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Eclipseでapkファイルを再インストールした後、getlastknownlocationは常にnullを返します

最近、GPSの位置を取得してAndroid電話で表示するシンプルなアプリケーションを作成しました。最初は、数回試してから位置を取得できましたが、apkファイルを再インストールした後、 getLastKnownLocation（）は常にnull値を返します。

使用した開発環境：-API 10 Gingerbread 2.3.6-GPSプロバイダーを使用

以下は、私のAndroidプロジェクトに適用したコードです：

        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();
            }

        }
    }

誰もがgetLastKnownLocation（）によって返されたnull値を解決する可能な解決策を提案できますか？助けていただければ幸いです。ありがとう。

androidgpslocation
24
Student

getLastKnownLocation()これは、最後の既知の場所を返します...アプリを再インストールした後、最後の既知の場所はありません...そのため、NPEになります...代わりに以下のコードを使用します

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;
            if (isNetworkEnabled) {
                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);
                    if (location != null) {
                        latitude = location.getLatitude();
                        longitude = location.getLongitude();
                    }
                }
            }
            // 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", "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;
}

それは私のために働いた...あなたのためにも働くはずです...

45
karan

このソリューションは、@ Karan Merコードの私の小さな改善です。

    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();
    }

楽しい

1
Davido

次のコードを試してください

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());
0
Dhanveer thakur

コードにもう1行追加するだけです

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();
    }
}
0
Shirish Shinde