Question

我刚刚开始工作但是当我关闭我的Wifi以确定我是否可以使用我的GPS获得更准确的位置时，它现在给我带来了NullPointer错误，我看不出原因。< / p>

首先调用以下代码;

 public void onConnected(Bundle dataBundle) {
        connected = true;
        //Request an update from the location client to get current Location details
        mLocationClient.requestLocationUpdates(mLocationRequest,this);
        Toast.makeText(this, "Connected", Toast.LENGTH_SHORT).show();
    }

然后需要调用此方法

public void onLocationChanged(android.location.Location location) {
        // Report to the UI that the location was updated
        String msg = "Updated Location: " +
                Double.toString(location.getLatitude()) + "," +
                Double.toString(location.getLongitude());
        if(tmp != location.getLatitude())
        {
            Toast.makeText(this, msg, Toast.LENGTH_SHORT).show();
        }
        tmp = location.getLatitude();
    }

你可以看到我在那里有两个祝酒词并且他们用实际的GPS坐标回来了很好但是当我打电话给下面的代码时它会在新的位置线getLastKnownLocation上崩溃

public String getLocation()
    {
        // Get the location manager
        LocationManager locationManager = (LocationManager) getSystemService(LOCATION_SERVICE);
        Criteria criteria = new Criteria();
        String bestProvider = locationManager.getBestProvider(criteria, false);
        android.location.Location location = locationManager.getLastKnownLocation(bestProvider);
        Double lat,lon;
        DateFormat dateFormat = new SimpleDateFormat("yyyy/MM/dd HH:mm:ss");
        Date date = new Date();
        try {
            lat = location.getLatitude ();
            lon = location.getLongitude ();
            Toast.makeText(this,""+lat.toString()+"-"+lon.toString(),Toast.LENGTH_SHORT).show();
            return new LatLng(lat, lon).toString();
        }
        catch (NullPointerException e){
            Toast.makeText(this,"HELL-NO",Toast.LENGTH_SHORT).show();
            Log.e("HELL-NO","n",e);
            e.printStackTrace();
            return null;
        }
    }

我只是不明白为什么当我尝试检索位置时，它似乎已经在onLocationChanged方法中检索到了，它只是出现了一个nullpointer。

Answer 1

我只是改变了

locationManager.getLastKnownLocation(LocationManager.GPS_PROVIDER) to 
locationManager.getLastKnownLocation(LocationManager.PASSIVE_PROVIDER);

这解决了我的解决方案。完整代码段：

map  = ((MapFragment) getFragmentManager().
            findFragmentById(R.id.map)).getMap();

    map.setMyLocationEnabled(true);

    locationManager = (LocationManager)getSystemService
            (Context.LOCATION_SERVICE); 
    getLastLocation = locationManager.getLastKnownLocation
            (LocationManager.PASSIVE_PROVIDER);
    currentLongitude = getLastLocation.getLongitude();
    currentLatitude = getLastLocation.getLatitude();

    currentLocation = new LatLng(currentLatitude, currentLongitude);

希望这会有所帮助。

Answer 2

当你不应该将新的和旧的位置API混合在一起时。

要获取最后一个已知位置，您只需致电

mLocationClient.getLastLocation();

连接位置服务后。

阅读如何使用新的位置API

http://developer.android.com/training/location/retrieve-current.html#GetLocation

Answer 3

我很长时间都在努力解决这个问题。但谷歌刚刚想出了一个解决方案。

googleMap.getMyLocation();

获取api V2上蓝点的位置。

Answer 4

试试这段代码：

LocationManager mLocationManager;
Location myLocation = getLastKnownLocation();

private Location getLastKnownLocation() {
    mLocationManager = (LocationManager)getApplicationContext().getSystemService(LOCATION_SERVICE);
    List<String> providers = mLocationManager.getProviders(true);
    Location bestLocation = null;
    for (String provider : providers) {
        Location l = mLocationManager.getLastKnownLocation(provider);
        if (l == null) {
            continue;
        }
        if (bestLocation == null || l.getAccuracy() < bestLocation.getAccuracy()) {
            // Found best last known location: %s", l);
            bestLocation = l;
        }
    }
    return bestLocation;
}

getLastKnownLocation返回NULL

4 个答案: