Android getLastKnownLocation(LocationManager.GPS_PROVIDER) 返回 null

Question

我正在使用以下代码来获取我当前的位置。它使用 NETWORK_PROVIDER 完美运行。但是每当我使用 GPS_PROVIDER 时，它总是返回 null。我知道同样的问题已被问过很多次，但没有一个能解决我的问题

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;

    android.location.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 android.location.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) {
                // location service disabled
            } else {
                this.canGetLocation = true;

                // if GPS Enabled get lat/long using GPS Services

                if (isGPSEnabled) {
                    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();
                    }
                }

                // First get location from Network Provider
                if (isNetworkEnabled) {
                    if (location == null) {
                        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();
                        }
                    }

                }
            }
        } 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();
        }
    }

    public boolean canGetLocation() {
            return this.canGetLocation;
    }

    public void onLocationChanged(Location location) {
    }

    public void onProviderDisabled(String provider) {
    }

    public void onProviderEnabled(String provider) {
    }

    public IBinder onBind(Intent intent) {
        return null;
    }
}

要从其他 Activity 中获取位置，我很简单

GPSTracker gps = new GPSTracker(this);
double lat = gps.latitude;
double lon = gps.longitude;

Answer 1

测试以下内容

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;

    android.location.Location location;
    double latitude;
    double longitude;

    // The minimum distance to change updates in metters
    private static final long MIN_DISTANCE_CHANGE_FOR_UPDATES = 0; 

    // The minimum time beetwen updates in milliseconds
    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 android.location.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) {
                // location service disabled
            } else {
                this.canGetLocation = true;

                // if GPS Enabled get lat/long using GPS Services

                if (isGPSEnabled) {
                    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();
                    }
                }

                // First get location from Network Provider
                if (isNetworkEnabled) {
                    if (location == null) {
                        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();
                        }
                    }

                }
            }
        } catch (Exception e) {
            // e.printStackTrace();
            Log.e("Error : Location",
                    "Impossible to connect to LocationManager", e);
        }

        return location;
    }

    public void updateGPSCoordinates(Location location) {
        if (location != null) {
            latitude = location.getLatitude();
            longitude = location.getLongitude();
        }
    }

    public boolean canGetLocation() {
            return this.canGetLocation;
    }

    public void onLocationChanged(Location location) {
     Toast.makeText(getApplicationContext(), Ubicación Obtenida: " + location.toString(), Toast.LENGTH_LONG).show();
     updateGPSCoordinates(Location location);
    }

    public void onProviderDisabled(String provider) {
    }

    public void onProviderEnabled(String provider) {
    }

    public IBinder onBind(Intent intent) {
        return null;
    }
}

要获得LastKnowLocation，首先GPS 需要找到一个坐标，最好的方法是使用onLocationChanged 方法，因为是实时的，网络定位比建筑物内的gps 定位要快。您可以在 Toast 的帮助下查看 onLocationChanged 何时触发。之后，您可以在您正在构建的应用程序上检索 GPS 获取的最后一个位置。