在我的程序中，使用 JSON Web服务 在地图上显示多个标记，但现在我只想显示位置接近我当前的位置，如10Kms内的 。
所以在这里我想知道而不是显示所有标记，我怎样才能显示最接近的标记！
我正在放置我的整个代码，我用它来标记 Map V2
public class MainActivity extends FragmentActivity implements LocationListener {
private static final String LOG_TAG = "JsOn ErRoR";
private static final String SERVICE_URL = " ";
protected GoogleMap mapB;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
setUpMapIfNeeded();
// Getting Google Play availability status
int status = GooglePlayServicesUtil.isGooglePlayServicesAvailable(getBaseContext());
// Showing status
if(status!=ConnectionResult.SUCCESS){ // Google Play Services are not available
int requestCode = 10;
Dialog dialog = GooglePlayServicesUtil.getErrorDialog(status, this, requestCode);
dialog.show();
}else { // Google Play Services are available
// Getting reference to the SupportMapFragment of activity_main.xml
SupportMapFragment fm = (SupportMapFragment) getSupportFragmentManager().findFragmentById(R.id.map);
// Getting GoogleMap object from the fragment
mapB = fm.getMap();
// Enabling MyLocation Layer of Google Map
mapB.setMyLocationEnabled(true);
// Getting LocationManager object from System Service LOCATION_SERVICE
LocationManager locationManager = (LocationManager) getSystemService(LOCATION_SERVICE);
// Creating a criteria object to retrieve provider
Criteria criteria = new Criteria();
// Getting the name of the best provider
String provider = locationManager.getBestProvider(criteria, true);
// Getting Current Location
Location location = locationManager.getLastKnownLocation(provider);
if(location!=null){
onLocationChanged(location);
}
locationManager.requestLocationUpdates(provider, 20000, 0, this);
}
}
@Override
protected void onResume() {
super.onResume();
setUpMapIfNeeded();
}
private void setUpMapIfNeeded() {
if (mapB == null) {
mapB = ((SupportMapFragment) getSupportFragmentManager().findFragmentById(R.id.map))
.getMap();
if (mapB != null) {
setUpMap();
}
}
}
private void setUpMap() {
new Thread(new Runnable() {
public void run() {
try {
retrieveAndAddCities();
} catch (IOException e) {
Log.e(LOG_TAG, "Cannot retrive cities", e);
return;
}
}
}).start();
}
protected void retrieveAndAddCities() throws IOException {
HttpURLConnection conn = null;
final StringBuilder json = new StringBuilder();
try {
// Connect to the web service
URL url = new URL(SERVICE_URL);
conn = (HttpURLConnection) url.openConnection();
InputStreamReader in = new InputStreamReader(conn.getInputStream());
// Read the JSON data into the StringBuilder
int read;
char[] buff = new char[1024];
while ((read = in.read(buff)) != -1) {
json.append(buff, 0, read);
}
} catch (IOException e) {
Log.e(LOG_TAG, "Error connecting to service", e);
throw new IOException("Error connecting to service", e);
} finally {
if (conn != null) {
conn.disconnect();
}
}
// Must run this on the UI thread since it's a UI operation.
runOnUiThread(new Runnable() {
public void run() {
try {
createMarkersFromJson(json.toString());
} catch (JSONException e) {
Log.e(LOG_TAG, "Error processing JSON", e);
}
}
});
}
void createMarkersFromJson(String json) throws JSONException {
JSONArray jsonArray = new JSONArray(json);
System.out.print(json);
List<Marker> markers = new ArrayList<Marker>();
for (int i = 0; i < jsonArray.length(); i++) {
JSONObject jsonObj = jsonArray.getJSONObject(i);
System.out.print(jsonObj.getJSONArray("latlng"));
Marker marker = mapB.addMarker(new MarkerOptions()
.title(jsonObj.getString("business_name"))
.position(new LatLng(
jsonObj.getJSONArray("latlng").getDouble(0),
jsonObj.getJSONArray("latlng").getDouble(1)))
.icon(BitmapDescriptorFactory.defaultMarker(BitmapDescriptorFactory.HUE_GREEN))
);
markers.add(marker);
}
}
@Override
public void onLocationChanged(Location location) {
// Getting latitude of the current location
double latitude = location.getLatitude();
// Getting longitude of the current location
double longitude = location.getLongitude();
// Creating a LatLng object for the current location
LatLng latLng = new LatLng(latitude, longitude);
// Showing the current location in Google Map
mapB.moveCamera(CameraUpdateFactory.newLatLng(latLng));
// Zoom in the Google Map
mapB.animateCamera(CameraUpdateFactory.zoomTo(15));
}
@Override
public void onProviderDisabled(String provider) {
// TODO Auto-generated method stub
}
@Override
public void onProviderEnabled(String provider) {
// TODO Auto-generated method stub
}
@Override
public void onStatusChanged(String provider, int status, Bundle extras) {
// TODO Auto-generated method stub
}
}
我的 JSON 看起来像： -
[
{
"business_name":"Connaught Place",
"latlng":
[
"28.632777800000000000",
"77.219722199999980000"
]
},
{
"business_name":"Moolchand",
"latlng":
[
"28.568927000000000000",
"77.235073000000060000"
]
}
]
答案 0 :(得分：1)
获取您当前的位置。循环遍历位置，确定每个位置的距离（使用Location.distanceBetween计算它）。按距离对位置进行排序。然后只将N个最接近的标记添加到地图中。
答案 1 :(得分：0)
我相信有很多帖子可以告诉你如何计算两点之间的距离，你必须先尝试找到你的解决方案才能在这里发布，我认为这对你有用。它未经测试但
void createMarkersFromJson(String json) throws JSONException {
JSONArray jsonArray = new JSONArray(json);
System.out.print(json);
List<Marker> markers = new ArrayList<Marker>();
for (int i = 0; i < jsonArray.length(); i++) {
JSONObject jsonObj = jsonArray.getJSONObject(i);
System.out.print(jsonObj.getJSONArray("latlng"));
Location myLocation = new Location("Current location");
myLocation.setLatitude(mapB.getMyLocation().getLatitude());
myLocation.setLongitude(mapB.getMyLocation().getLongitude());
Location markerLocation= new Location("Destination");
double markerLat = jsonObj.getJSONArray("latlng").getDouble(0);
double markerLong = jsonObj.getJSONArray("latlng").getDouble(1);
markerLocation.setLatitude(markerLat);
markerLocation.setLongitude(markerLong);
float distance = myLocation.distanceTo(markerLocation);
final int KM = 1000;
if(distance <= (10*KM)
{
Marker marker = mapB.addMarker(new MarkerOptions()
.title(jsonObj.getString("business_name"))
.position(new LatLng(markerLat,markerLong))
.icon(BitmapDescriptorFactory.defaultMarker(BitmapDescriptorFactory.HUE_GREEN))
);
markers.add(marker);
}
}