Android GPS定位监听器

我希望只获得一次以下值。如何阻止听众？我获取这些值，然后在

onLocationChanged（）

中

removeUpdates（）

方法给我一个空指针异常。所有这些都是通过单击按钮调用的

 public void onLocationChanged(Location loc) {
             locationManager.removeUpdates(this);
                //editLocation.setText("");
                //pb.setVisibility(View.INVISIBLE);
                Toast.makeText(
                        getBaseContext(),
                        "Location changed: Lat: " + loc.getLatitude() + " Lng: "
                                + loc.getLongitude(), Toast.LENGTH_SHORT).show();
                String longitude = "Longitude: " + loc.getLongitude();
                //Log.v(TAG, longitude);
                String latitude = "Latitude: " + loc.getLatitude();
                //Log.v(TAG, latitude);

            /*------- To get city name from coordinates -------- */
                String cityName = null;
                String StreetName = null;
                Geocoder gcd = new Geocoder(getBaseContext(), Locale.getDefault());
                List<Address> addresses;
                            try {
                                locationManager=null;
                    addresses = gcd.getFromLocation(loc.getLatitude(),
                            loc.getLongitude(), 1);
                    if (addresses.size() > 0)
                        System.out.println(addresses.get(0).getLocality());
                    cityName = addresses.get(0).getLocality();
                    if (addresses.size() > 0)
                        System.out.println(addresses.get(0).getThoroughfare());
                    StreetName=addresses.get(0).getThoroughfare();
                }
                catch (IOException e) {
                    e.printStackTrace();
                }
                String s = longitude + "\n" + latitude + "\n\nMy Current City is: "
                        + cityName;
                //editLocation.setText(s);
                Toast.makeText(
                        getBaseContext(),
                        "Location: " + s, Toast.LENGTH_SHORT).show();
                Toast.makeText(
                        getBaseContext(),
                        "Street Name: " + StreetName, Toast.LENGTH_LONG).show();
                //locationManager.removeUpdates(locationListener);

            }

在重新创建之前：

private LocationManager locationManager;
private LocationListener locationListener;

---

我明白问题所在。您正在

Punchout（）

方法中创建局部变量，而不是使用活动中定义的实例变量

只要确保始终使用实例变量，就可以在

onLocationChanged（）

---

显示您在何处声明和初始化

locationManager

。只需编辑以反映

private LocationManager locationManager;
private LocationListener locationListener;

public void Punchout(View view) {
    boolean hasNetwrokProvider;
    Toast.makeText(getApplicationContext(), "Getting Location", Toast.LENGTH_LONG).show();

  /* These lines created local variables:
  LocationManager locationManager = (LocationManager)
          getSystemService(Context.LOCATION_SERVICE);
  LocationListener locationListener = new MyLocationListener();
  */

  //use the instance variables instead:
  locationManager = (LocationManager)
          getSystemService(Context.LOCATION_SERVICE);
  locationListener = new MyLocationListener();

  locationManager.requestLocationUpdates(LocationManager.GPS_PROVIDER, 3000, 3, locationListener);
}