Question

我正在尝试显示计算到目的地的剩余距离，以便用以下代码显示给用户：

public class MyService extends Service {
    private LocationManager locManager;
    private LocationListener locListener = new myLocationListener();
    static final Double EARTH_RADIUS = 6371.00;

    private boolean gps_enabled = false;
    private boolean network_enabled = false;

    private Handler handler = new Handler();
    Thread t;

    @Override
    public IBinder onBind(Intent intent) {
        return null;
    }

    @Override
    public void onCreate() {
    }

    @Override
    public void onDestroy() {
    }

    @Override
    public void onStart(Intent intent, int startid) {
    }

    @Override
    public int onStartCommand(Intent intent, int flags, int startId) {

        Toast.makeText(getBaseContext(), "Service Started", Toast.LENGTH_SHORT).show();

        final Runnable r = new Runnable() {
            public void run() {
                Log.v("Debug", "Hello");
                location();
                handler.postDelayed(this, 5000);
            }
        };
        handler.postDelayed(r, 5000);
        return START_STICKY;
    }

    public void location() {
        locManager = (LocationManager) getSystemService(Context.LOCATION_SERVICE);

        try {
            gps_enabled = locManager.isProviderEnabled(LocationManager.GPS_PROVIDER);
        } catch (Exception ex) {
        }
        try {
            network_enabled = locManager.isProviderEnabled(LocationManager.NETWORK_PROVIDER);
        } catch (Exception ex) {
        }
        Log.v("Debug", "in on create.. 2");
        if (gps_enabled) {
            if (ActivityCompat.checkSelfPermission(getApplicationContext(), android.Manifest.permission.ACCESS_FINE_LOCATION) != PackageManager.PERMISSION_GRANTED && ActivityCompat.checkSelfPermission(getApplicationContext(), android.Manifest.permission.ACCESS_COARSE_LOCATION) != PackageManager.PERMISSION_GRANTED) {
                // TODO: Consider calling
                //    ActivityCompat#requestPermissions
                // here to request the missing permissions, and then overriding
                //   public void onRequestPermissionsResult(int requestCode, String[] permissions,
                //                                          int[] grantResults)
                // to handle the case where the user grants the permission. See the documentation
                // for ActivityCompat#requestPermissions for more details.
                return;
            }
            locManager.requestLocationUpdates(LocationManager.GPS_PROVIDER, 0, 0, locListener);
            Log.v("Debug", "Enabled..");
        }
        if (network_enabled) {
            locManager.requestLocationUpdates(LocationManager.NETWORK_PROVIDER, 0, 0, locListener);
            Log.v("Debug", "Disabled..");
        }
        Log.v("Debug", "in on create..3");
    }

    private class myLocationListener implements LocationListener {
        double lat_old = 34.629678;
        double lon_old = 50.860293;
        double lat_new;
        double lon_new;
        double time = 10;
        double speed = 0.0;

        @Override
        public void onLocationChanged(Location location) {
            Log.v("Debug", "in onLocation changed..");
            if (location != null) {
                if (ActivityCompat.checkSelfPermission(getApplicationContext(), android.Manifest.permission.ACCESS_FINE_LOCATION) != PackageManager.PERMISSION_GRANTED && ActivityCompat.checkSelfPermission(getApplicationContext(), android.Manifest.permission.ACCESS_COARSE_LOCATION) != PackageManager.PERMISSION_GRANTED) {
                    return;
                }
                locManager.removeUpdates(locListener);
                lat_new = location.getLongitude();
                lon_new = location.getLatitude();
                String longitude = "Longitude: " + location.getLongitude();
                String latitude = "Latitude: " + location.getLatitude();
                double distance = CalculationByDistance(lat_new, lon_new, lat_old, lon_old);
                Toast.makeText(getApplicationContext(), longitude + "\n" + latitude + "\nDistance is: "
                        + distance , Toast.LENGTH_SHORT).show();
            }
        }

        @Override
        public void onProviderDisabled(String provider) {
        }

        @Override
        public void onProviderEnabled(String provider) {
        }

        @Override
        public void onStatusChanged(String provider, int status, Bundle extras) {
        }
    }

    public double CalculationByDistance(double lat1, double lon1, double lat2, double lon2) {
        double Radius = EARTH_RADIUS;
        double dLat = Math.toRadians(lat2 - lat1);
        double dLon = Math.toRadians(lon2 - lon1);
        double a = Math.sin(dLat / 2) * Math.sin(dLat / 2) +
                Math.cos(Math.toRadians(lat1)) * Math.cos(Math.toRadians(lat2)) *
                        Math.sin(dLon / 2) * Math.sin(dLon / 2);
        double c = 2 * Math.asin(Math.sqrt(a));
        return Radius * c;
    }
}

问题：

1- distance的值不变！

2-当我停下来时，我会看到每个5000的吐司：

Toast.makeText(getApplicationContext(), longitude + "\n" + latitude + "\nDistance is: " + distance , Toast.LENGTH_SHORT).show();

我不会看到祝酒词，因为我正在使用onLocationChanged！

当我停下来时，我没有看到任何祝酒词。

Answer 1

尝试使用distanceTo方法

Location locationOne = new Location("point First");

locationOne.setLatitude(latA);

locationOne.setLongitude(lngA);

Location locationTwo = new Location("point Second");

locationTwo.setLatitude(latB);

locationTwo.setLongitude(lngB);

float distance = locationOne.distanceTo(locationTwo);

计算目标编程android google map API V2的剩余距离？

1 个答案: