我正在使用简单的位置管理器对象来获取设备的lastKnownLocation() 但是在 return 中得到 null object 任何人都可以告诉我为什么吗？
代码：
public Location getLocation() {
LocationManager locationManager = (LocationManager) this.getSystemService(Context.LOCATION_SERVICE);
if (locationManager != null) {
Location lastKnownLocationGPS = locationManager.getLastKnownLocation(LocationManager.GPS_PROVIDER);
if (lastKnownLocationGPS != null) {
return lastKnownLocationGPS;
} else {
Location loc = locationManager.getLastKnownLocation(LocationManager.PASSIVE_PROVIDER);
System.out.println("1::"+loc);----getting null over here
System.out.println("2::"+loc.getLatitude());
return loc;
}
} else {
return null;
}
}
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.location);
getLocation();-----calling service
}
授予权限：
<uses-permission android:name="android.permission.INTERNET" />
<uses-permission android:name="android.permission.ACCESS_NETWORK_STATE" />
<uses-permission android:name="android.permission.READ_PHONE_STATE" />
<uses-permission android:name="android.permission.ACCESS_COARSE_LOCATION" />
<uses-permission android:name="android.permission.ACCESS_FINE_LOCATION" />
那么还有什么需要设置的吗？我已检查设备中的位置服务是否已开启 请提供一些工作示例的链接
在获取最后一个位置之前，也许您想获取当前位置，检查是否为空或有。如果没有设置最后一个位置，如果你想使用 FusedLocationProviderClient 在使用之前添加以下内容：
实现“com.google.android.gms:play-services-location:16.0.0”
在你的 build.gradle(Module: app) 上，并调用方法 ZoomMyCurentLocation() 来创建活动。
private void zoomMyCuurentLocation() {
LocationManager locationManager = (LocationManager) getSystemService(LOCATION_SERVICE);
Criteria criteria = new Criteria();
if (ActivityCompat.checkSelfPermission(this, Manifest.permission.ACCESS_FINE_LOCATION) != PackageManager.PERMISSION_GRANTED) {
ActivityCompat.checkSelfPermission(this, Manifest.permission.ACCESS_COARSE_LOCATION);
}
Location location = locationManager.getLastKnownLocation(locationManager.getBestProvider(criteria, false));
if (location != null) {
double lat = location.getLatitude();
double longi = location.getLongitude();
LatLng latLng = new LatLng(lat,longi);
mMap.animateCamera(CameraUpdateFactory.newLatLngZoom(latLng, 14.f));
Log.d(TAG, "zoomMyCuurentLocation: location not null");
} else {
setMyLastLocation();
}
}
private void setMyLastLocation() {
Log.d(TAG, "setMyLastLocation: excecute, and get last location");
FusedLocationProviderClient fusedLocationClient = LocationServices.getFusedLocationProviderClient(this);
if (ActivityCompat.checkSelfPermission(this, Manifest.permission.ACCESS_FINE_LOCATION) != PackageManager.PERMISSION_GRANTED && ActivityCompat.checkSelfPermission(this, Manifest.permission.ACCESS_COARSE_LOCATION) != PackageManager.PERMISSION_GRANTED) {
return;
}
fusedLocationClient.getLastLocation().addOnSuccessListener(this, new OnSuccessListener<Location>() {
@Override
public void onSuccess(Location location) {
if (location != null){
double lat = location.getLatitude();
double longi = location.getLongitude();
LatLng latLng = new LatLng(lat,longi);
Log.d(TAG, "MyLastLocation coordinat :"+latLng);
mMap.animateCamera(CameraUpdateFactory.newLatLngZoom(latLng, 14.f));
}
}
});
}
愚蠢的事情作为答案...我重新启动了我的设备...并且它起作用了...请确保您的位置服务已启用并正常工作
我用来通过地点名称获取位置的东西是
GPSTracker gpsTracker = new GPSTracker(CameraActivity.this);
String stringLatitude = "", stringLongitude = "", nameOfLocation="";
if (gpsTracker.canGetLocation()) {
stringLatitude = String.valueOf(gpsTracker.latitude);
stringLongitude = String.valueOf(gpsTracker.longitude);
nameOfLocation = ConvertPointToLocation(stringLatitude,stringLongitude);
}
public String ConvertPointToLocation(String Latitude, String Longitude) {
String address = "";
Geocoder geoCoder = new Geocoder(getBaseContext(), Locale.getDefault());
try {
List<Address> addresses = geoCoder.getFromLocation(
Float.parseFloat(Latitude), Float.parseFloat(Longitude), 1);
if (addresses.size() > 0) {
for (int index = 0; index < addresses.get(0)
.getMaxAddressLineIndex(); index++)
address += addresses.get(0).getAddressLine(index) + " ";
}
} catch (IOException e) {
e.printStackTrace();
}
return address;
}
GPSTracker.java
package in.appology.lss;
import java.io.IOException;
import java.util.List;
import java.util.Locale;
import android.app.AlertDialog;
import android.app.Service;
import android.content.Context;
import android.content.DialogInterface;
import android.content.Intent;
import android.location.Address;
import android.location.Geocoder;
import android.location.Location;
import android.location.LocationListener;
import android.location.LocationManager;
import android.os.Bundle;
import android.os.IBinder;
import android.provider.Settings;
import android.util.Log;
/**
* Create this Class from tutorial :
* http://www.androidhive.info/2012/07/android-gps-location-manager-tutorial
*
* For Geocoder read this :
* http://stackoverflow.com/questions/472313/android-reverse
* -geocoding-getfromlocation
*
*/
public class GPSTracker extends Service implements LocationListener {
private final Context mContext;
// flag for GPS Status
boolean isGPSEnabled = false;
// flag for network status
boolean isNetworkEnabled = false;
boolean canGetLocation = false;
Location location;
double latitude;
double longitude;
// The minimum distance to change updates in metters
private static final long MIN_DISTANCE_CHANGE_FOR_UPDATES = 10; // 10
// metters
// The minimum time beetwen updates in milliseconds
private static final long MIN_TIME_BW_UPDATES = 1000 * 60 * 1; // 1 minute
// Declaring a Location Manager
protected LocationManager locationManager;
public GPSTracker(Context context) {
this.mContext = context;
getLocation();
}
public Location getLocation() {
try {
locationManager = (LocationManager) mContext
.getSystemService(LOCATION_SERVICE);
// getting GPS status
isGPSEnabled = locationManager
.isProviderEnabled(LocationManager.GPS_PROVIDER);
// getting network status
isNetworkEnabled = locationManager
.isProviderEnabled(LocationManager.NETWORK_PROVIDER);
if (!isGPSEnabled && !isNetworkEnabled) {
// no network provider is enabled
} else {
this.canGetLocation = true;
// First get location from Network Provider
if (isNetworkEnabled) {
locationManager.requestLocationUpdates(
LocationManager.NETWORK_PROVIDER,
MIN_TIME_BW_UPDATES,
MIN_DISTANCE_CHANGE_FOR_UPDATES, this);
Log.d("Network", "Network");
if (locationManager != null) {
location = locationManager
.getLastKnownLocation(LocationManager.NETWORK_PROVIDER);
updateGPSCoordinates();
}
}
// if GPS Enabled get lat/long using GPS Services
if (isGPSEnabled) {
if (location == null) {
locationManager.requestLocationUpdates(
LocationManager.GPS_PROVIDER,
MIN_TIME_BW_UPDATES,
MIN_DISTANCE_CHANGE_FOR_UPDATES, this);
Log.d("GPS Enabled", "GPS Enabled");
if (locationManager != null) {
location = locationManager
.getLastKnownLocation(LocationManager.GPS_PROVIDER);
updateGPSCoordinates();
}
}
}
}
} catch (Exception e) {
// e.printStackTrace();
Log.e("Error : Location",
"Impossible to connect to LocationManager", e);
}
return location;
}
public void updateGPSCoordinates() {
if (location != null) {
latitude = location.getLatitude();
longitude = location.getLongitude();
}
}
/**
* Stop using GPS listener Calling this function will stop using GPS in your
* app
*/
public void stopUsingGPS() {
if (locationManager != null) {
locationManager.removeUpdates(GPSTracker.this);
}
}
/**
* Function to get latitude
*/
public double getLatitude() {
if (location != null) {
latitude = location.getLatitude();
}
return latitude;
}
/**
* Function to get longitude
*/
public double getLongitude() {
if (location != null) {
longitude = location.getLongitude();
}
return longitude;
}
/**
* Function to check GPS/wifi enabled
*/
public boolean canGetLocation() {
return this.canGetLocation;
}
/**
* Function to show settings alert dialog
*/
public void showSettingsAlert() {
AlertDialog.Builder alertDialog = new AlertDialog.Builder(mContext);
// Setting Dialog Title
alertDialog.setTitle("GPS");
// Setting Dialog Message
alertDialog
.setMessage("Please enable location in settings for accurate results!");
// On Pressing Setting button
alertDialog.setPositiveButton("Settings",
new DialogInterface.OnClickListener() {
@Override
public void onClick(DialogInterface dialog, int which) {
Intent intent = new Intent(
Settings.ACTION_LOCATION_SOURCE_SETTINGS);
mContext.startActivity(intent);
}
});
// On pressing cancel button
alertDialog.setNegativeButton("Cancel",
new DialogInterface.OnClickListener() {
@Override
public void onClick(DialogInterface dialog, int which) {
dialog.cancel();
}
});
alertDialog.show();
}
/**
* Get list of address by latitude and longitude
*
* @return null or List<Address>
*/
public List<Address> getGeocoderAddress(Context context) {
if (location != null) {
Geocoder geocoder = new Geocoder(context, Locale.ENGLISH);
try {
List<Address> addresses = geocoder.getFromLocation(latitude,
longitude, 1);
return addresses;
} catch (IOException e) {
// e.printStackTrace();
Log.e("Error : Geocoder", "Impossible to connect to Geocoder",
e);
}
}
return null;
}
/**
* Try to get AddressLine
*
* @return null or addressLine
*/
public String getAddressLine(Context context) {
List<Address> addresses = getGeocoderAddress(context);
if (addresses != null && addresses.size() > 0) {
Address address = addresses.get(0);
String addressLine = address.getAddressLine(0);
return addressLine;
} else {
return null;
}
}
/**
* Try to get Locality
*
* @return null or locality
*/
public String getLocality(Context context) {
List<Address> addresses = getGeocoderAddress(context);
if (addresses != null && addresses.size() > 0) {
Address address = addresses.get(0);
String locality = address.getLocality();
return locality;
} else {
return null;
}
}
/**
* Try to get Postal Code
*
* @return null or postalCode
*/
public String getPostalCode(Context context) {
List<Address> addresses = getGeocoderAddress(context);
if (addresses != null && addresses.size() > 0) {
Address address = addresses.get(0);
String postalCode = address.getPostalCode();
return postalCode;
} else {
return null;
}
}
/**
* Try to get CountryName
*
* @return null or postalCode
*/
public String getCountryName(Context context) {
List<Address> addresses = getGeocoderAddress(context);
if (addresses != null && addresses.size() > 0) {
Address address = addresses.get(0);
String countryName = address.getCountryName();
return countryName;
} else {
return null;
}
}
@Override
public void onLocationChanged(Location location) {
}
@Override
public void onProviderDisabled(String provider) {
}
@Override
public void onProviderEnabled(String provider) {
}
@Override
public void onStatusChanged(String provider, int status, Bundle extras) {
}
@Override
public IBinder onBind(Intent intent) {
return null;
}
}
要获取最后一个位置，您可以参考上面提供的答案，您可以使用位置管理器或 FusedLocationClient
但是您也可以使用LocationServices，它比其他方法更快。
所以让我提供一个简短的工作：
1) 在你的gradle应用程序文件中添加这两个依赖项
implementation 'com.google.android.gms:play-services-maps:17.0.0'
implementation 'com.google.android.gms:play-services-location:17.0.0'
2) 在 applicationtag 之外的清单文件中添加这些权限
<uses-permission android:name="android.permission.ACCESS_COARSE_LOCATION" />
<uses-permission android:name="android.permission.ACCESS_FINE_LOCATION" />
3) 在 onCreate 之外声明变量
private FusedLocationProviderClient fusedLocationClient;
4) 现在进入 onCreate :
fusedLocationClient = LocationServices.getFusedLocationProviderClient(this);
fetchLastLocation();
5) 未定义 fetchLastLocation 方法
private void fetchLastLocation() {
if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.M) {
if (checkSelfPermission(Manifest.permission.ACCESS_FINE_LOCATION) != PackageManager.PERMISSION_GRANTED && checkSelfPermission(Manifest.permission.ACCESS_COARSE_LOCATION) != PackageManager.PERMISSION_GRANTED) {
// TODO: Consider calling
// Activity#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 Activity#requestPermissions for more details.
// Toast.makeText(MainActivity.this, "Permission not granted, Kindly allow permission", Toast.LENGTH_LONG).show();
showPermissionAlert();
return;
}
}
fusedLocationClient.getLastLocation()
.addOnSuccessListener(this, new OnSuccessListener<Location>() {
@Override
public void onSuccess(Location location) {
// Got last known location. In some rare situations this can be null.
if (location != null) {
// Logic to handle location object
Log.e("LAST LOCATION: ", location.toString());
}
}
});
}
6) 现在定义另外两个权限请求方法
@Override
public void onRequestPermissionsResult(int requestCode, @NonNull String[] permissions, @NonNull int[] grantResults) {
switch (requestCode) {
case 123: {
// If request is cancelled, the result arrays are empty.
if (grantResults[0] == PackageManager.PERMISSION_DENIED) {
// permission was denied, show alert to explain permission
showPermissionAlert();
}else{
//permission is granted now start a background service
if (ActivityCompat.checkSelfPermission(getApplicationContext(), Manifest.permission.ACCESS_FINE_LOCATION) == PackageManager.PERMISSION_GRANTED
&& ActivityCompat.checkSelfPermission(getApplicationContext(), Manifest.permission.ACCESS_COARSE_LOCATION) == PackageManager.PERMISSION_GRANTED) {
fetchLastLocation();
}
}
}
}
}
private void showPermissionAlert(){
if (ActivityCompat.checkSelfPermission(MainHomeActivity.this, Manifest.permission.ACCESS_FINE_LOCATION) != PackageManager.PERMISSION_GRANTED
&& ActivityCompat.checkSelfPermission(MainHomeActivity.this, Manifest.permission.ACCESS_COARSE_LOCATION) != PackageManager.PERMISSION_GRANTED) {
ActivityCompat.requestPermissions(MainHomeActivity.this, new String[]{Manifest.permission.ACCESS_COARSE_LOCATION, Manifest.permission.ACCESS_FINE_LOCATION}, 123);
}
}
注意：将上下文替换为您的类上下文
您将在 Logcat 中获取您的位置。
希望这会希望你或其他人
我发现的最佳方法：
private Location getLastKnownLocation() {
if (ActivityCompat.checkSelfPermission(this, Manifest.permission.ACCESS_FINE_LOCATION) != PackageManager.PERMISSION_GRANTED || ActivityCompat.checkSelfPermission(this, Manifest.permission.ACCESS_COARSE_LOCATION) != PackageManager.PERMISSION_GRANTED) {
return null;
}
List<String> providers = locationManager.getProviders(true);
Location bestLocation = null;
for (String provider : providers) {
Location l = locationManager.getLastKnownLocation(provider);
if (l == null) {
continue;
}
if (bestLocation == null || l.getAccuracy() < bestLocation.getAccuracy()) {
// Found best last known location:
bestLocation = l;
}
}
return bestLocation;
}
您可以从系统服务
locationManagerLOCATION // Get the location from the given provider
Location location = locationManager
.getLastKnownLocation(provider);
locationManager.requestLocationUpdates(provider, 1000, 1, this);
以下是我尝试获取最后位置的方法。
private void setUpMap(){
//Location location = mMap.getMyLocation();
mMap.setMyLocationEnabled(true);
//mMap.addMarker(new MarkerOptions().position(new LatLng(0, 0)).title("Marker"));
mMap.setOnMyLocationChangeListener(new GoogleMap.OnMyLocationChangeListener() {
@Override
public void onMyLocationChange(Location location) {
mMap.addMarker(new MarkerOptions().position(new LatLng(location.getLatitude(), location.getLongitude())).title("My Location"));
mMap.moveCamera(CameraUpdateFactory.newLatLngZoom(new LatLng(location.getLatitude(),location.getLongitude()),10));
mMap.setOnMyLocationChangeListener(null);
}
});
}
用 Kotlin 解决这个问题： 抱歉，可怕的缩进
在你的gradle应用程序文件中添加这两个依赖项
implementation 'com.google.android.gms:play-services-maps:17.0.0'
implementation 'com.google.android.gms:play-services-location:17.0.0'
在 applicationtag 之外的清单文件中添加这些权限
<uses-permission android:name="android.permission.ACCESS_COARSE_LOCATION" />
<uses-permission android:name="android.permission.ACCESS_FINE_LOCATION" />
在 onCreate 之外声明变量
private lateinit var fusedLocationClient: FusedLocationProviderClient
现在在 onCreate 中：
fusedLocationClient= LocationServices.getFusedLocationProviderClient(this)
getCurrentLocation()
没有定义 fetchLastLocation 方法 注意：这里的getCurrentLocation表示的是最后一个位置。
private fun getCurrentLocation(){
if(checkPermissions())
{
if(isLocationEnabled()){
//final latitude and longitude
if (ActivityCompat.checkSelfPermission(
this,
Manifest.permission.ACCESS_FINE_LOCATION
) != PackageManager.PERMISSION_GRANTED && ActivityCompat.checkSelfPermission(
this,
Manifest.permission.ACCESS_COARSE_LOCATION
) != PackageManager.PERMISSION_GRANTED
) {
requestPermission()
return
}
// fusedLocationClient.getCurrentLocation()
fusedLocationClient.lastLocation.addOnCompleteListener(this){ task->
val location:Location?=task.result
if(location==null)
{
Toast.makeText(this,"NULL Received",Toast.LENGTH_SHORT).show()
}
else{
Toast.makeText(this,"Location SUCCESS",Toast.LENGTH_SHORT).show()
val geocoder = Geocoder(this, Locale.getDefault())
val addresses: MutableList<android.location.Address>? = geocoder.getFromLocation(location.latitude, location.longitude, 1)
cityName = addresses!![0].locality
startActivity(intent)
}
}
}
else
{
Toast.makeText(this,"Turn on location",Toast.LENGTH_SHORT).show()
val intent= Intent(Settings.ACTION_LOCATION_SOURCE_SETTINGS)
startActivity(intent)
}
}
else
{
//request permission here
requestPermission()
}
}
现在定义其他权限请求方法
private fun requestPermission() {
ActivityCompat.requestPermissions(this, arrayOf(android.Manifest.permission.ACCESS_COARSE_LOCATION,android.Manifest.permission.ACCESS_FINE_LOCATION),
PERMISSION_REQUEST_ACCESS_LOCATION)
}
companion object{
private const val PERMISSION_REQUEST_ACCESS_LOCATION=100
}
private fun checkPermissions():Boolean {
if (ActivityCompat.checkSelfPermission(
this,
android.Manifest.permission.ACCESS_FINE_LOCATION
) == PackageManager.PERMISSION_GRANTED && ActivityCompat.checkSelfPermission(
this,
android.Manifest.permission.ACCESS_COARSE_LOCATION
) == PackageManager.PERMISSION_GRANTED
) {
return true
}
return false
}
override fun onRequestPermissionsResult(
requestCode: Int,
permissions: Array<out String>,
grantResults: IntArray
) {
super.onRequestPermissionsResult(requestCode, permissions, grantResults)
if(requestCode== PERMISSION_REQUEST_ACCESS_LOCATION)
{
if(grantResults.isNotEmpty() && grantResults[0]==PackageManager.PERMISSION_GRANTED){
Toast.makeText(applicationContext,"Granted",Toast.LENGTH_SHORT).show()
getCurrentLocation()
}
else{
Toast.makeText(applicationContext,"DENIED",Toast.LENGTH_SHORT).show()
}
}
}
private fun isLocationEnabled():Boolean{
val locationManager:LocationManager=getSystemService(Context.LOCATION_SERVICE) as LocationManager
return locationManager.isProviderEnabled(LocationManager.GPS_PROVIDER)||locationManager.isProviderEnabled(LocationManager.NETWORK_PROVIDER)
}
这里有一个更好的解决方案：
@Nullable
public static Location getLastKnownLocation(Context context, LocationManager locationManager) {
if (ActivityCompat.checkSelfPermission(context, Manifest.permission.ACCESS_FINE_LOCATION) != PackageManager.PERMISSION_GRANTED ||
ActivityCompat.checkSelfPermission(context, Manifest.permission.ACCESS_COARSE_LOCATION) != PackageManager.PERMISSION_GRANTED) {
return null;
}
Criteria criteria = new Criteria();
criteria.setAccuracy(Criteria.ACCURACY_FINE);
String provider = locationManager.getBestProvider(criteria, true);
if (provider == null) return null;
return locationManager.getLastKnownLocation(provider);
}
这行：
criteria.setAccuracy(Criteria.ACCURACY_FINE);我在这个问题上做了完整的工作在此处输入链接描述。这是中等故事。