Question

我有一个使用位置管理器的片段，但是它出现了这个错误：

03-10 17:40:59.875    3909-3909/com.beerportfolio.beerportfoliopro E/AndroidRuntime﹕ FATAL EXCEPTION: main
    java.lang.NullPointerException
            at com.beerportfolio.beerportfoliopro.FindBrewery.<init>(FindBrewery.java:25)
            at java.lang.Class.newInstanceImpl(Native Method)
            at java.lang.Class.newInstance(Class.java:1130)
            at android.support.v4.app.Fragment.instantiate(Fragment.java:402)
            at android.support.v4.app.Fragment.instantiate(Fragment.java:377)
            at com.beerportfolio.beerportfoliopro.MainDrawer2.displayNavFragment(MainDrawer2.java:172)
            at com.beerportfolio.beerportfoliopro.MainDrawer2.access$000(MainDrawer2.java:28)
            at com.beerportfolio.beerportfoliopro.MainDrawer2$1.onItemClick(MainDrawer2.java:71)
            at android.widget.AdapterView.performItemClick(AdapterView.java:298)
            at android.widget.AbsListView.performItemClick(AbsListView.java:1237)
            at android.widget.ListView.performItemClick(ListView.java:4555)
            at android.widget.AbsListView$PerformClick.run(AbsListView.java:3037)
            at android.widget.AbsListView$1.run(AbsListView.java:3724)
            at android.os.Handler.handleCallback(Handler.java:730)
            at android.os.Handler.dispatchMessage(Handler.java:92)
            at android.os.Looper.loop(Looper.java:158)
            at android.app.ActivityThread.main(ActivityThread.java:5789)
            at java.lang.reflect.Method.invokeNative(Native Method)
            at java.lang.reflect.Method.invoke(Method.java:525)
            at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1027)
            at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:843)
            at dalvik.system.NativeStart.main(Native Method)

FindBrewery第25行是这样的：

LocationManager locationManager =(LocationManager)getActivity().getSystemService(Context.LOCATION_SERVICE);

FindBrewery的整个代码是：

public class FindBrewery extends Fragment implements LocationListener {

    private TextView latituteField;
    private TextView longitudeField;
    LocationManager locationManager =(LocationManager)getActivity().getSystemService(Context.LOCATION_SERVICE);
    private String provider;
    Context c = getActivity().getApplicationContext();



    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);

    }

    public View onCreateView(LayoutInflater inflater, ViewGroup container,
                             Bundle savedInstanceState) {
        //todo change view
        View rootView = inflater.inflate(R.layout.beer_location_list,container, false);

        // Get the location manager
        // Define the criteria how to select the locatioin provider -> use
        // default
        Criteria criteria = new Criteria();
        provider = locationManager.getBestProvider(criteria, false);
        Location location = locationManager.getLastKnownLocation(provider);

        // Initialize the location fields
        if (location != null) {
            System.out.println("Provider " + provider + " has been selected.");
            onLocationChanged(location);
        } else {

        }


        return rootView;
    }




    /* Request updates at startup */
    @Override
    public void onResume() {
        super.onResume();
        locationManager.requestLocationUpdates(provider, 400, 1, this);
    }

    /* Remove the locationlistener updates when Activity is paused */
    @Override
    public void onPause() {
        super.onPause();
        locationManager.removeUpdates(this);
    }

    @Override
    public void onLocationChanged(Location location) {
        int lat = (int) (location.getLatitude());
        int lng = (int) (location.getLongitude());
        //latituteField.setText(String.valueOf(lat));
        //longitudeField.setText(String.valueOf(lng));

        //Toast.makeText(this, "Finding your loaction",Toast.LENGTH_SHORT).show();

        //call asycn task for location
        String url = "myURL";

        Log.d("urlTest", url);

        //async task goes here
        new GetNearbyBreweries(this.getActivity()).execute(url);



    }

    @Override
    public void onStatusChanged(String provider, int status, Bundle extras) {
        // TODO Auto-generated method stub

    }

    @Override
    public void onProviderEnabled(String provider) {
        //Toast.makeText(this, "Enabled new provider " + provider,Toast.LENGTH_SHORT).show();

    }

    @Override
    public void onProviderDisabled(String provider) {
        //Toast.makeText(this, "Disabled provider " + provider,Toast.LENGTH_SHORT).show();
    }



}

Answer 1

getActivity()将返回null，直到Fragment附加到Activity。您应该将代码移至onAttach()：

@Override
public void onAttach(Activity activity) {
    super.onAttach(activity);
    locationManager =(LocationManager)activity.getSystemService(Context.LOCATION_SERVICE);

}

位置管理器NULL FC

1 个答案: