getlastknownlocation在我通过eclipse重新安装apk文件后总是返回null

Question

最近，我创建了一个简单的应用程序来获取GPS位置并在Android手机上显示它。一开始，经过几次尝试，我能够获得位置。但是，在我重新安装APK文件后，getLastKnownLocation()总是返回null值。

开发环境:

• API 10 Gingerbread 2.3.6
• 使用GPS提供程序

下面是我应用到我的Android项目的代码:

public class MyActivity extends MapActivity {
  protected void onCreate(Bundle savedInstanceState) {
    mapView = (MapView) findViewById(R.id.myTripMap);
    mapController = mapView.getController();
    mapView.setSatellite(false);
    mapView.setStreetView(true);
    mapView.displayZoomControls(false);
    mapView.setBuiltInZoomControls(true);//
    mapView.setClickable(true);
    mapController.setZoom(14);
    Criteria criteria = new Criteria();
    criteria.setAccuracy(Criteria.ACCURACY_FINE);
    criteria.setAltitudeRequired(false);
    criteria.setBearingRequired(false);
    criteria.setCostAllowed(true);
    criteria.setPowerRequirement(Criteria.POWER_LOW);
    provider = locationManager.getBestProvider(criteria, true);
    location = locationManager.getLastKnownLocation(provider);
    updateMyCurrentLoc(location);
    locationManager.requestLocationUpdates(provider, 2, 1, locationListener);
  }
  private final LocationListener locationListener = new LocationListener() {
    public void onLocationChanged(Location location) {
      updateMyCurrentLoc(location);
    }
    public void onProviderDisabled(String provider) {
      updateMyCurrentLoc(null);
    }
    public void onProviderEnabled(String provider) {
    }
    public void onStatusChanged(String provider, int status,
        Bundle extras) {
    }
  };
  private void updateMyCurrentLoc(Location location) {
    if (location != null) {
      // other codes to get the address and display
      Toast.makeText(getBaseContext(), "provider used : " + provider).show();  //testing purpose
    } else {
      str = "No location found";
      Toast.makeText(getBaseContext(), str, Toast.LENGTH_SHORT).show();
    }
  }
}

对于getLastKnownLocation()返回的null值，有什么解决方案吗?

Answer 1

试试下面的代码

LocationManager locationManager = (LocationManager) getActivity()
            .getSystemService(Context.LOCATION_SERVICE);
    String locationProvider = LocationManager.NETWORK_PROVIDER;
    Location lastlocation = locationManager.getLastKnownLocation(locationProvider);
    String CurLat = String.valueOf(lastlocation.getLatitude());
    String Curlongi= String.valueOf(lastlocation.getLongitude());

Answer 2

这个解决方案是我对Ravi Tamada代码的一点改进。

    public Location getLocation() {
    int MIN_TIME_BW_UPDATES = 10000;
    int MIN_DISTANCE_CHANGE_FOR_UPDATES = 10000;
    try {
        locationManager = (LocationManager) getApplicationContext()
                .getSystemService(LOCATION_SERVICE);
        boolean isGPSEnabled = locationManager
                .isProviderEnabled(LocationManager.GPS_PROVIDER);
        boolean isPassiveEnabled = locationManager
                .isProviderEnabled(LocationManager.PASSIVE_PROVIDER);
        boolean isNetworkEnabled = locationManager
                .isProviderEnabled(LocationManager.NETWORK_PROVIDER);
        if (isGPSEnabled || isNetworkEnabled || isPassiveEnabled) {
            this.canGetLocation = true;
            // if GPS Enabled get lat/long using GPS Services
            if (isGPSEnabled && location == null) {
                    locationManager.requestLocationUpdates(
                            LocationManager.GPS_PROVIDER,
                            MIN_TIME_BW_UPDATES,
                            MIN_DISTANCE_CHANGE_FOR_UPDATES, this);
                    Log.d("GPS", "GPS Enabled");
                    if (locationManager != null) {
                        location = locationManager
                                .getLastKnownLocation(LocationManager.GPS_PROVIDER);
                    }
            }
            if (isPassiveEnabled && location == null) {
                locationManager.requestLocationUpdates(
                        LocationManager.PASSIVE_PROVIDER,
                        MIN_TIME_BW_UPDATES,
                        MIN_DISTANCE_CHANGE_FOR_UPDATES, this);
                Log.d("Network", "Network Enabled");
                if (locationManager != null) {
                    location = locationManager
                            .getLastKnownLocation(LocationManager.PASSIVE_PROVIDER);
                }
            }
            if (isNetworkEnabled && location == null) {
                locationManager.requestLocationUpdates(
                        LocationManager.NETWORK_PROVIDER,
                        MIN_TIME_BW_UPDATES,
                        MIN_DISTANCE_CHANGE_FOR_UPDATES, this);
                Log.d("Network", "Network Enabled");
                if (locationManager != null) {
                    location = locationManager
                            .getLastKnownLocation(LocationManager.NETWORK_PROVIDER);
                }
            }
        }else{
            return null;
        }
    } catch (Exception e) {
        e.printStackTrace();
    }

Answer 3

您只需要在代码中再添加一行

if (locationManager != null) {
    locationManager.requestLocationUpdates(LocationManager.GPS_PROVIDER, 0, 0, this);
    location = locationManager
            .getLastKnownLocation(LocationManager.GPS_PROVIDER);
    if (location != null) {
        latitude = location.getLatitude();
        longitude = location.getLongitude();
    } else {
        Toast.makeText(
                mContext,
                "Location Null", Toast.LENGTH_SHORT).show();
    }
}

Answer 4

通过eclipse重新安装后，我得到了同样的问题。我解决了去Android设置/安全/应用程序权限，并确认应用程序的位置权限。