java - 如何在android中获取谷歌地图蓝点纬度和经度

Question

我的目标是跟踪用户的位置并在到达标记位置时发出警报。所以首先我得到要到达的位置并标记它。然后我获取当前位置并将其与标记位置进行比较。但它不起作用。即使我将标记放置在当前位置。它没有给出 toast 消息。这是代码 -

public class MainActivity extends FragmentActivity implements LocationListener{
    LocationManager locationManager;
    String provider;
    ToggleButton toggle;

    public static double lat,lang,value1,value2,value3,value4;
    public static String strlat,strlat1;
    public LatLng loc,loc1;
    public  double latitude,longitude; 
    public static String strlang,strlang1 ;
    Location location;

    public LocationManager locationmanager;
        // Google Map
            private GoogleMap googleMap;
            LocationListener Locationlistener;

            @Override
            protected void onCreate(Bundle savedInstanceState) {
                super.onCreate(savedInstanceState);
                setContentView(R.layout.activity_main);

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

                // Creating an empty criteria object
                Criteria criteria = new Criteria();

                // Getting the name of the provider that meets the criteria
                provider = locationManager.getBestProvider(criteria, false);

               if(provider!=null && !provider.equals("")){

                    // Get the location from the given provider 
                    final Location location = locationManager.getLastKnownLocation(provider);

                    locationManager.requestLocationUpdates(provider, 1000, 1, this);

                    final Handler handler = new Handler();

                    Runnable runnable = new Runnable() {

                        public void run() {
                            if(location!=null){
                                lat = location.getLatitude();
                            lang = location.getLongitude();

                             value3 =Double.parseDouble(new DecimalFormat("##.##").format(lat));
                             value4 =Double.parseDouble(new DecimalFormat("##.##").format(lang));
                             strlat = String.valueOf(value3);
                                strlang = String.valueOf(value4);
                             loc1 =new LatLng(lat, lang);
                            if((value1 == value3) && (value2 == value4))
                            {
                                Toast.makeText(getApplicationContext(), "target reached", Toast.LENGTH_SHORT).show();
                            }
                            else
                                Toast.makeText(getBaseContext(), "Location can't be retrieved", Toast.LENGTH_SHORT).show();

                        }
                            else{
                            Toast.makeText(getBaseContext(), "No Provider Found", Toast.LENGTH_SHORT).show();
                        }
                            handler.postDelayed(this, 1000);
                        }
                    };

                    handler.post(runnable);
               }

                try {
                    // Loading map
                    initilizeMap();

                    // Changing map type
                    googleMap.setMapType(GoogleMap.MAP_TYPE_NORMAL);
                    // googleMap.setMapType(GoogleMap.MAP_TYPE_HYBRID);
                    // googleMap.setMapType(GoogleMap.MAP_TYPE_SATELLITE);
                    // googleMap.setMapType(GoogleMap.MAP_TYPE_TERRAIN);
                    // googleMap.setMapType(GoogleMap.MAP_TYPE_NONE);

                    // Showing / hiding your current location

                googleMap.setMyLocationEnabled(true);

                    // Enable / Disable zooming controls
                    googleMap.getUiSettings().setZoomControlsEnabled(false);

                    // Enable / Disable my location button
                    googleMap.getUiSettings().setMyLocationButtonEnabled(true);

                    // Enable / Disable Compass icon
                    googleMap.getUiSettings().setCompassEnabled(true);

                    // Enable / Disable Rotate gesture
                    googleMap.getUiSettings().setRotateGesturesEnabled(true);

                    // Enable / Disable zooming functionality
                    googleMap.getUiSettings().setZoomGesturesEnabled(true);

                    // create marker
                googleMap.animateCamera(CameraUpdateFactory.newLatLngZoom(loc, 16.0f));

                } catch (Exception e) {
                    e.printStackTrace();
                }

                googleMap.setOnMapClickListener(new OnMapClickListener(){
                    public void onMapClick(LatLng point){
                        Toast.makeText(getBaseContext(),
                            point.latitude + ", " + point.longitude,
                            Toast.LENGTH_LONG).show();
                        latitude = point.latitude;
                        longitude = point.longitude;
                        value1 =Double.parseDouble(new DecimalFormat("##.##").format(latitude));
                        value2 =Double.parseDouble(new DecimalFormat("##.##").format(longitude));
                        strlat1 = String.valueOf(value1);
                        strlang1 = String.valueOf(value2);
                        loc=new LatLng(point.latitude, point.longitude);
                        MarkerOptions marker = new MarkerOptions().position(loc).title("Hello Maps ");

                        // adding marker
                        googleMap.addMarker(marker);

                    }
                });
            }

            @Override
            protected void onResume() {
                super.onResume();
                initilizeMap();
            }

            /**
             * function to load map If map is not created it will create it for you
             * */
            private void initilizeMap() {
                if (googleMap == null) {
                    googleMap = ((MapFragment) getFragmentManager().findFragmentById(
                            R.id.map)).getMap();

                    // check if map is created successfully or not
                    if (googleMap == null) {
                        Toast.makeText(getApplicationContext(),
                                "Sorry! unable to create maps", Toast.LENGTH_SHORT)
                                .show();
                    }
                }
            }

            /*
             * creating random position around a location for testing purpose only
             */

            @Override
            public void onLocationChanged(Location location) {
                // TODO Auto-generated method stub

            }

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

            }

            @Override
            public void onProviderEnabled(String provider) {
                // TODO Auto-generated method stub

            }

            @Override
            public void onProviderDisabled(String provider) {
                // TODO Auto-generated method stub

            }
    }

Answer 1

您的代码中有一些错误。

您无法将坐标与 == 进行比较，因为在跟踪设备位置时，您永远不会获得完全匹配的纬度/经度坐标。您需要找出一个阈值，如果设备达到该阈值，则显示警报。

接下来，您没有使用 onLocationChanged() 回调，因此您只是在应用启动时查看一次当前位置。

看一下 my other answer here 中的代码这是关于确定设备是否在圆圈内。这是一个类似的问题。

因此，如果您将阈值设置为 10 米，并考虑设备距离目标位置 10 米以内时达到的目标，您将实现如下所示的 onLocationChanged() 方法:

@Override
public void onLocationChanged(Location location) {

    float[] distance = new float[2];

    Location.distanceBetween( location.getLatitude(), location.getLongitude(),
            latitude, longitude, distance);

    if( distance[0] < 10 ){
        //target location reached
        Toast.makeText(getApplicationContext(), "target reached", Toast.LENGTH_SHORT).show();
    }
}