Question

我使用简单的 位置管理器 对象获取设备的lastKnownLocation（） 但在返回中获取空对象可以告诉我为什么？

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" />

设置错过了什么？我已检查我的位置服务已在设备中请提供一些工作示例的链接

Answer 1

我用地点名称来获取位置的东西是

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;
}

的 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; } }

Answer 2

愚蠢的事情作为对此的答案...我重新启动了我的设备...并且它有效...请确保您的位置服务已启用并且正常工作

Answer 3

            // Get the location from the given provider
            Location location = locationManager
                    .getLastKnownLocation(provider);

            locationManager.requestLocationUpdates(provider, 1000, 1, this);

Answer 4

要获取上一个位置，可以参考上面提供的答案，在这里可以使用位置管理器或FusedLocationClient

但是您也可以使用 LocationServices ，它比其他方法要快。

所以让我提供一个简短的工作内容：

1）在gradle应用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）将这些权限添加到applicationtag之外的清单文件中

<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）现在在onCreate内：

fusedLocationClient = LocationServices.getFusedLocationProviderClient(this);
fetchLastLocation();

5）没有定义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）现在为权限请求定义另外两种方法

@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：用类上下文替换上下文

您将在Logcat中获得您的位置。

希望这会希望您或其他人

Answer 5

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locationManager获得的LOCATION变量。

Answer 6

以下是我尝试获取最后位置的方式。

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);
        }
    });
}

Answer 7

在获取上一个位置之前，也许您想获取当前位置，请检查是否为空或具有。如果未设置最后的位置（如果要使用FusedLocationProviderClient 并在使用前添加以下内容：

实现'com.google.android.gms：play-services-location：16.0.0'

在build.gradle（Module：app）上，并在活动创建后调用zoomMyCuurentLocation（）方法。

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));
            }
        }
    });
}

如何获取Android中位置管理器的上一个已知位置？

7 个答案: