Android 通过eclipse重新安装apk文件后，getlastknownlocation始终返回null

最近，我创建了一个简单的应用程序来获取android手机上的gps位置和显示。 开始时，我尝试了几次后就可以获得位置，但在重新安装apk文件后，getLastKnownLocation（）总是返回空值

使用的开发环境： -API 10姜饼2.3.6 -使用GPS提供程序

下面是我在android项目中应用的代码：

        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();
            }

        }
    }

有人能提出一个可能的解决方案来解决getLastKnownLocation（）返回的空值吗？

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任何帮助都将不胜感激。谢谢。

这个

getLastKnownLocation（）

返回最后一个已知位置…重新安装应用程序后，它将没有任何最后一个已知位置…因此它将导致NPE…而不是使用下面的代码

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;
}

---

它对我有用…应该对你也有用…

你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();
    }
}

尝试以下代码

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());

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在通过eclipse重新安装之后，我遇到了同样的问题。

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我解决了进入Android设置/安全/应用程序权限和确认应用程序的位置权限的问题。

这个解决方案是我对@Karan Mer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();
    }

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享受吧

这不是那么好的代码。。将所有代码放在try/catch中，而不显式地使用任何代码，原则上这是糟糕的编程。如果你真的想要一段很棒的代码，试试这个：@Karan Mer我在同一地点使用同一网络（沃达丰）的不同手机上获得不同的经度和纬度。在这种情况下我该怎么办这在很多层面上都是错误的，我不知道该怎么说。首先，getLastKnownLocation返回设备最后的已知位置，而不是应用程序。如果设备尚未跟踪该位置，它将返回null。因此，您的代码仍然可以返回null，并且将定期返回null。作为奖励，该代码中还有十几个其他错误。在我的例子中，即使启用了GPS，也无法从GPS_提供商处获取位置。每次都是从网络供应商那里得到的。有什么想法吗？？有人能帮我吗。getLastKnownLocation仍然返回null！在运行时，您不需要要求用户授予这些权限。没有回答此问题。如果位置==null怎么办？如何找到准确的位置等等，你怎么了，我不知道你到底想回答什么。这里的问题是有人告诉他解决方案，如何摆脱getLastKnownLocation（PROVIDER）方法返回的空对象。不显示祝酒词，不建议下一步做什么。