java - android getLastKnownLocation() 返回总是返回 null

Question

我正在创建一个仅在用户单击按钮时检查位置的应用程序。

这是我的代码，当我调用 getLastKnownLocation 时，即使在调用 requestLocationUpdates 之后，它也会返回 null:

public void main(String[] args, int iteration, Context context){
    Criteria criteria = new Criteria();
    LocationManager locationManager = (LocationManager) context.getSystemService(Context.LOCATION_SERVICE);

    LocationListener loc_listener = new LocationListener() {
        public void onLocationChanged(Location l) {
        }
        public void onProviderEnabled(String p) {}
        public void onProviderDisabled(String p) {}
        public void onStatusChanged(String p, int status, Bundle extras) {}

        };

    String bestProvider = locationManager.getBestProvider(criteria, false);
    locationManager.requestLocationUpdates(bestProvider, 0, 0, loc_listener);
    Location location = locationManager.getLastKnownLocation(bestProvider);
    location = locationManager.getLastKnownLocation(bestProvider);
    double lat;
    double lon;
    try {
        lat = location.getLatitude();
        lon = location.getLongitude();

    } catch (NullPointerException e) {
        lat = -1.0;
        lon = -1.0;

    }
    Log.i("results:",  String.valueOf(lat) + " " + String.valueOf(lon) + " 10NN");}}

设备上的定位服务已启用。非常感谢!

Answer 1

getLastKnownLocation 将返回 null，直到回调 onLocationChanged() 被触发。即使天空清晰可见，GPS 也可能需要几分钟的时间。如果您在室内，它可能永远不会运行。您必须等待它运行。