Question

因此，我正在制作这个应用程序，它使用JSoup库查找您附近的餐馆，并从食品配送应用程序中获取信息。唯一的问题是，有时纬度和经度会变为空值。我的应用程序正常工作的情况： -开启GPS并等待至少1-2分钟； -打开google地图，将其关闭，然后返回到应用程序；

因此，主要问题是：启用位置并点击“查找餐厅”按钮后，我无法立即获取位置，启用位置后我需要等待1-2分钟，然后它才能正常工作。

    private TextView result;
    private FusedLocationProviderClient client;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        requestPermission();
        client = LocationServices.getFusedLocationProviderClient(this);

       getBtn = findViewById(R.id.getRestaurants);
       result = findViewById(R.id.restaurantsList);

       getBtn.setOnClickListener(this);
    }



    private void requestPermission(){
        ActivityCompat.requestPermissions(this, new String[]{ACCESS_FINE_LOCATION}, 1 );
    }


public void onClick(View v) {
        if (ActivityCompat.checkSelfPermission(MainActivity.this, ACCESS_FINE_LOCATION) != PackageManager.PERMISSION_GRANTED){
                return;
        }

        client.getLastLocation().addOnSuccessListener(MainActivity.this, new OnSuccessListener<Location>() {
            @Override
            public void onSuccess(Location location) {
                result.setText("Getting location...");
                if(location != null){
                double latitude = getLat(location);
                double longitude = getLng(location);

                    result.setText("Finding restaurants near you...");
                getWebsite(latitude, longitude);
                }else{
                    result.setText("Couldn't fetch location!");
                }

            }
            });

Answer 1

您必须使用requestLocationUpdates() 您正在使用getLastLocation()，并且在最后一个已知位置变为空后关闭GPS并重新打开时，必须致电requestLocationUpdates() 您可以在下面的链接中找到更多信息

https://developer.android.com/training/location/receive-location-updates

Answer 2

这是在Kotlin中实现FusedLocationProvider的好方法（您可能适应Java或并排使用Java和Kotlin）：

private fun startLoc() {
        fusedLocationClient = LocationServices.getFusedLocationProviderClient(this)
        try {
            fusedLocationClient.lastLocation
                .addOnSuccessListener { location: Location? ->
                    //showDialog(this@MapsActivity, TAG, "last know loc = ${location?.latitude} + ${location?.longitude}")
                    if (location != null){
                        lastKnowLoc = LatLng(location.latitude, location.longitude)
                        addMarkerToLocation(lastKnowLoc)
                    }
                }
            val locationRequest = LocationRequest()
            locationRequest.interval = 10000
            locationRequest.fastestInterval = 10000
            locationRequest.priority = LocationRequest.PRIORITY_HIGH_ACCURACY

            locationCallback = object : LocationCallback() {
                override fun onLocationResult(locationResult: LocationResult?) {
                    locationResult ?: return
                    for (location in locationResult.locations){
                        //showDialog(this@MapsActivity, "locationResult", "location=${location.latitude};${location.longitude}")
                        addMarkerToLocation(LatLng(location.latitude, location.longitude))
                        val speed = location.speed
                        updateCamera(location.bearing)
                    }
                }
            }

            fusedLocationClient.requestLocationUpdates(locationRequest, locationCallback, null)

            btnStartLoc.isEnabled = false
            btnStopLoc.isEnabled = true
        }catch (e:SecurityException){}

    }

Answer 3

创建一个GPSTracker类

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; // location
double latitude=0.0; // latitude
double longitude=0.0; // longitude

// The minimum distance to change Updates in meters
//private static final long MIN_DISTANCE_CHANGE_FOR_UPDATES = 10; // 10 meters
private static final long MIN_DISTANCE_CHANGE_FOR_UPDATES = 0;
// The minimum time between updates in milliseconds
//private static final long MIN_TIME_BW_UPDATES = 1000 * 60 * 1; // 1 minute
private static final long MIN_TIME_BW_UPDATES = 0;

// 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);
                    if (location != null) {
                        latitude = location.getLatitude();
                        longitude = location.getLongitude();
                    }
                }
            }
            // if GPS Enabled get lat/long using GPS Services
            if (isGPSEnabled) {

                if(latitude==0 || longitude==0)
                {

                    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);
                        if (location != null) {
                            latitude = location.getLatitude();
                            longitude = location.getLongitude();
                        }
                    }
                }

            }
        }

    } catch (Exception e) {
        e.printStackTrace();
    }

    return location;
}
/**
 * Function to get latitude
 * */
public double getLatitude(){
    if(location != null){
        latitude = location.getLatitude();
    }

    // return latitude
    return latitude;
}

/**
 * Function to get longitude
 * */
public double getLongitude(){
    if(location != null){
        longitude = location.getLongitude();
    }

    // return longitude
    return longitude;
}
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 is settings");

    // Setting Dialog Message
    alertDialog.setMessage("GPS is not enabled. Please go to settings menu and Switch it on");

    // Setting Icon to Dialog
    //alertDialog.setIcon(R.drawable.delete);

    // On pressing Settings button
    alertDialog.setPositiveButton("Settings", new DialogInterface.OnClickListener() {
        public void onClick(DialogInterface dialog,int which) {
            Intent intent = new Intent(Settings.ACTION_LOCATION_SOURCE_SETTINGS);
            mContext.startActivity(intent);
        }
    });

    // on pressing cancel button
    //not required comment by kp on 19-03-2017
 /*   alertDialog.setNegativeButton("Cancel", new DialogInterface.OnClickListener() {
        public void onClick(DialogInterface dialog, int which) {
        dialog.cancel();
        }
    });
  */
    // Showing Alert Message
    alertDialog.show();
}

@Override
public void onLocationChanged(Location location) {
    // TODO Auto-generated method stub

    latitude = location.getLatitude();
    longitude = location.getLongitude();

}

@Override
public void onStatusChanged(String provider, int status, Bundle extras) {
    // TODO Auto-generated method stub

}

@Override
public void onProviderEnabled(String provider) {
    // TODO Auto-generated method stub

}

@Override
public void onProviderDisabled(String provider) {
    // TODO Auto-generated method stub

}

@Override
public IBinder onBind(Intent intent) {
    // TODO Auto-generated method stub
    return null;
}


}

无论您想获取经纬度，长值还是哪里，都可以使用LocationListener 及以下代码

        locationManager = (LocationManager)getSystemService(Context.LOCATION_SERVICE);    
        // Creating an empty criteria object
        Criteria criteria = new Criteria();
        // Getting the name of the provider that meets the criteria
        provider = locationManager.getBestProvider(criteria, false);
        if(provider!=null && !provider.equals("")){
        // Get the location from the given provider 
         Location location = locationManager.getLastKnownLocation(provider);
         locationManager.requestLocationUpdates(provider, 20000, 1,BillingManual.this );

         if(location!=null){
            onLocationChanged(location);}

            }else{
                //Toast.makeText(getBaseContext(), "No Provider Found", Toast.LENGTH_SHORT).show();
        }
        GPSTracker gps = new GPSTracker(this);

        // check if GPS enabled     
        if(gps.canGetLocation()){

            double latitude = gps.getLatitude();
            double longitude = gps.getLongitude();
            latitude_1 = latitude;
            longitude_1 =longitude;
            // \n is for new line
           // Toast.makeText(getApplicationContext(), "Your Location is - \nLat: " + latitude + "\nLong: " + longitude, Toast.LENGTH_LONG).show();    
        }else{
            // can't get location
            // GPS or Network is not enabled
            // Ask user to enable GPS/network in settings
            gps.showSettingsAlert();
        }

@Override
public void onLocationChanged(Location location) {
    // TODO Auto-generated method stub
    try{
        latitude_1=location.getLatitude();
        longitude_1=location.getLongitude() ;
        }catch (Exception e) {
            e.printStackTrace();
            // TODO: handle exception
        }
}

如何适应Android设备的经度和纬度？

3 个答案: