val TAG = "MainActivity"
}
}
回答4:
In 2019 Best Offical Solution in Kotlin
Google API Client/FusedLocationApi are deprecated and Location Manager is not useful at all. So Google prefer Fused Location Provider Using the Google Play services location APIs "FusedLocationProviderClient" is used to get location and its better way for battery saving and accuracy
Here is sample code in kotlin to get the last known location /one-time location( equivalent to the current location)
// declare a global variable of FusedLocationProviderClient
private lateinit var fusedLocationClient: FusedLocationProviderClient
// in onCreate() initialize FusedLocationProviderClient
fusedLocationClient = LocationServices.getFusedLocationProviderClient(context!!)
/**
* call this method for receive location
* get location and give callback when successfully retrieve
* function itself check location permission before access related methods
*
*/
fun getLastKnownLocation() {
fusedLocationClient.lastLocation
.addOnSuccessListener { location->
if (location != null) {
// use your location object
// get latitude , longitude and other info from this
}
}
}
If your app can continuously track the location then you have to receive Receive location updates
Check the sample for that in kotlin
// declare a global variable FusedLocationProviderClient
private lateinit var fusedLocationClient: FusedLocationProviderClient
// in onCreate() initialize FusedLocationProviderClient
fusedLocationClient = LocationServices.getFusedLocationProviderClient(context!!)
// globally declare LocationRequest
private lateinit var locationRequest: LocationRequest
// globally declare LocationCallback
private lateinit var locationCallback: LocationCallback
/**
* call this method in onCreate
* onLocationResult call when location is changed
*/
private fun getLocationUpdates()
{
fusedLocationClient = LocationServices.getFusedLocationProviderClient(context!!)
locationRequest = LocationRequest()
locationRequest.interval = 50000
locationRequest.fastestInterval = 50000
locationRequest.smallestDisplacement = 170f // 170 m = 0.1 mile
locationRequest.priority = LocationRequest.PRIORITY_HIGH_ACCURACY //set according to your app function
locationCallback = object : LocationCallback() {
override fun onLocationResult(locationResult: LocationResult?) {
locationResult ?: return
if (locationResult.locations.isNotEmpty()) {
// get latest location
val location =
locationResult.lastLocation
// use your location object
// get latitude , longitude and other info from this
}
}
}
}
//start location updates
private fun startLocationUpdates() {
fusedLocationClient.requestLocationUpdates(
locationRequest,
locationCallback,
null /* Looper */
)
}
// stop location updates
private fun stopLocationUpdates() {
fusedLocationClient.removeLocationUpdates(locationCallback)
}
// stop receiving location update when activity not visible/foreground
override fun onPause() {
super.onPause()
stopLocationUpdates()
}
// start receiving location update when activity visible/foreground
override fun onResume() {
super.onResume()
startLocationUpdates()
}
Make sure you take care about Mainfaist permission and runtime permission for location
<uses-permission android:name="android.permission.ACCESS_FINE_LOCATION"/>
and for Gradle add this
implementation 'com.google.android.gms:play-services-location:17.0.0'
For more details follow these official documents
https://developer.android.com/training/location/retrieve-current
https://developer.android.com/training/location/receive-location-updates
https://developers.google.com/android/reference/com/google/android/gms/location/FusedLocationProviderClient
来源：https://stackoverflow.com/questions/45958226/get-location-android-kotlin